Technical Specification Improvement for Combustion Engineering Plants to Risk-Inform Requirements Regarding Conditions Leading to Exigent Plant Shutdown Using the Consolidated Line Item Improvement Process, 41264-41280 [06-6364]
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Federal Register / Vol. 71, No. 139 / Thursday, July 20, 2006 / Notices
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FOR FURTHER INFORMATION CONTACT: John
T. Larkins, Executive Director of the
Committee, U.S. Nuclear Regulatory
Commission, Washington, DC 20555,
telephone (301) 415–7360.
Dated: July 14, 2006.
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Federal Advisory Committee, Management
Officer.
[FR Doc. E6–11514 Filed 7–19–06; 8:45 am]
BILLING CODE 7590–01–P
NUCLEAR REGULATORY
COMMISSION
Technical Specification Improvement
for Combustion Engineering Plants to
Risk-Inform Requirements Regarding
Conditions Leading to Exigent Plant
Shutdown Using the Consolidated Line
Item Improvement Process
Nuclear Regulatory
Commission.
ACTION: Request for comment.
rwilkins on PROD1PC63 with NOTICES_1
AGENCY:
SUMMARY: Notice is hereby given that
the staff of the Nuclear Regulatory
Commission (NRC) has prepared a
model safety evaluation (SE) relating to
changes in Combustion Engineering
(CE) plant conditions leading to exigent
plant shutdown in technical
specifications (TS). The NRC staff has
also prepared a model no-significanthazards-consideration (NSHC)
determination relating to this matter and
a model license amendment request
(LAR). The purpose of these models is
to permit the NRC to efficiently process
amendments that propose to adopt
technical specifications changes,
designated as TSTF–426, related to
Topical Report WCAP–16125–NP,
Revision 0 (Rev 0), September 2003
(previously CE NPSD–1208, Rev. 0),
‘‘Justification for the Risk Informed
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Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent Plant Shutdown,’’ which was
approved by an NRC SE dated July 9,
2004. Licensees of CE nuclear power
reactors to which the models apply
could then request amendments,
confirming the applicability of the SE
and NSHC determination to their
reactors. The NRC staff is requesting
comment on the model SE and model
NSHC determination prior to
announcing their availability for
referencing in license amendment
applications.
The comment period expires
August 21, 2006. Comments received
after this date will be considered if it is
practical to do so, but the Commission
is able to ensure consideration only for
comments received on or before this
date.
DATES:
Comments may be
submitted either electronically or via
U.S. mail. Submit written comments to
Chief, Rules and Directives Branch,
Division of Administrative Services,
Office of Administration, Mail Stop: T–
6 D59, U.S. Nuclear Regulatory
Commission, Washington, DC 20555–
0001. Hand deliver comments to: 11545
Rockville Pike, Rockville, Maryland,
between 7:45 a.m. and 4:15 p.m. on
Federal workdays. Copies of comments
received may be examined at the NRC’s
Public Document Room, 11555
Rockville Pike (Room O–1F21),
Rockville, Maryland. Comments may be
submitted by electronic mail to
CLIIP@nrc.gov.
ADDRESSES:
T.R.
Tjader, Mail Stop: O–12H2, Division of
Inspection & Regional Support, Office of
Nuclear Reactor Regulation, U.S.
Nuclear Regulatory Commission,
Washington, DC 20555–0001, telephone
301–415–1187.
SUPPLEMENTARY INFORMATION:
FOR FURTHER INFORMATION CONTACT:
Background
Regulatory Issue Summary 2000–06,
‘‘Consolidated Line Item Improvement
Process for Adopting Standard
Technical Specifications Changes for
Power Reactors,’’ was issued on March
20, 2000. The consolidated line item
improvement process (CLIIP) is
intended to improve the efficiency of
NRC licensing processes, by processing
proposed changes to the standard
technical specifications (STS) in a
manner that supports subsequent
license amendment applications. The
CLIIP includes an opportunity for the
public to comment on proposed changes
to the STS after a preliminary
assessment by the NRC staff and finding
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that the change will likely be offered for
adoption by licensees. This notice
solicits comment on a proposed change
to the STS that allows changes in CE
plant conditions leading to exigent plant
shutdown in technical specifications
(TS), if risk is assessed and managed.
The CLIIP directs the NRC staff to
evaluate any comments received for a
proposed change to the STS and to
either reconsider the change or
announce the availability of the change
for adoption by licensees. Licensees
opting to apply for this TS change are
responsible for reviewing the staff’s
evaluation, referencing the applicable
technical justifications, and providing
any necessary plant-specific
information. Each amendment
application made in response to the
notice of availability will be processed
and noticed in accordance with
applicable NRC rules and procedures.
This notice involves the changes in
CE plant conditions leading to exigent
plant shutdown in TS, if risk is assessed
and managed. The change was proposed
in Topical Report WCAP–16125–NP Rev
0, September 2003 (previously CE
NPSD–1208, Rev 0), ‘‘Justification for
the Risk Informed Modifications to
Selected Technical Specifications for
Conditions Leading to Exigent Plant
Shutdown,’’ which was approved by an
NRC SE dated July 9, 2004. This change
was proposed for incorporation into the
STS by the owners groups participants
in the Technical Specification Task
Force (TSTF) and is designated TSTF–
426, Rev 0. TSTF–426, Rev 0, can be
viewed on the NRC’s web page at
https://www.nrc.gov/reactors/operating/
licensing/techspecs.html.
Applicability
This proposal to modify TS
requirements by the adoption of TSTF–
426, Rev 0, is applicable to all licensees
of CE plants who commit to WCAP–
16446–NP, Rev 0, ‘‘Actions to Preclude
Entry into LCO 3.0.3 Implementation
Guidance (PA–RMCS–0196),’’ June
2005.
To efficiently process the incoming
license amendment applications, the
staff requests that each licensee
applying for the changes proposed in
TSTF–426 include Bases for the
proposed TS consistent with the Bases
proposed in TSTF–426. The CLIIP does
not prevent licensees from requesting an
alternative approach or proposing the
changes without the requested Bases.
However, deviations from the approach
recommended in this notice may require
additional review by the NRC staff and
may increase the time and resources
needed for the review. Significant
variations from the approach, or
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Federal Register / Vol. 71, No. 139 / Thursday, July 20, 2006 / Notices
inclusion of additional changes to the
license, will result in staff rejection of
the submittal. Instead, licensees desiring
significant variations and/or additional
changes should submit a LAR that does
not claim to adopt TSTF–426.
Public Notices
This notice requests comments from
interested members of the public within
30 days of the date of publication in the
Federal Register. After evaluating the
comments received as a result of this
notice, the staff will either reconsider
the proposed change or announce the
availability of the change in a
subsequent notice (perhaps with some
changes to the safety evaluation or the
proposed NSHC determination as a
result of public comments). If the staff
announces the availability of the
change, licensees wishing to adopt the
change must submit an application in
accordance with applicable rules and
other regulatory requirements. For each
application, the staff will publish a
notice of consideration of issuance of
amendment to facility operating
licenses, a proposed NSHC
determination, and a notice of
opportunity for a hearing. The staff will
also publish a notice of issuance of an
amendment to operating license to
announce the modifications of
conditions leading to exigent plant
shutdown in selected technical
specifications.
Dated at Rockville, Maryland, this 13th day
of July 2006.
For the Nuclear Regulatory Commission.
Carl S. Schulten,
Acting Chief, Technical Specifications
Branch, Division of Inspection & Regional
Support, Office of Nuclear Reactor
Regulation.
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Attachment—Proposed Safety
Evaluation, United States Nuclear
Regulatory Commission; Office of
Nuclear Reactor Regulation;
Consolidated Line Item Improvement
Technical Specification Task Force
(TSTF) Change TSTF–426 Risk
Informed Modifications to Selected
Technical Specifications for Conditions
Leading to Exigent Plant Shutdown
1.0 Introduction
On August 30, 2004, the Owners
Group (OG) Technical Specifications
Task Force (TSTF) submitted a
proposed change, TSTF–426, Revision 0
(Rev 0), to the Combustion Engineering
(CE) standard technical specifications
(STS) (NUREG–1432) on behalf of the
industry. TSTF–426, Rev 0, is a
proposal to incorporate WCAP–16125–
NP Rev 0, (previously CE NPSD–1208,
Rev 0), of September 2003, ‘‘Justification
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for the Risk Informed Modifications to
Selected Technical Specifications for
Conditions Leading to Exigent Plant
Shutdown,’’ which was approved by an
NRC safety evaluation (SE) dated July 9,
2004 into the CE STS. This proposal is
part of Nuclear Energy Institute (NEI)
Risk Informed Technical Specifications
Task Force (RITSTF) Initiative 6, one of
the industry’s initiatives being
developed under the Risk Management
Technical Specifications (RMTS)
program. These initiatives are intended
to maintain or improve safety through
the incorporation of risk assessment and
management techniques in technical
specifications (TS), while reducing
unnecessary burden and making
technical specification requirements
consistent with the Commission’s other
risk-informed regulatory requirements.
The Code of Federal Regulations, 10
CFR 50.36(c)(2)(I), ‘‘Technical
Specifications; Limiting Conditions for
Operation,’’ states: ‘‘When a limiting
condition for operation of a nuclear
reactor is not met, the licensee shall
shut down the reactor or follow any
remedial action permitted by the
technical specifications until the
condition can be met.’’ TS provide a
completion time (CT) limit for following
any remedial action permitted by the TS
until the limiting condition for
operation (LCO) can be met. If the LCO
or the remedial action cannot be met on
the specified CT, then the reactor is
required to be shutdown.
The Required Action for Conditions
that imply a loss of function, related to
a system or component included within
the scope of the plant TS, is entry into
LCO 3.0.3. Currently, upon entering
LCO 3.0.3, one hour is allowed to
prepare for an orderly shutdown before
initiating a change in plant operation.
This includes time to permit the
operator to coordinate the reduction in
electrical generation with the load
dispatcher to ensure the stability and
availability of the electrical grid. The
OG is proposing to define and/or modify
various TS Conditions to accommodate
extension of the currently required time
of one hour to initiate plant shutdown
for members with Combustion
Engineering (CE) Nuclear Steam Supply
Systems (NSSS) designs. The proposed
extension, related to specific systems or
components, is based on the system’s
risk significance and varies from 4 hours
to 72 hours.
The proposed changes are typically
associated with plant conditions where
both trains of a two-train redundant
system are declared inoperable and at
the same time there is either no
specified action in the TS for the
condition (requiring a default LCO 3.0.3
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entry) or conditions exist where the
defined action includes an explicit LCO
3.0.3 entry. The intent of the proposed
TS changes is to provide a risk-informed
alternative to the current LCO 3.0.3
requirements such that the plant staff
has adequate time to fully evaluate the
situation or restore loss of function
while the plant remains operating at
power, thus avoiding unnecessary
unscheduled plant shutdowns and
minimizing transition and realignment
risks.
WCAP–16125–NP also provides
system-specific integrated justifications
(i.e., risk and defense-in-depth
arguments) for several proposed TS
Required Action statement changes to
allow a MODE 4 (hot shutdown) end
state, for repair purposes of two-train
redundant systems that do not have
explicit LCO 3.0.3 entry requirements,
when the proposed extended time
cannot be met.
The intent of the proposed TS
changes is to provide needed flexibility
in the performance of corrective
maintenance during power operation
and at the same time enhance overall
plant safety by:
• Avoiding unnecessary unscheduled
plant shutdowns,
• Minimizing plant transitions and
associated transition and realignment
risks,
• Providing increased flexibility in
scheduling and performing maintenance
and surveillance activities, and
• Providing explicit guidance in areas
that currently does not exist.
It should be noted that many of the
proposed TS changes affect the existing
plant shutdown requirements for plant
conditions where the plant operation is
not in explicit compliance with the
plant design basis. The proposed actions
provide a risk-informed process for
establishing shutdown priorities aiming
at reducing overall plant risk and
increasing public health and safety
protection.
2.0 Regulatory Evaluation
In 10 CFR 50.36, the Commission
established its regulatory requirements
related to the content of TS. Pursuant to
10 CFR 50.36(c)(1)–(5), TS are required
to include items in the following five
specific categories related to station
operation: (1) Safety limits, limiting
safety system settings, and limiting
control settings; (2) limiting conditions
for operation (LCOs); (3) surveillance
requirements (SRs); (4) design features;
and (5) administrative controls. The rule
does not specify the particular
requirements to be included in a plant’s
TS. As stated in 10 CFR 50.36(c)(2)(i),
the ‘‘Limiting conditions for operation
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are the lowest functional capability or
performance levels of equipment
required for safe operation of the
facility. When a limiting condition for
operation of a nuclear reactor is not met,
the licensee shall shut down the reactor
or follow any remedial action permitted
by the technical specifications * * *.’’
Topical Report WCAP–16125,
‘‘Justification for Risk-Informed
Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent plant Shutdown’’ (Reference 1),
justifies modifications to various TS
Action Statements for conditions that
result in a loss of safety function related
to a system or component included
within the scope of the plant TS. It
revises the current Required Actions
from either a default or explicit LCO
3.0.3 entry to a risk-informed action
based on the system’s risk significance
with an associated completion time
(CT). In most instances, a CT of 24 hours
is justified.
3.0 Technical Evaluation
The changes proposed in TSTF–426,
Rev 0, are consistent with the changes
proposed and justified in Topical Report
WCAP–16125–NP Rev 0, and approved
by the associated NRC SE of July 9, 2004
(Reference 2). The evaluation included
in Reference 2, as appropriate and
applicable to the changes of TSTF–426,
Rev 0, (Reference 3), is not reiterated
here, except where differences from the
SE are justified and in discussing the
TSTF–426 changes with respect to the
individual specifications. In its
application the licensee commits to PA–
RMSC–0196, ‘‘Actions to Preclude Entry
into LCO 3.0.3, Implementation
Guidance’’ (Reference 4) for
implementing TSTF–426, Rev 0, which
addresses a variety of issues such as
considerations and compensatory
actions for risk-significant plant
configurations. An overview of the
generic evaluation and associated risk
assessment is provided below, along
with a summary of the associated TS
changes justified by Reference 1.
The proposed TS changes, including
end state changes (i.e., approved TSTF–
422 end state changes), are summarized
in Table 1 of this safety evaluation
report (SER). Such changes cover a
diverse range of systems and
components with essentially four
separate impacts on plant risk. They are:
• TS changes related to systems or
components contributing to accident
prevention. The removal of these
systems/components has the potential
to increase the plant risk through the
increased potential for plant upsets (i.e.,
potential for increased initiated event
frequencies). A typical example in this
category are the pressurizer heaters
whose unavailability could complicate
plant pressure control and lead to a
plant trip.
• TS changes related to systems or
components contributing to accident
mitigation. These systems are in standby
during normal plant operation and are
intended to function during accidents to
prevent core damage. Typical examples
in this category are the Emergency Core
Cooling System (ECCS) and the
pressurizer Power Operated Relief
Valves (PORVs).
• TS changes related to systems or
components contributing to large early
release prevention. The primary role of
these systems is to function during a
core damage accident to prevent large
releases of radioactive materials. A
typical example in this category is the
containment (the only component in
this category for which a TS change is
proposed).
• TS changes related to systems/
components contributing to control of
delayed radiation releases to the
environment. The primary role of these
systems is to prevent radiation releases
above TS limits and meet design basis
requirements. Thus, the unavailability
of these systems has no impact on the
surrogate risk metrics associated with
core damage and large early releases.
Typical examples in this category are
the ECCS room ventilation system and
the containment iodine cleanup system.
Although the improved standard
technical specification (STS) numbering
system (NUREG–1432, Reference 5) is
used for convenience in Table 1, the
analyses provided in WCAP–16125–NP
support these changes for all CE
designed NSSS plants.
TABLE 1.—SUMMARY OF PROPOSED MODIFICATIONS TO TECHNICAL SPECIFICATIONS
System
Inoperability condition
Current action and associated
completion time (CT)
Proposed changes: completion time (CT) and end state
LCO 3.4.9 ....
Pressurizer Heaters ................
LCO 3.4.11 ..
Pressurizer Power Operated
Relief Valves (PORVs) and
Associated Block Valves
(BVs).
Both groups of class 1E heaters inoperable.
STS LCO 3.4.11 CONDITION
E (or equivalent): Two
PORVs inoperable and not
capable of being manually
cycled.
STS LCO 3.4.11 CONDITION
F (or equivalent): Two BVs
inoperable.
Safety Injection Tanks (SITs)
Two or more SITs inoperable
(STS CONDITION D).
No condition defined. Default
LCO 3.0.3 entry.
Varies with plant.
STS LCO 3.4.11 CONDITION
E (or equivalent): Close associated block valve in 1
hour AND remove power
from associated block valve
in one hour, AND be in
MODE 3 in 6 hours AND
MODE 4 in [12] hours.
STS LCO 3.4.11 CONDITION
F (or equivalent): Restore
one block valve to operable
in 2 hours. STS Condition
G requires MODE 3 in 6
hours and MODE 4 in [12]
hours if Condition F not
met.
Explicit 3.0.3 entry ..................
24 hrs CT for restoring one
group.
STS LCO 3.4.11 CONDITION
E (or equivalent): Allow 8
hours CT to restore one
PORV, for conditions where
a PORV is unable to
reclose once challenged but
may be isolated.
STS LCO 3.4.11 CONDITION
F (or equivalent): Allow 8
hours to restore one BV.
LCO 3.5.1 ....
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STS #
LCO 3.5.2 ....
Low Pressure Safety Injection
(LPSI).
Two LPSI subsystems inoperable.
Default 3.0.3 entry ..................
LCO 3.5.2 ....
High Pressure Safety Injection
(HPSI).
Two HPSI subsystems inoperable (STS Condition D).
Explicit 3.0.3 entry ..................
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Revise STS Condition D to
allow 24 hours CT for restoring one SIT.
24 hours for restoring one
LPSI subsystem (STS Condition D would be deleted).
4 hours CT for restoring one
HPSI subsystem.
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41267
TABLE 1.—SUMMARY OF PROPOSED MODIFICATIONS TO TECHNICAL SPECIFICATIONS—Continued
Current action and associated
completion time (CT)
STS #
System
Inoperability condition
LCO 3.6.1 ....
Containment (CTMT) ..............
Inoperable ...............................
Defined 1 hour shutdown
(MODE 5 in 36 hours).
LCO
3.6.6A&B.
Containment Spray System
(CS).
Explicit 3.0.3 entry ..................
LCO 3.6.10 ..
Iodine Cleanup System (ICS)
Two CS trains inoperable OR
any combination of three or
more trains inoperable (i.e.,
containment air coolers
(CAC*)) (STS Condition F).
Two ICS trains inoperable ......
LCO 3.6.13 ..
Shield Building Exhaust Air
Cleanup System (SBEACS).
Two trains inoperable .............
No condition defined. Default
3.0.3 entry.
LCO 3.7.11 ..
Control Room Emergency Air
Two trains inoperable .............
Cleanup System (CREACS).
No condition defined. Default
3.0.3 entry.
LCO 3.7.12 ..
