Notice of Availability of Model Application Concerning Technical Specification Improvement To Modify Requirements Regarding the Addition of Limiting Condition for Operation 3.0.8 on the Inoperability of Snubbers Using the Consolidated Line Item Improvement Process, 23252-23262 [E5-2171]
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Federal Register / Vol. 70, No. 85 / Wednesday, May 4, 2005 / Notices
certain required end states when the TS
Completion Times for remaining in
power operation are exceeded, i.e., entry
into hot shutdown rather than cold
shutdown to repair equipment, if risk is
assessed and managed, will not
introduce new failure modes or effects
and will not, in the absence of other
unrelated failures, lead to an accident
whose consequences exceed the
consequences of accidents previously
evaluated. The addition of a
requirement to assess and manage the
risk introduced by this change and the
commitment by the licensee to adhere to
the guidance in WCAP–16364–NP,
Rev[0], ‘‘Implementation Guidance for
Risk Informed Modification to Selected
Required Action End States at
Combustion Engineering NSSS Plants
(TSTF–422),’’ will further minimize
possible concerns. Thus, this change
does not create the possibility of a new
or different kind of accident from an
accident previously evaluated.
Criterion 3—The Proposed Change Does
Not Involve a Significant Reduction in
the Margin of Safety
The proposed change allows, for some
systems, entry into hot shutdown rather
than cold shutdown to repair
equipment, if risk is assessed and
managed. The CEOG’s risk assessment
approach is comprehensive and follows
staff guidance as documented in RGs
1.174 and 1.177. In addition, the
analyses show that the criteria of the
three-tiered approach for allowing TS
changes are met. The risk impact of the
proposed TS changes was assessed
following the three-tiered approach
recommended in RG 1.177. A risk
assessment was performed to justify the
proposed TS changes. The net change to
the margin of safety is insignificant.
Therefore, this 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 27th day
of April 2005.
For the Nuclear Regulatory Commission.
Theodore R. Tjader,
Senior Reactor Engineer, Technical
Specifications Section, Operating
Improvements Branch, Division of Inspection
Program Management, Office of Nuclear
Reactor Regulation.
[FR Doc. E5–2174 Filed 5–3–05; 8:45 am]
BILLING CODE 7590–01–P
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Background
NUCLEAR REGULATORY
COMMISSION
Notice of Availability of Model
Application Concerning Technical
Specification Improvement To Modify
Requirements Regarding the Addition
of Limiting Condition for Operation
3.0.8 on the Inoperability of Snubbers
Using the Consolidated Line Item
Improvement Process
Nuclear Regulatory
Commission.
ACTION: Notice of availability.
AGENCY:
SUMMARY: Notice is hereby given that
the staff of the Nuclear Regulatory
Commission (NRC) has prepared a
model application relating to the
modification of requirements regarding
the impact of inoperable snubbers not in
technical specifications, on supported
systems in technical specifications (TS).
The purpose of this model is to permit
the NRC to efficiently process
amendments that propose to modify
requirements by adding to the TS a
limiting condition for operation (LCO)
3.0.8 that provides a delay time for
entering a supported system TS when
the inoperability is due solely to an
inoperable snubber, if risk is assessed
and managed, as generically approved
by this notice. Licensees of nuclear
power reactors to which the model
applies could request amendments
utilizing the model application.
DATES: The NRC staff issued a Federal
Register Notice (69 FR 68412, November
24, 2004) which provided a Model
Safety Evaluation (SE) relating to
modification of requirements regarding
the addition 1 to the TS of LCO 3.0.8 on
the impact of inoperable snubbers;
similarly the NRC staff herein provides
a Model Application, including a
revised Model Safety Evaluation. The
NRC staff can most efficiently consider
applications based upon the Model
Application, which references the
Model Safety Evaluation, if the
application is submitted within one year
of this Federal Register notice.
FOR FURTHER INFORMATION CONTACT: Tom
Boyce, Mail Stop: O–12H2, Division of
Inspection Program Management, Office
of Nuclear Reactor Regulation, U.S.
Nuclear Regulatory Commission,
Washington, DC 20555–0001, telephone
301–415–0184.
SUPPLEMENTARY INFORMATION:
1 In conjunction with the proposed change,
technical specification (TS) requirements for a
Bases Control Program, consistent with the TSBases Control Program described in section 5.5 of
the applicable vendor’s standard TS (STS), shall be
incorporated into the licensee’s TS, if not already
in the TS.
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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. This is
accomplished 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
following a preliminary assessment by
the NRC staff and finding that the
change will likely be offered for
adoption by licensees. 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 to proceed with announcing the
availability of the change for proposed
adoption by licensees. Those licensees
opting to apply for the subject change to
technical specifications 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 rules and
NRC procedures.
This notice involves the modification
of requirements regarding the addition
to the TS of LCO 3.0.8 that provides a
delay time for entering a supported
system TS when the inoperability is due
solely to an inoperable snubber, if risk
is assessed and managed. This change
was proposed for incorporation into the
standard technical specifications by all
Owners Groups participants in the
Technical Specification Task Force
(TSTF) and is designated TSTF–372
Revision 4, which was referenced in the
Federal Register Notice (FRN) 69 FR
68412, of November 24, 2004, and can
both be viewed on the NRC’s Web page
at https://www.nrc.gov/reactors/
operating/licensing/techspecs.html.
Applicability
This proposed change to modify
technical specification requirements for
the impact of inoperable non-technical
specification snubbers on supported
systems in TS is applicable to all
licensees who currently have or who
will adopt, in conjunction with the
proposed change, technical
specification requirements for a Bases
control program consistent with the
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Technical Specifications Bases Control
Program described in section 5.5 of the
applicable vendor’s STS.
To efficiently process the incoming
license amendment applications, the
staff requests each licensee applying for
the changes addressed by TSTF–372
Revision 4 using the CLIIP to include
the Bases for the proposed technical
specifications. In addition, for those
licensees that have not adopted
requirements for a Bases control
program by converting to the improved
STS or by other means, the staff requests
that you include the requirements for a
Bases control program consistent with
the STS in your request for the proposed
change. The need for a Bases control
program stems from the need for
adequate regulatory control of some key
elements of the proposal that are
contained in the proposed Bases for
surveillance requirement (SR) 3.0.8. The
staff is requesting that the Bases be
included with the proposed license
amendments because, in this case, the
changes to the technical specifications
and changes to the associated Bases
form an integrated change to a plant’s
licensing bases. To ensure that the
overall change, including the Bases,
includes the appropriate regulatory
controls, the staff plans to condition the
issuance of each license amendment on
incorporation of the changes to the
Bases document and on ensuring the
licensee’s TS have a Bases Control
Program for controlling changes to the
Bases. The CLIIP does not prevent
licensees from requesting an alternative
approach or proposing the changes
without the requested Bases and Bases
control program. Variations from the
approach recommended in this notice
may, however, require additional
justification, additional review by the
NRC staff and may increase the time and
resources needed for the review.
Public Notices
The staff issued a Federal Register
Notice (69 FR 68412, November 24,
2004) that requested public comment on
the NRC’s pending action to approve
modification of TS requirements
regarding the impact of inoperable nontechnical specification snubbers on
supported systems in TS. In particular,
following an assessment and draft safety
evaluation by the NRC staff, the staff
sought public comment on proposed
changes to the STS, designated as
TSTF–372 Revision 4. The TSTF–372
Revision 4 can be viewed on the NRC’s
Web page at https://www.nrc.gov/
reactors/operating/licensing/
techspecs.html. TSTF–372 Revision 4
may be examined, and/or copied for a
fee, at the NRC’s Public Document
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Room, located at One White Flint North,
11555 Rockville Pike (first floor),
Rockville, Maryland. Publicly available
records are accessible electronically
from the ADAMS Public Library
component on the NRC Web site (the
Electronic Reading Room), at https://
www.nrc.gov/reading-rm/adams.html.
In response to the notice soliciting
comments from interested members of
the public about modifying the TS
requirements regarding the impact of
inoperable non-technical specification
snubbers on supported systems in TS,
the staff received three sets of comments
(from licensees and the TSTF Owners
Groups, representing licensees). Specific
comments on the model SE were
offered, and are summarized and
discussed below:
1. Comment: Performing and
documenting the engineering
assessment every time LCO 3.0.8 is used
is unnecessary as it is unlikely that the
design function of the snubbers will
change. The Safety Evaluation should be
revised to state that when LCO 3.0.8 is
used, licensees must confirm that at
least one train of each system that is
supported by the inoperable snubber(s)
would remain capable of performing its
required safety or support functions for
postulated design loads other than
seismic loads.
The evaluation described is not an
‘‘operability assessment.’’ In order for
LCO 3.0.8 to be needed, the system
supported by the snubber to be removed
from service would not be considered
operable. The phrases ‘‘operability
assessment’’ and ‘‘engineering
assessment’’ should be replaced as
described in the previous bullet.
Response: The terms ‘‘engineering
assessment’’ and ‘‘operability
assessment’’ were used to describe the
determination licensees must make,
when a snubber is inoperable, that the
snubber is seismic or non-seismic in
function, the number of trains affected,
and that the underlying assumptions of
LCO 3.0.8 apply, before invoking LCO
3.0.8. It is recognized that the
determination is only required when the
inoperable snubber is required to
support a system that is required to be
operable by a TS, and when that TS is
in a mode of applicability. Also, when
a train is removed from service for
maintenance, the risk assessment for the
performance of the maintenance would
encompass that for snubbers supporting
only equipment on that train. So there
are circumstances in which
assessments/determinations for
inoperable snubbers are not required. In
recognition of the variability of the
degree of determination required for an
inoperable snubber, and the fact that the
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term ‘‘assessment’’ has formal
procedural connotations, the wording
has been changed as suggested, to
require that ‘‘* * * licensees confirm
* * * ’’ and not assess, every time a
snubber is inoperable.
2. Comment: In [section 3.2] item
1.(e), the Safety Evaluation uses the
phrase ‘‘perform a risk assessment.’’
This phrase also appears on page 68420
of the Federal Register notice, third
column, in the No Significant Hazards
Consideration (NSHC), Criterion 3
discussion. The proposed Technical
Specifications state that ‘‘risk must be
assessed and managed.’’ Item 1.(e) and
the NSHC should be revised to be
consistent with the proposed Technical
Specifications.
Response: The staff agrees. The
wording will be changed to be
consistent with 10 CFR 50.65(a)(4),
which requires the licensee to ‘‘assess
and manage the increase in risk.’’
3. Comment: Documenting the design
functions of the snubber(s) for NRC
inspection should not be required. As
stated in TSTF–372, the risk
assessments will be consistent with
those performed to meet the
requirements of 10 CFR 50.65(a)(4). It is
not required that the risk assessments
performed to meet the requirements of
10 CFR 50.65(a)(4) be documented. It
would be inconsistent to require
documentation of the particular portion
of the 10 CFR 50.65(a)(4) risk
assessments related to snubbers. In
addition, this information exists in the
plant’s design documentation and it
imposes an unnecessary burden on the
licensee to record for this particular
purpose otherwise generic information.
Response: To be consistent with the
requirements of 10 CFR 50.65(a)(4),
which does not require the
documentation discussed in this
comment, and in light of the variability
of assessments associated with
inoperable snubbers (as noted in the
response to comment 1 above), the
requirement for every evaluation to be
documented has been removed. The
staff nonetheless considers that it would
be prudent in many circumstances for
the evaluation to be documented, and
that it would also be efficient if
licensees were able to refer to prior
evaluations. LCO 3.0.8 does not apply to
non-seismic snubbers. In addition, a
record of the design function of the
inoperable snubber (i.e., seismic vs.
non-seismic), implementation of any
applicable Tier 2 restrictions, and the
associated plant configuration shall be
available on a recoverable basis for staff
inspection.
4. Comment: On page 68415 of the
Federal Register Notice, the third
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column, first paragraph, the following
statement is made: ‘‘Since the licensee
controlled testing is done on only a
small (about 10%) representative
sample of the total snubber population,
it is not expected to have more than a
few snubbers supporting a given safety
system out for testing at a time.’’ The
statement ‘‘it is not expected to have
more than a few snubbers supporting a
given safety system out for testing at a
time’’ does not appear in TSTF–372 and
is not an assumption of the risk
assessment that was performed to
support the Traveler. The Traveler risk
assessment assumed that the systems
affected by removed snubbers are
unavailable. Therefore, the number of
removed snubbers is irrelevant. The
statement implies that plants must
impose some undefined limit (i.e., a
‘‘few’’) on the number of snubbers that
can be simultaneously removed from a
given system. Such a restriction is
unnecessary and confusing. It is
recommended that the sentence be
revised to state, ‘‘Since the licensee
controlled testing is done on only a
small (about 10%) representative
sample of the total snubber population,
typically only a few snubbers
supporting a given safety system are out
for testing at a time.’’ This changes the
sentence from what could be construed
as a requirement to a statement of fact.
Response: The staff accepts the use of
the phrase, ‘‘typically only,’’ as a
substitute; the staff considers the
phrases equivalent.
5. Comment: On page 68419 of the
Federal Register Notice, the third
column, first paragraph prior to Section
4.0, State Consultation, the following
statement is made: ‘‘Since the 10 CFR
50.65(a)(4) guidance, section 11 of
NUMARC 93–01, does not currently
address seismic risk, implementation
guidance must be developed by
licensees adopting this change to ensure
that the proposed LCO 3.0.8 is
considered in conjunction with other
plant maintenance activities and
integrated into the existing 10 CFR
50.65(a)(4) process.’’
