Proposed Generic Communication; Grid Reliability and the Impact on Plant Risk and the Operability of Offsite Power, 19125-19132 [E5-1674]

Agencies

• NUCLEAR REGULATORY COMMISSION

[Federal Register Volume 70, Number 69 (Tuesday, April 12, 2005)]
[Notices]
[Pages 19125-19132]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E5-1674]


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NUCLEAR REGULATORY COMMISSION


Proposed Generic Communication; Grid Reliability and the Impact 
on Plant Risk and the Operability of Offsite Power

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is proposing to 
issue a generic letter (GL) to request that addressees submit 
information to the NRC concerning the status of their compliance with 
GDC 17, 10 CFR 50.63, 10 CFR 50.65, and plant technical specifications 
governing electric power in accordance with 10 CFR 50.54(f). This 
request is to obtain information from addressees in four areas: (1) Use 
of nuclear power plant/transmission system operator protocols and real 
time contingency analysis programs to monitor grid conditions to 
determine operability of offsite power systems under plant technical 
specifications, (2) use of nuclear power plant/transmission system 
operator protocols and real time contingency analysis programs to 
monitor grid conditions for consideration in maintenance risk 
assessments, (3) offsite power restoration procedures in accordance 
with Section 2 of Regulatory Guide 1.155, ``Station Blackout,'' and (4) 
losses of offsite power caused by grid failures at a frequency of >= 20 
Years in accordance with Regulatory Guide 1.155.
    This Federal Register notice is available through the NRC's 
Agencywide Documents Access and Management System (ADAMS) under 
accession number ML050810504.

DATES: Comment period expires June 13, 2005. Comments submitted after 
this date will be considered if it is practical to do so, but assurance 
of consideration cannot be given except for comments received on or 
before this date.

ADDRESSEES: Submit written comments to the Chief, Rules and Directives 
Branch, Division of Administrative Services, Office of Administration, 
U.S. Nuclear Regulatory Commission, Mail Stop T6-D59, Washington, DC 
20555-0001, and cite the publication date and page number of this 
Federal Register notice. Written comments may also be delivered to NRC 
Headquarters, 11545 Rockville Pike (Room T-6D59), Rockville, Maryland, 
between 7:30 am and 4:15 pm on Federal workdays.

FOR FURTHER INFORMATION, CONTACT: John G. Lamb at 301-415-1446 or by e-
mail at jgl1@nrc.gov or Jose Calvo at 301-415-2774 or by e-mail at 
jac7@nrc.gov.

SUPPLEMENTARY INFORMATION:

NRC Generic Letter 2005-XX: Grid Reliability and the Impact on Plant 
Risk and the Operability of Offsite Power

ADDRESSES: All holders of operating licenses for nuclear power reactors 
except those who have permanently ceased operations and have certified 
that fuel has been permanently removed from the reactor vessel.
    Purpose: In order to determine if compliance is being maintained 
with U.S. Nuclear Regulatory Commission (NRC) regulatory requirements 
governing electric power for your plant, the NRC is issuing this 
generic letter to obtain information from its licensees in four areas:
    (1) Use of nuclear power plant/transmission system operator 
protocols and real time contingency analysis programs to monitor grid 
conditions to determine operability of offsite power systems under 
plant technical specifications
    (2) Use of nuclear power plant/transmission system operator 
protocols and real time contingency analysis programs to monitor grid 
conditions for consideration in maintenance risk assessments
    (3) Offsite power restoration procedures in accordance with Section 
2 of Regulatory Guide 1.155, ``Station Blackout''
    (4) Losses of offsite power caused by grid failures at a frequency 
of >= 20 Years

[[Page 19126]]

in accordance with Regulatory Guide 1.155.
    Pursuant to 10 CFR 50.54(f), addressees are required to submit a 
written response to this generic letter.