Control Room Emergency Air
Temperature Control System (CREATCS).
Emergency Core Cooling System (ECCS), Pump Room
Exhaust Air Cleanup System (ECCS PREACS).
Penetration Room, Exhaust
Air Cleanup System
(PREACS).
Two trains inoperable (STS
Condition E).
Explicit 3.0.3 ...........................
Two trains inoperable .............
No condition defined. Default
3.0.3 entry.
Two trains inoperable .............
No condition defined. Default
3.0.3 entry.
LCO 3.7.13 ..
LCO 3.7.15 ..
No condition defined. Default
3.0.3 entry.
Proposed changes: completion time (CT) and end state
8 hours CT restoring containment operability. Allow
MODE 4 end state.
12 hrs CT for restoring one
CS train if CAC is not available. 72 hours CT for restoring one CS if one train
of CAC is available.
24 hours CT for restoring one
train. Allow MODE 4 end
state.
24 hours CT for restoring one
train. Allow MODE 4 end
state.
24 hours CT for restoring one
train (or the time to reach 5
REM, which may be less
than 24 hours). Proposed
change applies to radiation
protection function only.
Allow MODE 4 end state.
24 hours CT for restoring one
train. Allow MODE 4 end
state.
24 hours CT for restoring one
train. Allow MODE 4 end
state.
24 hours CT for restoring one
train. Allow MODE 4 end
state.
* Also known as containment air recirculation coolers (CARC)
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WCAP–16125–NP documents a riskinformed analysis of the proposed TS
changes. Probabilistic Risk Assessment
(PRA) results and insights are used, in
combination with results of
deterministic assessments, to identify
and justify the proposed TS changes for
all CE NSSS design plants. This is in
accordance with guidance provided in
Regulatory Guides (RGs) 1.174 and
1.177 (References 6 and 7, respectively).
The approach used to assess the risk
impact of the proposed changes is
discussed and evaluated in Section 3.0.
Section 3.1 evaluates the results of the
risk assessment. Section 3.2 provides
integrated justifications (i.e., both
probabilistic and deterministic
arguments) for each of the proposed
system-specific TS changes. Finally,
Section 3.3 summarizes the staff’s
conclusions from the review of the
proposed TS changes.
3.1 Risk Assessment
The objective of the OG’s risk
assessment was to show that the
implementation of the proposed TS
changes are not expected to lead to any
significant risk increases. In performing
the risk-informed assessments and
interpreting the results, the following
two assumptions are tacitly made:
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• A condition resulting in the
inoperability of a system or component
which currently results in the need for
an immediate shutdown is an infrequent
event. This is evidenced by the fact that
plant shutdowns due to entries into
LCO 3.0.3 conditions are rare.
Furthermore, when such a condition
does arise, the actual cause of the
inoperability is often due to an
incomplete ‘‘paper trail’’ or a partial
system failure rather than a deleterious
common-cause failure of critical
components leading to a functional
failure of an entire system.
• The risk incurred by increasing the
required shutdown action time is
controlled to acceptable levels using a
risk informed approach that considers
the component risk worth and offsetting
benefits of avoiding plant transitions.
The risk impact of the proposed TS
changes was assessed following the
three-tiered approach recommended in
RG 1.177 for evaluating proposed
extensions in currently allowed
Completion Times (CTs):
• The first tier involves the
assessment of the change in plant risk
due to the proposed TS change. Such
risk change is expressed (1) by the
change in the average yearly core
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damage frequency (DCDF) and the
average yearly large early release
frequency (DLERF) and (2) by the
incremental conditional core damage
probability (ICCDP) and the incremental
conditional large early release
probability (ICLERP). The assessed
DCDF and DLERF values are compared
to acceptance guidelines, consistent
with the Commission’s Safety Goal
Policy Statement as documented in RG
1.174, so that the plant’s average
baseline risk is maintained within a
minimal range. The assessed ICCDP and
ICLERP values are compared to
acceptance guidelines provided in RG
1.177 which aim at ensuring that the
plant risk does not increase
unacceptably during the period the
equipment is taken out of service.
• The second tier involves the
identification of potentially high-risk
configurations that could exist if
equipment in addition to that associated
with the change were to be taken out of
service simultaneously, or other risksignificant operational factors such as
concurrent equipment testing were also
involved. The objective is to ensure that
appropriate restrictions are in place to
avoid any potential high-risk
configurations.
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• The third tier involves the
establishment of an overall
configuration risk management program
(CRMP) to ensure that potentially risksignificant configurations resulting from
maintenance and other operational
activities are identified. The objective of
the CRMP is to manage configurationspecific risk by appropriate scheduling
of plant activities and/or appropriate
compensatory measures.
The approach used in implementing
the three-tiered approach of RG 1.177 to
support the proposed TS changes is
fully evaluated in the SE (Reference 2)
to WCAP–16125–NP Rev 0. The staff
found that the risk assessment results
support the proposed changes. The risk
increases associated with the proposed
TS changes, if any, will be insignificant
based on guidance provided in RGs
1.174 and 1.177. Furthermore, the
sensitivity studies and the many
conservative assumptions used in the
analyses provide adequate assurance
about the robustness of the results used
to support the proposed TS changes.
3.2 Assessment of Technical
Specification Changes
There are two categories of proposed
system-specific TS changes. The first
category includes changes associated
with plant conditions requiring entry
into LCO 3.0.3 to extend the time for
restoring the system’s or component’s
loss of function, thus avoiding
unnecessary unscheduled plant
shutdowns and minimizing transition
and realignment risks. The second
category includes changes to TS
Required Action statements to allow a
MODE 4 (hot shutdown) end state, for
repair purposes of two-train redundant
systems that do not have implicit LCO
3.0.3 entry requirements, when the
proposed extended time cannot be met.
The generic risk assessment for the
proposed end state changes is
documented in topical report CE–
NPSD–1186 (Reference 8) which has
been reviewed and approved by the
staff. While all proposed system-specific
TS changes include changes to extend
the time for restoring the system’s or
component’s loss of function (first
category changes), some proposed
system-specific TS changes include
changes to modify the end state (second
category changes). Therefore, the
integrated justifications, discussed in
this section, include insights from the
generic risk assessments documented in
both topical reports WCAP–16125–NP
(Reference 1) and CE–NPSD–1186
(Reference 8).
Due to the nature of the plant
conditions associated with the proposed
TS changes (i.e., loss of a system’s or
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component’s function), the redundancy
and diversity typically associated with
ensuring the deterministic aspect of
defense-in-depth position is not always
strictly possible. In these cases, defensein-depth is considered by (1) controlling
the outage time for related equipment,
(2) restricting activities which may
challenge the unavailable systems or
functions, (3) allowing only small time
intervals for plant operation at power
with a system or function unavailable,
(4) using, whenever possible,
contingency actions to limit concurrent
unavailabilities appropriately, and (5)
evaluating repair activities and
alternatives. Defense-in-depth is
evaluated in conjunction with the
generic risk assessment results which
conclude that the proposed systemspecific TS changes would lead to
insignificant risk increases and in most
cases to net risk reductions. This
conclusion is a consequence of the low
expected challenge frequency of the
systems or functions associated with the
proposed TS changes, the very short
proposed exposure times to the
specified plant conditions and the
offsetting benefits of avoiding plant
transitions.
The proposed change in shutdown
mode end states will result in plants
remaining within the applicability of
the specific LCOs for the length of time
it takes to restore the LCO conditions.
Since corrective maintenance will be
necessary, the 10 CFR 50.65(a)(4)
requirement to assess and manage risk
will apply, and should confirm that
remaining in the shutdown mode that is
within the applicability of the LCO is
acceptable for the plant specific
configuration. NRC Regulatory Guide
1.182 (Reference 9) endorses NUMARC
93–01 Section 11 guidance for
implementation of 10 CFR 50.65(a)(4),
and shall be followed; including the
conduct of an (a)(4) reevaluation for
emergent conditions.
3.2.1 Pressurizer Heaters (STS LCO
3.4.9)
The pressurizer provides a point in
the RCS where the liquid and vapor
water phases are maintained in
equilibrium under saturated conditions
for pressure control purposes to prevent
bulk boiling in the remainder of the
RCS. The pressure control components
addressed by this LCO include the
pressurizer, the required groups of
heaters and their controls and the Class
1E power supplies. The liquid to vapor
interface permits RCS pressure control
by using the sprays and heaters during
normal operation and in response to
anticipated design basis accidents. The
unavailability of Class 1E pressurizer
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heaters covered by the TS may
complicate steady state plant pressure
control and, thus, increase the potential
for an unplanned reactor trip.
Another function of the Class 1E
pressurizer heaters is to maintain plant
subcooling during post accident
cooldown by natural circulation.
Although the unavailability of
pressurizer heaters during natural
circulation cooldown will extend the
time to reach the shutdown cooling
system entry conditions, heat removal
will be adequately established via steam
generator cooling.
Plant Applicability: All OG member
plants with CE NSSS designs except St
Lucie-2.
Limiting Condition for Operation
(LCO): Two groups of pressurizer
heaters, [capable of being powered from
an emergency power supply], must be
operable in MODES 1, 2 and 3.
Condition Requiring Entry into
Shutdown Required Action: Two safetyrelated pressurizer heater groups
inoperable (default entry into LCO 3.0.3
is required).
Proposed Modification to Shutdown
Required Actions: Increase the time
available to take action to restore one
group of safety-related heaters before
entry into STS LCO 3.4.9 Condition C to
24 hours.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one group of safety-related
pressurizer heaters before entering STS
LCO 3.4.9 Condition C will not lead to
a significant increase in risk and may
actually decrease risk. The risk impact
of the proposed completion time
extension was assessed to be well
within the acceptance criteria reported
in Regulatory Guides 1.174 and 1.177.
Specifically, the proposed completion
time extension would lead to the
following risk increases: (1) The
probability of core damage when the
safety-related pressurizer heaters are
inoperable will increase by about 3E–7
(the acceptance guideline for ICCDP is
5E–7); (2) the CDF will increase by
about 6E–8/year (the acceptance
guideline for DCDF is 1E–6/year); (3) the
large early release probability when the
safety-related pressurizer heaters are
inoperable will increase by less than
1E–8 (the acceptance guideline for
ICLERP is 5E–8); and (4) the LERF will
increase by about 2E–9/year (the
acceptance guideline for DLERF is 1E–
7/year). Furthermore, the proposed time
extension may actually be risk neutral
or result in a decrease in risk if credit
for avoiding the transition to shutdown
risk is taken.
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The risk impact argument is
consistent with the following
observations. TS include requirements
for both groups of safety-related
pressurizer heaters to have minimum
heating power [and emergency power
supply capability]. The safety-related
pressurizer heaters have two primary
functions. One function is to keep the
reactor coolant in a subcooled condition
with natural circulation following a loss
of offsite power (LOOP) event during
which the normally available station
powered non-safety related heaters
become unavailable. Although no credit
is taken in design basis accident
analyses for the pressurizer heaters, they
have been included in the TS because
they are needed to maintain long term
subcooling during a LOOP event.
However, pressurizer heaters are not
required to achieve a post-trip plant
cooldown since successful cooldown
can be achieved, with minimal impact
on plant risk, due to the availability of
reactor vessel and pressurizer vents.
Consequently, the pressurizer heaters do
not have a significant role in the
mitigation of core damage events. A
second function of the safety-related
pressurizer heaters is to back up the
station powered non-safety related
heaters which are normally available to
control reactor coolant pressure during
steady state operation. The
unavailability of these heaters would
reduce the plant’s ability to control the
normal operating parameters and
consequently will increase the potential
of plant trip.
The presence of both safety-related
and non-safety-related heaters provides
considerable defense-in-depth for many
transient events, except following a
LOOP event. For LOOP events and
without the safety-related pressurizer
heaters, a natural circulation cooldown
may be required. Such cooldowns can
be conducted via use of reactor vessel
and pressurizer vents or SG venting via
the atmospheric dump valves (ADVs).
The intent of the proposed
completion time extension is to extend
plant operation at power when the
ability to control normal plant operation
is not significantly degraded. Therefore,
the proposed completion time extension
should not be utilized when there is
reason to believe that plant pressure and
level cannot be controlled within
operating bounds, as is the case when
both the safety and non-safety
pressurizer heaters are unavailable. This
restriction should be reflected in the TS
bases.
Finding: The requested change to
increase the time available to take action
to restore one pressurizer heater group
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to 24 hours for cases when both groups
are inoperable is acceptable.
Tier 2 Restrictions: None.
3.2.2 Pressurizer PORVs and
Associated Block Valves (STS LCO
3.4.11)
PORVs are automatically opened at a
specific set pressure when the
pressurizer pressure increases and
automatically closed on decreasing
pressure. The PORVs may be manually
operated using controls installed in the
control room. An electric, normally
open, block valve (BV) is installed
between the pressurizer and the PORV.
The function of the BV is to ensure RCS
integrity by isolating a leaking or stuckopen PORV to permit continued power
operation. Most importantly, the BV is
used to isolate a stuck open PORV and
terminate the RCS depressurization and
coolant inventory loss.
Plant Applicability: Calvert Cliffs 1 &
2, St Lucie 1 & 2 (block valves),
Millstone 2, Palisades, and Fort Calhoun
Station.
Limiting Condition for Operation
(LCO): Each PORV and associated block
valve shall be operable in MODES 1, 2
and 3.
Condition Requiring Entry into
Shutdown Required Action: Two PORVs
inoperable and not capable of being
manually cycled (STS LCO 3.4.11
Condition E or equivalent) or two BVs
inoperable (STS LCO 3.4.11 Condition F
or equivalent). There is a variability in
LCO entry requirements among OG
member plants with CE NSSS designs
for conditions with both PORVs
inoperable or both BVs inoperable.
Typically, a plant shutdown is required
if the PORVs are not isolated and one
PORV is not restored within one hour
(STS LCO 3.4.11 Condition E or
equivalent) or when the PORVs are not
placed in manual control within one
hour and one BV is not recovered
within two hours (STS LCO 3.4.11
Condition F or equivalent).
Proposed Modification to Shutdown
Required Actions: Revise STS LCO
3.4.11 Condition E (or equivalent to
allow an 8-hour completion time (CT) to
restore one PORV for conditions where
a PORV is unable to re-close once
challenged, but may be isolated). This
extension would not apply to PORVs
that are leaking, and that cannot be
isolated by block valves, or to PORVs
that are not expected to be isolable
following a demand.
Revise STS LCO 3.4.11 Required
Action F.2 to allow 8 hours to restore
one BV, for conditions where the
associated PORV is unable to reclose.
Assessment: The risk assessment
results (in Reference 2) indicate that the
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proposed 8-hour completion time for
the actions required by TS (i.e., actions
associated with STS LCO 3.4.11
Conditions E and F or equivalent) will
not lead to a significant increase in risk
and, actually, may decrease risk by
avoiding the risk associated with the
transition to shutdown. The risk impact
of the proposed completion time
extension, without credit for avoiding
the transition to shutdown risk, was
assessed to be within the acceptance
criteria reported in Regulatory Guides
1.174 and 1.177. Specifically, the
proposed time extension would lead to
the following risk increases: (1) The
probability of core damage will increase
by about 8E–7, which is close to the
numerical guideline of 5E–7 for ICCDP
used in RG 1.177; (2) the CDF will
increase by about 2E–7/year, which is
significantly less than the acceptance
guideline of 1E–6/year for DCDF; (3) the
large early release probability will
increase by less than 7E–8, which is
close to the numerical guideline of 5E–
8 for ICLERP and in agreement with
guidance provided in RG 1.177; and (4)
the LERF will increase by about 1E–8/
year, which is significantly less than the
acceptance guideline of 1E–7/year for
DLERF. Furthermore, the proposed time
extension may actually be risk neutral
or result in a decrease in risk if credit
for avoiding the transition to shutdown
risk is taken.
The risk impact argument is
consistent with the following defensein-depth argument where the impact of
STS LCO 3.4.11 Conditions E and F on
defense-in-depth is discussed. The
primary purpose of this LCO is to
ensure that the PORVs and the BVs are
operable so the potential for a small
break LOCA through the PORV pathway
is minimized, or if a small LOCA were
to occur through a failed open PORV,
the block valve could be manually
operated to isolate the path. In addition,
one of the functions of the PORVs is to
limit the number of pressure transients
that may challenge the primary safety
valves (PSVs) since the PSVs, unlike the
PORVs, cannot be isolated.
When both PORVs are found
inoperable (i.e., STS LCO 3.4.11
Condition E or equivalent), the
associated BVs are manually closed,
within one hour, to isolate both PORV
paths. With none of the PORVs available
to open, the PSVs could be challenged
to provide overpressure protection.
However, a challenge to the PSVs
during the proposed completion time
extension to restore one PORV is
extremely unlikely and the PSVs are
available and highly reliable (i.e., even
if they are challenged, they would close
properly when the pressure is reduced
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below their setpoint). It should be noted
that overpressure protection is provided
by the PSVs in the design basis
analyses, without any credit for PORV
opening for accident mitigation (in fact
there are some plants built without
PORVs). For these reasons, there is
defense-in-depth against LOCA
accidents through the PORV and the
PSV paths as well as against
overpressure accidents during the very
short time interval when STS LCO
3.4.11 Condition E is proposed to be
allowed with the plant operating at
power.
When both BVs are found inoperable
(i.e., STS LCO 3.4.11 Condition F or
equivalent), the PORVs are placed in
manual control, within one hour, to
ensure that they do not open
automatically in the unlikely event they
are challenged. Therefore, there is
defense-in-depth against small LOCA
accidents through the PORV paths.
However, in the unlikely event of a
pressure transient during the proposed
completion time extension, the PSVs
could be challenged to provide
overpressure protection. This is the
same scenario discussed above for STS
LCO 3.4.11 Condition E. For these
reasons, there is defense-in-depth
against LOCA accidents through the
PORV and the PSV paths as well as
against overpressure accidents during
the very short time interval when STS
LCO 3.4.11 Condition F is proposed to
be allowed with the plant operating at
power.
The PORV paths provide an
alternative means of core cooling by
feed and bleed (once-through core
cooling) in the case of multiple
equipment failure events that are not
within the design basis, such as a total
loss of feedwater. The unavailability of
feed and bleed for core cooling, the
dominant contributor to risk associated
with the proposed changes to LCO
3.4.11. As discussed above, such risk is
very small.
Finding: The requested changes to
allow 8 hours for completing the actions
required by TS (i.e., actions associated
with STS LCO 3.4.11 Conditions E and
F or equivalent) are acceptable.
Tier 2 Restrictions: None.
3.2.3 Safety Injection Tanks (STS LCO
3.5.1)
The Safety Injection Tanks (SITs) are
pressurized passive injection devices
whose primary safety function is to
inject large quantities of borated water
into the reactor vessel during the
blowdown phase of a large LOCA and
to provide inventory to help accomplish
the refill phase that follows the
blowdown phase.
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Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): All SITs shall be operable during
MODES 1 and 2 as well as during
MODE 3 when the pressurizer pressure
is above [700] psia.
Condition Requiring Entry into
Shutdown Required Action: When two
or more SITs are inoperable (STS LCO
3.5.1 Condition D), immediate entry into
LCO 3.0.3 is required.