A similar statement is made on page
68418 of the Federal Register Notice,
the third column, the last paragraph of
Section 3.1.3. It is not necessary to
develop independent ‘‘implementation
guidance’’ to ensure that the proposed
LCO 3.0.8 is considered in conjunction
with other plant maintenance activities
and integrated into the existing 10 CFR
50.65(a)(4) process. We recommend that
the sentences be revised to state: Since
the 10 CFR 50.65(a)(4) guidance, Section
11 of NUMARC 93–01, does not
currently address seismic risk, licensees
adopting this change must ensure that
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the proposed LCO 3.0.8 is considered in
conjunction with other plant
maintenance activities and integrated
into the existing 10 CFR 50.65(a)(4)
process.
Response: The staff accepts the
wording change. In this case the use of
the term ‘‘implementation guidance’’
was not intended to convey formal
industry guidance. Therefore, to avoid
confusion using the words ‘‘must
ensure’’ is preferable. Wording has been
added in the Safety Evaluation to ensure
that seismic risk assessments used to
satisfy the 10 CFR 50.65(a)(4) process
will be based upon either detailed
seismic probabilistic risk assessment
(PRA) based evaluations or bounding
risk analyses, such as utilized in the
assessment included in the Safety
Evaluation.
6. Comment: On page 68414 of the
Federal Register Notice, middle
column, first paragraph, it is stated that
prior to conversion to improved STS,
the 72-hour delay time provision that
was typically included in the snubber
technical specification was applicable
only to snubbers found to be inoperable
(i.e., emergent conditions only). This
characterization is contrary to previous
NRC positions (see References 4 and 5
of TSTF–372, Revision 4). It is a long
standing industry practice to utilize the
72-hour delay for the removal of
snubbers for maintenance and testing
purposes, not only emergent conditions.
Response: There remain some
differing interpretations on what preimproved STS allowed. Regardless of
prior practices and what older
specifications permitted, this change
will clarify and make consistent
practices and understanding of what is
permitted. Therefore, statements of what
pre-improved STS allowed are removed
from the text.
7. Comment: In the first paragraph of
the Summary, the term ‘‘non-technical
specifications snubbers’’ is used. That
term is not defined or used elsewhere.
In section 1.0, INTRODUCTION, the
new LCO 3.0.8 identifies the snubbers of
interest as ‘‘required snubbers.’’ In
section 2.0, Regulatory Evaluation, the
snubbers of interest are characterized as
‘‘relocated snubbers.’’
Some clarification is requested to
ensure that the snubbers of interest are
clearly understood to be those required
to support Technical Specifications
functions.
Response: In the first paragraph of the
Summary, the term ‘‘non-technical
specifications snubbers’’ is changed to
‘‘snubbers not in technical
specifications.’’ In section 1.0,
INTRODUCTION, the new LCO 3.0.8
identifies the snubbers of interest as
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‘‘required snubbers.’’ In technical
specifications the term ‘‘required
snubbers’’ is understood to be those
required to support Technical
Specifications functions. In section 2.0,
REGULATORY EVALUATION, the term
‘‘relocated snubber requirements’’ has
been changed to ‘‘snubber requirements
that have been relocated from technical
specifications* * *’’.
8. Comment: For licensees who have
not converted to the improved STS,
some clarification is needed for the
‘‘other means’’ by which a licensee
could have adopted a Bases control
program. Is it necessary that the Bases
control program be incorporated into
the Technical Specifications, or would
the establishment of a procedure in the
plant operating manual be sufficient?
Response: The Risk Management
Technical Specifications (RMTS)
Initiatives that have been approved todate have each required the adoption of
a Bases Control Program, if not
previously adopted through conversion
to the STS. It is necessary that the Bases
Control Program be incorporated into
the TS. At this point it is expected that
most plants have adopted a Bases
Control Program in the Administrative
Controls Section of their TS. As noted,
licensees are not prevented from
requesting an alternative approach or
proposing the changes without the
requested Bases and Bases control
program. Variations from the approach
recommended in this notice may,
however, require additional
justification, additional review by the
NRC staff and may increase the time and
resources needed for the review. In
addition, an alternative approach will
most likely have to similarly involve a
change to the plant license.
9. Comment: Section 3.1.2 of the
model safety evaluation regarding the
use of LCO 3.0.8b for boiling water
reactors requires that ‘‘at least one
success path exists, using equipment
not associated with the inoperable
snubber(s), to provide makeup and
cooling needed to mitigate LOOP
accident sequences.’’ The phrase
‘‘needed to mitigate LOOP accident
sequences’’ is absent in the
corresponding implementation
requirements in Section 3.2.1(d), which
implies all accident sequences must be
considered. This phrase should be
restored to Section 3.2.1(d) to clarify the
type of analysis that must be performed.
Response: The staff agrees. The phrase
‘‘needed to mitigate LOOP accident
sequences’’ is added to Section 3.2.1(d).
Dated at Rockville, Maryland, this 27th day
of April 2005.
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For the Nuclear Regulatory Commission.
Theodore R. Tjader,
Senior Reactor Engineer, Technical
Specifications Section, Operating
Improvements Branch, Division of Inspection
Program Management, Office of Nuclear
Reactor Regulation.
Model Safety Evaluation
Technical Specification Task Force
(TSTF) Change TSTF–372
1.0 Introduction
On April 23, 2004, the Nuclear Energy
Institute (NEI) Risk Informed Technical
Specifications Task Force (RITSTF)
submitted a proposed change, TSTF–
372, Revision 4, to the standard
technical specifications (STS) (NUREGs
1430–1434) on behalf of the industry
(TSTF–372, Revisions 1 through 3 were
prior draft iterations). TSTF–372,
Revision 4, is a proposal to add an STS
Limiting Condition for Operation (LCO)
3.0.8, allowing a delay time for entering
a supported system technical
specification (TS), when the
inoperability is due solely to an
inoperable snubber, if risk is assessed
and managed. The postulated seismic
event requiring snubbers is a lowprobability occurrence and the overall
TS system safety function would still be
available for the vast majority of
anticipated challenges.
This proposal is one of the industry’s
initiatives being developed under the
risk-informed technical specifications
program. These initiatives are intended
to maintain or improve safety through
the incorporation of risk assessment and
management techniques in TS, while
reducing unnecessary burden and
making technical specification
requirements consistent with the
Commission’s other risk-informed
regulatory requirements, in particular
the Maintenance Rule.
The proposed change adds a new
limiting condition of operation, LCO
3.0.8, to the TS. LCO 3.0.8 allows
licensees to delay declaring an LCO not
met for equipment, supported by
snubbers unable to perform their
associated support functions, when risk
is assessed and managed. This new LCO
3.0.8 states: When one or more required
snubbers are unable to perform their
associated support function(s), any
affected supported LCO(s) are not
required to be declared not met solely
for this reason if risk is assessed and
managed, and:
a. The snubbers not able to perform
their associated support function(s) are
associated with only one train or
subsystem of a multiple train or
subsystem supported system or are
associated with a single train or
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subsystem supported system and are
able to perform their associated support
function within 72 hours; or
b. The snubbers not able to perform
their associated support function(s) are
associated with more than one train or
subsystem of a multiple train or
subsystem supported system and are
able to perform their associated support
function within 12 hours.
At the end of the specified period the
required snubbers must be able to
perform their associated support
function(s), or the affected supported
system LCO(s) shall be declared not
met.’’
The proposed TS change is described
in sections 1.0 and 2.0. The technical
evaluation and approach used to assess
its risk impact is discussed in section
3.0. The results and insights of the risk
assessment are presented and discussed
in section 3.1. Section 3.2 summarizes
the staff’s conclusions from the review
of the proposed TS change.
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, 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
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 specification * * * .’’
TS section 3.0, on ‘‘LCO and SR
Applicability,’’ provides details or
ground rules for complying with the
LCOs.
Snubbers are chosen in lieu of rigid
supports in areas where restricting
thermal growth during normal operation
would induce excessive stresses in the
piping nozzles or other equipment.
Although they are classified as
component standard supports, they are
not designed to provide any
transmission of force during normal
plant operations. However, in the
presence of dynamic transient loadings,
which are induced by seismic events as
well as by plant accidents and
transients, a snubber functions as a rigid
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support. The location and size of the
snubbers are determined by stress
analysis based on different
combinations of load conditions,
depending on the design classification
of the particular piping.
Prior to the conversion to the
improved STS, TS requirements applied
directly to snubbers. These
requirements included:
• A requirement that snubbers be
functional and in service when the
supported equipment is required to be
operable,
• A requirement that snubber removal
for testing be done only during plant
shutdown,
• A requirement that snubber removal
for testing be done on a one-at-a-time
basis when supported equipment is
required to be operable during
shutdown,
• A requirement to repair or replace
within 72 hours any snubbers, found to
be inoperable during operation in
Modes 1 through 4, to avoid declaring
any supported equipment inoperable,
• A requirement that each snubber be
demonstrated operable by periodic
visual inspections, and
• A requirement to perform
functional tests on a representative
sample of at least 10% of plant
snubbers, at least once every 18 months
during shutdown.
In the late 1980s, a joint initiative of
the NRC and industry was undertaken
to improve the STS. This effort
identified the snubbers as candidates for
relocation to a licensee-controlled
document based on the fact that the TS
requirements for snubbers did not meet
any of the four criteria in 10 CFR
50.36(c)(2)(ii) for inclusion in the
improved STS. The NRC approved the
relocation without placing any
restriction on the use of the relocated
requirements. However, this relocation
resulted in different interpretations
between the NRC and the industry
regarding its implementation. The NRC
has stated, that since snubbers are
supporting safety equipment that is in
the TS, the definition of OPERABILITY
must be used to immediately evaluate
equipment supported by a removed
snubber and, if found inoperable, the
appropriate TS required actions must be
entered. This interpretation has in
practice eliminated the 72-hour delay to
enter the actions for the supported
equipment that existed prior to the
conversion to the improved STS (the
only exception is if the supported
system has been analyzed and
determined to be OPERABLE without
the snubber). The industry has argued
that since the NRC approved the
relocation without placing any
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restriction on the use of the relocated
requirements, the licensee controlled
document requirements for snubbers
should be invoked before the supported
system’s TS requirements become
applicable. The industry’s interpretation
would, in effect, restore the 72-hour
delay to enter the actions for the
supported equipment that existed prior
to the conversion to the improved STS.
The industry’s proposal would allow a
time delay for all conditions, including
snubber removal for testing at power.
The option to relocate the snubbers to
a licensee controlled document, as part
of the conversion to improved STS, has
resulted in non-uniform and
inconsistent treatment of snubbers. On
the one hand, plants that have relocated
snubbers from their TS are allowed to
change the TS requirements for
snubbers under the auspices of 10 CFR
50.59, but they are not allowed a 72hour delay before they enter the actions
for the supported equipment. On the
other hand, plants that have not
converted to improved STS have
retained the 72-hour delay if snubbers
are found to be inoperable, but they are
not allowed to use 10 CFR 50.59 to
change TS requirements for snubbers. It
should also be noted that a few plants
that converted to the improved STS
chose not to relocate the snubbers to a
licensee-controlled document and, thus,
retained the 72-hour delay. In addition,
it is important to note that unlike plants
that have not relocated, plants that have
relocated can perform functional tests
on the snubbers at power (as long as
they enter the actions for the supported
equipment) and at the same time can
reduce the testing frequency (as
compared to plants that have not
relocated) if it is justified by 10 CFR
50.59 assessments. Some potential
undesirable consequences of this
inconsistent treatment of snubbers are:
• Performance of testing during
crowded time period windows when the
supported system is inoperable with the
potential to reduce the snubber testing
to a minimum since the snubber
requirements that have been relocated
from TS are controlled by the licensee,
• Performance of testing during
crowded windows when the supported
system is inoperable with the potential
to increase the unavailability of safety
systems, and
• Performance of testing and
maintenance on snubbers affecting
multiple trains of the same supported
system during the 7 hours allotted
before entering MODE 3 under LCO
3.0.3.
To remove the inconsistency in the
treatment of snubbers among plants, the
TSTF proposed a risk-informed TS
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change that introduces a delay time
before entering the actions for the
supported equipment, when one or
more snubbers are found inoperable or
removed for testing, if risk is assessed
and managed. Such a delay time will
provide needed flexibility in the
performance of maintenance and testing
during power operation and at the same
time will enhance overall plant safety
by:
• Avoiding unnecessary unscheduled
plant shutdowns and, thus, minimizing
plant transition and realignment risks,
• Avoiding reduced snubber testing
and, thus, increasing the availability of
snubbers to perform their supporting
function,
• Performing most of the required
testing and maintenance during the
delay time when the supported system
is available to mitigate most challenges
and, thus, avoiding increases in safety
system unavailability, and
• Providing explicit risk-informed
guidance in areas in which that
guidance currently does not exist, such
as the treatment of snubbers impacting
more than one redundant train of a
supported system.
3.0 Technical Evaluation
The industry submitted TSTF–372,
Revision 4, ‘‘Addition of LCO 3.0.8,
Inoperability of Snubbers’’ in support of
the proposed TS change. This submittal
(Ref. 1) documents a risk-informed
analysis of the proposed TS change.
Probabilistic risk assessment (PRA)
results and insights are used, in
combination with deterministic and
defense-in-depth arguments, to identify
and justify delay times for entering the
actions for the supported equipment
associated with inoperable snubbers at
nuclear power plants. This is in
accordance with guidance provided in
Regulatory Guides (RGs) 1.174 and
1.177 (Refs. 2 and 3, respectively).
The risk impact associated with the
proposed delay times for entering the
TS actions for the supported equipment
can be assessed using the same
approach as for allowed completion
time (CT) extensions. Therefore, the risk
assessment was performed following the
three-tiered approach recommended in
RG 1.177 for evaluating proposed
extensions in currently allowed 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 (DCDF) and the
average yearly large early release
frequency (DLERF) and (2) by the
incremental conditional core damage
probability (ICCDP) and the incremental
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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.