Background

    Based on information obtained from inspections and risk insights 
developed by an internal NRC expert panel, and further described below, 
the staff is concerned with several conditions associated with 
assurance of grid reliability such that compliance with applicable 
regulations may not be assured. Use of long term periodic grid studies 
and informal communication arrangements to monitor real time grid 
operability, potential shortcomings in grid reliability evaluations 
performed as part of maintenance risk assessments, lack of 
preestablished arrangements identifying local grid power sources and 
transmission paths, and potential elimination of grid events from 
operating experience are some conditions that could potentially impact 
compliance. The staff identified these issues as a result of 
considering the August 14, 2003 blackout event.
    On August 14, 2003, the largest power outage in U.S. history 
occurred in the Northeastern United States and parts of Canada. Nine 
U.S. nuclear power plants (NPPs) tripped. Eight of these, along with 
one NPP that was already shut down, lost offsite power. The length of 
time until power was available to the switchyard ranged from 
approximately 1 hour to six and one-half hours. Although the onsite 
emergency diesel generators (EDGs) functioned to maintain safe shutdown 
conditions, this event was significant in terms of the number of plants 
affected and the duration of the power outage.
    The loss of all alternating current (AC) power to the essential and 
nonessential switchgear buses at a NPP involves the simultaneous loss 
of offsite power (LOOP), turbine trip, and the loss of the onsite 
emergency power supplies (typically EDGs). Such an event is referred to 
as a station blackout (SBO). Risk analyses performed for NPPs indicate 
that the loss of all AC power can be a significant contributor to the 
core damage frequency. Although NPPs are designed to cope with a LOOP 
event through the use of onsite power supplies, LOOP events are 
considered precursors to SBO. An increase in the frequency or duration 
of LOOP events increases the probability of core damage.
    The NRC issued a regulatory issue summary (RIS 2004-5, ``Grid 
Operability and the Impact on Plant Risk and the Operability of Offsite 
Power,'' dated April 15, 2004) to advise NPP addressees of the 
requirements in Section 50.65 of Title 10 of the Code of Federal 
Regulations (10 CFR 50.65), ``Requirements for monitoring the 
effectiveness of maintenance at nuclear power plants''; 10 CFR 50.63, 
``Loss of all alternating current power''; 10 CFR Part 50, Appendix A, 
General Design Criterion (GDC) 17, ``Electric power systems''; and 
plant technical specifications on operability of offsite power. In 
addition, the NRC issued Temporary Instruction (TI) 2515/156, ``Offsite 
Power System Operational Readiness,'' dated April 29, 2004, which 
instructed the regional offices to perform follow up inspections at 
plant sites on the issues identified in the RIS. The NRC needs 
additional information from its licensees in the four areas identified 
above in order to determine if regulatory compliance is being 
maintained.

Applicable Regulatory Requirements

GDC 17 and Plant Technical Specifications (TSs)

    For NPPs licensed in accordance with the GDC in Appendix A to 10 
CFR Part 50, the design criteria for onsite and offsite electrical 
power systems are provided in GDC 17. For NPPs not licensed in 
accordance with the GDC in Appendix A, the applicable design criteria 
are provided in the updated final safety analysis report. These reports 
set forth criteria similar to GDC 17, which requires, among other 
things, that an offsite electric power system be provided to permit the 
functioning of certain structures, systems, and components (SSCs) 
important to safety in the event of anticipated operational occurrences 
and postulated accidents.
    The transmission network (grid) is the source of power to the 
offsite power system. The final paragraph of GDC 17 requires, in part, 
provisions to minimize the probability of the loss of power from the 
transmission network given a loss of power generated by the nuclear 
power unit. The loss of power generated by the nuclear power unit 
(trip) is an anticipated operational occurrence. It is therefore 
necessary that the offsite power circuits be designed to be available 
following a trip of the unit in order to permit the functioning of SSCs 
necessary to respond to the event.
    The trip of an NPP, however, can affect the grid so as to result in 
a LOOP. Foremost among such effects is a reduction in the plant's 
switchyard voltage as a result of the loss of the reactive power supply 
to the grid from the NPP's generator. If the voltage is low enough, the 
plant's degraded voltage protection could actuate and separate the 
plant safety buses from offsite power. A less likely event would be 
that the trip of a nuclear plant causes grid instability, potential 
grid collapse, and subsequent LOOP due to the loss of the real and/or 
reactive power support supplied to the grid from the plant's generator.
    In general, plant TSs require the offsite power system to be 
operable as part of the limiting condition for operation and specify 
what actions to be taken when the offsite power system is not operable. 
Plant operators should therefore be aware of (1) the capability of the 
offsite power system to supply power, as specified by TS, during 
operation and (2) situations that can result in a LOOP following a trip 
of the plant. If the offsite power system is not capable of providing 
the requisite power in either situation, the system should be declared 
inoperable and pertinent plant TS provisions followed.