Proposed Modification to Shutdown
Required Actions: Increase the time
available to restore one SIT before entry
into LCO 3.0.3 to 24 hours.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one SIT before entering LCO
3.0.3 will not lead to a significant
increase in risk and may actually
decrease risk. The risk impact of the
proposed 23-hour extension, without
credit for avoiding the transition to
shutdown risk, was assessed to be well
within the acceptance criteria reported
in Regulatory Guides 1.174 and 1.177.
Specifically, the proposed time
extension would lead to the following
risk increases: (1) The probability of
core damage will increase by about 1E–
8, which is less than the numerical
guideline of 5E–7 for ICCDP; (2) the CDF
will increase by about 3E–9/year, which
is significantly less than the acceptance
guideline of 1E–6/year for DCDF; (3) the
large early release probability will
increase by about 4E–11, which is much
less than the numerical guideline of 5E–
8 for ICLERP; and (4) the LERF will
increase by about 9E–12/year, which is
much less than the acceptance guideline
of 1E–7/year for DLERF. Furthermore,
the proposed time extension would,
most likely, result in a risk reduction if
credit for avoiding the transition to
shutdown risk is taken.
The risk impact argument is also
supported by the following defense-indepth discussion. The SITs are needed
primarily to mitigate large LOCAs. The
unavailability of two or more SITs will
compromise the ability of the plant to
respond to a large LOCA. However, as
discussed above, even if it is
conservatively assumed that all large
LOCAs proceed to core damage, the risk
impact is negligible (much less than the
risk estimated to incur during plant
transition to shutdown). On the other
hand, the unavailability of two or more
SITs may alter the progression of some
smaller break size LOCAs and the extent
of core damage. However, their impact
on the core damage potential is
negligible. In addition, long term core
cooling, provided via the plant’s LPSI
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and HPSI systems, partially offsets the
impact of SIT unavailability.
Finding: The requested change to
increase the time available to take action
to restore all SITs (from one to 24 hours)
for cases when two or more SITs are
inoperable is acceptable.
Tier 2 Restrictions: None.
3.2.4 Low Pressure Safety Injection
(STS LCO 3.5.2)
The low pressure safety injection
(LPSI) system is part of the emergency
core cooling system (ECCS). The
function of the ECCS is to provide core
cooling and negative reactivity to ensure
that the reactor core is protected
following certain accidents, such as
LOCAs, SGTRs and loss of feedwater.
There are two phases of ECCS operation:
injection and recirculation. In the
injection phase, borated water is
injected into the RCS via the cold legs.
After the blowdown stage of the LOCA
stabilizes, injection flow is split equally
between the hot and cold legs. After the
RWST is depleted, the ECCS
recirculation phase is entered as the
ECCS suction is automatically
transferred to the containment sump. TS
require that in MODES 1, 2 and 3, with
pressurizer pressure greater than or
equal to [1700] psia, both redundant
(100% capacity) ECCS trains must be
operable. Each ECCS train consists of a
high pressure safety injection (HPSI)
subsystem, a low pressure safety
injection (LPSI) subsystem and a
charging subsystem.
Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): Two redundant, 100% capacity
LPSI trains must be operable in MODES
1 and 2 as well as in MODE 3 when the
pressurizer pressure is greater than or
equal to [1700] psia.
Condition Requiring Entry into
Shutdown Required Action: When both
LPSI trains are inoperable, the design
basis assumptions for the large break
LOCA analyses are not met and a
default entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown
Required Actions: Add separate
condition for both LPSI trains
inoperable to restore at least one LPSI
train to operable in 24 hours. In
addition, with the proposed condition
taken with the proposed changes to
HPSI discussed below, the existing
condition (STS LCO 3.5.2 Condition D)
of ‘‘Less than 100% of the ECCS flow
equivalent to a single OPERABLE train
available’’ will no longer be required
since that condition will be addressed
by the conditions for two HPSI
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subsystems inoperable or two LPSI
subsystems inoperable.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one LPSI train will not lead to
a significant increase in risk and may
actually decrease risk. The risk impact
of the proposed completion time
extension, without credit for avoiding
the transition to shutdown risk, was
assessed to be well within the
acceptance criteria reported in
Regulatory Guides 1.174 and 1.177.
Specifically, the proposed completion
time extension would lead to the
following risk increases: (1) The
probability of core damage will increase
by about 1E–7, which is less than the
numerical guideline of 5E–7 for ICCDP;
(2) the CDF will increase by about 2E–
8/year, which is significantly less than
the acceptance guideline of 1E–6/year
for DCDF; (3) the large early release
probability will increase by about 4E–
10, which is much less than the
numerical guideline of 5E–8 for ICLERP;
and (4) the LERF will increase by about
8E–11/year, which is much less than the
acceptance guideline of 1E–7/year for
DLERF. Furthermore, the proposed
completion time extension would, most
likely, result in a risk reduction if credit
for avoiding the transition to shutdown
risk is taken.
The risk impact argument is also
supported by the following defense-indepth discussion. The primary impact
of the unavailability of the LPSI system
will be the reduction in the capability
of the plant to provide RCS inventory
makeup to mitigate a large LOCA.
However, the unavailability of the LPSI
system will impair the ability of the
plant to maneuver to shutdown cooling.
Therefore, the proposed 24-hour
completion time to repair one LPSI train
is reasonable due to the very small
incremental risk associated with the
continued plant operation at power and
the inadvisability of a plant shutdown
without the LPSI pumps which are
needed for shutdown cooling.
STS LCO 3.5.2 Condition D requires
that for a condition where the ECCS
flow is less than 100% of the ECCS flow
assumed in the LOCA analysis. WCAP–
16125–NP proposed to delete this
condition because it would no longer be
necessary, based on the new conditions
for two HPSI trains or two LPSI trains
inoperable. The NRC staff has
concluded that an adequate basis has
not been provided to justify the deletion
of STS LCO 3.5.2 Condition D.
Specifically, licensees should discuss
the functions of the HPSI and LPSI
systems in terms of reactivity control,
RCS inventory control, RCS pressure
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control, and core heat removal for
system operations such as safety
injection and recirculation, hot leg
injection and once through core cooling
to mitigate the consequences of LOCAs,
SLB, and SGTR events. The licensees
should also discuss the safety and
nonsafety related accident mitigation
systems, and show that, for a condition
when the ECCS flow is less than 100%
of the ECCS flow equivalent to a single
OPERABLE train, alternative flow
injection systems and backup accident
management strategies are available and
effective. Licensees should also list
specific compensatory measures
(including a description of pertinent
operating procedures, maintenance
process and training programs) and
contingency plans with acceptable
justification for the proposed deletion of
STS LCO 3.5.2 Condition D.
Finding: The requested change to
increase the time available to restore an
LPSI train to operable is acceptable. The
proposed change to delete STS LCO
3.5.2 Condition D needs to be
adequately justified on a plant-specific
basis.
Tier 2 Restrictions: None.
3.2.5 High Pressure Safety Injection
(STS LCO 3.5.2)
The high pressure safety injection
system is part of the ECCS. The function
of the ECCS is to provide core cooling
and negative reactivity to ensure that
the reactor core is protected following
certain accidents, such as LOCAs,
SGTRs and loss of feedwater. There are
two phases of ECCS operation: injection
and recirculation. In the injection phase,
borated water is injected into the RCS
via the cold legs. After the blowdown
stage of the LOCA stabilizes injection
flow is split equally between the hot
and cold legs. After the RWST is
depleted, the ECCS recirculation phase
is entered as the ECCS suction is
automatically transferred to the
containment sump. TS require that in
MODES 1, 2 and 3, with pressurizer
pressure greater than or equal to [1700]
psia, both redundant (100% capacity)
ECCS trains must be operable. Each
ECCS train consists of a high pressure
safety injection subsystem, a low
pressure safety injection subsystem and
a charging subsystem.
Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): In MODES 1 and 2 as well as in
MODE 3 when the pressurizer pressure
is greater than or equal to [1700] psia,
both trains of HPSI must be operable.
Condition Requiring Entry into
Shutdown Required Action: When both
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HPSI trains are inoperable, a default
entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown
Required Actions: Increase the time for
restoring one HPSI pump or subsystem,
before initiating shutdown per LCO
3.0.3, to four hours.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 4-hour completion time for
the actions required by TS before
entering LCO 3.0.3 will not lead to a
significant increase in risk and, actually,
may decrease risk by avoiding the risk
associated with the transition to
shutdown. The risk impact of the
proposed completion time extension,
without credit for avoiding the
transition to shutdown risk, was
assessed to be in agreement with the
acceptance guidelines reported in
Regulatory Guides 1.174 and 1.177.
Specifically, the proposed completion
time extension would lead to the
following risk increases: (1) An ICCDP
of 1.7E–6 for plants with PORVs and
1.1E–6 for plants without PORVs, which
are close to the numerical guideline of
5E–7 for ICCDP used in RG 1.177; (2) a
DCDF of 3.5E–7/year for plants with
PORVs and 2.1E–7 for plants without
PORVs, which are significantly less than
the acceptance guideline of 1E–6/year
for DCDF; (3) an ICLERP of about 4E–8
for plants with PORVs and less than 3E–
8 for plants without PORVs, which are
less than the numerical guideline of 5E–
8 for ICLERP; and (4) a DLERF of about
8E–9/year for plants with PORVs and
about 5E–9 for plants without PORVs,
which are much less than the
acceptance guideline of 1E–7/year for
DLERF. Furthermore, the proposed time
extension may actually be risk neutral
or result in a decrease in risk if credit
for avoiding the transition to shutdown
risk is taken.
The risk impact argument is also
supported by the following defense-indepth discussion. The subject LCO
requires the operability of a number of
independent subsystems. In many
instances due to the redundancy of
trains and the diversity of subsystems,
the inoperability of one component in a
train does not necessarily render the
HPSI incapable of performing its
function. Neither does the inoperability
of two different components, each in a
different train, necessarily result in a
loss of function for the ECCS. Examples
of typical inoperabilities would include
the unavailability of a single header
injection valve or degradation of HPSI
delivery curves below minimum design
basis levels. The proposed completion
time extension allows for potential
resolution of minor HPSI system
inoperabilities and provides time to
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prepare for a controlled plant shutdown
without increasing the plant’s risk
significantly.
Finding: The requested change to
allow four hours to resolve the
inoperability and restore one pump or
subsystem of HPSI capability before
required to commence a plant shutdown
per LCO 3.0.3, is acceptable.
Tier 2 Restrictions: None.
3.2.6 Containment (STS LCO 3.6.1)
The requirements stated in this LCO
define the performance of the
containment as a fission barrier.
Specifically, LCO 3.6.1 requires that the
containment maximum leakage rate be
limited in accordance with 10 CFR part
50 Appendix J. Other LCOs place
additional restrictions on containment
air locks and containment isolation
valves. The integrated effect of these
TSs is to ensure that the containment
leakage is well controlled within limits
which assure that the post accident
whole body and thyroid dose limits of
10 CFR 100.11 or 10 CFR 50.67, as
applicable, are satisfied following a
Maximum Hypothetical Accident
(MHA) initiated from full power.
Inability to meet this leakage limit
renders the containment inoperable.
Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): Containment shall be operable in
MODES 1, 2, 3 and 4.
Condition Requiring Entry into
Shutdown Required Action:
Containment is declared to be
inoperable due to excessive leakage,
including leakage from air locks and
isolation valves, for a time period
greater than one hour. If the
containment is not restored to operable
status within one hour, a plant
shutdown is required.
Proposed Modification to Shutdown
Required Actions: Define a specific
action to allow 8 hours to restore an
inoperable containment to operable.
Allow MODE 4 to become a designated
end state for correcting containment
impairments for conditions where the
containment leakage is excessive due to
reasons other than the inoperability of
two or more containment isolation
valves (CIVs) in the same flow paths.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 8-hour completion time for
restoring an inoperable containment to
operable status will not lead to a
significant increase in risk and may
actually decrease risk. The risk impact
of the proposed completion time
extension was assessed to be well
within the acceptance criteria reported
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in Regulatory Guides 1.174 and 1.177.
Specifically, the proposed time
extension would lead to the following
conservatively assessed risk increases:
(1) The large early release probability
will increase by about 9E–8, which is
close to the numerical guideline of 5E–
8 for ICLERP; and (2) the LERF will
increase by about 2E–8/year, which is
significantly less than the acceptance
guideline of 1E–7/year for DLERF.
Furthermore, the proposed completion
time extension may actually be risk
neutral or result in a decrease in risk if
credit for avoiding the transition to
shutdown risk is taken.
The proposed changes apply to
containment conditions where
containment integrity is essentially
maintained and adequate ECCS net
positive suction head (NPSH) is
expected following an event.
Containment ‘‘leakage’’ at or near design
basis levels is not explicitly modeled in
PRAs. The PRA implicitly requires that
containment ‘‘gross’’ integrity must be
available to ensure adequate NPSH for
ECCS pumps. Even though the PRA
models do not consider that
containment ‘‘leakage’’ contributes to a
large early release, the assessed risk
impact of the proposed completion time
extension is based on the assumption
that all core damage events will proceed
to a large early release.
The requirement for an immediate
(within one hour) shutdown is based on
the philosophy that inoperability of the
containment is a violation of the plant
design basis and, therefore, a plant
shutdown must be initiated as soon as
possible. The selection of one hour was
based on the requirement for
‘‘immediate shutdown’’ and the
assumption that one hour is adequate
time for operators to effect shutdown
plans. The goal was to place the plant
in a condition where the health and
safety of the public could be better
assured. No specific risk assessments
were performed. In fact, it is more
appropriate from the health and safety
objective viewpoint to consider the risk
of continued plant operation as well as
that introduced by the shutdown. In
consideration of the total plant risk, it
is more risk beneficial to allow a small
increase in risk at power to resolve a TS
inoperability rather than to undertake
an immediate (within one hour)
shutdown.
In addition to the completion time
extension, it is also proposed that
MODE 4 be allowed as the end state to
repair the containment. This is
supported by the following arguments.
If accidents were to occur in MODE 4,
resulting containment pressures would
be significantly less than the design
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basis accident (DBA) conditions. Hence,
leakage would be further reduced.
While in MODE 4, the probability of
LOCA or MSLB is significantly reduced
from MODE 1 levels. The implied
licensing basis assumption that MODE 5
is inherently of lower operational risk
than MODE 4 is not supported by risk
evaluations (Reference 8). MODE 5 risks
are either about equal to or likely greater
than equivalent risks in MODE 4, and
therefore produce radiation releases to
containment on par with those of MODE
4. Thus, remaining in MODE 4, while
the containment excess leakage
condition is being corrected, is an
appropriate action.
The STS LCO 3.6.1 requirement that
the plant be brought to MODE 5 end
state is not based on consideration of
risks. Accidents initiated from MODE 4
are far less challenging to the
containment than those initiated from
MODE 1. The lower energy content in
MODE 4 results in containment
pressures and potential leakage
approximately one half of that
associated with MODE 1 releases.
Furthermore, by having the plant in a
shutdown condition in advance, fission
product releases are significantly
reduced. Thus, while leakage
restrictions should be maintained,
MODE 4 leakage in excess of that
allowed in MODE 1 can be safely
allowed for a limited time sufficient to
resolve the inoperability and return the
plant to power operation.
From a deterministic perspective,
MODE 4 with SG heat removal would
maintain more mitigating systems
available, as compared to MODE 5, to
respond to loss of RCS inventory or
decay heat removal events and therefore
reduce the overall public risk. In MODE
4, the Safety Injection Actuation Signal
(SIAS) and the Containment Isolation
Actuation Signal (CIAS) will be
available to aid the operators in
responding to events that threaten the
reactor or containment integrity.
Therefore, the proposed TS end state
change does not adversely affect the
plant defense-in-depth.
Finding: The requested changes to (1)
increase the time available to take action
to restore the containment to 8 hours
and (2) allow MODE 4 as the repair end
state, are acceptable.
Tier 2 Restrictions: None.
3.2.7 Containment Spray System (STS
LCO 3.6.6 A)
The containment spray (CS) and
containment cooling (CC) systems
provide containment atmosphere
cooling to limit post accident pressure
and temperature in containment to less
than the design values. For most CE
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NSSS design plants the containment
sprays represent a portion of a diverse
and redundant heat removal system. In
addition to containment heat removal,
CSs enhance post-accident fission
product removal.
Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): Two containment spray trains
and two containment cooling (CAC or
CARC) trains shall be operable in
MODES 1, 2, 3 and [4].
Condition Requiring Entry into
Shutdown Required Action:
Inoperability of both CS trains or any
combination of three or more trains
inoperable (STS LCO 3.6.6.A Condition
F), immediate entry into LCO 3.0.3 is
required.
Proposed Modification to Shutdown
Required Actions: (1) Increase the time
available for restoring one CS train to 72
hours when at least one CARC train is
available for containment heat removal;
(2) increase the time available for
restoring one CS train to 12 hours when
two trains of the CARC system is
unavailable for containment heat
removal. Based on Table 5.2.3–2 of
WCAP–16125–NP, STS LCO 3.6.6.A
would be revised to allow shutdown
modes of MODE 3 in 6 hours and MODE
5 in 36 hours versus the current
requirement of immediate entry into
LCO 3.0.3 if the Required Action and
associated Completion Time not met.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 12-hour completion time for
restoring one CS train when two trains
of the CARC system is unavailable for
containment heat removal before
entering LCO 3.0.3 will not lead to a
significant increase in risk and may
actually decrease risk. The risk impact
of the proposed completion time
extension was assessed to be well
within the acceptance criteria reported
in Regulatory Guides 1.174 and 1.177.
Specifically, the proposed completion
time extension would lead to the
following risk increases: (1) The
probability of core damage will increase
by less than 7E–7 which is close to the
numerical guideline of 5E–7 for ICCDP
used in RG 1.177; (2) the CDF will
increase by about 1.4E–7/year
(acceptance criteria for DCDF about 1E–
6/year); (3) the large early release
probability during the condition will
increase by about 1E–8 (acceptance
criteria for ICLERP is 5E–8); and (4) the
LERF will increase by about 2.5E–9/year
(acceptance criteria for DLERF is 1E–7/
year). Furthermore, the proposed
completion time extension may actually
be risk neutral or result in a decrease in
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risk if credit for avoiding the transition
to shutdown risk is taken.
When at least one CARC train is
available for containment heat removal,
the risk impact in terms of CDF and
LERF is insignificant. However, credit is
taken for post accident fission product
removal by the CS system. The radiation
release ‘‘non-LER’’ risk impact
associated with the proposed increase of
the time available for restoring one CS
train to 72 hours was conservatively
assessed. Specifically, the proposed
completion time extension would lead
to the following ‘‘non-LER’’ risk
increases: (1) The probability of a ‘‘nonLER’’ release during the completion
time extension would increase by about
8E–7; and (2) the ‘‘non-LER’’ frequency
would increase by 1.6E–7/year. These
increases in ‘‘non-LER’’ risk are slightly
above the values used in the criteria
discussed in Section 3.1 of this report.