• 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.
A simplified bounding risk
assessment was performed to justify the
proposed addition of LCO 3.0.8 to the
TS. This approach was necessitated by
(1) the general nature of the proposed
TS changes (i.e., they apply to all plants
and are associated with an
undetermined number of snubbers that
are not able to perform their function),
(2) the lack of detailed engineering
analyses that establish the relationship
between earthquake level and supported
system pipe failure probability when
one or more snubbers are inoperable,
and (3) the lack of seismic risk
assessment models for most plants. The
simplified risk assessment is based on
the following major assumptions, which
the staff finds acceptable, as discussed
below:
• The accident sequences
contributing to the risk increase
associated with the proposed TS
changes are assumed to be initiated by
a seismically-induced loss-of-offsitepower (LOOP) event with concurrent
loss of all safety system trains supported
by the out-of-service snubbers. In the
case of snubbers associated with more
than one train (or subsystem) of the
same system, it is assumed that all
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affected trains (or subsystems) of the
supported system are failed. This
assumption was introduced to allow the
performance of a simple bounding risk
assessment approach with application
to all plants. This approach was selected
due to the lack of detailed plant-specific
seismic risk assessments for most plants
and the lack of fragility data for piping
when one or more supporting snubbers
are inoperable.
• The LOOP event is assumed to
occur due to the seismically-induced
failure of the ceramic insulators used in
the power distribution systems. These
ceramic insulators have a high
confidence (95%) of low probability
(5%) of failure (HCLPF) of about 0.1g,
expressed in terms of peak ground
acceleration. Thus, a magnitude 0.1g
earthquake is conservatively assumed to
have 5% probability of causing a LOOP
initiating event. The fact that no LOOP
events caused by higher magnitude
earthquakes were considered is justified
because (1) the frequency of earthquakes
decreases with increasing magnitude
and (2) historical data (References 4 and
5) indicate that the mean seismic
capacity of ceramic insulators (used in
seismic PRAs), in terms of peak ground
acceleration, is about 0.3g, which is
significantly higher than the 0.1g
HCLPF value. Therefore, the simplified
analysis, even though it does not
consider LOOP events caused by
earthquakes of magnitude higher than
0.1g, bounds a detailed analysis which
would use mean seismic failure
probabilities (fragilities) for the ceramic
insulators.
• Analytical and experimental results
obtained in the mid-eighties as part of
the industry’s ‘‘Snubber Reduction
Program’’ (References 4 and 6) indicated
that piping systems have large margins
against seismic stress. The assumption
that a magnitude 0.1g earthquake would
cause the failure of all safety system
trains supported by the out-of-service
snubbers is very conservative because
safety piping systems could withstand
much higher seismic stresses even when
one or more supporting snubbers are out
of service. The actual piping failure
probability is a function of the stress
allowable and the number of snubbers
removed for maintenance or testing.
Since the licensee controlled testing is
done on only a small (about 10%)
representative sample of the total
snubber population, typically only a few
snubbers supporting a given safety
system out for testing at a time.
Furthermore, since the testing of
snubbers is a planned activity, licensees
have flexibility in selecting a sample set
of snubbers for testing from a much
larger population by conducting
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configuration-specific engineering and/
or risk assessments. Such a selection of
snubbers for testing provides confidence
that the supported systems would
perform their functions in the presence
of a design-basis earthquake and other
dynamic loads and, in any case, the risk
impact of the activity will remain
within the limits of acceptability
defined in risk-informed RGs 1.174 and
1.177.
• The analysis assumes that one train
(or subsystem) of all safety systems is
unavailable during snubber testing or
maintenance (an entire system is
assumed unavailable if a removed
snubber is associated with both trains of
a two-train system). This is a very
conservative assumption for the case of
corrective maintenance since it is
unlikely that a visual inspection will
reveal that one or more snubbers across
all supported systems are inoperable.
This assumption is also conservative for
the case of the licensee-controlled
testing of snubbers since such testing is
performed only on a small
representative sample.
• In general, no credit is taken for
recovery actions and alternative means
of performing a function, such as the
function performed by a system
assumed failed (e.g., when LCO 3.0.8b
applies). However, most plants have
reliable alternative means of performing
certain critical functions. For example,
feed and bleed (F&B) can be used to
remove heat in most pressurized water
reactors (PWRs) when auxiliary
feedwater (AFW), the most important
system in mitigating LOOP accidents, is
unavailable. Similarly, if high pressure
makeup (e.g., reactor core isolation
cooling) and heat removal capability
(e.g., suppression pool cooling) are
unavailable in boiling water reactors
(BWRs), reactor depressurization in
conjunction with low pressure makeup
(e.g., low pressure coolant injection) and
heat removal capability (e.g., shutdown
cooling) can be used to cool the core. A
10% failure probability for recovery
actions to provide core cooling using
alternative means is assumed for Diablo
Canyon, the only West Coast PWR plant
with F&B capability, when a snubber
impacting more than one train of the
AFW system (i.e., when LCO 3.0.8b is
applicable) is out of service. This failure
probability value is significantly higher
than the value of 2.2E–2 used in Diablo
Canyon’s PRA. Furthermore, Diablo
Canyon has analyzed the impact of a
single limiting snubber failure, and
concluded that no single snubber failure
would impact two trains of AFW. No
credit for recovery actions to provide
core cooling using alternative means is
necessary for West Coast PWR plants
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with no F&B capability because it has
been determined that there is no single
snubber whose non-functionality would
disable two trains of AFW in a seismic
event of magnitude up to the plant’s safe
shutdown earthquake (SSE). It should
be noted that a similar credit could have
been applied to most Central and
Eastern U.S. plants but this was not
necessary to demonstrate the low risk
impact of the proposed TS change due
to the lower earthquake frequencies at
Central and Eastern U.S. plants as
compared to West Coast plants.
• The earthquake frequency at the
0.1g level was assumed to be 1E–3/year
for Central and Eastern U.S. plants and
1E–1/year for West Coast plants. Each of
these two values envelop the range of
earthquake frequency values at the 0.1g
level, for Eastern U.S. and West Cost
sites, respectively (References 5 and 7).
• The risk impact associated with
non-LOOP accident sequences (e.g.,
seismically initiated loss-of-coolantaccident (LOCA) or anticipatedtransient-without-scram (ATWS)
sequences) was not assessed. However,
this risk impact is small compared to
the risk impact associated with the
LOOP accident sequences modeled in
the simplified bounding risk
assessment. Non-LOOP accident
sequences, due to the ruggedness of
nuclear power plant designs, require
seismically-induced failures that occur
at earthquake levels above 0.3g. Thus,
the frequency of earthquakes initiating
non-LOOP accident sequences is much
smaller than the frequency of
seismically-initiated LOOP events.
Furthermore, because of the
conservative assumption made for
LOOP sequences that a 0.1g level
earthquake would fail all piping
associated with inoperable snubbers,
non-LOOP sequences would not include
any more failures associated with
inoperable snubbers than LOOP
sequences. Therefore, the risk impact of
inoperable snubbers associated with
non-LOOP accident sequences is small
compared to the risk impact associated
with the LOOP accident sequences
modeled in the simplified bounding risk
assessment.
• The risk impact of dynamic
loadings other than seismic loads is not
assessed. These shock-type loads
include thrust loads, blowdown loads,
waterhammer loads, steamhammer
loads, LOCA loads and pipe rupture
loads. However, there are some
important distinctions between nonseismic (shock-type) loads and seismic
loads which indicate that, in general,
the risk impact of the out-of-service
snubbers is smaller for non-seismic
loads than for seismic loads. First, while
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a seismic load affects the entire plant,
the impact of a non-seismic load is
localized to a certain system or area of
the plant. Second, although non-seismic
shock loads may be higher in total force
and the impact could be as much or
more than seismic loads, generally they
are of much shorter duration than
seismic loads. Third, the impact of nonseismic loads is more plant specific, and
thus harder to analyze generically, than
for seismic loads. For these reasons,
licensees will be required to confirm
every time LCO 3.0.8 is used, that at
least one train of each system that is
supported by the inoperable snubber(s)
would remain capable of performing
their required safety or support
functions for postulated design loads
other than seismic loads.
3.1 Risk Assessment Results and
Insights
The results and insights from the
implementation of the three-tiered
approach of RG 1.177 to support the
proposed addition of LCO 3.0.8 to the
TS are summarized and evaluated in the
following sections 3.1.1 to 3.1.3.
3.1.1 Risk Impact
The bounding risk assessment
approach, discussed in Section 3.0, was
implemented generically for all U.S.
operating nuclear power plants. Risk
assessments were performed for two
categories of plants, Central and East
Coast plants and West Coast plants,
based on historical seismic hazard
curves (earthquake frequencies and
associated magnitudes). The first
category, Central and East Coast plants,
includes the vast majority of the U.S.
nuclear power plant population
(Reference 7). For each category of
plants, two risk assessments were
performed:
• The first risk assessment applies to
cases where all inoperable snubbers are
associated with only one train (or
subsystem) of the impacted safety
systems. It was conservatively assumed
that a single train (or subsystem) of each
safety system is unavailable. It was also
assumed that the probability of nonmitigation using the unaffected
redundant trains (or subsystems) is 2%.
This is a conservative value given that
for core damage to occur under those
conditions, two or more failures are
required.
• The second risk assessment applies
to the case where one or more of the
inoperable snubbers are associated with
multiple trains (or subsystems) of the
same safety systems. It was assumed in
this bounding analysis that all safety
systems are unavailable to mitigate the
accident, except for West Coast PWR
plants. Credit for using F&B to provide
core cooling is taken for plants having
F&B capability (e.g., Diablo Canyon)
when a snubber impacting more than
one train of the AFW system is
inoperable. Credit for one AFW train to
provide core cooling is taken for West
Coast PWR plants with no F&B
capability (e.g., San Onofre) because it
has been determined that there is no
single snubber whose non-functionality
would disable two trains of AFW in a
seismic event of magnitude up to the
plant’s SSE.
The results of the performed risk
assessments, in terms of core damage
and large early release risk impacts, are
summarized in Table 1. The first row
lists the conditional risk increase, in
terms of CDF (core damage frequency),
DRCDF, caused by the out-of-service
snubbers (as assumed in the bounding
analysis). The second and third rows list
the ICCDP (incremental conditional core
damage probability) and the ICLERP
(incremental conditional large early
release probability) values, respectively.
The ICCDP for the case where all
inoperable snubbers are associated with
only one train (or subsystem) of the
supported safety systems, was obtained
by multiplying the corresponding DRCDF
value by the time fraction of the
proposed 72-hour delay to enter the
actions for the supported equipment.
The ICCDP for the case where one or
more of the inoperable snubbers are
associated with multiple trains (or
subsystems) of the same safety system,
was obtained by multiplying the
corresponding DRCDF value by the time
fraction of the proposed 12-hour delay
to enter the actions for the supported
equipment. The ICLERP values were
obtained by multiplying the
corresponding ICCDP values by 0.1 (i.e.,
by assuming that the ICLERP value is an
order of magnitude less than the
ICCDP). This assumption is conservative
since containment bypass scenarios,
such as steam generator tube rupture
accidents and interfacing system loss-ofcoolant accidents, would not be
uniquely affected by the out-of-service
snubbers. Finally, the fourth and fifth
rows list the assessed DCDF and DLERF
values, respectively. These values were
obtained by dividing the corresponding
ICCDP and ICLERP values by 1.5 (i.e., by
assuming that the snubbers are tested
every 18 months, as was the case before
the snubbers were relocated to a
licensee-controlled document). This
assumption is reasonable because (1) it
is not expected that licensees would test
the snubbers more often than what used
to be required by the TS, and (2) testing
of snubbers is associated with higher
risk impact than the average corrective
maintenance of snubbers found
inoperable by visual inspection (testing
is expected to involve significantly more
snubbers out of service than corrective
maintenance). 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.
This comparison indicates that the
addition of LCO 3.0.8 to the existing TS
would have an insignificant risk impact.
TABLE 1.—BOUNDING RISK ASSESSMENT RESULTS FOR SNUBBERS IMPACTING A SINGLE TRAIN AND MULTIPLE TRAINS OF
A SUPPORTED SYSTEM
Central and east coast plants
Single train
DRCDF/yr ...................................................................................
ICCDP ......................................................................................
ICLERP ....................................................................................
DCDF / yr ..................................................................................
DLERF / yr ................................................................................
The assessed DCDF and DLERF values
meet the acceptance criteria of 1E–6/
year and 1E–7/year, respectively, based
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Multiple train
1E–6
8E–9
8E–10
5E–9
5E–10
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Single train
5E–6
7E–9
7E–10
5E–9
5E–10
on guidance provided in RG 1.174. This
conclusion is true without taking any
credit for the removal of potential
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West coast plants
1E–4
8E–7
8E–8
5E–7
5E–8
Multiple train
5E–4
7E–7
7E–8
5E–7
5E–8
undesirable consequences associated
with the current inconsistent treatment
of snubbers (e.g., reduced snubber
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testing frequency, increased safety
system unavailability and treatment of
snubbers impacting multiple trains)
discussed in Section 1 above, and given
the bounding nature of the risk
assessment.
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. This comparison indicates that
the addition of LCO 3.0.8 to the existing
TS meets the RG 1.177 numerical
guidelines of 5E–7 for ICCDP and 5E–8
for ICLERP. The small deviations shown
for West Coast plants are acceptable
because of the bounding nature of the
risk assessments, as discussed in section
2.