10 CFR 50.65

    Section 50.65(a)(4) requires that licensees assess and manage the 
increase in risk that may result from proposed maintenance activities 
before performing the maintenance activities. These activities include, 
but are not limited to, surveillances, post-maintenance testing, and 
corrective and preventive maintenance. The scope of the assessment may 
be limited to structures, systems, and components (SSCs) that a risk-
informed evaluation process has shown to be significant to public 
health and safety.
    In NRC Regulatory Guide (RG) 1.182, the NRC endorsed the February 
22, 2000, revision to Section 11 of NUMARC 93-01, Revision 2, as 
providing methods that are acceptable for meeting 10 CFR 50.65(a)(4). 
The revised Section 11 addressed grid stability and offsite power 
availability in several areas. Section 11.3.2.8 states:

Emergent conditions may result in the need for action prior to 
conduct of the assessment, or could change the conditions of a 
previously performed assessment. Examples include plant 
configuration or mode changes, additional SSCs out of service due to 
failures, or significant changes in external conditions (weather, 
offsite power availability) [emphasis added].

    Additionally, Section 11.3.4 states, in part, that ``the assessment 
for removal from service of a single SSC for the planned amount of time 
may be limited to the consideration of unusual external conditions that 
are present or imminent (e.g., severe weather, offsite power 
instability)'' [emphasis added].
    Accordingly, licensees should perform grid reliability evaluations 
as

[[Page 19127]]

part of the maintenance risk assessment required by 10 CFR 50.65 before 
taking a risk-significant piece of equipment (including but not limited 
to an EDG, a battery, a steam-driven pump, an alternate AC power 
source, etc.) out of service to do maintenance activities, including 
surveillances, post-maintenance testing, and corrective and preventive 
maintenance. The likelihood of LOOP and SBO should be considered in the 
maintenance risk assessment, whether quantitatively or qualitatively. 
If the grid reliability evaluation indicates that marginally adequate 
grid conditions may exist during maintenance activities, the licensee 
should consider rescheduling maintenance activities that tend to 
increase the LOOP frequency or reduce the capability to cope with a 
LOOP or SBO. If there is some overriding need to perform maintenance on 
risk-significant equipment under conditions of degraded grid stability, 
the licensee should consider alternate equipment protection measures 
and compensatory actions to reduce the risk. With regard to conditions 
that emerge during a maintenance activity in progress, Section 11.3.2.8 
in NUMARC 93-01, Revision 2, states that emergent conditions could 
change the conditions of a previously performed risk assessment. 
Offsite power availability is one of the examples given of an emergent 
condition that could change the conditions of a previously performed 
risk assessment. Therefore, licensees should reassess the plant risk in 
view of an emergent condition, taking the worsening grid condition into 
account. However, this reassessment of the risk should not interfere 
with or delay measures to place and maintain the plant in a safe 
condition in response to or preparation for those worsening grid 
conditions. 10 CFR 50.63
    Pursuant to 10 CFR 50.63, ``Loss of all alternating current 
power,'' the NRC requires that each NPP licensed to operate be able to 
withstand an SBO for a specified duration and recover from the SBO. NRC 
Regulatory Guide (RG) 1.155 provides guidance for licensees to use in 
developing their approach for complying with 10 CFR 50.63. The RG has a 
series of tables that define a set of pertinent plant and plant site 
parameters that have been found to affect the likelihood of a plant 
experiencing an SBO event of a given duration. Using the tables allows 
a licensee to determine a plant's relative vulnerability to SBO events 
of a given duration and identify an acceptable minimum SBO coping 
duration for the plant. With regard to grid-related losses of offsite 
power, Table 4 in RG 1.155 indicates that the following plant sites 
should be assigned to Offsite Power Design Characteristic Group P3:

Sites that expect to experience a total loss of offsite power caused 
by grid failures at a frequency equal to or greater than once in 20 
site-years, unless the site has procedures to recover AC power from 
reliable alternative (nonemergency) ac power sources within 
approximately one-half hour following a grid failure.

    The majority of U.S. NPPs fall into the 4-hour minimum coping 
capability category set forth in RG 1.155. Table 2 in RG 1.155, 
however, indicates that a typical plant with two redundant EDGs per 
nuclear unit should have at least an 8-hour minimum coping duration if 
it falls into the P3 group. Therefore, plants that have experienced a 
grid-related LOOP since they were evaluated in accordance with the SBO 
guidance in RG 1.155 may no longer be consistent with that guidance.
    Section 2 of RG 1.155 provides guidance on the procedures necessary 
to restore offsite power, including losses following ``grid 
undervoltage and collapse.'' Section 2 states: ``Procedures should 
include the actions necessary to restore offsite power and use nearby 
power sources when offsite power is unavailable.'' These procedures are 
a necessary element in minimizing LOOP durations following a LOOP or 
SBO event.