However, such increases in ‘‘non-LER’’
risk are still comparable in magnitude to
what is considered acceptable for
increases in the much higher
consequence risks associated with core
damage and large early release.
Furthermore, the proposed completion
time extension is definitely risk
beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
In addition to the risk argument, the
proposed 72-hour completion time is
selected for compatibility with
improved standard technical
specification (STS) LCO 3.6.6B. STS
LCO 3.6.6B calls for a Completion Time
of 72 hours when two CS trains are
inoperable (Condition C) and is
applicable to conditions where the
sprays are not credited for fission
product removal. Inoperability of the CS
or CARC will degrade the capability of
the plant to respond to a containment
threat. However, provided the other
system is available the plant remains
capable of controlling pressure. The loss
of sprays will expose some plant
equipment to beyond environmental
qualification temperature limits should
a MSLB occur. However, the probability
of such an event during the proposed
completion time extension is very small
(about 1E–3/year or less than 1E–5 per
71 hours). Furthermore, the ability of
the plant to cope with a MSLB event is
not compromised.
Finding: The requested changes to (1)
increase the time available for restoring
one CS train to 72 hours when at least
one CARC train is available for
containment heat removal; and (2)
increase the time available for restoring
one CS train to 12 hours when two
trains of the CARC system is unavailable
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41273
for containment heat removal, are
acceptable. The requested change
described in Table 5.2.3–2 of WCAP–
16125–NP, that is, STS LCO 3.6.6.A
would be revised to allow shutdown
modes of MODE 3 in 6 hours and MODE
5 in 36 hours versus the current
requirement of immediate entry into
LCO 3.0.3 if the Required Action and
associated Completion Time is not met,
was not justified in the topical report.
Therefore, the proposed change is not
acceptable without further justification.
Tier 2 Restrictions: None.
3.2.8 Iodine Cleanup System (ICS)
(STS LCO 3.6.10)
The purpose of the ICS is to remove
elemental iodine from the post-accident
containment atmosphere. These systems
were initially incorporated into plants
in the belief that radiological iodine
releases would be predominantly in
elemental form. However, extensive
research has indicated that most iodine
will be released in the form of Cesium
Iodine (CsI) particulates. Consequently,
the actual impact of system
functionality on actual public doses is
negligible. ICS consists of two 100%
capacity trains.
Plant Applicability: Calvert Cliffs 1 &
2, St Lucie 1 & 2.
Limiting Condition for Operation
(LCO): Two ICS trains shall be operable
in MODES 1, 2, 3 & 4.
Condition Requiring Entry into LCO
3.0.3: Both ICS trains inoperable.
Currently a default entry into LCO 3.0.3
is required.
Proposed Modification to Shutdown
Required Actions: Add a condition to (1)
allow 24 hours to restore one train to
operable status, and (2) allow MODE 4
as the final end state for repairing the
inoperable system.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of ICS will not lead
to a significant increase in risk and may
actually decrease risk. The proposed
completion time extension will not
contribute to any risk increases, in terms
of core damage and large early release.
The radiation release ‘‘non-LER’’ risk
impact associated with the proposed
time increase was conservatively
assessed. Specifically, the proposed
completion time extension would lead
to the following ‘‘non-LER’’ risk
increases: (1) The probability of a ‘‘nonLER’’ release during the completion
time extension would increase by about
2.6E–7; and (2) the ‘‘non-LER’’
frequency would increase by about
5.0E–8/year. These increases in ‘‘nonLER’’ risk, which are comparable in
magnitude to what is considered
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acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is risk
beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is supported by risk
assessments (Reference 8) which
indicated that, in general, there is less
risk associated with staying in MODE 4
to repair the inoperable system than
proceeding to MODE 5. This is due to
the fact that there are more systems
available in MODE 4 than in MODE 5
to mitigate accidents initiated at
shutdown and the risk of transition
between MODES 4 and 5 is avoided.
The ICS functions together with the
containment spray and the containment
cooling systems following a design basis
accident (DBA) that causes failure of the
fuel cladding, and release of radioactive
material (principally iodine) to the
containment. The ICS is specifically
designed to respond to the maximum
hypothetical accident with a large
assumed contribution due to elemental
iodine. The DBAs that result in a release
of radioactive iodine within
containment are LOCA and MSLB or a
control element assembly (CEA) ejection
accident. In the analysis for each of
these accidents, it is assumed that
adequate containment leak tightness is
present at event initiation to limit
potential leakage to the environment.
Additionally, it is assumed that the
amount of radioactive iodine release is
limited by reducing the iodine
concentration in the containment
atmosphere via use of containment
sprays. The unavailability of the ICS
will have no significant impact on
anticipated radiological releases to the
public or the control room. This is due
to the fact that: (1) Iodine releases are
predominantly particulate and removal
via sprays and precipitation is effective,
(2) availability of elemental iodine is
low so that ICS has limited utility, and
(3) containment leak tightness
significantly limits potential releases.
Significant release events that
contribute to large early release, such as
containment bypass and SGTR with loss
of secondary isolation events, will
bypass these filters regardless of their
availability.
Finding: The requested changes to (1)
increase the time available to restore
one ICS train to 24 hours and (2) allow
MODE 4 as the final end state, for cases
when both ICS trains are inoperable, are
acceptable.
Tier 2 Restrictions: None.
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3.2.9 Shield Building Exhaust Air
Cleanup System (STS LCO 3.6.13)
The shield building exhaust air
cleanup system (SBEACS) provides
radionuclide removal capability for
fission products leaked into the shield
building. The SBEACS consists of two
separate and redundant trains. Each
train includes a heater, cooling coils, a
prefilter, a moisture separator, a high
efficiency particulate air (HEPA) filter,
an activated charcoal absorber section
for removal of radionuclides and a fan.
Ductwork, valves and/or dampers and
instrumentation also form part of the
system.
Plant Applicability: St Lucie 1 & 2,
Waterford 3 and Millstone 2.
Limiting Condition for Operation
(LCO): Two SBEACS trains shall be
operable in MODES 1, 2, 3 and 4.
Condition Requiring Entry into
Shutdown Required Action:Both
SBEACS trains inoperable. Currently a
default entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown
Required Actions: Add a condition to (1)
allow 24 hours to take action for both
SBEACS trains unavailable, and (2)
allow MODE 4 as the final end state for
repairing the inoperable system.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of SBEACS will not
lead to a significant increase in risk and
may actually decrease risk. The
proposed completion time extension
will not contribute to any risk increases,
in terms of core damage and large early
release. The radiation release ‘‘nonLER’’ risk impact associated with the
proposed time increase was
conservatively assessed. Specifically,
the proposed completion time extension
would lead to the following ‘‘non-LER’’
risk increases: (1) The probability of a
‘‘non-LER’’ release during the
completion time extension would
increase by about 2.6E–7; and (2) the
‘‘non-LER’’ frequency would increase by
about 5.0E–8/year. These increases in
‘‘non-LER’’ risk, which are comparable
in magnitude to what is considered
acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is definitely
risk beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is supported by risk
assessments (Reference 8) which
indicated that, in general, there is less
risk associated with staying in MODE 4
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to repair the inoperable system than
proceeding to MODE 5. This is due to
the fact that there are more systems
available in MODE 4 than in MODE 5
to mitigate accidents initiated at
shutdown and the risk of transition
between MODES 4 and 5 is avoided.
The proposed changes are also
supported by the following qualitative
discussion. The SBEACS is required to
ensure that the radioactive material
leaking from the primary containment of
a dual containment into the Shield
Building (secondary containment)
following a DBA are filtered and
absorbed prior to exhausting to the
environment. Loss of the SBEACS could
cause site boundary doses, in the event
of a DBA, to exceed the values given in
the licensing basis. However,
containment ‘‘leakage’’ at or near design
basis levels is not explicitly modeled in
PRAs. PRAs implicitly require that
containment ‘‘gross’’ integrity must be
available to ensure NPSH for ECCS
pumps. In the PRA Level 2 models,
containment ‘‘leakage’’ is not
considered to contribute to large early
release. If accidents were to occur in
MODE 4, resulting containment
pressures would be significantly less
than the DBA conditions. Hence,
leakage would be further reduced. In
addition, while in MODE 4, the
probability of LOCA and MSLB is
significantly reduced from MODE 1
levels. By keeping the plant in MODE 4,
operator actions required for entry into
shutdown cooling and which introduce
potential containment bypass risks are
avoided.
Finding: The requested changes to (1)
increase the time available to restore
one SBEACS train to 24 hours and (2)
allow MODE 4 as the final end state, for
cases when both SBEACS trains are
inoperable, are acceptable.
Tier 2 Restrictions: None.
3.2.10 Control Room Emergency Air
Cleanup System (STS LCO 3.7.11)
The control room emergency air
cleanup system (CREACS) provides a
protected environment from which
operators can control the plant
following an uncontrolled release of
radioactivity, chemicals or toxic gas.
Alternate designations of this system
include the acronyms CREACUS,
CREACS, CREVAS, CREVS, or CREAFS.
The current TS require operability of
CREACS from MODE 1 through MODE
4 to support operator response to a DBA.
The system’s operability in MODES 5
and 6 may also be required at some
plants for chemical and toxic gas
concerns. The CREACS is needed to
protect the control room (CR) in a wide
variety of circumstances.
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Plant Applicability: Applicable to all
OG member plants with CE NSSS
designs.
Limiting Condition for Operation
(LCO): Two CREACS trains shall be
operable in MODES 1, 2, 3 and 4 and
during movement of [recently]
irradiated fuel assemblies in MODES [5
and 6].
Condition Requiring Entry into
Shutdown Required Action: Both trains
inoperable for conditions other than
inoperable control room boundary in
MODES 1, 2, 3, and 4. Explicit entry
into LCO 3.0.3 required (STS LCO
3.7.11 Condition F).
Proposed Modification to Shutdown
Required Actions: (1) Increase the time
available to take action to 24 hours (or
the time to reach 5 REM, which may be
less than 24 hours, from the radiation
field associated with main steam safety
valves lifting concurrent with a SGTR)
for the cases in which both CREACS
trains are unavailable, and (2) allow
MODE 4 as the final end state for
repairing the inoperable system. This
modification applies to the radiation
protection function only. Site specific
validation is necessary to support
extension to toxic gas and chemical
protection functions.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of CREACS before
entering LCO 3.0.3 will not lead to a
significant increase in risk and may
actually decrease risk. The proposed
completion time extension will not
contribute to any risk increases, in terms
of core damage and large early release.
The radiation release ‘‘non-LER’’ risk
impact associated with the proposed
time increase was conservatively
assessed. Specifically, the proposed
completion time extension would lead
to the following ‘‘non-LER’’ risk
increases: (1) The probability of a ‘‘nonLER’’ release during the completion
time extension would increase by about
2.6E–7; and (2) the ‘‘non-LER’’
frequency would increase by about
5.0E–8/year. These increases in ‘‘nonLER’’ risk, which are comparable in
magnitude to what is considered
acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is definitely
risk beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is not justified. STS
LCO 3.7.11 Condition F has an explicit
LCO 3.0.3 entry. WCAP–16125–NP does
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not provide justification for modifying
Condition F Required Action from
‘‘Enter LCO 3.0.3’’ to an end state of
MODE 4.
Finding: The requested change to
increase the time available to take action
to restore one CREACS train to 24 hours
for the radiation protection function
only is acceptable. The requested
change to allow MODE 4 as the final
end state, for cases when both CREACS
trains are inoperable, is not justified in
WCAP–16125–NP and is not acceptable.
Tier 2 Restrictions: None.
3.2.11 Control Room Emergency Air
Temperature Control System (STS LCO
3.7.12)
The control room emergency air
temperature control system (CREATCS)
provides temperature control for the CR
following isolation of the CR. The
CREATCS consists of two independent,
redundant trains that provide cooling
and heating of recirculated CR air. Each
train consists of heating coils, cooling
coils, instrumentation and controls to
provide for CR temperature control.
Plant Applicability: Applicable to
Calvert Cliffs 1 & 2, Fort Calhoun,
Palisades, PVNGS 1, 2, & 3, Waterford
3 and ANO 2. It is noted that cooling for
the St Lucie units are included in the air
cleanup system discussed in TS 3.7.11
but the cooling system arguments
contained in this section apply to St
Lucie Units 1 & 2.
Limiting Condition for Operation
(LCO): Two CREATCS trains shall be
operable in MODES 1, 2, 3 and 4 and
during movement of [recently]
irradiated fuel assemblies in MODES [5
and 6].
Condition Requiring Entry into
Shutdown Required Action: Both trains
inoperable in MODES 1, 2, 3, and 4
requires an explicit LCO 3.0.3 entry
(STS LCO 3.7.12 Condition E).
Proposed Modification to Shutdown
Required Actions: Modify STS LCO
3.7.12 Condition E to (1) increase the
time available to take action under LCO
3.0.3 to 24 hours for the cases in which
both CREATCS trains are unavailable,
and (2) allow MODE 4 as the final end
state for repairing the inoperable
system.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of CREATCS before
entering LCO 3.0.3 will not lead to a
significant increase in risk and may
actually decrease risk. The proposed
completion time extension will not
contribute to any risk increases, in terms
of core damage and large early release.
The radiation release ‘‘non-LER’’ risk
impact associated with the proposed
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completion time increase was
conservatively assessed. Specifically,
the proposed completion time extension
would lead to the following ‘‘non-LER’’
risk increases: (1) The probability of a
‘‘non-LER’’ release during the
completion time extension would
increase by about 2.6E–7; and (2) the
‘‘non-LER’’ frequency would increase by
about 5.0E–8/year. These increases in
‘‘non-LER’’ risk, which are comparable
in magnitude to what is considered
acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is definitely
risk beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is not justified. STS
LCO 3.7.12 Condition E has an explicit
LCO 3.0.3 entry. WCAP–16125–NP does
not provide justification for modifying
Condition E Required Action from
‘‘Enter LCO 3.0.3’’ to an end state of
MODE 4.
Several short term actions associated
with cooling the CR may be
implemented to mitigate risk
consequences further. These actions
include use of portable fans and
propping open doors. Several plants
have such actions in procedures.
Finding: The requested change to
increase the time available to take action
to restore one CREATCS train to 24
hours is acceptable. The requested
change to allow MODE 4 as the final
end state, for cases when both trains are
inoperable, is not justified in WCAP–
16125–NP and is not acceptable.
Tier 2 Restrictions: None.
3.2.12 Emergency Core Cooling System
(ECCS) Pump Room Exhaust Air
Cleanup System (PREACS) (STS LCO
3.7.13)
The ECCS pump room exhaust air
cleanup system (ECCS PREACS) is an
emergency system that filters air from
the area of the active Engineered Safety
Features (ESF) components during the
recirculation phase of a LOCA. The
ECCS PREACS consists of two
independent, redundant trains of
equipment that provide filtering of air in
the ECCS pump rooms during postLOCA recirculation cooling.
Plant Applicability: Calvert Cliffs 1 &
2, St Lucie 1 & 2, Waterford 3. It is noted
that at Waterford 3 the functions of the
ECCS PREACS and Penetration Room
Exhaust Air Cleanup System (PREACS),
which is discussed below under LCO
3.7.15, are combined within the
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Controlled Ventilation Area System
(CVAS) TS.
Limiting Condition for Operation
(LCO): Two ECCS PREACS trains shall
be operable in MODES 1, 2, 3 and 4.
Condition Requiring Entry into
Shutdown Required Action: Both trains
inoperable, default entry into LCO 3.0.3.
Proposed Modification to Shutdown
Required Actions: (1) Increase the time
available to restore one train to 24
hours, and (2) allow MODE 4 as the
final end state for repairing the
inoperable system.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of ECCS PREACS
will not lead to a significant increase in
risk and may actually decrease risk. The
proposed completion time extension
will not contribute to any risk increases,
in terms of core damage and large early
release. The radiation release ‘‘nonLER’’ risk impact associated with the
proposed completion time increase was
conservatively assessed. Specifically,
the proposed completion time extension
would lead to the following ‘‘non-LER’’
risk increases: (1) The probability of a
‘‘non-LER’’ release during the
completion time extension would
increase by about 1.1E–7; and (2) the
‘‘non-LER’’ frequency would increase by
about 2.0E–8/year. These increases in
‘‘non-LER’’ risk, which are comparable
in magnitude to what is considered
acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is definitely
risk beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is supported by risk
assessments (Reference 8) which
indicated that, in general, there is less
risk associated with staying in MODE 4
to repair the inoperable system than
proceeding to MODE 5. This is due to
the fact that there are more systems
available in MODE 4 than in MODE 5
to mitigate accidents initiated at
shutdown and the risk of transition
between MODES 4 and 5 is avoided.
The unavailability of the ECCS
PREACS only impacts radiation releases
to the public when the ECCS
recirculation is in progress during a
LOCA. Since successful recirculation
also implies successful event mitigation,
the releases this system is designed to
mitigate are relatively low.
Finding: The requested changes to (1)
increase the time available to take action
to restore one ECCS–PREACS train to 24
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hours and (2) allow MODE 4 as the final
end state, for cases when both trains are
inoperable, are acceptable.
Tier 2 Restrictions: None.
3.2.13 Penetration Room Exhaust Air
Cleanup System (PREACS) (STS LCO
3.7.15)
The Penetration Room Exhaust Air
Cleanup System (PREACS) filters air
from the penetration area between the
containment and the auxiliary building.
The PREACS consists of two
independent, redundant trains. Each
train consists of a heater, demister or
prefilter, HEPA filter, activated charcoal
absorber and a fan.
Plant Applicability: Calvert Cliffs 1 &
2, and Waterford 3. It is noted that at
Waterford 3 the functions of the
PREACS and ECCS PREACS, which is
discussed above under LCO 3.7.13, are
combined within the Controlled
Ventilation Area System (CVAS) TS.
Limiting Condition for Operation
(LCO): Two PREACS trains shall be
operable in MODES 1, 2, 3 and 4.
Condition Requiring Entry into
Shutdown Required Action: Both trains
inoperable for reasons other than an
inoperable penetration room boundary,
default entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown
Required Actions: (1) Increase the time
available to restore one train to 24
hours, and (2) allow MODE 4 as the
final end state for repairing the
inoperable system.
Assessment: The risk assessment
results (in Reference 2) indicate that the
proposed 24-hour completion time for
restoring one train of PREACS will not
lead to a significant increase in risk and
may actually decrease risk. The
proposed completion time extension
will not contribute to any risk increases,
in terms of core damage and large early
release. The radiation release ‘‘nonLER’’ risk impact associated with the
proposed completion time increase was
conservatively assessed. Specifically,
the proposed completion time extension
would lead to the following ‘‘non-LER’’
risk increases: (1) The probability of a
‘‘non-LER’’ release during the
completion time extension would
increase by about 2.6E–7; and (2) the
‘‘non-LER’’ frequency would increase by
about 5.0E–8/year. These increases in
‘‘non-LER’’ risk, which are comparable
in magnitude to what is considered
acceptable for core damage and large
early release risk increases, are very
small. Furthermore, the proposed
completion time extension is definitely
risk beneficial when the averted core
damage and large early release risks
associated with avoiding plant
shutdown are taken into consideration.