The risk assessment results of Table 1
are also compared to guidance provided
in the revised section 11 of NUMARC
93–01, Revision 2 (Reference 8),
endorsed by RG 1.182 (Reference 9), for
implementing the requirements of
paragraph (a)(4) of the Maintenance
Rule, 10 CFR 50.65. Such guidance is
summarized in Table 2. Guidance
regarding the acceptability of
conditional risk increase in terms of
CDF (i.e., DRCDF) for a planned
configuration is provided. This
guidance states that a specific
configuration that is associated with a
CDF higher than 1E–3/year should not
be entered voluntarily. Since the
assessed conditional risk increase,
DRCDF, is significantly less than 1E–3/
year, plant configurations including out
of service snubbers and other equipment
may be entered voluntarily if supported
by the results of the risk assessment
required by 10 CFR 50.65(a)(4), by LCO
3.0.8, or by other TS.
TABLE 2.—GUIDANCE FOR IMPLEMENTING 10 CFR 50.65(A)(4)
DRCDF
Guidance
Greater than 1E–3 / year ...........................................................................
Configuration should not normally be entered voluntarily.
ICCDP
Guidance
Greater than 1E–5 ..........
1E–6 to 1E–5 ..................
Less than 1E–6 ..............
Configuration should not normally be entered voluntarily .....................................................
Assess non-quantifiable factors; Establish risk management actions ...................................
Normal work controls .............................................................................................................
Guidance regarding the acceptability
of ICCDP and ICLERP values for a
specific planned configuration and the
establishment of risk management
actions is also provided in NUMARC
93–01. This guidance, as shown in
Table 2, states that a specific plant
configuration that is associated with
ICCDP and ICLERP values below 1E–6
and 1E–7, respectively, is considered to
require ‘‘normal work controls.’’ Table 1
shows that for the majority of plants
(i.e., for all plants in the Central and
East Coast category) the conservatively
assessed ICCDP and ICLERP values are
over an order of magnitude less than
what is recommended as the threshold
for the ‘‘normal work controls’’ region.
For West Coast plants, the
conservatively assessed ICCDP and
ICLERP values are still within the
‘‘normal work controls’’ region. Thus,
the risk contribution from out of service
snubbers is within the normal range of
maintenance activities carried out at a
plant. Therefore, plant configurations
involving out of service snubbers and
other equipment may be entered
voluntarily if supported by the results of
the risk assessment required by 10 CFR
50.65(a)(4), by LCO 3.0.8, or by other
TS. However, this simplified bounding
analysis indicates that for West Coast
plants the provisions of LCO 3.0.8 must
be used cautiously and in conjunction
with appropriate management actions,
especially when equipment other than
snubbers is also inoperable, based on
the results of configuration-specific risk
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ICLERP
assessments required by 10 CFR
50.65(a)(4), by LCO 3.0.8, or by other
TS.
The staff finds that the risk
assessment results support the proposed
addition of LCO 3.0.8 to the TS. The risk
increases associated with this TS change
will be insignificant based on guidance
provided in RGs 1.174 and 1.177 and
within the range of risks associated with
normal maintenance activities. In
addition, LCO 3.0.8 will remove
potential undesirable consequences
stemming from the current inconsistent
treatment of snubbers in the TS, such as
reduced frequency of snubber testing,
increased safety system unavailability
and the treatment of snubbers impacting
multiple trains.
3.1.2 Identification of High-Risk
Configurations
The second tier of the three-tiered
approach recommended in RG 1.177
involves the identification of potentially
high-risk configurations that could exist
if equipment, in addition to that
associated with the TS change, were to
be taken out of service simultaneously.
Insights from the risk assessments, in
conjunction with important
assumptions made in the analysis and
defense-in-depth considerations, were
used to identify such configurations. To
avoid these potentially high-risk
configurations, specific restrictions to
the implementation of the proposed TS
changes were identified.
For cases where all inoperable
snubbers are associated with only one
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Greater than 1E–6.
1E–7 to 1E–6.
Less than1E–7.
train (or subsystem) of the impacted
systems (i.e., when LCO 3.0.8a applies),
it was assumed in the analysis that there
will be unaffected redundant trains (or
subsystems) available to mitigate the
seismically initiated LOOP accident
sequences. This assumption implies that
there will be at least one success path
available when LCO 3.0.8a applies.
Therefore, potentially high-risk
configurations can be avoided by
ensuring that such a success path exists
when LCO 3.0.8a applies. Based on a
review of the accident sequences that
contribute to the risk increase associated
with LCO 3.0.8a, as modeled by the
simplified bounding analysis (i.e.,
accident sequences initiated by a
seismically-induced LOOP event with
concurrent loss of all safety system
trains supported by the out of service
snubbers), the following restrictions
were identified to prevent potentially
high-risk configurations:
• For PWR plants, at least one AFW
train (including a minimum set of
supporting equipment required for its
successful operation) not associated
with the inoperable snubber(s), must be
available when LCO 3.0.8a is used.
• For BWR plants, one of the
following two means of heat removal
must be available when LCO 3.0.8a is
used:
—At least one high pressure makeup
path (e.g., using high pressure coolant
injection (HPCI) or reactor core
isolation cooling (RCIC) or equivalent)
and heat removal capability (e.g.,
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suppression pool cooling), including a
minimum set of supporting
equipment required for success, not
associated with the inoperable
snubber(s), or
—At least one low pressure makeup
path (e.g., low pressure coolant
injection (LPCI) or containment spray
(CS)) and heat removal capability
(e.g., suppression pool cooling or
shutdown cooling), including a
minimum set of supporting
equipment required for success, not
associated with the inoperable
snubber(s).
For cases where one or more of the
inoperable snubbers are associated with
multiple trains (or subsystems) of the
same safety system (i.e., when LCO
3.0.8b applies), it was assumed in the
bounding analysis that all safety
systems are unavailable to mitigate the
accident, except for West Coast plants.
Credit for using F&B to provide core
cooling is taken for plants having F&B
capability (e.g., Diablo Canyon) when a
snubber impacting more than one train
of the AFW system is inoperable. Credit
for one AFW train to provide core
cooling is taken for West Coast PWR
plants with no F&B capability (e.g., San
Onofre) because it has been determined
that there is no single snubber whose
non-functionality would disable more
than one train of AFW in a seismic
event of magnitude up to the plant’s
SSE. Based on a review of the accident
sequences that contribute to the risk
increase associated with LCO 3.0.8b (as
modeled by the simplified bounding
analysis) and defense-in-depth
considerations, the following
restrictions were identified to prevent
potentially high-risk configurations:
• LCO 3.0.8b cannot be used at West
Coast PWR plants with no F&B
capability when a snubber whose nonfunctionality would disable more than
one train of AFW in a seismic event of
magnitude up to the plant’s SSE is
inoperable (it should be noted, however,
that based on information provided by
the industry, there is no plant that falls
in this category)
• When LCO 3.0.8b is used at PWR
plants, at least one AFW train
(including a minimum set of supporting
equipment required for its successful
operation) not associated with the
inoperable snubber(s), or some
alternative means of core cooling (e.g.,
F&B, firewater system or ‘‘aggressive
secondary cooldown’’ using the steam
generators) must be available.
• When LCO 3.0.8b is used at BWR
plants, it must be verified that at least
one success path exists, using
equipment not associated with the
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inoperable snubber(s), to provide
makeup and core cooling needed to
mitigate LOOP accident sequences.
3.1.3
Configuration Risk Management
The third tier of the three-tiered
approach recommended in RG 1.177
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. This objective
is met by licensee programs to comply
with the requirements of paragraph
(a)(4) of the Maintenance Rule (10 CFR
50.65) to assess and manage risk
resulting from maintenance activities,
and by the TS requiring risk
assessments and management using
(a)(4) processes if no maintenance is in
progress. These programs can support
licensee decision making regarding the
appropriate actions to manage risk
whenever a risk-informed TS is entered.
Since the 10 CFR 50.65(a)(4) guidance,
the revised (May 2000) Section 11 of
NUMARC 93–01, does not currently
address seismic risk, licensees adopting
this change must ensure that the
proposed LCO 3.0.8 is considered with
respect to other plant maintenance
activities and integrated into the
existing 10 CFR 50.65(a)(4) process
whether the process is invoked by a TS
or (a)(4) itself.
3.2
Summary and Conclusions
The option to relocate the snubbers to
a licensee controlled document, as part
of the conversion to Improved STS, has
resulted in non-uniform and
inconsistent treatment of snubbers.
Some potential undesirable
consequences of this inconsistent
treatment of snubbers are:
• Performance of testing during
crowded windows when the supported
system is inoperable with the potential
to reduce the snubber testing to a
minimum since the relocated snubber
requirements are controlled by the
licensee.
• Performance of testing during
crowded windows when the supported
system is inoperable with the potential
to increase the unavailability of safety
systems.
• Performance of testing and
maintenance on snubbers affecting
multiple trains of the same supported
system during the 7 hours allotted
before entering MODE 3 under LCO
3.0.3.
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Fmt 4703
Sfmt 4703
To remove the inconsistency among
plants in the treatment of snubbers,
licensees are proposing a risk-informed
TS change which introduces a delay
time before entering the actions for the
supported equipment when one or more
snubbers are found inoperable or
removed for testing. Such a delay time
will provide needed flexibility in the
performance of maintenance and testing
during power operation and at the same
time will enhance overall plant safety
by (1) avoiding unnecessary
unscheduled plant shutdowns, thus,
minimizing plant transition and
realignment risks; (2) avoiding reduced
snubber testing, thus, increasing the
availability of snubbers to perform their
supporting function; (3) performing
most of the required testing and
maintenance during the delay time
when the supported system is available
to mitigate most challenges, thus,
avoiding increases in safety system
unavailability; and (4) providing
explicit risk-informed guidance in areas
in which that guidance currently does
not exist, such as the treatment of
snubbers impacting more than one
redundant train of a supported system.
The risk impact of the proposed TS
changes was assessed following the
three-tiered approach recommended in
RG 1.177. A simplified bounding risk
assessment was performed to justify the
proposed TS changes. This bounding
assessment assumes that the risk
increase associated with the proposed
addition of LCO 3.0.8 to the TS is
associated with accident sequences
initiated by a seismically-induced LOOP
event with concurrent loss of all safety
system trains supported by the out-ofservice snubbers. In the case of snubbers
associated with more than one train, it
is assumed that all affected trains of the
supported system are failed. This
assumption was introduced to allow the
performance of a simple bounding risk
assessment approach with application
to all plants and was selected due to the
lack of detailed plant-specific seismic
risk assessments for most plants and the
lack of fragility data for piping when
one or more supporting snubbers are
inoperable. The impact from the
addition of the proposed LCO 3.0.8 to
the TS on defense-in-depth was also
evaluated in conjunction with the risk
assessment results.
Based on this integrated evaluation,
the staff concludes that the proposed
addition of LCO 3.0.8 to the TS would
lead to insignificant risk increases, if
any. Indeed, this conclusion is true
without taking any credit for the
removal of potential undesirable
consequences associated with the
current inconsistent treatment of
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snubbers, such as the effects of avoiding
a potential reduction in the snubber
testing frequency and increased safety
system unavailability. Consistent with
the staff’s approval and inherent in the
implementation of TSTF–372, licensees
interested in implementing LCO 3.0.8
must, as applicable, operate in
accordance with the following
stipulations:
1. Appropriate plant procedures and
administrative controls will be used to
implement the following Tier 2
Restrictions.
(a) At least one AFW train (including
a minimum set of supporting equipment
required for its successful operation) not
associated with the inoperable
snubber(s), must be available when LCO
3.0.8a is used at PWR plants.
(b) At least one AFW train (including
a minimum set of supporting equipment
required for its successful operation) not
associated with the inoperable
snubber(s), or some alternative means of
core cooling (e.g., F&B, fire water system
or ‘‘aggressive secondary cooldown’’
using the steam generators) must be
available when LCO 3.0.8b is used at
PWR plants.
(c) LCO 3.0.8b cannot be used by West
Coast PWR plants with no F&B
capability when a snubber, whose nonfunctionality would disable more than
one train of AFW in a seismic event of
magnitude up to the plant’s SSE, is
inoperable.
(d) BWR plants must verify, every
time the provisions of LCO 3.0.8 are
used, that at least one success path,
involving equipment not associated
with the inoperable snubber(s), exists to
provide makeup and core cooling
needed to mitigate LOOP accident
sequences.
(e) Every time the provisions of LCO
3.0.8 are used licensees will be required
to confirm that at least one train (or
subsystem) of systems supported by the
inoperable snubbers would remain
capable of performing their required
safety or support functions for
postulated design loads other than
seismic loads. LCO 3.0.8 does not apply
to non-seismic snubbers. In addition, a
record of the design function of the
inoperable snubber (i.e., seismic vs.
non-seismic), implementation of any
applicable Tier 2 restrictions, and the
associated plant configuration shall be
available on a recoverable basis for staff
inspection.
2. Should licensees implement the
provisions of LCO 3.0.8 for snubbers,
which include delay times to enter the
actions for the supported equipment
when one or more snubbers are out of
service for maintenance or testing, it
must be done in accordance with an
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overall CRMP to ensure that potentially
risk-significant configurations resulting
from maintenance and other operational
activities are identified and avoided, as
discussed in the proposed TS Bases.
This objective is met by licensee
programs to comply with the
requirements of paragraph (a)(4) of the
Maintenance Rule, 10 CFR 50.65, to
assess and manage risk resulting from
maintenance activities or when this
process is invoked by LCO 3.0.8 or other
TS. These programs can support
licensee decisionmaking regarding the
appropriate actions to manage risk
whenever a risk-informed TS is entered.
Since the 10 CFR 50.65(a)(4) guidance,
the revised (May 2000) Section 11 of
NUMARC 93–01, does not currently
address seismic risk, licensees adopting
this change must ensure that the
proposed LCO 3.0.8 is considered in
conjunction with other plant
maintenance activities and integrated
into the existing 10 CFR 50.65(a)(4)
process. In the absence of a detailed
seismic PRA, a bounding risk
assessment, such as utilized in this
Safety Evaluation, shall be followed.
4.0 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].
5.0 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. [For
licensees adding a Bases Control
Program: The amendment also changes
record keeping, reporting, or
administrative procedures or
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 nosignificant-hazards considerations, and
there has been no public comment on
the finding [FR]. Accordingly, the
amendments meet the eligibility criteria
for categorical exclusion set forth in 10
CFR 51.22(c)(9) [and (c)(10)]. Pursuant
to 10 CFR 51.22(b), no environmental
impact statement or environmental
PO 00000
Frm 00174
Fmt 4703
Sfmt 4703
23261
assessment need be prepared in
connection with the issuance of the
amendments.
6.0 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.
7.0 References
1. TSTF–372, Revision 4, ‘‘Addition
of LCO 3.0.8, Inoperability of
Snubbers,’’ April 23, 2004.
2. Regulatory Guide 1.174, ‘‘An
Approach for Using Probabilistic Risk
Assessment in Risk-Informed Decisions
on Plant-Specific Changes to the
Licensing Basis,’’ USNRC, August 1998.
3. Regulatory Guide 1.177, ‘‘An
Approach for Plant-Specific, RiskInformed Decisionmaking: Technical
Specifications,’’ USNRC, August 1998.
4. Budnitz, R.J. et al., ‘‘An Approach
to the Quantification of Seismic Margins
in Nuclear Power Plants,’’ NUREG/CR–
4334, Lawrence Livermore National
Laboratory, July 1985.
5. Advanced Light Water Reactor
Utility Requirements Document,
Volume 2, ALWR Evolutionary Plant,
PRA Key Assumptions and
Groundrules, Electric Power Research
Institute, August 1990.
6. Bier V.M. et al., ‘‘Development and
Application of a Comprehensive
Framework for Assessing Alternative
Approaches to Snubber Reduction,’’
International Topical Conference on
Probabilistic Safety Assessment and
Risk Management PSA ’87, Swiss
Federal Institute of Technology, Zurich,
August 30–September 4, 1987.
7. NUREG–1488, ‘‘Revised Livermore
Seismic Hazard Estimates for Sixty-Nine
Nuclear Power Plant Sites East of the
Rocky Mountains,’’ April 1994.
8. NEI, Revised Section 11 of Revision
2 of NUMARC 93–01, May 2000.
9. Regulatory Guide 1.182, ‘‘Assessing
and Managing Risk Before Maintenance
Activities at Nuclear Power Plants,’’
May 2000.
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 Revise Technical
Specifications Regarding Missed
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Surveillance (and Adoption of a
Technical Specification Bases Control
Program) * 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 Regulatory Commission,
Document Control Desk,
Washington, DC 20555.
Subject: Plant Name
Docket No. 50—Application for Technical
Specification Change To Add LCO 3.0.8 on
the Inoperability of Snubbers (and
Adoption of a Technical Specifications
Bases Control Program) * 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 requirements for inoperable snubbers by
adding LCO 3.0.8, (and, in conjunction with
the proposed change, TS requirements for a
Bases control program consistent with TS
Bases Control Program described in Section
5.5 of the applicable vendor’s Standard
Technical Specifications).
Attachment 1 provides a description of the
proposed change, the requested confirmation
of applicability, and plant-specific
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. (IF
APPLICABLE: 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 is true and
correct. (Note that request 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
* If not already in the facility Technical
Specifications.
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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 (TS) requirements for
inoperable snubbers by adding LCO 3.0.8.2
The changes are consistent with Nuclear
Regulatory Commission (NRC) approved
Industry/Technical Specification Task Force
(TSTF) STS change TSTF–372 Revision 4.
The availability of this 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 Published Safety
Evaluation
[LICENSEE] has reviewed the safety
evaluation dated [DATE] as part of the CLIIP.
This review included a review of the NRC
staff’s evaluation, as well as the supporting
information provided to support TSTF–372.
[LICENSEE] has concluded that the
justifications presented in the TSTF proposal
and 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.
2.2 Optional Changes and Variations
[LICENSEE] is not proposing any variations
or deviations from the TS changes described
in the TSTF–372 Revision 4 or the NRC
staff’s model safety evaluation dated [DATE].
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:
The licensee has established TS Bases for
LCO 3.0.8 which provide guidance and
details on how to implement the new
requirements. LCO 3.0.8 requires that risk be
managed and assessed. The Bases also state
that while the Industry and NRC guidance on
implementation of 10 CFR 50.65(a)(4), the
Maintenance Rule, does not address seismic
risk, LCO 3.0.8 should be considered with
2 [In conjunction with the proposed change,
technical specifications (TS) requirements for a
Bases Control Program, consistent with the TS
Bases Control Program described in Section 5.5 of
the applicable vendor’s standard TS (STS), shall be
incorporated into the licensee’s TS, if not already
in the TS.]
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Fmt 4703
Sfmt 4703
respect to other plant maintenance activities,
and integrated into the existing Maintenance
Rule process to the extent possible so that
maintenance on any unaffected train or
subsystem is properly controlled, and
emergent issues are properly addressed. The
risk assessment need not be quantified, but
may be a qualitative assessment of the
vulnerability of systems and components
when one or more snubbers are not able to
perform their associated support function.
Finally, the licensee is expected to have a
Bases Control Program consistent with
Section 5.5 of the STS.
4.0 Environmental Evaluation
[LICENSEE] has reviewed the
environmental evaluation included in the
model safety evaluation dated [DATE] as part
of the CLIIP. [LICENSEE] has concluded that
the staff’s findings presented in that
evaluation are applicable to [PLANT] and the
evaluation is hereby incorporated by
reference for this application.
Attachment 2—Proposed Technical
Specification Changes (Mark-Up)
Attachment 3—Proposed Technical
Specification Pages
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—[LICENSEE]
will establish the Technical Specification
Bases for LCO 3.0.8 as adopted with the
applicable license amendment.
Due date/event—[Complete, implemented
with amendment OR within X days of
implementation of amendment]
Attachment 5—Proposed Changes to
Technical Specification Bases Pages
[FR Doc. E5–2171 Filed 5–3–05; 8:45 am]
BILLING CODE 7590–01–P
SECURITIES AND EXCHANGE
COMMISSION
[Investment Company Act Release No.
26861; 812–13163]
Edward D. Jones & Co., L.P.; Notice of
Application
April 28, 2005.
Securities and Exchange
Commission (‘‘Commission’’).
ACTION: Notice of an application for an
order under section 6(c) of the
Investment Company Act of 1940 (the
‘‘Act’’) for an exemption from section
22(d) of the Act, as well as certain
disclosure requirements.
AGENCY:
Edward D.
Jones & Co., L.P. (‘‘Edward Jones’’)
SUMMARY OF APPLICATION:
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Agencies
[Federal Register Volume 70, Number 85 (Wednesday, May 4, 2005)]
[Notices]
[Pages 23252-23262]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E5-2171]
-----------------------------------------------------------------------
NUCLEAR REGULATORY COMMISSION
Notice of Availability of Model Application Concerning Technical
Specification Improvement To Modify Requirements Regarding the Addition
of Limiting Condition for Operation 3.0.8 on the Inoperability of
Snubbers Using the Consolidated Line Item Improvement Process
AGENCY: Nuclear Regulatory Commission.
ACTION: Notice of availability.
-----------------------------------------------------------------------
SUMMARY: Notice is hereby given that the staff of the Nuclear
Regulatory Commission (NRC) has prepared a model application relating
to the modification of requirements regarding the impact of inoperable
snubbers not in technical specifications, on supported systems in
technical specifications (TS). The purpose of this model is to permit
the NRC to efficiently process amendments that propose to modify
requirements by adding to the TS a limiting condition for operation
(LCO) 3.0.8 that provides a delay time for entering a supported system
TS when the inoperability is due solely to an inoperable snubber, if
risk is assessed and managed, as generically approved by this notice.
Licensees of nuclear power reactors to which the model applies could
request amendments utilizing the model application.
DATES: The NRC staff issued a Federal Register Notice (69 FR 68412,
November 24, 2004) which provided a Model Safety Evaluation (SE)
relating to modification of requirements regarding the addition \1\ to
the TS of LCO 3.0.8 on the impact of inoperable snubbers; similarly the
NRC staff herein provides a Model Application, including a revised
Model Safety Evaluation. The NRC staff can most efficiently consider
applications based upon the Model Application, which references the
Model Safety Evaluation, if the application is submitted within one
year of this Federal Register notice.
---------------------------------------------------------------------------
\1\ In conjunction with the proposed change, technical
specification (TS) requirements for a Bases Control Program,
consistent with the TS-Bases Control Program described in section
5.5 of the applicable vendor's standard TS (STS), shall be
incorporated into the licensee's TS, if not already in the TS.
FOR FURTHER INFORMATION CONTACT: Tom Boyce, Mail Stop: O-12H2, Division
of Inspection Program Management, Office of Nuclear Reactor Regulation,
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001,
---------------------------------------------------------------------------
telephone 301-415-0184.
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. This is accomplished
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 following a preliminary
assessment by the NRC staff and finding that the change will likely be
offered for adoption by licensees. 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 to proceed with announcing the
availability of the change for proposed adoption by licensees. Those
licensees opting to apply for the subject change to technical
specifications 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 rules and NRC procedures.
This notice involves the modification of requirements regarding the
addition to the TS of LCO 3.0.8 that provides a delay time for entering
a supported system TS when the inoperability is due solely to an
inoperable snubber, if risk is assessed and managed. This change was
proposed for incorporation into the standard technical specifications
by all Owners Groups participants in the Technical Specification Task
Force (TSTF) and is designated TSTF-372 Revision 4, which was
referenced in the Federal Register Notice (FRN) 69 FR 68412, of
November 24, 2004, and can both be viewed on the NRC's Web page at
https://www.nrc.gov/reactors/operating/licensing/techspecs.html.
Applicability
This proposed change to modify technical specification requirements
for the impact of inoperable non-technical specification snubbers on
supported systems in TS is applicable to all licensees who currently
have or who will adopt, in conjunction with the proposed change,
technical specification requirements for a Bases control program
consistent with the
[[Page 23253]]
Technical Specifications Bases Control Program described in section 5.5
of the applicable vendor's STS.
To efficiently process the incoming license amendment applications,
the staff requests each licensee applying for the changes addressed by
TSTF-372 Revision 4 using the CLIIP to include the Bases for the
proposed technical specifications. In addition, for those licensees
that have not adopted requirements for a Bases control program by
converting to the improved STS or by other means, the staff requests
that you include the requirements for a Bases control program
consistent with the STS in your request for the proposed change. The
need for a Bases control program stems from the need for adequate
regulatory control of some key elements of the proposal that are
contained in the proposed Bases for surveillance requirement (SR)
3.0.8. The staff is requesting that the Bases be included with the
proposed license amendments because, in this case, the changes to the
technical specifications and changes to the associated Bases form an
integrated change to a plant's licensing bases. To ensure that the
overall change, including the Bases, includes the appropriate
regulatory controls, the staff plans to condition the issuance of each
license amendment on incorporation of the changes to the Bases document
and on ensuring the licensee's TS have a Bases Control Program for
controlling changes to the Bases. The CLIIP does not prevent licensees
from requesting an alternative approach or proposing the changes
without the requested Bases and Bases control program. Variations from
the approach recommended in this notice may, however, require
additional justification, additional review by the NRC staff and may
increase the time and resources needed for the review.
Public Notices
The staff issued a Federal Register Notice (69 FR 68412, November
24, 2004) that requested public comment on the NRC's pending action to
approve modification of TS requirements regarding the impact of
inoperable non-technical specification snubbers on supported systems in
TS. In particular, following an assessment and draft safety evaluation
by the NRC staff, the staff sought public comment on proposed changes
to the STS, designated as TSTF-372 Revision 4. The TSTF-372 Revision 4
can be viewed on the NRC's Web page at https://www.nrc.gov/reactors/
operating/licensing/techspecs.html. TSTF-372 Revision 4 may be
examined, and/or copied for a fee, at the NRC's Public Document Room,
located at One White Flint North, 11555 Rockville Pike (first floor),
Rockville, Maryland. Publicly available records are accessible
electronically from the ADAMS Public Library component on the NRC Web
site (the Electronic Reading Room), at https://www.nrc.gov/reading-rm/
adams.html.
In response to the notice soliciting comments from interested
members of the public about modifying the TS requirements regarding the
impact of inoperable non-technical specification snubbers on supported
systems in TS, the staff received three sets of comments (from
licensees and the TSTF Owners Groups, representing licensees). Specific
comments on the model SE were offered, and are summarized and discussed
below:
1. Comment: Performing and documenting the engineering assessment
every time LCO 3.0.8 is used is unnecessary as it is unlikely that the
design function of the snubbers will change. The Safety Evaluation
should be revised to state that when LCO 3.0.8 is used, licensees must
confirm that at least one train of each system that is supported by the
inoperable snubber(s) would remain capable of performing its required
safety or support functions for postulated design loads other than
seismic loads.
The evaluation described is not an ``operability assessment.'' In
order for LCO 3.0.8 to be needed, the system supported by the snubber
to be removed from service would not be considered operable. The
phrases ``operability assessment'' and ``engineering assessment''
should be replaced as described in the previous bullet.
Response: The terms ``engineering assessment'' and ``operability
assessment'' were used to describe the determination licensees must
make, when a snubber is inoperable, that the snubber is seismic or non-
seismic in function, the number of trains affected, and that the
underlying assumptions of LCO 3.0.8 apply, before invoking LCO 3.0.8.