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The proposed change to allow MODE
4 as the final end state for repairing the
inoperable system is supported by risk
assessments (Reference 8) which
indicated that, in general, there is less
risk associated with staying in MODE 4
to repair the inoperable system than
proceeding to MODE 5. This is due to
the fact that there are more systems
available in MODE 4 than in MODE 5
to mitigate accidents initiated at
shutdown and the risk of transition
between MODES 4 and 5 is avoided.
Finding: The requested changes to (1)
increase the time available to take action
to restore one PREACS train to 24 hours
and (2) allow MODE 4 as the final end
state, for cases when both trains are
inoperable, are acceptable.
Tier 2 Restrictions: None.
3.3 Summary and Conclusions
The above requested changes are
found acceptable by the staff. The staff
approval applies only to operation as
described and acceptably justified in
References 2 and 8. To be consistent
with the staff’s approval, any licensee
requesting to operate in accordance with
TSTF–426, as approved in this safety
evaluation, should commit to operate in
accordance with WCAP–16446–NP, Rev
0, ‘‘Actions to Preclude Entry into LCO
3.0.3 Implementation Guidance (PA–
RMCS–0196),’’ June 2005, which
includes a requirement for the licensee
to commit to adhere to the guidance of
the revised Section 11 of NUMARC–93–
01, Revision 3. The implementation
guidance includes alternative systems
that must be operable and compensating
measures for the systems included in
TSTF–426. The licensees shall update
relevant operating procedures,
maintenance procedures, and training
programs to reflect this change.
The required action for conditions
that imply a loss of function, is entry
into LCO 3.0.3. Currently, upon entering
LCO 3.0.3, one hour is allowed to
prepare for an orderly shutdown before
initiating a change in plant operation.
The OG is proposing to define or modify
various TS Conditions to accommodate
extension of the currently required time
of one hour to initiate plant shutdown
for member plants with CE NSSS
designs. The proposed extension,
related to specific systems or
components, is based on the system’s
risk significance. In addition, WCAP–
16125–NP provides a proposal to
modify several Required Action
statements, related to specific systems
or components, to allow for a MODE 4
(hot shutdown) end state for repair
purposes of two-train redundant
systems that do not have explicit LCO
3.0.3 entry requirements, when the time
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requirements of the action statement for
staying at power cannot be met.
The intent of the proposed TS
changes is to provide needed flexibility
in the performance of corrective
maintenance during power operation to
fully evaluate the situation or restore
loss of function and at the same time
enhance overall plant safety by:
• Avoiding unnecessary unscheduled
plant shutdowns,
• Minimizing plant transitions and
associated transition and realignment
risks,
• Providing increased flexibility in
scheduling and performing maintenance
and surveillance activities, and
• Providing explicit guidance in areas
that currently does not exist.
It should be noted that many of the
proposed TS changes affect the existing
plant shutdown requirements for plant
conditions where the plant operation is
not in explicit compliance with the
plant design basis. The proposed actions
provide a risk-informed process for
establishing shutdown priorities aiming
at reducing overall plant risk and
increasing public health and safety
protection. In performing the riskinformed assessments and interpreting
the results, the following assumptions
were made:
• A condition resulting in the
inoperability of a system or component
which currently results in the need for
an immediate shutdown is a low
frequency event.
• The frequency of events leading to
LCO 3.0.3 is not expected to increase
significantly following the proposed
change because such events may be
reportable and may require a licensee
event report. In addition, events leading
to LCO 3.0.3 are used in performance
indicators and the reactor oversight
program. Therefore, licensees will have
no incentive to allow the current low
frequency of these events to increase
after the proposed extensions are
granted.
• The risk incurred by increasing the
required shutdown action time is
controlled to acceptable levels using a
risk informed approach that considers
the component risk worth and offsetting
benefits of avoiding plant transitions.
The risk impact of the proposed TS
changes was assessed following the
three-tiered approach recommended in
RG 1.177 for evaluating proposed
extensions in currently allowed
Completion Times (CTs):
• The first tier involves the
assessment of the change in plant risk
due to the proposed TS change;
• The second tier involves the
identification of potentially high-risk
configurations that could exist if
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equipment in addition to that associated
with the change were to be taken out of
service simultaneously;
• The third tier involves the
implementation of the proposed
changes in conjunction with a
configuration risk management program
(CRMP).
The impact of each proposed systemspecific TS change on defense-in-depth
was evaluated in conjunction with the
risk assessment results. Due to the
nature of the plant conditions associated
with the proposed TS changes (i.e., loss
of a system’s or component’s function),
the redundancy and diversity typically
associated with ensuring the
deterministic aspect of defense-in-depth
position is not always strictly possible.
In these cases defense-in-depth was
considered by identifying specific
restrictions to the implementation of the
proposed changes. Such restrictions aim
at (1) controlling the outage time for
related equipment, (2) restricting
activities which may challenge the
unavailable systems or functions, (3)
allowing only small time intervals for
plant operation at power with a system
or function unavailable, (4) using,
whenever possible, contingency actions
to limit concurrent outages, and (5)
evaluating repair activities and
alternatives.
Based on this integrated evaluation,
the staff concludes that the proposed
system-specific TS changes would at
most lead to acceptably small risk
increases. In addition, defense-in-depth
is taken into consideration. This
conclusion is a consequence of the low
expected challenge frequency of the
systems or functions associated with the
proposed TS changes, the very short
proposed exposure times to the
specified plant conditions, the offsetting
benefits of avoiding plant transitions,
and the identification of specific
restrictions to the implementation of the
proposed changes.
4.0
Verifications and Commitments
In order to efficiently process
incoming license amendment
applications and ensure consistent
implementation of the change by the
various licensees, the NRC staff
requested each licensee requesting the
changes addressed by TSTF–426, Rev 0,
using the CLIIP to address the following
plant-specific regulatory commitments.
4.1 Each licensee should make a
regulatory commitment to follow the
implementation guidance of WCAP–
16446–NP, Rev 0, ‘‘Actions to Preclude
Entry into LCO 3.0.3 Implementation
Guidance (PA–RMCS–0196),’’ June
2005.
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41277
4.2 Each licensee should make a
regulatory commitment to follow
Section 11 of NUMARC–93–01,
Revision 3.
The licensee has made a regulatory
commitment to follow the
implementation guidance of WCAP–
16446–NP and Section 11 of NUMARC–
93–01, Revision 3.
The NRC staff finds that reasonable
controls for the implementation and for
subsequent evaluation of proposed
changes pertaining to the above
regulatory commitment(s) can be
provided by the licensee’s
administrative processes, including its
commitment management program. The
NRC staff has agreed that NEI 99–04,
Revision 0, ‘‘Guidelines for Managing
NRC Commitment Changes,’’ provides
reasonable guidance for the control of
regulatory commitments made to the
NRC staff (see Regulatory Issue
Summary 2000–17, ‘‘Managing
Regulatory Commitments Made by
Power Reactor Licensees to the NRC
Staff,’’ dated September 21, 2000). The
NRC staff notes that NEI 99–04
establishes a voluntary reporting system
for the operating data that is similar to
the system established for the ROP PI
program. Should the licensee choose to
incorporate a regulatory commitment
into the final safety analysis report or
other document with established
regulatory controls, the associated
regulations would define the
appropriate change-control and
reporting requirements.
5.0 State Consultation
In accordance with the Commission’s
regulations, the [ ] State official was
notified of the proposed issuance of the
amendment. The State official had [(1)
no comments or (2) the following
comments—with subsequent
disposition by the staff].
6.0 Environmental Consideration
The amendments change a
requirement with respect to the
installation or use of a facility
component located within the restricted
area as defined in 10 CFR part 20 and
change surveillance requirements. The
NRC staff has determined that the
amendments involve no significant
increase in the amounts and no
significant change in the types of any
effluents that may be released offsite,
and that there is no significant increase
in individual or cumulative
occupational radiation exposure. The
Commission has previously issued a
proposed finding that the amendments
involve no-significant-hazardsconsiderations, and there has been no
public comment on the finding [FR ].
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Accordingly, the amendments meet the
eligibility criteria for categorical
exclusion set forth in 10 CFR
51.22(c)(9). Pursuant to 10 CFR 51.22(b),
no environmental impact statement or
environmental assessment need be
prepared in connection with the
issuance of the amendments.
7.0
Conclusion
The Commission has concluded, on
the basis of the considerations discussed
above, that (1) there is reasonable
assurance that the health and safety of
the public will not be endangered by
operation in the proposed manner, (2)
such activities will be conducted in
compliance with the Commission’s
regulations, and (3) the issuance of the
amendments will not be inimical to the
common defense and security or to the
health and safety of the public.
rwilkins on PROD1PC63 with NOTICES_1
8.0
References
1. WCAP–16125–NP, Revision 0,
‘‘Justification for Risk-Informed
Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent Plant Shutdown,’’ October 3,
2003.
2. Beckner, William D., ‘‘Safety
Evaluation of WCAP–16125–NP, Rev 0,
‘‘Justification for Risk-Informed
Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent Plant Shutdown,’’ Letter to
Gordon Bischoff, Westinghouse
3. TSTF–426, Revision 0, ‘‘Revise or
Add Actions to Preclude Entry into LCO
3.0.3,’’ August 2004.
4. WCAP–16446–NP, Revision 0,
‘‘Actions to Preclude Entry into LCO
3.0.3, Implementation Guidance,’’ June
2005.
5. NUREG–1432, ‘‘Standard Technical
Specifications, Combustion Engineering
Plants,’’ Revision 2, USNRC, June 2001.
6. Regulatory Guide 1.174, ‘‘An
Approach for Using Probabilistic Risk
Assessment in Risk-Informed Decision
Making on Plant Specific Changes to the
Licensing Basis,’’ USNRC, August 1998.
7. Regulatory Guide 1.177, ‘‘An
Approach for Plant Specific RiskInformed Decision Making: Technical
Specifications,’’ USNRC, August 1998.
8. CE–NPSD–1186, ‘‘Technical
Justification for the Risk-Informed
Modification to Selected Required
Action End States for CEOG PWRs,’’ CE
Owner’s Group, April 2000.
9. Regulatory Guide 1.182, ‘‘Assessing
and Managing Risk Before Maintenance
Activities at Nuclear Power Plants,’’
May 2000.
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Attachment—For Inclusion on the
Technical Specification Web Page
The following example of an
application was prepared by the NRC
staff to facilitate use of the consolidated
line item improvement process (CLIIP).
The model provides the expected level
of detail and content for an application
to adopt TSTF–426, Revision 0, ‘‘RiskInformed modifications to selected
technical specifications for conditions
leading to exigent plant shutdowns,’’ for
CE plants using CLIIP. Licensees remain
responsible for ensuring that their actual
application fulfills their administrative
requirements as well as Nuclear
Regulatory Commission regulations.
U.S. Nuclear Regular Commission,
Document Control Desk, Washington,
DC 20555.
Subject: Plant Name, Docket No. 50—
Application for Technical
Specification Change TSTF–426,
Risk Informed Modification to
Selected Technical Specifications
for Conditions Leading to Exigent
Plant Shutdowns Using the
Consolidated Line Item
Improvement Process
Gentleman: In accordance with the
provisions of 10 CFR 50.90 [LICENSEE]
is submitting a request for an
amendment to the technical
specifications (TS) for [PLANT NAME,
UNIT NOS.].
The proposed amendment would
modify TS to risk-inform requirements
regarding selected technical
specifications for conditions leading to
exigent plant shutdowns.
Attachment 1 provides a description
of the proposed change, the requested
confirmation of applicability, and plantspecific verifications. Attachment 2
provides the existing TS pages marked
up to show the proposed change.
Attachment 3 provides revised (clean)
TS pages. Attachment 4 provides a
summary of the regulatory commitments
made in this submittal. Attachment 5
provides the existing TS Bases pages
marked up to show the proposed change
(for information only).)
[LICENSEE] requests approval of the
proposed license amendment by
[DATE], with the amendment being
implemented [BY DATE OR WITHIN X
DAYS].
In accordance with 10 CFR 50.91, a
copy of this application, with
attachments, is being provided to the
designated [STATE] Official.
I declare under penalty of perjury
under the laws of the United States of
America that I am authorized by
[LICENSEE] to make this request and
that the foregoing and the attachment
are true and correct. (Note that request
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may be notarized in lieu of using this
oath or affirmation statement).
If you should have any questions
regarding this submittal, please contact
[NAME, TELEPHONE NUMBER].
Sincerely,
[Name, Title]
Attachments:
1. Description and Assessment.
2. Proposed Technical Specification
Changes.
3. Revised Technical Specification
Pages.
4. Regulatory Commitments.
5. Proposed Technical Specification
Bases Changes.
cc: NRC Project Manager
NRC Regional Office
NRC Resident Inspector
State Contact
Attachment 1—Description and
Assessment
1.0
Description
The proposed amendment would
modify technical specifications to riskinform requirements regarding selected
technical specifications for conditions
leading to exigent plant shutdowns.
The changes are consistent with
Nuclear Regulatory Commission (NRC)
approved Industry/Technical
Specification Task Force (TSTF) TSTF–
426, Revision 0. The availability of this
Technical Specification (TS)
improvement was published in the
Federal Register on [DATE] as part of
the consolidated line item improvement
process (CLIIP).
2.0
Assessment
2.1 Applicability of Topical Report,
TSTF–426, and Published Safety
Evaluation
[LICENSEE] has reviewed GE topical
report (Reference 1), TSTF–426
(Reference 2), and the NRC model safety
evaluation (Reference 3) as part of the
CLIIP. [LICENSEE] has concluded that
the information in the GE topical report
and TSTF–426, as well as the safety
evaluation prepared by the NRC staff are
applicable to [PLANT, UNIT NOS.] and
justify this amendment for the
incorporation of the changes to the
[PLANT] TS. [NOTE: Only those
changes proposed in TSTF–426 are
addressed in the model SE. The model
SE and associated topical report address
the entire fleet of CE plants, and the
plants adopting TSTF–426 must confirm
the applicability of the changes to their
plant.]
2.2
Optional Changes and Variations
[LICENSEE] is not proposing any
variations or deviations from the GE
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topical report and the TS changes
described in the TSTF–426, Revision 0
or the NRC staff’s model safety
evaluation dated [DATE]. [NOTE: The
CLIIP does not prevent licensees from
requesting an alternate approach or
proposing changes without the
requested Bases or Bases control
program. However, deviations from the
approach recommended in this notice
may require additional review by the
NRC staff and may increase the time and
resources needed for the review.
Significant variations from the
approach, or inclusion of additional
changes to the license, will result in
staff rejection of the submittal. Instead,
licensees desiring significant variations
and/or additional changes should
submit a LAR that does not claim to
adopt TSTF–426.]
3.0
Regulatory Analysis
3.1 No Significant Hazards
Consideration Determination
[LICENSEE] has reviewed the
proposed no significant hazards
consideration determination (NSHCD)
published in the Federal Register as
part of the CLIIP. [LICENSEE] has
concluded that the proposed NSHCD
presented in the Federal Register notice
is applicable to [PLANT] and is hereby
incorporated by reference to satisfy the
requirements of 10 CFR 50.91(a).
3.2
Verification and Commitments
As discussed in the notice of
availability published in the Federal
Register on [DATE] for this TS
improvement, plant-specific
verifications were performed as follows:
[LICENSEE] commits to the regulatory
commitments in Attachment 4. In
addition, [LICENSEE] has proposed TS
Bases consistent with the Westinghouse
topical report and TSTF–426, which
provide guidance and details on how to
implement the new requirements.
Implementation of TSTF–426 requires
that risk be managed and assessed, and
the licensee’s configuration risk
management program is adequate to
satisfy this requirement. The risk
assessment need not be quantified, but
may be a qualitative assessment of the
vulnerability of systems and
components when one or more systems
are not able to perform their associated
function.
4.0
Environmental Evaluation
The amendment changes
requirements with respect to the
installation or use of a facility
component located within the restricted
area as defined in 10 CFR part 20. The
NRC staff has determined that the
amendment adopting TSTF–426, Rev. 0,
involves no significant increase in the
amounts and no significant change in
the types of any effluents that may be
released offsite, and that there is no
significant increase in individual or
cumulative occupational radiation
exposure. The Commission has
previously issued a proposed finding
that TSTF–426, Rev. 0, involves no
significant hazards considerations, and
there has been no public comment on
the finding in Federal Register Notice [#
and [DATE]]. Accordingly, the
amendment meets the eligibility criteria
for categorical exclusion set forth in 10
CFR 51.22(c)(9). Pursuant to 10 CFR
51.22(b), no environmental impact
statement or environmental assessment
need be prepared in connection with the
issuance of the amendment.
5.0
References
1. WCAP–16125–NP, Revision 0,
‘‘Justification for Risk-Informed
Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent Plant Shutdown,’’ October 3,
2003.
2. TSTF–426, Revision 0, ‘‘Revise or
Add Actions to Preclude Entry into LCO
3.0.3,’’ August 2004.
3. Federal Register, Vol. XX, No. XX,
p. XXXXX, ‘‘Notice of Availability of
Model Application Concerning
Technical Specification Improvement
for Combustion Engineering Plants To
Risk-Inform Requirements Regarding
Conditions Leading to Exigent Plant
Shutdown Using the Consolidated Line
Item Improvement Process,’’ [DATE].
Attachment 2—Proposed Technical
Specification Changes (Mark-Up)
Attachment 3—Proposed Technical
Specification Pages
[Clean copies of Licensee specific
Technical Specification (TS) pages,
corresponding to the TS pages changed
by TSTF–426, Rev. 0, are to be included
in Attachment 3]
Attachment 4—List of Regulatory
Commitments
The following table identifies those
actions committed to by [LICENSEE] in
this document. Any other statements in
this submittal are provided for
information purposes and are not
considered to be regulatory
commitments. Please direct questions
regarding these commitments to
[CONTACT NAME].
Regulatory commitments
Due date/event
[LICENSEE] will follow the guidance established in Section 11 of NUMARC 93–01, ‘‘Industry Guidance for
Monitoring the Effectiveness of Maintenance at Nuclear Power Plants,’’ Nuclear Management and Resource Council, Revision 3, July 2000.
[LICENSEE] will follow the guidance established in WCAP–16446–NP, Revision [No.] ‘‘Actions to Preclude
Entry into LCO 3.0.3, Implementation Guidance,’’ [DATE].
Attachment 5—Proposed Changes to
Technical Specification Bases Pages
rwilkins on PROD1PC63 with NOTICES_1
Proposed No Significant Hazards
Consideration Determination
Description of Amendment Request:
On August 30, 2004, the Owners Group
(OG) Technical Specifications Task
Force (TSTF) submitted a proposed
change, TSTF–426, Revision 0 (Rev. 0),
to the Combustion Engineering (CE)
standard technical specifications (STS)
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(NUREG–1432) on behalf of the
industry. TSTF–426, Rev. 0, is a
proposal to incorporate WCAP–16125–
NP, Rev. 0, of September 2003,
‘‘Justification for the Risk Informed
Modifications to Selected Technical
Specifications for Conditions Leading to
Exigent Plant Shutdown,’’ which was
approved by an NRC safety evaluation
(SE) dated July 9, 2004 into the CE STS.