It is recognized that the determination is only required when the
inoperable snubber is required to support a system that is required to
be operable by a TS, and when that TS is in a mode of applicability.
Also, when a train is removed from service for maintenance, the risk
assessment for the performance of the maintenance would encompass that
for snubbers supporting only equipment on that train. So there are
circumstances in which assessments/determinations for inoperable
snubbers are not required. In recognition of the variability of the
degree of determination required for an inoperable snubber, and the
fact that the term ``assessment'' has formal procedural connotations,
the wording has been changed as suggested, to require that `` * * *
licensees confirm * * * '' and not assess, every time a snubber is
inoperable.
2. Comment: In [section 3.2] item 1.(e), the Safety Evaluation uses
the phrase ``perform a risk assessment.'' This phrase also appears on
page 68420 of the Federal Register notice, third column, in the No
Significant Hazards Consideration (NSHC), Criterion 3 discussion. The
proposed Technical Specifications state that ``risk must be assessed
and managed.'' Item 1.(e) and the NSHC should be revised to be
consistent with the proposed Technical Specifications.
Response: The staff agrees. The wording will be changed to be
consistent with 10 CFR 50.65(a)(4), which requires the licensee to
``assess and manage the increase in risk.''
3. Comment: Documenting the design functions of the snubber(s) for
NRC inspection should not be required. As stated in TSTF-372, the risk
assessments will be consistent with those performed to meet the
requirements of 10 CFR 50.65(a)(4). It is not required that the risk
assessments performed to meet the requirements of 10 CFR 50.65(a)(4) be
documented. It would be inconsistent to require documentation of the
particular portion of the 10 CFR 50.65(a)(4) risk assessments related
to snubbers. In addition, this information exists in the plant's design
documentation and it imposes an unnecessary burden on the licensee to
record for this particular purpose otherwise generic information.
Response: To be consistent with the requirements of 10 CFR
50.65(a)(4), which does not require the documentation discussed in this
comment, and in light of the variability of assessments associated with
inoperable snubbers (as noted in the response to comment 1 above), the
requirement for every evaluation to be documented has been removed. The
staff nonetheless considers that it would be prudent in many
circumstances for the evaluation to be documented, and that it would
also be efficient if licensees were able to refer to prior evaluations.
LCO 3.0.8 does not apply to non-seismic snubbers. In addition, a record
of the design function of the inoperable snubber (i.e., seismic vs.
non-seismic), implementation of any applicable Tier 2 restrictions, and
the associated plant configuration shall be available on a recoverable
basis for staff inspection.
4. Comment: On page 68415 of the Federal Register Notice, the third
[[Page 23254]]
column, first paragraph, the following statement is made: ``Since the
licensee controlled testing is done on only a small (about 10%)
representative sample of the total snubber population, it is not
expected to have more than a few snubbers supporting a given safety
system out for testing at a time.'' The statement ``it is not expected
to have more than a few snubbers supporting a given safety system out
for testing at a time'' does not appear in TSTF-372 and is not an
assumption of the risk assessment that was performed to support the
Traveler. The Traveler risk assessment assumed that the systems
affected by removed snubbers are unavailable. Therefore, the number of
removed snubbers is irrelevant. The statement implies that plants must
impose some undefined limit (i.e., a ``few'') on the number of snubbers
that can be simultaneously removed from a given system. Such a
restriction is unnecessary and confusing. It is recommended that the
sentence be revised to state, ``Since the licensee controlled testing
is done on only a small (about 10%) representative sample of the total
snubber population, typically only a few snubbers supporting a given
safety system are out for testing at a time.'' This changes the
sentence from what could be construed as a requirement to a statement
of fact.
Response: The staff accepts the use of the phrase, ``typically
only,'' as a substitute; the staff considers the phrases equivalent.
5. Comment: On page 68419 of the Federal Register Notice, the third
column, first paragraph prior to Section 4.0, State Consultation, the
following statement is made: ``Since the 10 CFR 50.65(a)(4) guidance,
section 11 of NUMARC 93-01, does not currently address seismic risk,
implementation guidance must be developed by licensees adopting this
change to ensure that the proposed LCO 3.0.8 is considered in
conjunction with other plant maintenance activities and integrated into
the existing 10 CFR 50.65(a)(4) process.''
A similar statement is made on page 68418 of the Federal Register
Notice, the third column, the last paragraph of Section 3.1.3. It is
not necessary to develop independent ``implementation guidance'' to
ensure that the proposed LCO 3.0.8 is considered in conjunction with
other plant maintenance activities and integrated into the existing 10
CFR 50.65(a)(4) process. We recommend that the sentences be revised to
state: Since the 10 CFR 50.65(a)(4) guidance, Section 11 of NUMARC 93-
01, does not currently address seismic risk, licensees adopting this
change must ensure that the proposed LCO 3.0.8 is considered in
conjunction with other plant maintenance activities and integrated into
the existing 10 CFR 50.65(a)(4) process.
Response: The staff accepts the wording change. In this case the
use of the term ``implementation guidance'' was not intended to convey
formal industry guidance. Therefore, to avoid confusion using the words
``must ensure'' is preferable. Wording has been added in the Safety
Evaluation to ensure that seismic risk assessments used to satisfy the
10 CFR 50.65(a)(4) process will be based upon either detailed seismic
probabilistic risk assessment (PRA) based evaluations or bounding risk
analyses, such as utilized in the assessment included in the Safety
Evaluation.
6. Comment: On page 68414 of the Federal Register Notice, middle
column, first paragraph, it is stated that prior to conversion to
improved STS, the 72-hour delay time provision that was typically
included in the snubber technical specification was applicable only to
snubbers found to be inoperable (i.e., emergent conditions only). This
characterization is contrary to previous NRC positions (see References
4 and 5 of TSTF-372, Revision 4). It is a long standing industry
practice to utilize the 72-hour delay for the removal of snubbers for
maintenance and testing purposes, not only emergent conditions.
Response: There remain some differing interpretations on what pre-
improved STS allowed. Regardless of prior practices and what older
specifications permitted, this change will clarify and make consistent
practices and understanding of what is permitted. Therefore, statements
of what pre-improved STS allowed are removed from the text.
7. Comment: In the first paragraph of the Summary, the term ``non-
technical specifications snubbers'' is used. That term is not defined
or used elsewhere. In section 1.0, INTRODUCTION, the new LCO 3.0.8
identifies the snubbers of interest as ``required snubbers.'' In
section 2.0, Regulatory Evaluation, the snubbers of interest are
characterized as ``relocated snubbers.''
Some clarification is requested to ensure that the snubbers of
interest are clearly understood to be those required to support
Technical Specifications functions.
Response: In the first paragraph of the Summary, the term ``non-
technical specifications snubbers'' is changed to ``snubbers not in
technical specifications.'' In section 1.0, INTRODUCTION, the new LCO
3.0.8 identifies the snubbers of interest as ``required snubbers.'' In
technical specifications the term ``required snubbers'' is understood
to be those required to support Technical Specifications functions. In
section 2.0, REGULATORY EVALUATION, the term ``relocated snubber
requirements'' has been changed to ``snubber requirements that have
been relocated from technical specifications* * *''.
8. Comment: For licensees who have not converted to the improved
STS, some clarification is needed for the ``other means'' by which a
licensee could have adopted a Bases control program. Is it necessary
that the Bases control program be incorporated into the Technical
Specifications, or would the establishment of a procedure in the plant
operating manual be sufficient?
Response: The Risk Management Technical Specifications (RMTS)
Initiatives that have been approved to-date have each required the
adoption of a Bases Control Program, if not previously adopted through
conversion to the STS. It is necessary that the Bases Control Program
be incorporated into the TS. At this point it is expected that most
plants have adopted a Bases Control Program in the Administrative
Controls Section of their TS. As noted, licensees are not prevented
from requesting an alternative approach or proposing the changes
without the requested Bases and Bases control program. Variations from
the approach recommended in this notice may, however, require
additional justification, additional review by the NRC staff and may
increase the time and resources needed for the review. In addition, an
alternative approach will most likely have to similarly involve a
change to the plant license.
9. Comment: Section 3.1.2 of the model safety evaluation regarding
the use of LCO 3.0.8b for boiling water reactors requires that ``at
least one success path exists, using equipment not associated with the
inoperable snubber(s), to provide makeup and cooling needed to mitigate
LOOP accident sequences.'' The phrase ``needed to mitigate LOOP
accident sequences'' is absent in the corresponding implementation
requirements in Section 3.2.1(d), which implies all accident sequences
must be considered. This phrase should be restored to Section 3.2.1(d)
to clarify the type of analysis that must be performed.
Response: The staff agrees. The phrase ``needed to mitigate LOOP
accident sequences'' is added to Section 3.2.1(d).
Dated at Rockville, Maryland, this 27th day of April 2005.
[[Page 23255]]
For the Nuclear Regulatory Commission.
Theodore R. Tjader,
Senior Reactor Engineer, Technical Specifications Section, Operating
Improvements Branch, Division of Inspection Program Management, Office
of Nuclear Reactor Regulation.
Model Safety Evaluation
Technical Specification Task Force (TSTF) Change TSTF-372
1.0 Introduction
On April 23, 2004, the Nuclear Energy Institute (NEI) Risk Informed
Technical Specifications Task Force (RITSTF) submitted a proposed
change, TSTF-372, Revision 4, to the standard technical specifications
(STS) (NUREGs 1430-1434) on behalf of the industry (TSTF-372, Revisions
1 through 3 were prior draft iterations). TSTF-372, Revision 4, is a
proposal to add an STS Limiting Condition for Operation (LCO) 3.0.8,
allowing a delay time for entering a supported system technical
specification (TS), when the inoperability is due solely to an
inoperable snubber, if risk is assessed and managed. The postulated
seismic event requiring snubbers is a low-probability occurrence and
the overall TS system safety function would still be available for the
vast majority of anticipated challenges.
This proposal is one of the industry's initiatives being developed
under the risk-informed technical specifications program. These
initiatives are intended to maintain or improve safety through the
incorporation of risk assessment and management techniques in TS, while
reducing unnecessary burden and making technical specification
requirements consistent with the Commission's other risk-informed
regulatory requirements, in particular the Maintenance Rule.
The proposed change adds a new limiting condition of operation, LCO
3.0.8, to the TS. LCO 3.0.8 allows licensees to delay declaring an LCO
not met for equipment, supported by snubbers unable to perform their
associated support functions, when risk is assessed and managed. This
new LCO 3.0.8 states: When one or more required snubbers are unable to
perform their associated support function(s), any affected supported
LCO(s) are not required to be declared not met solely for this reason
if risk is assessed and managed, and:
a. The snubbers not able to perform their associated support
function(s) are associated with only one train or subsystem of a
multiple train or subsystem supported system or are associated with a
single train or subsystem supported system and are able to perform
their associated support function within 72 hours; or
b. The snubbers not able to perform their associated support
function(s) are associated with more than one train or subsystem of a
multiple train or subsystem supported system and are able to perform
their associated support function within 12 hours.
At the end of the specified period the required snubbers must be
able to perform their associated support function(s), or the affected
supported system LCO(s) shall be declared not met.''
The proposed TS change is described in sections 1.0 and 2.0. The
technical evaluation and approach used to assess its risk impact is
discussed in section 3.0. The results and insights of the risk
assessment are presented and discussed in section 3.1. Section 3.2
summarizes the staff's conclusions from the review of the proposed TS
change.
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, 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 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 specification * * * .'' TS section 3.0, on ``LCO and SR
Applicability,'' provides details or ground rules for complying with
the LCOs.
Snubbers are chosen in lieu of rigid supports in areas where
restricting thermal growth during normal operation would induce
excessive stresses in the piping nozzles or other equipment. Although
they are classified as component standard supports, they are not
designed to provide any transmission of force during normal plant
operations. However, in the presence of dynamic transient loadings,
which are induced by seismic events as well as by plant accidents and
transients, a snubber functions as a rigid support. The location and
size of the snubbers are determined by stress analysis based on
different combinations of load conditions, depending on the design
classification of the particular piping.
Prior to the conversion to the improved STS, TS requirements
applied directly to snubbers. These requirements included:
A requirement that snubbers be functional and in service
when the supported equipment is required to be operable,
A requirement that snubber removal for testing be done
only during plant shutdown,
A requirement that snubber removal for testing be done on
a one-at-a-time basis when supported equipment is required to be
operable during shutdown,
A requirement to repair or replace within 72 hours any
snubbers, found to be inoperable during operation in Modes 1 through 4,
to avoid declaring any supported equipment inoperable,
A requirement that each snubber be demonstrated operable
by periodic visual inspections, and
A requirement to perform functional tests on a
representative sample of at least 10% of plant snubbers, at least once
every 18 months during shutdown.
In the late 1980s, a joint initiative of the NRC and industry was
undertaken to improve the STS. This effort identified the snubbers as
candidates for relocation to a licensee-controlled document based on
the fact that the TS requirements for snubbers did not meet any of the
four criteria in 10 CFR 50.36(c)(2)(ii) for inclusion in the improved
STS. The NRC approved the relocation without placing any restriction on
the use of the relocated requirements. However, this relocation
resulted in different interpretations between the NRC and the industry
regarding its implementation. The NRC has stated, that since snubbers
are supporting safety equipment that is in the TS, the definition of
OPERABILITY must be used to immediately evaluate equipment supported by
a removed snubber and, if found inoperable, the appropriate TS required
actions must be entered. This interpretation has in practice eliminated
the 72-hour delay to enter the actions for the supported equipment that
existed prior to the conversion to the improved STS (the only exception
is if the supported system has been analyzed and determined to be
OPERABLE without the snubber). The industry has argued that since the
NRC approved the relocation without placing any
[[Page 23256]]
restriction on the use of the relocated requirements, the licensee
controlled document requirements for snubbers should be invoked before
the supported system's TS requirements become applicable. The
industry's interpretation would, in effect, restore the 72-hour delay
to enter the actions for the supported equipment that existed prior to
the conversion to the improved STS. The industry's proposal would allow
a time delay for all conditions, including snubber removal for testing
at power. The option to relocate the snubbers to a licensee controlled
document, as part of the conversion to improved STS, has resulted in
non-uniform and inconsistent treatment of snubbers. On the one hand,
plants that have relocated snubbers from their TS are allowed to change
the TS requirements for snubbers under the auspices of 10 CFR 50.59,
but they are not allowed a 72-hour delay before they enter the actions
for the supported equipment. On the other hand, plants that have not
converted to improved STS have retained the 72-hour delay if snubbers
are found to be inoperable, but they are not allowed to use 10 CFR
50.59 to change TS requirements for snubbers. It should also be noted
that a few plants that converted to the improved STS chose not to
relocate the snubbers to a licensee-controlled document and, thus,
retained the 72-hour delay. In addition, it is important to note that
unlike plants that have not relocated, plants that have relocated can
perform functional tests on the snubbers at power (as long as they
enter the actions for the supported equipment) and at the same time can
reduce the testing frequency (as compared to plants that have not
relocated) if it is justified by 10 CFR 50.59 assessments. Some
potential undesirable consequences of this inconsistent treatment of
snubbers are:
Performance of testing during crowded time period windows
when the supported system is inoperable with the potential to reduce
the snubber testing to a minimum since the snubber requirements that
have been relocated from TS are controlled by the licensee,
Performance of testing during crowded windows when the
supported system is inoperable with the potential to increase the
unavailability of safety systems, and
Performance of testing and maintenance on snubbers
affecting multiple trains of the same supported system during the 7
hours allotted before entering MODE 3 under LCO 3.0.3.
To remove the inconsistency in the treatment of snubbers among
plants, the TSTF proposed a risk-informed TS change that introduces a
delay time before entering the actions for the supported equipment,
when one or more snubbers are found inoperable or removed for testing,
if risk is assessed and managed. Such a delay time will provide needed
flexibility in the performance of maintenance and testing during power
operation and at the same time will enhance overall plant safety by:
Avoiding unnecessary unscheduled plant shutdowns and,
thus, minimizing plant transition and realignment risks,
Avoiding reduced snubber testing and, thus, increasing the
availability of snubbers to perform their supporting function,
Performing most of the required testing and maintenance
during the delay time when the supported system is available to
mitigate most challenges and, thus, avoiding increases in safety system
unavailability, and
Providing explicit risk-informed guidance in areas in
which that guidance currently does not exist, such as the treatment of
snubbers impacting more than one redundant train of a supported system.
3.0 Technical Evaluation
The industry submitted TSTF-372, Revision 4, ``Addition of LCO
3.0.8, Inoperability of Snubbers'' in support of the proposed TS
change. This submittal (Ref. 1) documents a risk-informed analysis of
the proposed TS change. Probabilistic risk assessment (PRA) results and
insights are used, in combination with deterministic and defense-in-
depth arguments, to identify and justify delay times for entering the
actions for the supported equipment associated with inoperable snubbers
at nuclear power plants. This is in accordance with guidance provided
in Regulatory Guides (RGs) 1.174 and 1.177 (Refs. 2 and 3,
respectively).
The risk impact associated with the proposed delay times for
entering the TS actions for the supported equipment can be assessed
using the same approach as for allowed completion time (CT) extensions.
Therefore, the risk assessment was performed following the three-tiered
approach recommended in RG 1.177 for evaluating proposed extensions in
currently allowed 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.
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.
A simplified bounding risk assessment was performed to justify the
proposed addition of LCO 3.0.8 to the TS. This approach was
necessitated by (1) the general nature of the proposed TS changes
(i.e., they apply to all plants and are associated with an undetermined
number of snubbers that are not able to perform their function), (2)
the lack of detailed engineering analyses that establish the
relationship between earthquake level and supported system pipe failure
probability when one or more snubbers are inoperable, and (3) the lack
of seismic risk assessment models for most plants. The simplified risk
assessment is based on the following major assumptions, which the staff
finds acceptable, as discussed below:
The accident sequences contributing to the risk increase
associated with the proposed TS changes are assumed to be initiated by
a seismically-induced loss-of-offsite-power (LOOP) event with
concurrent loss of all safety system trains supported by the out-of-
service snubbers. In the case of snubbers associated with more than one
train (or subsystem) of the same system, it is assumed that all
[[Page 23257]]
affected trains (or subsystems) of the supported system are failed.
This assumption was introduced to allow the performance of a simple
bounding risk assessment approach with application to all plants. This
approach was selected due to the lack of detailed plant-specific
seismic risk assessments for most plants and the lack of fragility data
for piping when one or more supporting snubbers are inoperable.
The LOOP event is assumed to occur due to the seismically-
induced failure of the ceramic insulators used in the power
distribution systems. These ceramic insulators have a high confidence
(95%) of low probability (5%) of failure (HCLPF) of about 0.1g,
expressed in terms of peak ground acceleration. Thus, a magnitude 0.1g
earthquake is conservatively assumed to have 5% probability of causing
a LOOP initiating event. The fact that no LOOP events caused by higher
magnitude earthquakes were considered is justified because (1) the
frequency of earthquakes decreases with increasing magnitude and (2)
historical data (References 4 and 5) indicate that the mean seismic
capacity of ceramic insulators (used in seismic PRAs), in terms of peak
ground acceleration, is about 0.3g, which is significantly higher than
the 0.1g HCLPF value. Therefore, the simplified analysis, even though
it does not consider LOOP events caused by earthquakes of magnitude
higher than 0.1g, bounds a detailed analysis which would use mean
seismic failure probabilities (fragilities) for the ceramic insulators.
Analytical and experimental results obtained in the mid-
eighties as part of the industry's ``Snubber Reduction Program''
(References 4 and 6) indicated that piping systems have large margins
against seismic stress. The assumption that a magnitude 0.1g earthquake
would cause the failure of all safety system trains supported by the
out-of-service snubbers is very conservative because safety piping
systems could withstand much higher seismic stresses even when one or
more supporting snubbers are out of service. The actual piping failure
probability is a function of the stress allowable and the number of
snubbers removed for maintenance or testing. Since the licensee
controlled testing is done on only a small (about 10%) representative
sample of the total snubber population, typically only a few snubbers
supporting a given safety system out for testing at a time.
Furthermore, since the testing of snubbers is a planned activity,
licensees have flexibility in selecting a sample set of snubbers for
testing from a much larger population by conducting configuration-
specific engineering and/or risk assessments. Such a selection of
snubbers for testing provides confidence that the supported systems
would perform their functions in the presence of a design-basis
earthquake and other dynamic loads and, in any case, the risk impact of
the activity will remain within the limits of acceptability defined in
risk-informed RGs 1.174 and 1.177.
The analysis assumes that one train (or subsystem) of all
safety systems is unavailable during snubber testing or maintenance (an
entire system is assumed unavailable if a removed snubber is associated
with both trains of a two-train system). This is a very conservative
assumption for the case of corrective maintenance since it is unlikely
that a visual inspection will reveal that one or more snubbers across
all supported systems are inoperable. This assumption is also
conservative for the case of the licensee-controlled testing of
snubbers since such testing is performed only on a small representative
sample.
In general, no credit is taken for recovery actions and
alternative means of performing a function, such as the function
performed by a system assumed failed (e.g., when LCO 3.0.8b applies).
However, most plants have reliable alternative means of performing
certain critical functions. For example, feed and bleed (F&B) can be
used to remove heat in most pressurized water reactors (PWRs) when
auxiliary feedwater (AFW), the most important system in mitigating LOOP
accidents, is unavailable. Similarly, if high pressure makeup (e.g.,
reactor core isolation cooling) and heat removal capability (e.g.,
suppression pool cooling) are unavailable in boiling water reactors
(BWRs), reactor depressurization in conjunction with low pressure
makeup (e.g., low pressure coolant injection) and heat removal
capability (e.g., shutdown cooling) can be used to cool the core. A 10%
failure probability for recovery actions to provide core cooling using
alternative means is assumed for Diablo Canyon, the only West Coast PWR
plant with F&B capability, when a snubber impacting more than one train
of the AFW system (i.e., when LCO 3.0.8b is applicable) is out of
service. This failure probability value is significantly higher than
the value of 2.2E-2 used in Diablo Canyon's PRA. Furthermore, Diablo
Canyon has analyzed the impact of a single limiting snubber failure,
and concluded that no single snubber failure would impact two trains of
AFW. No credit for recovery actions to provide core cooling using
alternative means is necessary for West Coast PWR plants with no F&B
capability because it has been determined that there is no single
snubber whose non-functionality would disable two trains of AFW in a
seismic event of magnitude up to the plant's safe shutdown earthquake
(SSE). It should be noted that a similar credit could have been applied
to most Central and Eastern U.S. plants but this was not necessary to
demonstrate the low risk impact of the proposed TS change due to the
lower earthquake frequencies at Central and Eastern U.S. plants as
compared to West Coast plants.
The earthquake frequency at the 0.1g level was assumed to
be 1E-3/year for Central and Eastern U.S. plants and 1E-1/year for West
Coast plants. Each of these two values envelop the range of earthquake
frequency values at the 0.1g level, for Eastern U.S. and West Cost
sites, respectively (References 5 and 7).
The risk impact associated with non-LOOP accident
sequences (e.g., seismically initiated loss-of-coolant-accident (LOCA)
or anticipated-transient-without-scram (ATWS) sequences) was not
assessed. However, this risk impact is small compared to the risk
impact associated with the LOOP accident sequences modeled in the
simplified bounding risk assessment. Non-LOOP accident sequences, due
to the ruggedness of nuclear power plant designs, require seismically-
induced failures that occur at earthquake levels above 0.3g. Thus, the
frequency of earthquakes initiating non-LOOP accident sequences is much
smaller than the frequency of seismically-initiated LOOP events.
Furthermore, because of the conservative assumption made for LOOP
sequences that a 0.1g level earthquake would fail all piping associated
with inoperable snubbers, non-LOOP sequences would not include any more
failures associated with inoperable snubbers than LOOP sequences.
Therefore, the risk impact of inoperable snubbers associated with non-
LOOP accident sequences is small compared to the risk impact associated
with the LOOP accident sequences modeled in the simplified bounding
risk assessment.
The risk impact of dynamic loadings other than seismic
loads is not assessed. These shock-type loads include thrust loads,
blowdown loads, waterhammer loads, steamhammer loads, LOCA loads and
pipe rupture loads. However, there are some important distinctions
between non-seismic (shock-type) loads and seismic loads which indicate
that, in general, the risk impact of the out-of-service snubbers is
smaller for non-seismic loads than for seismic loads. First, while
[[Page 23258]]
a seismic load affects the entire plant, the impact of a non-seismic
load is localized to a certain system or area of the plant. Second,
although non-seismic shock loads may be higher in total force and the
impact could be as much or more than seismic loads, generally they are
of much shorter duration than seismic loads. Third, the impact of non-
seismic loads is more plant specific, and thus harder to analyze
generically, than for seismic loads. For these reasons, licensees will
be required to confirm every time LCO 3.0.8 is used, that at least one
train of each system that is supported by the inoperable snubber(s)
would remain capable of performing their required safety or support
functions for postulated design loads other than seismic loads.
3.1 Risk Assessment Results and Insights
The results and insights from the implementation of the three-
tiered approach of RG 1.177 to support the proposed addition of LCO
3.0.8 to the TS are summarized and evaluated in the following sections
3.1.1 to 3.1.3.
3.1.1 Risk Impact
The bounding risk assessment approach, discussed in Section 3.0,
was implemented generically for all U.S. operating nuclear power
plants. Risk assessments were performed for two categories of plants,
Central and East Coast plants and West Coast plants, based on
historical seismic hazard curves (earthquake frequencies and associated
magnitudes). The first category, Central and East Coast plants,
includes the vast majority of the U.S. nuclear power plant population
(Reference 7). For each category of plants, two risk assessments were
performed:
The first risk assessment applies to cases where all
inoperable snubbers are associated with only one train (or subsystem)
of the impacted safety systems. It was conservatively assumed that a
single train (or subsystem) of each safety system is unavailable. It
was also assumed that the probability of non-mitigation using the
unaffected redundant trains (or subsystems) is 2%. This is a
conservative value given that for core damage to occur under those
conditions, two or more failures are required.
The second risk assessment applies to the case where one
or more of the inoperable snubbers are associated with multiple trains
(or subsystems) of the same safety systems. It was assumed in this
bounding analysis that all safety systems are unavailable to mitigate
the accident, except for West Coast PWR plants. Credit for using F&B to
provide core cooling is taken for plants having F&B capability (e.g.,
Diablo Canyon) when a snubber impacting more than one train of the AFW
system is inoperable. Credit for one AFW train to provide core cooling
is taken for West Coast PWR plants with no F&B capability (e.g., San
Onofre) because it has been determined that there is no single snubber
whose non-functionality would disable two trains of AFW in a seismic
event of magnitude up to the plant's SSE.
The results of the performed risk assessments, in terms of core
damage and large early release risk impacts, are summarized in Table 1.