This proposal is part of Nuclear Energy
Institute (NEI) Risk Informed Technical
PO 00000
Frm 00083
Fmt 4703
Sfmt 4703
[Ongoing, or
amendment].
implement
with
[Implement with amendment, when
TS Required Action End State
remains within the APPLICABILITY of TS].
Specifications Task Force (RITSTF)
Initiative 6, one of the industry’s
initiatives being developed under the
Risk Management Technical
Specifications (RMTS) program.
WCAP–16125–NP, Rev. 0 provides
technical justification for the
modification of various TS to define
and/or modify Actions to extend the
time required to initiate a plant
shutdown from 1 hour in accordance
with LCO 3.0.3 to a risk-informed time
E:\FR\FM\20JYN1.SGM
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41280
Federal Register / Vol. 71, No. 139 / Thursday, July 20, 2006 / Notices
varying from 4 hours to 72 hours. The
intent of the proposed modifications to
the plant TS is to enhance overall plant
safety by:
a. Avoiding unnecessary plant
shutdowns.
b. Minimizing plant transitions and
associated transition and realignment
risks.
c. Providing for increased flexibility
in scheduling and performing
maintenance and surveillance activities.
d. Providing explicit guidance where
none currently exists.
Basis for proposed no-significanthazards-consideration determination:
As required by 10 CFR 50.91(a), an
analysis of the issue of no-significanthazards-consideration is presented
below:
rwilkins on PROD1PC63 with NOTICES_1
Criterion 1—The Proposed Change Does
Not Involve a Significant Increase in the
Probability or Consequences of an
Accident Previously Evaluated
The proposed change provides a short
Completion Time to restore an
inoperable system for conditions under
which the existing Technical
Specifications require a plant shutdown
to begin within one hour in accordance
with Limiting Condition for Operation
(LCO) 3.0.3. Entering into Technical
Specification Actions is not an initiator
of any accident previously evaluated. As
a result, the probability of an accident
previously evaluated is not significantly
increased. The consequences of any
accident previously evaluated that may
occur during the proposed Completion
Times are no different from the
consequences of the same accident
during the existing one hour allowance.
As a result, the consequences of any
accident previously evaluated are not
significantly increased. Therefore, the
proposed change does not involve a
significant increase in the probability or
consequences of an accident previously
evaluated.
Criterion 2—The Proposed Change Does
Not Create the Possibility of a New or
Different Kind of Accident From Any
Previously Evaluated
No new or different accidents result
from utilizing the proposed change. The
changes do not involve a physical
alteration of the plant (i.e., no new or
different type of equipment will be
installed) or a change in the methods
governing normal plant operation. In
addition, the changes do not impose any
new or different requirements. The
changes do not alter assumptions made
in the safety analysis. Therefore, the
proposed change does not create the
possibility of a new or different kind of
accident from any previously evaluated.
VerDate Aug<31>2005
19:44 Jul 19, 2006
Jkt 208001
Criterion 3—The Proposed Change Does
Not Involve a Significant Reduction in
the Margin of Safety
The proposed change increases the
time the plant may operate without the
ability to perform an assumed safety
function. The analyses in WCAP–
16125–NP, Rev. 0, ‘‘Justification for
Risk-Informed Modifications to Selected
Technical Specifications for Conditions
Leading to Exigent Plant Shutdown,’’
Revision 0, September 2003,
demonstrated that there is an acceptably
small increase in risk due to a limited
period of continued operation in these
conditions and that this risk is balanced
by avoiding the risks associated with a
plant shutdown. As a result, the change
to the margin of safety provided by
requiring a plant shutdown within one
hour is not significant. Therefore, the
proposed change does not involve a
significant reduction in a margin of
safety.
Based upon the reasoning presented
above and the previous discussion of
the amendment request, the requested
change does not involve a significant
hazards consideration.
Dated at Rockville, Maryland, this 13th day
of July 2006.
For the Nuclear Regulatory Commission.
Carl S. Schutlen,
Chief, Technical Specifications Branch,
Division of Inspection & Regional Support,
Office of Nuclear Reactor Regulation.
[FR Doc. 06–6364 Filed 7–19–06; 8:45 am]
BILLING CODE 7590–01–P
SECURITIES AND EXCHANGE
COMMISSION
Proposed Collection; Comment
Request
Upon Written Request, Copies Available
From: Securities and Exchange
Commission, Office of Filings and
Information Services, Washington, DC
20549.
Extension:
Rules 17h–1T and 17h–2T, SEC File No.
270–359, OMB Control No. 3235–0410.
Notice is hereby given that pursuant
to the Paperwork Reduction Act of 1995
(44 U.S.C. 3501 et seq.) the Securities
and Exchange Commission
(‘‘Commission’’) has submitted to the
Office of Management and Budget
requests for extension of the previously
approved collections of information
discussed below. The Code of Federal
Regulation citations to this collection of
information are the following rules: 17
CFR 240.17h–1T and 17 CFR 240.17h–
2T under the Securities Exchange Act of
1934 (17 U.S.C. 78a et seq.) (the ‘‘Act’’).
PO 00000
Frm 00084
Fmt 4703
Sfmt 4703
Rule 17h–1T requires a broker-dealer
to maintain and preserve records and
other information concerning certain
entities that are associated with the
broker-dealer. This requirement extends
to the financial and securities activities
of the holding company, affiliates and
subsidiaries of the broker-dealer that are
reasonably likely to have a material
impact on the financial or operational
condition of the broker-dealer. Rule
17h–2T requires a broker-dealer to file
with the Commission quarterly reports
and a cumulative year-end report
concerning the information required to
be maintained and preserved under
Rule 17h–1T.
The collection of information required
by Rules 17h–1T and 17h–2T is
necessary to enable the Commission to
monitor the activities of a broker-dealer
affiliate whose business activities is
reasonably likely to have a material
impact on the financial and operational
condition of the broker-dealer. Without
this information, the Commission would
be unable to assess the potentially
damaging impact of the affiliate’s
activities on the broker-dealer.
There are currently 200 respondents
that must comply with Rules 17h–1T
and 17h–2T. Each of these 200
respondents require approximately 10
hours per year, or 2.5 hours per quarter,
to maintain the records required under
Rule 17h–1T, for an aggregate annual
burden of 2,000 hours (200 respondents
× 10 hours). In addition, each of these
200 respondents must make five annual
responses under Rule 17h–2T. These
five responses require approximately 14
hours per respondent per year, or 3.5
hours per quarter, for an aggregate
annual burden of 2,800 hours (200
respondents × 14 hours). In addition,
there are approximately five new
respondents per year that must draft an
organizational chart required under
Rule 17h–1T and establish a system for
complying with the Rules. The staff
estimates that drafting the required
organizational chart requires one hour
and establishing a system for complying
with the Rules requires three hours,
thus requiring an aggregate of 20 hours
(5 new respondents × 4 hours). Thus,
the total compliance burden per year is
approximately 4,820 burden hours
(2,000 + 2,800 + 20).
Written comments are invited on: (a)
Whether the proposed collection of
information is necessary for the proper
performance of the functions of the
agency, including whether the
information will have practical utility;
(b) the accuracy of the agency’s estimate
of the burden of the collection of
information; (c) ways to enhance the
quality, utility, and clarity of the
E:\FR\FM\20JYN1.SGM
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]]>Agencies
[Federal Register Volume 71, Number 139 (Thursday, July 20, 2006)]
[Notices]
[Pages 41264-41280]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-6364]
-----------------------------------------------------------------------
NUCLEAR REGULATORY COMMISSION
Technical Specification Improvement for Combustion Engineering
Plants to Risk-Inform Requirements Regarding Conditions Leading to
Exigent Plant Shutdown Using the Consolidated Line Item Improvement
Process
AGENCY: Nuclear Regulatory Commission.
ACTION: Request for comment.
-----------------------------------------------------------------------
SUMMARY: Notice is hereby given that the staff of the Nuclear
Regulatory Commission (NRC) has prepared a model safety evaluation (SE)
relating to changes in Combustion Engineering (CE) plant conditions
leading to exigent plant shutdown in technical specifications (TS). The
NRC staff has also prepared a model no-significant-hazards-
consideration (NSHC) determination relating to this matter and a model
license amendment request (LAR). The purpose of these models is to
permit the NRC to efficiently process amendments that propose to adopt
technical specifications changes, designated as TSTF-426, related to
Topical Report WCAP-16125-NP, Revision 0 (Rev 0), September 2003
(previously CE NPSD-1208, Rev. 0), ``Justification for the Risk
Informed Modifications to Selected Technical Specifications for
Conditions Leading to Exigent Plant Shutdown,'' which was approved by
an NRC SE dated July 9, 2004. Licensees of CE nuclear power reactors to
which the models apply could then request amendments, confirming the
applicability of the SE and NSHC determination to their reactors. The
NRC staff is requesting comment on the model SE and model NSHC
determination prior to announcing their availability for referencing in
license amendment applications.
DATES: The comment period expires August 21, 2006. Comments received
after this date will be considered if it is practical to do so, but the
Commission is able to ensure consideration only for comments received
on or before this date.
ADDRESSES: Comments may be submitted either electronically or via U.S.
mail. Submit written comments to Chief, Rules and Directives Branch,
Division of Administrative Services, Office of Administration, Mail
Stop: T-6 D59, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001. Hand deliver comments to: 11545 Rockville Pike, Rockville,
Maryland, between 7:45 a.m. and 4:15 p.m. on Federal workdays. Copies
of comments received may be examined at the NRC's Public Document Room,
11555 Rockville Pike (Room O-1F21), Rockville, Maryland. Comments may
be submitted by electronic mail to CLIIP@nrc.gov.
FOR FURTHER INFORMATION CONTACT: T.R. Tjader, Mail Stop: O-12H2,
Division of Inspection & Regional Support, Office of Nuclear Reactor
Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555-
0001, telephone 301-415-1187.
SUPPLEMENTARY INFORMATION:
Background
Regulatory Issue Summary 2000-06, ``Consolidated Line Item
Improvement Process for Adopting Standard Technical Specifications
Changes for Power Reactors,'' was issued on March 20, 2000. The
consolidated line item improvement process (CLIIP) is intended to
improve the efficiency of NRC licensing processes, by processing
proposed changes to the standard technical specifications (STS) in a
manner that supports subsequent license amendment applications. The
CLIIP includes an opportunity for the public to comment on proposed
changes to the STS after a preliminary assessment by the NRC staff and
finding that the change will likely be offered for adoption by
licensees. This notice solicits comment on a proposed change to the STS
that allows changes in CE plant conditions leading to exigent plant
shutdown in technical specifications (TS), if risk is assessed and
managed. The CLIIP directs the NRC staff to evaluate any comments
received for a proposed change to the STS and to either reconsider the
change or announce the availability of the change for adoption by
licensees. Licensees opting to apply for this TS change are responsible
for reviewing the staff's evaluation, referencing the applicable
technical justifications, and providing any necessary plant-specific
information. Each amendment application made in response to the notice
of availability will be processed and noticed in accordance with
applicable NRC rules and procedures.
This notice involves the changes in CE plant conditions leading to
exigent plant shutdown in TS, if risk is assessed and managed. The
change was proposed in Topical Report WCAP-16125-NP Rev 0, September
2003 (previously CE NPSD-1208, Rev 0), ``Justification for the Risk
Informed Modifications to Selected Technical Specifications for
Conditions Leading to Exigent Plant Shutdown,'' which was approved by
an NRC SE dated July 9, 2004. This change was proposed for
incorporation into the STS by the owners groups participants in the
Technical Specification Task Force (TSTF) and is designated TSTF-426,
Rev 0. TSTF-426, Rev 0, can be viewed on the NRC's web page at https://
www.nrc.gov/reactors/operating/licensing/techspecs.html.
Applicability
This proposal to modify TS requirements by the adoption of TSTF-
426, Rev 0, is applicable to all licensees of CE plants who commit to
WCAP-16446-NP, Rev 0, ``Actions to Preclude Entry into LCO 3.0.3
Implementation Guidance (PA-RMCS-0196),'' June 2005.
To efficiently process the incoming license amendment applications,
the staff requests that each licensee applying for the changes proposed
in TSTF-426 include Bases for the proposed TS consistent with the Bases
proposed in TSTF-426. The CLIIP does not prevent licensees from
requesting an alternative approach or proposing the changes without the
requested Bases. However, deviations from the approach recommended in
this notice may require additional review by the NRC staff and may
increase the time and resources needed for the review. Significant
variations from the approach, or
[[Page 41265]]
inclusion of additional changes to the license, will result in staff
rejection of the submittal. Instead, licensees desiring significant
variations and/or additional changes should submit a LAR that does not
claim to adopt TSTF-426.
Public Notices
This notice requests comments from interested members of the public
within 30 days of the date of publication in the Federal Register.
After evaluating the comments received as a result of this notice, the
staff will either reconsider the proposed change or announce the
availability of the change in a subsequent notice (perhaps with some
changes to the safety evaluation or the proposed NSHC determination as
a result of public comments). If the staff announces the availability
of the change, licensees wishing to adopt the change must submit an
application in accordance with applicable rules and other regulatory
requirements. For each application, the staff will publish a notice of
consideration of issuance of amendment to facility operating licenses,
a proposed NSHC determination, and a notice of opportunity for a
hearing. The staff will also publish a notice of issuance of an
amendment to operating license to announce the modifications of
conditions leading to exigent plant shutdown in selected technical
specifications.
Dated at Rockville, Maryland, this 13th day of July 2006.
For the Nuclear Regulatory Commission.
Carl S. Schulten,
Acting Chief, Technical Specifications Branch, Division of Inspection &
Regional Support, Office of Nuclear Reactor Regulation.
Attachment--Proposed Safety Evaluation, United States Nuclear
Regulatory Commission; Office of Nuclear Reactor Regulation;
Consolidated Line Item Improvement Technical Specification Task Force
(TSTF) Change TSTF-426 Risk Informed Modifications to Selected
Technical Specifications for Conditions Leading to Exigent Plant
Shutdown
1.0 Introduction
On August 30, 2004, the Owners Group (OG) Technical Specifications
Task Force (TSTF) submitted a proposed change, TSTF-426, Revision 0
(Rev 0), to the Combustion Engineering (CE) standard technical
specifications (STS) (NUREG-1432) on behalf of the industry. TSTF-426,
Rev 0, is a proposal to incorporate WCAP-16125-NP Rev 0, (previously CE
NPSD-1208, Rev 0), of September 2003, ``Justification for the Risk
Informed Modifications to Selected Technical Specifications for
Conditions Leading to Exigent Plant Shutdown,'' which was approved by
an NRC safety evaluation (SE) dated July 9, 2004 into the CE STS. This
proposal is part of Nuclear Energy Institute (NEI) Risk Informed
Technical Specifications Task Force (RITSTF) Initiative 6, one of the
industry's initiatives being developed under the Risk Management
Technical Specifications (RMTS) program. These initiatives are intended
to maintain or improve safety through the incorporation of risk
assessment and management techniques in technical specifications (TS),
while reducing unnecessary burden and making technical specification
requirements consistent with the Commission's other risk-informed
regulatory requirements.
The Code of Federal Regulations, 10 CFR 50.36(c)(2)(I), ``Technical
Specifications; Limiting Conditions for Operation,'' states: ``When a
limiting condition for operation of a nuclear reactor is not met, the
licensee shall shut down the reactor or follow any remedial action
permitted by the technical specifications until the condition can be
met.'' TS provide a completion time (CT) limit for following any
remedial action permitted by the TS until the limiting condition for
operation (LCO) can be met. If the LCO or the remedial action cannot be
met on the specified CT, then the reactor is required to be shutdown.
The Required Action for Conditions that imply a loss of function,
related to a system or component included within the scope of the plant
TS, is entry into LCO 3.0.3. Currently, upon entering LCO 3.0.3, one
hour is allowed to prepare for an orderly shutdown before initiating a
change in plant operation. This includes time to permit the operator to
coordinate the reduction in electrical generation with the load
dispatcher to ensure the stability and availability of the electrical
grid. The OG is proposing to define and/or modify various TS Conditions
to accommodate extension of the currently required time of one hour to
initiate plant shutdown for members with Combustion Engineering (CE)
Nuclear Steam Supply Systems (NSSS) designs. The proposed extension,
related to specific systems or components, is based on the system's
risk significance and varies from 4 hours to 72 hours.
The proposed changes are typically associated with plant conditions
where both trains of a two-train redundant system are declared
inoperable and at the same time there is either no specified action in
the TS for the condition (requiring a default LCO 3.0.3 entry) or
conditions exist where the defined action includes an explicit LCO
3.0.3 entry. The intent of the proposed TS changes is to provide a
risk-informed alternative to the current LCO 3.0.3 requirements such
that the plant staff has adequate time to fully evaluate the situation
or restore loss of function while the plant remains operating at power,
thus avoiding unnecessary unscheduled plant shutdowns and minimizing
transition and realignment risks.
WCAP-16125-NP also provides system-specific integrated
justifications (i.e., risk and defense-in-depth arguments) for several
proposed TS Required Action statement changes to allow a MODE 4 (hot
shutdown) end state, for repair purposes of two-train redundant systems
that do not have explicit LCO 3.0.3 entry requirements, when the
proposed extended time cannot be met.
The intent of the proposed TS changes is to provide needed
flexibility in the performance of corrective maintenance during power
operation and at the same time enhance overall plant safety by:
Avoiding unnecessary unscheduled plant shutdowns,
Minimizing plant transitions and associated transition and
realignment risks,
Providing increased flexibility in scheduling and
performing maintenance and surveillance activities, and
Providing explicit guidance in areas that currently does
not exist.
It should be noted that many of the proposed TS changes affect the
existing plant shutdown requirements for plant conditions where the
plant operation is not in explicit compliance with the plant design
basis. The proposed actions provide a risk-informed process for
establishing shutdown priorities aiming at reducing overall plant risk
and increasing public health and safety protection.
2.0 Regulatory Evaluation
In 10 CFR 50.36, the Commission established its regulatory
requirements related to the content of TS. Pursuant to 10 CFR
50.36(c)(1)-(5), TS are required to include items in the following five
specific categories related to station operation: (1) Safety limits,
limiting safety system settings, and limiting control settings; (2)
limiting conditions for operation (LCOs); (3) surveillance requirements
(SRs); (4) design features; and (5) administrative controls. The rule
does not specify the particular requirements to be included in a
plant's TS. As stated in 10 CFR 50.36(c)(2)(i), the ``Limiting
conditions for operation
[[Page 41266]]
are the lowest functional capability or performance levels of equipment
required for safe operation of the facility. When a limiting condition
for operation of a nuclear reactor is not met, the licensee shall shut
down the reactor or follow any remedial action permitted by the
technical specifications * * *.'' Topical Report WCAP-16125,
``Justification for Risk-Informed Modifications to Selected Technical
Specifications for Conditions Leading to Exigent plant Shutdown''
(Reference 1), justifies modifications to various TS Action Statements
for conditions that result in a loss of safety function related to a
system or component included within the scope of the plant TS. It
revises the current Required Actions from either a default or explicit
LCO 3.0.3 entry to a risk-informed action based on the system's risk
significance with an associated completion time (CT). In most
instances, a CT of 24 hours is justified.