The first row lists the conditional risk increase, in terms of CDF
(core damage frequency), [Delta]RCDF, caused by the out-of-
service snubbers (as assumed in the bounding analysis). The second and
third rows list the ICCDP (incremental conditional core damage
probability) and the ICLERP (incremental conditional large early
release probability) values, respectively. The ICCDP for the case where
all inoperable snubbers are associated with only one train (or
subsystem) of the supported safety systems, was obtained by multiplying
the corresponding [Delta]RCDF value by the time fraction of
the proposed 72-hour delay to enter the actions for the supported
equipment. The ICCDP for the case where one or more of the inoperable
snubbers are associated with multiple trains (or subsystems) of the
same safety system, was obtained by multiplying the corresponding
[Delta]RCDF value by the time fraction of the proposed 12-
hour delay to enter the actions for the supported equipment. The ICLERP
values were obtained by multiplying the corresponding ICCDP values by
0.1 (i.e., by assuming that the ICLERP value is an order of magnitude
less than the ICCDP). This assumption is conservative since containment
bypass scenarios, such as steam generator tube rupture accidents and
interfacing system loss-of-coolant accidents, would not be uniquely
affected by the out-of-service snubbers. Finally, the fourth and fifth
rows list the assessed [Delta]CDF and [Delta]LERF values, respectively.
These values were obtained by dividing the corresponding ICCDP and
ICLERP values by 1.5 (i.e., by assuming that the snubbers are tested
every 18 months, as was the case before the snubbers were relocated to
a licensee-controlled document). This assumption is reasonable because
(1) it is not expected that licensees would test the snubbers more
often than what used to be required by the TS, and (2) testing of
snubbers is associated with higher risk impact than the average
corrective maintenance of snubbers found inoperable by visual
inspection (testing is expected to involve significantly more snubbers
out of service than corrective maintenance). 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. This comparison indicates that the
addition of LCO 3.0.8 to the existing TS would have an insignificant
risk impact.
Table 1.--Bounding Risk Assessment Results for Snubbers Impacting a Single Train and Multiple Trains of a
Supported System
----------------------------------------------------------------------------------------------------------------
Central and east coast plants West coast plants
---------------------------------------------------------------------------
Single train Multiple train Single train Multiple train
----------------------------------------------------------------------------------------------------------------
[Delta]RCDF/yr...................... 1E-6 5E-6 1E-4 5E-4
ICCDP............................... 8E-9 7E-9 8E-7 7E-7
ICLERP.............................. 8E-10 7E-10 8E-8 7E-8
[Delta]CDF / yr..................... 5E-9 5E-9 5E-7 5E-7
[Delta]LERF / yr.................... 5E-10 5E-10 5E-8 5E-8
----------------------------------------------------------------------------------------------------------------
The assessed [Delta]CDF and [Delta]LERF values meet the acceptance
criteria of 1E-6/year and 1E-7/year, respectively, based on guidance
provided in RG 1.174. This conclusion is true without taking any credit
for the removal of potential undesirable consequences associated with
the current inconsistent treatment of snubbers (e.g., reduced snubber
[[Page 23259]]
testing frequency, increased safety system unavailability and treatment
of snubbers impacting multiple trains) discussed in Section 1 above,
and given the bounding nature of the risk assessment.
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. This comparison indicates that the addition of
LCO 3.0.8 to the existing TS meets the RG 1.177 numerical guidelines of
5E-7 for ICCDP and 5E-8 for ICLERP. The small deviations shown for West
Coast plants are acceptable because of the bounding nature of the risk
assessments, as discussed in section 2.
The risk assessment results of Table 1 are also compared to
guidance provided in the revised section 11 of NUMARC 93-01, Revision 2
(Reference 8), endorsed by RG 1.182 (Reference 9), for implementing the
requirements of paragraph (a)(4) of the Maintenance Rule, 10 CFR 50.65.
Such guidance is summarized in Table 2. Guidance regarding the
acceptability of conditional risk increase in terms of CDF (i.e.,
[Delta]RCDF) for a planned configuration is provided. This
guidance states that a specific configuration that is associated with a
CDF higher than 1E-3/year should not be entered voluntarily. Since the
assessed conditional risk increase, [Delta]RCDF, is
significantly less than 1E-3/year, plant configurations including out
of service snubbers and other equipment may be entered voluntarily if
supported by the results of the risk assessment required by 10 CFR
50.65(a)(4), by LCO 3.0.8, or by other TS.
Table 2.--Guidance for Implementing 10 CFR 50.65(a)(4)
------------------------------------------------------------------------
[Delta]RCDF Guidance
------------------------------------------------------------------------
Greater than 1E-3 / year............... Configuration should not
normally be entered
voluntarily.
------------------------------------------------------------------------
ICCDP Guidance ICLERP
----------------------------------------------------------------------------------------------------------------
Greater than 1E-5....................... Configuration should not Greater than 1E-6.
normally be entered
voluntarily.
1E-6 to 1E-5............................ Assess non-quantifiable 1E-7 to 1E-6.
factors; Establish risk
management actions.
Less than 1E-6.......................... Normal work controls......... Less than1E-7.
----------------------------------------------------------------------------------------------------------------
Guidance regarding the acceptability of ICCDP and ICLERP values for
a specific planned configuration and the establishment of risk
management actions is also provided in NUMARC 93-01. This guidance, as
shown in Table 2, states that a specific plant configuration that is
associated with ICCDP and ICLERP values below 1E-6 and 1E-7,
respectively, is considered to require ``normal work controls.'' Table
1 shows that for the majority of plants (i.e., for all plants in the
Central and East Coast category) the conservatively assessed ICCDP and
ICLERP values are over an order of magnitude less than what is
recommended as the threshold for the ``normal work controls'' region.
For West Coast plants, the conservatively assessed ICCDP and ICLERP
values are still within the ``normal work controls'' region. Thus, the
risk contribution from out of service snubbers is within the normal
range of maintenance activities carried out at a plant. Therefore,
plant configurations involving out of service snubbers and other
equipment may be entered voluntarily if supported by the results of the
risk assessment required by 10 CFR 50.65(a)(4), by LCO 3.0.8, or by
other TS. However, this simplified bounding analysis indicates that for
West Coast plants the provisions of LCO 3.0.8 must be used cautiously
and in conjunction with appropriate management actions, especially when
equipment other than snubbers is also inoperable, based on the results
of configuration-specific risk assessments required by 10 CFR
50.65(a)(4), by LCO 3.0.8, or by other TS.
The staff finds that the risk assessment results support the
proposed addition of LCO 3.0.8 to the TS. The risk increases associated
with this TS change will be insignificant based on guidance provided in
RGs 1.174 and 1.177 and within the range of risks associated with
normal maintenance activities. In addition, LCO 3.0.8 will remove
potential undesirable consequences stemming from the current
inconsistent treatment of snubbers in the TS, such as reduced frequency
of snubber testing, increased safety system unavailability and the
treatment of snubbers impacting multiple trains.
3.1.2 Identification of High-Risk Configurations
The second tier of the three-tiered approach recommended in RG
1.177 involves the identification of potentially high-risk
configurations that could exist if equipment, in addition to that
associated with the TS change, were to be taken out of service
simultaneously. Insights from the risk assessments, in conjunction with
important assumptions made in the analysis and defense-in-depth
considerations, were used to identify such configurations. To avoid
these potentially high-risk configurations, specific restrictions to
the implementation of the proposed TS changes were identified.
For cases where all inoperable snubbers are associated with only
one train (or subsystem) of the impacted systems (i.e., when LCO 3.0.8a
applies), it was assumed in the analysis that there will be unaffected
redundant trains (or subsystems) available to mitigate the seismically
initiated LOOP accident sequences. This assumption implies that there
will be at least one success path available when LCO 3.0.8a applies.
Therefore, potentially high-risk configurations can be avoided by
ensuring that such a success path exists when LCO 3.0.8a applies. Based
on a review of the accident sequences that contribute to the risk
increase associated with LCO 3.0.8a, as modeled by the simplified
bounding analysis (i.e., accident sequences initiated by a seismically-
induced LOOP event with concurrent loss of all safety system trains
supported by the out of service snubbers), the following restrictions
were identified to prevent potentially high-risk configurations:
For PWR plants, at least one AFW train (including a
minimum set of supporting equipment required for its successful
operation) not associated with the inoperable snubber(s), must be
available when LCO 3.0.8a is used.
For BWR plants, one of the following two means of heat
removal must be available when LCO 3.0.8a is used:
--At least one high pressure makeup path (e.g., using high pressure
coolant injection (HPCI) or reactor core isolation cooling (RCIC) or
equivalent) and heat removal capability (e.g.,
[[Page 23260]]
suppression pool cooling), including a minimum set of supporting
equipment required for success, not associated with the inoperable
snubber(s), or
--At least one low pressure makeup path (e.g., low pressure coolant
injection (LPCI) or containment spray (CS)) and heat removal capability
(e.g., suppression pool cooling or shutdown cooling), including a
minimum set of supporting equipment required for success, not
associated with the inoperable snubber(s).
For cases where one or more of the inoperable snubbers are
associated with multiple trains (or subsystems) of the same safety
system (i.e., when LCO 3.0.8b applies), it was assumed in the bounding
analysis that all safety systems are unavailable to mitigate the
accident, except for West Coast plants. Credit for using F&B to provide
core cooling is taken for plants having F&B capability (e.g., Diablo
Canyon) when a snubber impacting more than one train of the AFW system
is inoperable. Credit for one AFW train to provide core cooling is
taken for West Coast PWR plants with no F&B capability (e.g., San
Onofre) because it has been determined that there is no single snubber
whose non-functionality would disable more than one train of AFW in a
seismic event of magnitude up to the plant's SSE. Based on a review of
the accident sequences that contribute to the risk increase associated
with LCO 3.0.8b (as modeled by the simplified bounding analysis) and
defense-in-depth considerations, the following restrictions were
identified to prevent potentially high-risk configurations:
LCO 3.0.8b cannot be used at West Coast PWR plants with no
F&B capability when a snubber whose non-functionality would disable
more than one train of AFW in a seismic event of magnitude up to the
plant's SSE is inoperable (it should be noted, however, that based on
information provided by the industry, there is no plant that falls in
this category)
When LCO 3.0.8b is used at PWR plants, at least one AFW
train (including a minimum set of supporting equipment required for its
successful operation) not associated with the inoperable snubber(s), or
some alternative means of core cooling (e.g., F&B, firewater system or
``aggressive secondary cooldown'' using the steam generators) must be
available.
When LCO 3.0.8b is used at BWR plants, it must be verified
that at least one success path exists, using equipment not associated
with the inoperable snubber(s), to provide makeup and core cooling
needed to mitigate LOOP accident sequences.
3.1.3 Configuration Risk Management
The third tier of the three-tiered approach recommended in RG 1.177
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. This objective is
met by licensee programs to comply with the requirements of paragraph
(a)(4) of the Maintenance Rule (10 CFR 50.65) to assess and manage risk
resulting from maintenance activities, and by the TS requiring risk
assessments and management using (a)(4) processes if no maintenance is
in progress. These programs can support licensee decision making
regarding the appropriate actions to manage risk whenever a risk-
informed TS is entered. Since the 10 CFR 50.65(a)(4) guidance, the
revised (May 2000) Section 11 of NUMARC 93-01, does not currently
address seismic risk, licensees adopting this change must ensure that
the proposed LCO 3.0.8 is considered with respect to other plant
maintenance activities and integrated into the existing 10 CFR
50.65(a)(4) process whether the process is invoked by a TS or (a)(4)
itself.
3.2 Summary and Conclusions
The option to relocate the snubbers to a licensee controlled
document, as part of the conversion to Improved STS, has resulted in
non-uniform and inconsistent treatment of snubbers. Some potential
undesirable consequences of this inconsistent treatment of snubbers
are:
Performance of testing during crowded windows when the
supported system is inoperable with the potential to reduce the snubber
testing to a minimum since the relocated snubber requirements are
controlled by the licensee.
Performance of testing during crowded windows when the
supported system is inoperable with the potential to increase the
unavailability of safety systems.
Performance of testing and maintenance on snubbers
affecting multiple trains of the same supported system during the 7
hours allotted before entering MODE 3 under LCO 3.0.3.
To remove the inconsistency among plants in the treatment of
snubbers, licensees are proposing a risk-informed TS change which
introduces a delay time before entering the actions for the supported
equipment when one or more snubbers are found inoperable or removed for
testing. Such a delay time will provide needed flexibility in the
performance of maintenance and testing during power operation and at
the same time will enhance overall plant safety by (1) avoiding
unnecessary unscheduled plant shutdowns, thus, minimizing plant
transition and realignment risks; (2) avoiding reduced snubber testing,
thus, increasing the availability of snubbers to perform their
supporting function; (3) performing most of the required testing and
maintenance during the delay time when the supported system is
available to mitigate most challenges, thus, avoiding increases in
safety system unavailability; and (4) providing explicit risk-informed
guidance in areas in which that guidance currently does not exist, such
as the treatment of snubbers impacting more than one redundant train of
a supported system.
The risk impact of the proposed TS changes was assessed following
the three-tiered approach recommended in RG 1.177. A simplified
bounding risk assessment was performed to justify the proposed TS
changes. This bounding assessment assumes that the risk increase
associated with the proposed addition of LCO 3.0.8 to the TS is
associated with accident sequences initiated by a seismically-induced
LOOP event with concurrent loss of all safety system trains supported
by the out-of-service snubbers. In the case of snubbers associated with
more than one train, it is assumed that all affected trains of the
supported system are failed. This assumption was introduced to allow
the performance of a simple bounding risk assessment approach with
application to all plants and was selected due to the lack of detailed
plant-specific seismic risk assessments for most plants and the lack of
fragility data for piping when one or more supporting snubbers are
inoperable. The impact from the addition of the proposed LCO 3.0.8 to
the TS on defense-in-depth was also evaluated in conjunction with the
risk as