3.0 Technical Evaluation
The changes proposed in TSTF-426, Rev 0, are consistent with the
changes proposed and justified in Topical Report WCAP-16125-NP Rev 0,
and approved by the associated NRC SE of July 9, 2004 (Reference 2).
The evaluation included in Reference 2, as appropriate and applicable
to the changes of TSTF-426, Rev 0, (Reference 3), is not reiterated
here, except where differences from the SE are justified and in
discussing the TSTF-426 changes with respect to the individual
specifications. In its application the licensee commits to PA-RMSC-
0196, ``Actions to Preclude Entry into LCO 3.0.3, Implementation
Guidance'' (Reference 4) for implementing TSTF-426, Rev 0, which
addresses a variety of issues such as considerations and compensatory
actions for risk-significant plant configurations. An overview of the
generic evaluation and associated risk assessment is provided below,
along with a summary of the associated TS changes justified by
Reference 1.
The proposed TS changes, including end state changes (i.e.,
approved TSTF-422 end state changes), are summarized in Table 1 of this
safety evaluation report (SER). Such changes cover a diverse range of
systems and components with essentially four separate impacts on plant
risk. They are:
TS changes related to systems or components contributing
to accident prevention. The removal of these systems/components has the
potential to increase the plant risk through the increased potential
for plant upsets (i.e., potential for increased initiated event
frequencies). A typical example in this category are the pressurizer
heaters whose unavailability could complicate plant pressure control
and lead to a plant trip.
TS changes related to systems or components contributing
to accident mitigation. These systems are in standby during normal
plant operation and are intended to function during accidents to
prevent core damage. Typical examples in this category are the
Emergency Core Cooling System (ECCS) and the pressurizer Power Operated
Relief Valves (PORVs).
TS changes related to systems or components contributing
to large early release prevention. The primary role of these systems is
to function during a core damage accident to prevent large releases of
radioactive materials. A typical example in this category is the
containment (the only component in this category for which a TS change
is proposed).
TS changes related to systems/components contributing to
control of delayed radiation releases to the environment. The primary
role of these systems is to prevent radiation releases above TS limits
and meet design basis requirements. Thus, the unavailability of these
systems has no impact on the surrogate risk metrics associated with
core damage and large early releases. Typical examples in this category
are the ECCS room ventilation system and the containment iodine cleanup
system.
Although the improved standard technical specification (STS)
numbering system (NUREG-1432, Reference 5) is used for convenience in
Table 1, the analyses provided in WCAP-16125-NP support these changes
for all CE designed NSSS plants.
Table 1.--Summary of Proposed Modifications to Technical Specifications
----------------------------------------------------------------------------------------------------------------
Current action and Proposed changes:
STS System Inoperability associated completion time (CT)
condition completion time (CT) and end state
----------------------------------------------------------------------------------------------------------------
LCO 3.4.9............. Pressurizer Heaters.. Both groups of class No condition 24 hrs CT for
1E heaters defined. Default restoring one
inoperable. LCO 3.0.3 entry. group.
LCO 3.4.11............ Pressurizer Power STS LCO 3.4.11 Varies with plant. STS LCO 3.4.11
Operated Relief CONDITION E (or STS LCO 3.4.11 CONDITION E (or
Valves (PORVs) and equivalent): Two CONDITION E (or equivalent): Allow
Associated Block PORVs inoperable and equivalent): Close 8 hours CT to
Valves (BVs). not capable of being associated block restore one PORV,
manually cycled. valve in 1 hour AND for conditions
STS LCO 3.4.11 remove power from where a PORV is
CONDITION F (or associated block unable to reclose
equivalent): Two BVs valve in one hour, once challenged but
inoperable.. AND be in MODE 3 in may be isolated.
6 hours AND MODE 4 STS LCO 3.4.11
in [12] hours.. CONDITION F (or
STS LCO 3.4.11 equivalent): Allow
CONDITION F (or 8 hours to restore
equivalent): one BV.
Restore one block
valve to operable
in 2 hours. STS
Condition G
requires MODE 3 in
6 hours and MODE 4
in [12] hours if
Condition F not
met..
LCO 3.5.1............. Safety Injection Two or more SITs Explicit 3.0.3 entry Revise STS Condition
Tanks (SITs). inoperable (STS D to allow 24 hours
CONDITION D). CT for restoring
one SIT.
LCO 3.5.2............. Low Pressure Safety Two LPSI subsystems Default 3.0.3 entry. 24 hours for
Injection (LPSI). inoperable. restoring one LPSI
subsystem (STS
Condition D would
be deleted).
LCO 3.5.2............. High Pressure Safety Two HPSI subsystems Explicit 3.0.3 entry 4 hours CT for
Injection (HPSI). inoperable (STS restoring one HPSI
Condition D). subsystem.
[[Page 41267]]
LCO 3.6.1............. Containment (CTMT)... Inoperable........... Defined 1 hour 8 hours CT restoring
shutdown (MODE 5 in containment
36 hours). operability. Allow
MODE 4 end state.
LCO 3.6.6A&B.......... Containment Spray Two CS trains Explicit 3.0.3 entry 12 hrs CT for
System (CS). inoperable OR any restoring one CS
combination of three train if CAC is not
or more trains available. 72 hours
inoperable (i.e., CT for restoring
containment air one CS if one train
coolers (CAC*)) (STS of CAC is
Condition F). available.
LCO 3.6.10............ Iodine Cleanup System Two ICS trains No condition 24 hours CT for
(ICS). inoperable. defined. Default restoring one
3.0.3 entry. train. Allow MODE 4
end state.
LCO 3.6.13............ Shield Building Two trains inoperable No condition 24 hours CT for
Exhaust Air Cleanup defined. Default restoring one
System (SBEACS). 3.0.3 entry. train. Allow MODE 4
end state.
LCO 3.7.11............ Control Room Two trains inoperable No condition 24 hours CT for
Emergency Air defined. Default restoring one train
Cleanup System 3.0.3 entry. (or the time to
(CREACS). reach 5 REM, which
may be less than 24
hours). Proposed
change applies to
radiation
protection function
only. Allow MODE 4
end state.
LCO 3.7.12............ Control Room Two trains inoperable Explicit 3.0.3...... 24 hours CT for
Emergency Air (STS Condition E). restoring one
Temperature Control train. Allow MODE 4
System (CREATCS). end state.
LCO 3.7.13............ Emergency Core Two trains inoperable No condition 24 hours CT for
Cooling System defined. Default restoring one
(ECCS), Pump Room 3.0.3 entry. train. Allow MODE 4
Exhaust Air Cleanup end state.
System (ECCS PREACS).
LCO 3.7.15............ Penetration Room, Two trains inoperable No condition 24 hours CT for
Exhaust Air Cleanup defined. Default restoring one
System (PREACS). 3.0.3 entry. train. Allow MODE 4
end state.
----------------------------------------------------------------------------------------------------------------
* Also known as containment air recirculation coolers (CARC)
WCAP-16125-NP documents a risk-informed analysis of the proposed TS
changes. Probabilistic Risk Assessment (PRA) results and insights are
used, in combination with results of deterministic assessments, to
identify and justify the proposed TS changes for all CE NSSS design
plants. This is in accordance with guidance provided in Regulatory
Guides (RGs) 1.174 and 1.177 (References 6 and 7, respectively).
The approach used to assess the risk impact of the proposed changes
is discussed and evaluated in Section 3.0. Section 3.1 evaluates the
results of the risk assessment. Section 3.2 provides integrated
justifications (i.e., both probabilistic and deterministic arguments)
for each of the proposed system-specific TS changes. Finally, Section
3.3 summarizes the staff's conclusions from the review of the proposed
TS changes.
3.1 Risk Assessment
The objective of the OG's risk assessment was to show that the
implementation of the proposed TS changes are not expected to lead to
any significant risk increases. In performing the risk-informed
assessments and interpreting the results, the following two assumptions
are tacitly made:
A condition resulting in the inoperability of a system or
component which currently results in the need for an immediate shutdown
is an infrequent event. This is evidenced by the fact that plant
shutdowns due to entries into LCO 3.0.3 conditions are rare.
Furthermore, when such a condition does arise, the actual cause of the
inoperability is often due to an incomplete ``paper trail'' or a
partial system failure rather than a deleterious common-cause failure
of critical components leading to a functional failure of an entire
system.
The risk incurred by increasing the required shutdown
action time is controlled to acceptable levels using a risk informed
approach that considers the component risk worth and offsetting
benefits of avoiding plant transitions.
The risk impact of the proposed TS changes was assessed following
the three-tiered approach recommended in RG 1.177 for evaluating
proposed extensions in currently allowed Completion Times (CTs):
The first tier involves the assessment of the change in
plant risk due to the proposed TS change. Such risk change is expressed
(1) by the change in the average yearly core damage frequency
([Delta]CDF) and the average yearly large early release frequency
([Delta]LERF) and (2) by the incremental conditional core damage
probability (ICCDP) and the incremental conditional large early release
probability (ICLERP). The assessed [Delta]CDF and [Delta]LERF values
are compared to acceptance guidelines, consistent with the Commission's
Safety Goal Policy Statement as documented in RG 1.174, so that the
plant's average baseline risk is maintained within a minimal range. The
assessed ICCDP and ICLERP values are compared to acceptance guidelines
provided in RG 1.177 which aim at ensuring that the plant risk does not
increase unacceptably during the period the equipment is taken out of
service.
The second tier involves the identification of potentially
high-risk configurations that could exist if equipment in addition to
that associated with the change were to be taken out of service
simultaneously, or other risk-significant operational factors such as
concurrent equipment testing were also involved. The objective is to
ensure that appropriate restrictions are in place to avoid any
potential high-risk configurations.
[[Page 41268]]
The third tier involves the establishment of an overall
configuration risk management program (CRMP) to ensure that potentially
risk-significant configurations resulting from maintenance and other
operational activities are identified. The objective of the CRMP is to
manage configuration-specific risk by appropriate scheduling of plant
activities and/or appropriate compensatory measures.
The approach used in implementing the three-tiered approach of RG
1.177 to support the proposed TS changes is fully evaluated in the SE
(Reference 2) to WCAP-16125-NP Rev 0. The staff found that the risk
assessment results support the proposed changes. The risk increases
associated with the proposed TS changes, if any, will be insignificant
based on guidance provided in RGs 1.174 and 1.177. Furthermore, the
sensitivity studies and the many conservative assumptions used in the
analyses provide adequate assurance about the robustness of the results
used to support the proposed TS changes.
3.2 Assessment of Technical Specification Changes
There are two categories of proposed system-specific TS changes.
The first category includes changes associated with plant conditions
requiring entry into LCO 3.0.3 to extend the time for restoring the
system's or component's loss of function, thus avoiding unnecessary
unscheduled plant shutdowns and minimizing transition and realignment
risks. The second category includes changes to TS Required Action
statements to allow a MODE 4 (hot shutdown) end state, for repair
purposes of two-train redundant systems that do not have implicit LCO
3.0.3 entry requirements, when the proposed extended time cannot be
met. The generic risk assessment for the proposed end state changes is
documented in topical report CE-NPSD-1186 (Reference 8) which has been
reviewed and approved by the staff. While all proposed system-specific
TS changes include changes to extend the time for restoring the
system's or component's loss of function (first category changes), some
proposed system-specific TS changes include changes to modify the end
state (second category changes). Therefore, the integrated
justifications, discussed in this section, include insights from the
generic risk assessments documented in both topical reports WCAP-16125-
NP (Reference 1) and CE-NPSD-1186 (Reference 8).
Due to the nature of the plant conditions associated with the
proposed TS changes (i.e., loss of a system's or component's function),
the redundancy and diversity typically associated with ensuring the
deterministic aspect of defense-in-depth position is not always
strictly possible. In these cases, defense-in-depth is considered by
(1) controlling the outage time for related equipment, (2) restricting
activities which may challenge the unavailable systems or functions,
(3) allowing only small time intervals for plant operation at power
with a system or function unavailable, (4) using, whenever possible,
contingency actions to limit concurrent unavailabilities appropriately,
and (5) evaluating repair activities and alternatives. Defense-in-depth
is evaluated in conjunction with the generic risk assessment results
which conclude that the proposed system-specific TS changes would lead
to insignificant risk increases and in most cases to net risk
reductions. This conclusion is a consequence of the low expected
challenge frequency of the systems or functions associated with the
proposed TS changes, the very short proposed exposure times to the
specified plant conditions and the offsetting benefits of avoiding
plant transitions.
The proposed change in shutdown mode end states will result in
plants remaining within the applicability of the specific LCOs for the
length of time it takes to restore the LCO conditions. Since corrective
maintenance will be necessary, the 10 CFR 50.65(a)(4) requirement to
assess and manage risk will apply, and should confirm that remaining in
the shutdown mode that is within the applicability of the LCO is
acceptable for the plant specific configuration. NRC Regulatory Guide
1.182 (Reference 9) endorses NUMARC 93-01 Section 11 guidance for
implementation of 10 CFR 50.65(a)(4), and shall be followed; including
the conduct of an (a)(4) reevaluation for emergent conditions.
3.2.1 Pressurizer Heaters (STS LCO 3.4.9)
The pressurizer provides a point in the RCS where the liquid and
vapor water phases are maintained in equilibrium under saturated
conditions for pressure control purposes to prevent bulk boiling in the
remainder of the RCS. The pressure control components addressed by this
LCO include the pressurizer, the required groups of heaters and their
controls and the Class 1E power supplies. The liquid to vapor interface
permits RCS pressure control by using the sprays and heaters during
normal operation and in response to anticipated design basis accidents.
The unavailability of Class 1E pressurizer heaters covered by the TS
may complicate steady state plant pressure control and, thus, increase
the potential for an unplanned reactor trip.
Another function of the Class 1E pressurizer heaters is to maintain
plant subcooling during post accident cooldown by natural circulation.
Although the unavailability of pressurizer heaters during natural
circulation cooldown will extend the time to reach the shutdown cooling
system entry conditions, heat removal will be adequately established
via steam generator cooling.
Plant Applicability: All OG member plants with CE NSSS designs
except St Lucie-2.
Limiting Condition for Operation (LCO): Two groups of pressurizer
heaters, [capable of being powered from an emergency power supply],
must be operable in MODES 1, 2 and 3.
Condition Requiring Entry into Shutdown Required Action: Two
safety-related pressurizer heater groups inoperable (default entry into
LCO 3.0.3 is required).
Proposed Modification to Shutdown Required Actions: Increase the
time available to take action to restore one group of safety-related
heaters before entry into STS LCO 3.4.9 Condition C to 24 hours.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 24-hour completion time for restoring one group of
safety-related pressurizer heaters before entering STS LCO 3.4.9
Condition C will not lead to a significant increase in risk and may
actually decrease risk. The risk impact of the proposed completion time
extension was assessed to be well within the acceptance criteria
reported in Regulatory Guides 1.174 and 1.177. Specifically, the
proposed completion time extension would lead to the following risk
increases: (1) The probability of core damage when the safety-related
pressurizer heaters are inoperable will increase by about 3E-7 (the
acceptance guideline for ICCDP is 5E-7); (2) the CDF will increase by
about 6E-8/year (the acceptance guideline for [Delta]CDF is 1E-6/year);
(3) the large early release probability when the safety-related
pressurizer heaters are inoperable will increase by less than 1E-8 (the
acceptance guideline for ICLERP is 5E-8); and (4) the LERF will
increase by about 2E-9/year (the acceptance guideline for [Delta]LERF
is 1E-7/year). Furthermore, the proposed time extension may actually be
risk neutral or result in a decrease in risk if credit for avoiding the
transition to shutdown risk is taken.
[[Page 41269]]
The risk impact argument is consistent with the following
observations. TS include requirements for both groups of safety-related
pressurizer heaters to have minimum heating power [and emergency power
supply capability]. The safety-related pressurizer heaters have two
primary functions. One function is to keep the reactor coolant in a
subcooled condition with natural circulation following a loss of
offsite power (LOOP) event during which the normally available station
powered non-safety related heaters become unavailable. Although no
credit is taken in design basis accident analyses for the pressurizer
heaters, they have been included in the TS because they are needed to
maintain long term subcooling during a LOOP event. However, pressurizer
heaters are not required to achieve a post-trip plant cooldown since
successful cooldown can be achieved, with minimal impact on plant risk,
due to the availability of reactor vessel and pressurizer vents.
Consequently, the pressurizer heaters do not have a significant role in
the mitigation of core damage events. A second function of the safety-
related pressurizer heaters is to back up the station powered non-
safety related heaters which are normally available to control reactor
coolant pressure during steady state operation. The unavailability of
these heaters would reduce the plant's ability to control the normal
operating parameters and consequently will increase the potential of
plant trip.
The presence of both safety-related and non-safety-related heaters
provides considerable defense-in-depth for many transient events,
except following a LOOP event. For LOOP events and without the safety-
related pressurizer heaters, a natural circulation cooldown may be
required. Such cooldowns can be conducted via use of reactor vessel and
pressurizer vents or SG venting via the atmospheric dump valves (ADVs).
The intent of the proposed completion time extension is to extend
plant operation at power when the ability to control normal plant
operation is not significantly degraded. Therefore, the proposed
completion time extension should not be utilized when there is reason
to believe that plant pressure and level cannot be controlled within
operating bounds, as is the case when both the safety and non-safety
pressurizer heaters are unavailable. This restriction should be
reflected in the TS bases.
Finding: The requested change to increase the time available to
take action to restore one pressurizer heater group to 24 hours for
cases when both groups are inoperable is acceptable.
Tier 2 Restrictions: None.
3.2.2 Pressurizer PORVs and Associated Block Valves (STS LCO 3.4.11)
PORVs are automatically opened at a specific set pressure when the
pressurizer pressure increases and automatically closed on decreasing
pressure. The PORVs may be manually operated using controls installed
in the control room. An electric, normally open, block valve (BV) is
installed between the pressurizer and the PORV. The function of the BV
is to ensure RCS integrity by isolating a leaking or stuck-open PORV to
permit continued power operation. Most importantly, the BV is used to
isolate a stuck open PORV and terminate the RCS depressurization and
coolant inventory loss.
Plant Applicability: Calvert Cliffs 1 & 2, St Lucie 1 & 2 (block
valves), Millstone 2, Palisades, and Fort Calhoun Station.
Limiting Condition for Operation (LCO): Each PORV and associated
block valve shall be operable in MODES 1, 2 and 3.
Condition Requiring Entry into Shutdown Required Action: Two PORVs
inoperable and not capable of being manually cycled (STS LCO 3.4.11
Condition E or equivalent) or two BVs inoperable (STS LCO 3.4.11
Condition F or equivalent). There is a variability in LCO entry
requirements among OG member plants with CE NSSS designs for conditions
with both PORVs inoperable or both BVs inoperable. Typically, a plant
shutdown is required if the PORVs are not isolated and one PORV is not
restored within one hour (STS LCO 3.4.11 Condition E or equivalent) or
when the PORVs are not placed in manual control within one hour and one
BV is not recovered within two hours (STS LCO 3.4.11 Condition F or
equivalent).
Proposed Modification to Shutdown Required Actions: Revise STS LCO
3.4.11 Condition E (or equivalent to allow an 8-hour completion time
(CT) to restore one PORV for conditions where a PORV is unable to re-
close once challenged, but may be isolated). This extension would not
apply to PORVs that are leaking, and that cannot be isolated by block
valves, or to PORVs that are not expected to be isolable following a
demand.
Revise STS LCO 3.4.11 Required Action F.2 to allow 8 hours to
restore one BV, for conditions where the associated PORV is unable to
reclose.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 8-hour completion time for the actions required by TS
(i.e., actions associated with STS LCO 3.4.11 Conditions E and F or
equivalent) will not lead to a significant increase in risk and,
actually, may decrease risk by avoiding the risk associated with the
transition to shutdown. The risk impact of the proposed completion time
extension, without credit for avoiding the transition to shutdown risk,
was assessed to be within the acceptance criteria reported in
Regulatory Guides 1.174 and 1.177. Specifically, the proposed time
extension would lead to the following risk increases: (1) The
probability of core damage will increase by about 8E-7, which is close
to the numerical guideline of 5E-7 for ICCDP used in RG 1.177; (2) the
CDF will increase by about 2E-7/year, which is significantly less than
the acceptance guideline of 1E-6/year for [Delta]CDF; (3) the large
early release probability will increase by less than 7E-8, which is
close to the numerical guideline of 5E-8 for ICLERP and in agreement
with guidance provided in RG 1.177; and (4) the LERF will increase by
about 1E-8/year, which is significantly less than the acceptance
guideline of 1E-7/year for [Delta]LERF. Furthermore, the proposed time
extension may actually be risk neutral or result in a decrease in risk
if credit for avoiding the transition to shutdown risk is taken.
The risk impact argument is consistent with the following defense-
in-depth argument where the impact of STS LCO 3.4.11 Conditions E and F
on defense-in-depth is discussed. The primary purpose of this LCO is to
ensure that the PORVs and the BVs are operable so the potential for a
small break LOCA through the PORV pathway is minimized, or if a small
LOCA were to occur through a failed open PORV, the block valve could be
manually operated to isolate the path. In addition, one of the
functions of the PORVs is to limit the number of pressure transients
that may challenge the primary safety valves (PSVs) since the PSVs,
unlike the PORVs, cannot be isolated.
When both PORVs are found inoperable (i.e., STS LCO 3.4.11
Condition E or equivalent), the associated BVs are manually closed,
within one hour, to isolate both PORV paths. With none of the PORVs
available to open, the PSVs could be challenged to provide overpressure
protection. However, a challenge to the PSVs during the proposed
completion time extension to restore one PORV is extremely unlikely and
the PSVs are available and highly reliable (i.e., even if they are
challenged, they would close properly when the pressure is reduced
[[Page 41270]]
below their setpoint). It should be noted that overpressure protection
is provided by the PSVs in the design basis analyses, without any
credit for PORV opening for accident mitigation (in fact there are some
plants built without PORVs). For these reasons, there is defense-in-
depth against LOCA accidents through the PORV and the PSV paths as well
as against overpressure accidents during the very short time interval
when STS LCO 3.4.11 Condition E is proposed to be allowed with the
plant operating at power.
When both BVs are found inoperable (i.e., STS LCO 3.4.11 Condition
F or equivalent), the PORVs are placed in manual control, within one
hour, to ensure that they do not open automatically in the unlikely
event they are challenged. Therefore, there is defense-in-depth against
small LOCA accidents through the PORV paths. However, in the unlikely
event of a pressure transient during the proposed completion time
extension, the PSVs could be challenged to provide overpressure
protection. This is the same scenario discussed above for STS LCO
3.4.11 Condition E. For these reasons, there is defense-in-depth
against LOCA accidents through the PORV and the PSV paths as well as
against overpressure accidents during the very short time interval when
STS LCO 3.4.11 Condition F is proposed to be allowed with the plant
operating at power.
The PORV paths provide an alternative means of core cooling by feed
and bleed (once-through core cooling) in the case of multiple equipment
failure events that are not within the design basis, such as a total
loss of feedwater. The unavailability of feed and bleed for core
cooling, the dominant contributor to risk associated with the proposed
changes to LCO 3.4.11. As discussed above, such risk is very small.
Finding: The requested changes to allow 8 hours for completing the
actions required by TS (i.e., actions associated with STS LCO 3.4.11
Conditions E and F or equivalent) are acceptable.
Tier 2 Restrictions: None.
3.2.3 Safety Injection Tanks (STS LCO 3.5.1)
The Safety Injection Tanks (SITs) are pressurized passive injection
devices whose primary safety function is to inject large quantities of
borated water into the reactor vessel during the blowdown phase of a
large LOCA and to provide inventory to help accomplish the refill phase
that follows the blowdown phase.
Plant Applicability: Applicable to all OG member plants with CE
NSSS designs.
Limiting Condition for Operation (LCO): All SITs shall be operable
during MODES 1 and 2 as well as during MODE 3 when the pressurizer
pressure is above [700] psia.
Condition Requiring Entry into Shutdown Required Action: When two
or more SITs are inoperable (STS LCO 3.5.1 Condition D), immediate
entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown Required Actions: Increase the
time available to restore one SIT before entry into LCO 3.0.3 to 24
hours.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 24-hour completion time for restoring one SIT before
entering LCO 3.0.3 will not lead to a significant increase in risk and
may actually decrease risk. The risk impact of the proposed 23-hour
extension, without credit for avoiding the transition to shutdown risk,
was assessed to be well within the acceptance criteria reported in
Regulatory Guides 1.174 and 1.177. Specifically, the proposed time
extension would lead to the following risk increases: (1) The
probability of core damage will increase by about 1E-8, which is less
than the numerical guideline of 5E-7 for ICCDP; (2) the CDF will
increase by about 3E-9/year, which is significantly less than the
acceptance guideline of 1E-6/year for DCDF; (3) the large early release
probability will increase by about 4E-11, which is much less than the
numerical guideline of 5E-8 for ICLERP; and (4) the LERF will increase
by about 9E-12/year, which is much less than the acceptance guideline
of 1E-7/year for [Delta]LERF. Furthermore, the proposed time extension
would, most likely, result in a risk reduction if credit for avoiding
the transition to shutdown risk is taken.
The risk impact argument is also supported by the following
defense-in-depth discussion. The SITs are needed primarily to mitigate
large LOCAs. The unavailability of two or more SITs will compromise the
ability of the plant to respond to a large LOCA. However, as discussed
above, even if it is conservatively assumed that all large LOCAs
proceed to core damage, the risk impact is negligible (much less than
the risk estimated to incur during plant transition to shutdown). On
the other hand, the unavailability of two or more SITs may alter the
progression of some smaller break size LOCAs and the extent of core
damage. However, their impact on the core damage potential is
negligible. In addition, long term core cooling, provided via the
plant's LPSI and HPSI systems, partially offsets the impact of SIT
unavailability.
Finding: The requested change to increase the time available to
take action to restore all SITs (from one to 24 hours) for cases when
two or more SITs are inoperable is acceptable.
Tier 2 Restrictions: None.
3.2.4 Low Pressure Safety Injection (STS LCO 3.5.2)
The low pressure safety injection (LPSI) system is part of the
emergency core cooling system (ECCS). The function of the ECCS is to
provide core cooling and negative reactivity to ensure that the reactor
core is protected following certain accidents, such as LOCAs, SGTRs and
loss of feedwater. There are two phases of ECCS operation: injection
and recirculation. In the injection phase, borated water is injected
into the RCS via the cold legs. After the blowdown stage of the LOCA
stabilizes, injection flow is split equally between the hot and cold
legs. After the RWST is depleted, the ECCS recirculation phase is
entered as the ECCS suction is automatically transferred to the
containment sump. TS require that in MODES 1, 2 and 3, with pressurizer
pressure greater than or equal to [1700] psia, both redundant (100%
capacity) ECCS trains must be operable. Each ECCS train consists of a
high pressure safety injection (HPSI) subsystem, a low pressure safety
injection (LPSI) subsystem and a charging subsystem.
Plant Applicability: Applicable to all OG member plants with CE
NSSS designs.
Limiting Condition for Operation (LCO): Two redundant, 100%
capacity LPSI trains must be operable in MODES 1 and 2 as well as in
MODE 3 when the pressurizer pressure is greater than or equal to [1700]
psia.
Condition Requiring Entry into Shutdown Required Action: When both
LPSI trains are inoperable, the design basis assumptions for the large
break LOCA analyses are not met and a default entry into LCO 3.0.3 is
required.
Proposed Modification to Shutdown Required Actions: Add separate
condition for both LPSI trains inoperable to restore at least one LPSI
train to operable in 24 hours. In addition, with the proposed condition
taken with the proposed changes to HPSI discussed below, the existing
condition (STS LCO 3.5.2 Condition D) of ``Less than 100% of the ECCS
flow equivalent to a single OPERABLE train available'' will no longer
be required since that condition will be addressed by the conditions
for two HPSI
[[Page 41271]]
subsystems inoperable or two LPSI subsystems inoperable.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 24-hour completion time for restoring one LPSI train
will not lead to a significant increase in risk and may actually
decrease risk. The risk impact of the proposed completion time
extension, without credit for avoiding the transition to shutdown risk,
was assessed to be well within the acceptance criteria reported in
Regulatory Guides 1.174 and 1.177. Specifically, the proposed
completion time extension would lead to the following risk increases:
(1) The probability of core damage will increase by about 1E-7, which
is less than the numerical guideline of 5E-7 for ICCDP; (2) the CDF
will increase by about 2E-8/year, which is significantly less than the
acceptance guideline of 1E-6/year for [Dgr]CDF; (3) the large early
release probability will increase by about 4E-10, which is much less
than the numerical guideline of 5E-8 for ICLERP; and (4) the LERF will
increase by about 8E-11/year, which is much less than the acceptance
guideline of 1E-7/year for [Dgr]LERF. Furthermore, the proposed
completion time extension would, most likely, result in a risk
reduction if credit for avoiding the transition to shutdown risk is
taken.
The risk impact argument is also supported by the following
defense-in-depth discussion. The primary impact of the unavailability
of the LPSI system will be the reduction in the capability of the plant
to provide RCS inventory makeup to mitigate a large LOCA. However, the
unavailability of the LPSI system will impair the ability of the plant
to maneuver to shutdown cooling. Therefore, the proposed 24-hour
completion time to repair one LPSI train is reasonable due to the very
small incremental risk associated with the continued plant operation at
power and the inadvisability of a plant shutdown without the LPSI pumps
which are needed for shutdown cooling.
STS LCO 3.5.2 Condition D requires that for a condition where the
ECCS flow is less than 100% of the ECCS flow assumed in the LOCA
analysis. WCAP-16125-NP proposed to delete this condition because it
would no longer be necessary, based on the new conditions for two HPSI
trains or two LPSI trains inoperable. The NRC staff has concluded that
an adequate basis has not been provided to justify the deletion of STS
LCO 3.5.2 Condition D. Specifically, licensees should discuss the
functions of the HPSI and LPSI systems in terms of reactivity control,
RCS inventory control, RCS pressure control, and core heat removal for
system operations such as safety injection and recirculation, hot leg
injection and once through core cooling to mitigate the consequences of
LOCAs, SLB, and SGTR events. The licensees should also discuss the
safety and nonsafety related accident mitigation systems, and show
that, for a condition when the ECCS flow is less than 100% of the ECCS
flow equivalent to a single OPERABLE train, alternative flow injection
systems and backup accident management strategies are available and
effective. Licensees should also list specific compensatory measures
(including a description of pertinent operating procedures, maintenance
process and training programs) and contingency plans with acceptable
justification for the proposed deletion of STS LCO 3.5.2 Condition D.
Finding: The requested change to increase the time available to
restore an LPSI train to operable is acceptable. The proposed change to
delete STS LCO 3.5.2 Condition D needs to be adequately justified on a
plant-specific basis.
Tier 2 Restrictions: None.
3.2.5 High Pressure Safety Injection (STS LCO 3.5.2)
The high pressure safety injection system is part of the ECCS. The
function of the ECCS is to provide core cooling and negative reactivity
to ensure that the reactor core is protected following certain
accidents, such as LOCAs, SGTRs and loss of feedwater. There are two
phases of ECCS operation: injection and recirculation. In the injection
phase, borated water is injected into the RCS via the cold legs. After
the blowdown stage of the LOCA stabilizes injection flow is split
equally between the hot and cold legs. After the RWST is depleted, the
ECCS recirculation phase is entered as the ECCS suction is
automatically transferred to the containment sump. TS require that in
MODES 1, 2 and 3, with pressurizer pressure greater than or equal to
[1700] psia, both redundant (100% capacity) ECCS trains must be
operable. Each ECCS train consists of a high pressure safety injection
subsystem, a low pressure safety injection subsystem and a charging
subsystem.
Plant Applicability: Applicable to all OG member plants with CE
NSSS designs.
Limiting Condition for Operation (LCO): In MODES 1 and 2 as well as
in MODE 3 when the pressurizer pressure is greater than or equal to
[1700] psia, both trains of HPSI must be operable.
Condition Requiring Entry into Shutdown Required Action: When both
HPSI trains are inoperable, a default entry into LCO 3.0.3 is required.
Proposed Modification to Shutdown Required Actions: Increase the
time for restoring one HPSI pump or subsystem, before initiating
shutdown per LCO 3.0.3, to four hours.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 4-hour completion time for the actions required by TS
before entering LCO 3.0.3 will not lead to a significant increase in
risk and, actually, may decrease risk by avoiding the risk associated
with the transition to shutdown. The risk impact of the proposed
completion time extension, without credit for avoiding the transition
to shutdown risk, was assessed to be in agreement with the acceptance
guidelines reported in Regulatory Guides 1.174 and 1.177. Specifically,
the proposed completion time extension would lead to the following risk
increases: (1) An ICCDP of 1.7E-6 for plants with PORVs and 1.1E-6 for
plants without PORVs, which are close to the numerical guideline of 5E-
7 for ICCDP used in RG 1.177; (2) a [Delta]CDF of 3.5E-7/year for
plants with PORVs and 2.1E-7 for plants without PORVs, which are
significantly less than the acceptance guideline of 1E-6/year for
[Delta]CDF; (3) an ICLERP of about 4E-8 for plants with PORVs and less
than 3E-8 for plants without PORVs, which are less than the numerical
guideline of 5E-8 for ICLERP; and (4) a [Delta]LERF of about 8E-9/year
for plants with PORVs and about 5E-9 for plants without PORVs, which
are much less than the acceptance guideline of 1E-7/year for
[Delta]LERF. Furthermore, the proposed time extension may actually be
risk neutral or result in a decrease in risk if credit for avoiding the
transition to shutdown risk is taken.
The risk impact argument is also supported by the following
defense-in-depth discussion. The subject LCO requires the operability
of a number of independent subsystems. In many instances due to the
redundancy of trains and the diversity of subsystems, the inoperability
of one component in a train does not necessarily render the HPSI
incapable of performing its function. Neither does the inoperability of
two different components, each in a different train, necessarily result
in a loss of function for the ECCS. Examples of typical inoperabilities
would include the unavailability of a single header injection valve or
degradation of HPSI delivery curves below minimum design basis levels.
The proposed completion time extension allows for potential resolution
of minor HPSI system inoperabilities and provides time to
[[Page 41272]]
prepare for a controlled plant shutdown without increasing the plant's
risk significantly.
Finding: The requested change to allow four hours to resolve the
inoperability and restore one pump or subsystem of HPSI capability
before required to commence a plant shutdown per LCO 3.0.3, is
acceptable.
Tier 2 Restrictions: None.
3.2.6 Containment (STS LCO 3.6.1)
The requirements stated in this LCO define the performance of the
containment as a fission barrier. Specifically, LCO 3.6.1 requires that
the containment maximum leakage rate be limited in accordance with 10
CFR part 50 Appendix J. Other LCOs place additional restrictions on
containment air locks and containment isolation valves. The integrated
effect of these TSs is to ensure that the containment leakage is well
controlled within limits which assure that the post accident whole body
and thyroid dose limits of 10 CFR 100.11 or 10 CFR 50.67, as
applicable, are satisfied following a Maximum Hypothetical Accident
(MHA) initiated from full power. Inability to meet this leakage limit
renders the containment inoperable.
Plant Applicability: Applicable to all OG member plants with CE
NSSS designs.
Limiting Condition for Operation (LCO): Containment shall be
operable in MODES 1, 2, 3 and 4.
Condition Requiring Entry into Shutdown Required Action:
Containment is declared to be inoperable due to excessive leakage,
including leakage from air locks and isolation valves, for a time
period greater than one hour. If the containment is not restored to
operable status within one hour, a plant shutdown is required.
Proposed Modification to Shutdown Required Actions: Define a
specific action to allow 8 hours to restore an inoperable containment
to operable. Allow MODE 4 to become a designated end state for
correcting containment impairments for conditions where the containment
leakage is excessive due to reasons other than the inoperability of two
or more containment isolation valves (CIVs) in the same flow paths.
Assessment: The risk assessment results (in Reference 2) indicate
that the proposed 8-hour completion time for restoring an inoperable
containment to operable status will not lead to a significant increase
in risk and may actually decrease risk. The risk impact of the proposed
completion time extension was assessed to be well within the acceptance
criteria reported in Regulatory Guides 1.174 and 1.177. Specifically,
the proposed time extension would lead to the following conservatively
assessed risk increases: (1) The large early release probability will
increase by about 9E-8, which is close to the numerical guideline of
5E-8 for ICLERP; and (2) the LERF will increase by about 2E-8/year,
which is significantly less than the acceptance guideline of 1E-7/year
for [Delta]LERF. Furthermore, the proposed completion time extension
may actually be risk neutral or result in a decrease in risk if credit
for avoiding the transition to shutdown risk is taken.
The proposed changes apply to containment conditions where
containment integrity is essentially maintained and adequate ECCS net
positive suction head (NPSH) is expected following an event.
Containment ``leakage'' at or near design basis levels is not
explicitly modeled in PRAs. The PRA implicitly requires that
containment ``gross'' integrity must be available to ensure adequate
NPSH for ECCS pumps. Even though the PRA models do not consider that
containment ``leakage'' contributes to a large early release, the
assessed risk impact of the proposed completion time extension is based
on the assumption that all core damage events will proceed to a large
early release.
The requirement for an immediate (within one hour) shutdown is
based on the philosophy that inoperability of the containment is a
violation of the plant design basis and, therefore, a plant shutdown
must be initiated as soon as possible. The selection of one hour was
based on the requirement for ``immediate shutdown'' and the assumption
that one hour is adequate time for operators to effect shutdown plans.
The goal was to place the plant in a condition where the health and
safety of the public could be better assured. No specific risk
assessments were performed. In fact, it is more appropriate from the
health and safety objective viewpoint to consider the risk of continued