Discussion

Use of Nuclear Power Plant/Transmission System Operator Protocols and 
Real Time Contingency Analysis Programs To Monitor Grid Conditions To 
Determine Operability of Offsite Power Systems Under Plant Technical 
Specifications

    As discussed above, a licensee's ability to comply with TS 
governing offsite power may depend on grid conditions and plant status, 
in particular, maintenance being performed on, and inoperability of, 
key elements of the plant switchyard and offsite power grid can affect 
the operability of the offsite power system, particularly during times 
of high grid load and high grid stress. A communication interface with 
the plant's transmission system operator (TSO), together with other 
local means used to maintain NPP operator awareness of changes in the 
plant switchyard and offsite power grid, is important to enable the 
licensee to determine the effects of these changes on operability of 
the offsite power system. The staff found a good deal of variability in 
the TI 2515/156 responses on the use of these NPP/TSO communication 
protocols. Some licensees appear to be relying on informal NPP/TSO 
communication arrangements and long term grid studies without real time 
control of operation to within the limits of the studies to assure 
offsite power operability. However, the staff also learned that most 
TSOs serving NPP sites now have, or will shortly have, enhanced 
computer capability in the form of real time contingency analysis 
(RTCAs) programs.
    The RTCAs give the TSO the capability to determine the impact of 
the loss or unavailability of various transmission system elements 
(called contingencies) on the condition of the transmission system. The 
transmission systems can generally cope with a number of contingencies 
without undue impairment of grid reliability, but it is important for 
the NPP operator to know when the transmission system near the NPP can 
no longer sustain NPP voltage based on the TSO's analysis of a 
reasonable level of contingencies. This knowledge can help the operator 
understand the general condition of the NPP offsite power system. In 
order to satisfy the maintenance rule, the NPP operator should know the 
grid's condition before taking a risk-significant piece of equipment 
out of service and monitor it for as long as the equipment remains out 
of service.
    It is especially important for the NPP operator to know when the 
trip of the NPP will result in the loss of offsite power to the plant. 
As indicated in RIS 2004-05, a reduction in NPP switchyard voltage due 
to a trip is the main cause of a LOOP event. It is important to 
understand that the transmission systems can generally tolerate 
voltages lower than those required for NPP SSC operability. As a 
result, the TSO will not necessarily keep the transmission system 
voltage above the level needed for the NPP unless the TSO has been 
informed of the needed voltage level, and agreements have been 
formalized to maintain the voltage level. It was not always clear from 
the data collected in accordance with TI 2515/156 whether the TSO would 
notify the NPP of inadequate transmission system contingency voltages 
or inadequate voltages required for the NPP SSC operability.
    Inadequate NPP contingency post-trip switchyard voltages will 
result in TS inoperability of the NPP offsite power system due to 
actuation of NPP degraded voltage protection circuits during certain 
events that result in an NPP trip. Occasionally NPPs of certain designs 
have experienced other inoperabilities under these

[[Page 19128]]

circumstances (e.g., overloaded EDGs or loss of certain safety features 
due to interaction with circuit breaker logic). Safety-related motors 
may also be started more than once under these circumstances, which 
could result in operation outside the motors' specifications and 
actuation of overload protection. Unavailability of plant controlled 
equipment such as voltage regulators, transformer auto tap changers, 
and generator automatic voltage regulation can contribute to the more 
frequent occurrence of inadequate NPP post-trip voltages.
    The RTCA programs in use by the TSOs, together with properly 
implemented NPP/TSO communication protocols, can keep NPP operators 
better informed about conditions affecting the NPP offsite power 
system. However, the RTCA programs are not always available to the TSO. 
This was the case during the period leading up to the August 14, 2003, 
blackout; and events have demonstrated the data used in the programs 
sometimes do not represent actual conditions and capabilities. These 
shortcomings have been offset to some degree by notification of RTCA 
unavailability to NPP operators and their subsequent performance of 
operability determinations and by verification of the actual post-trip 
switchyard voltages following inadvertent NPP trips.

Use of Nuclear Power Plant/Transmission System Operator Protocols To 
Monitor Grid Conditions for Consideration in Maintenance Risk 
Assessments

    As set forth above, grid reliability evaluations should be 
performed as part of the maintenance risk assessment required by 10 CFR 
50.65 before taking a risk-significant piece of equipment (including 
but not limited to an EDG, a battery, a steam-driven pump, an alternate 
AC power source, etc.) out of service to do maintenance activities, 
including surveillances, post-maintenance testing, and corrective and 
preventive maintenance. Further, worsening grid conditions that emerge 
during a maintenance activity in progress could affect offsite power 
availability, thereby changing the conditions of a previously performed 
assessment. A licensee should therefore reassess the plant risk under 
such circumstances, taking the worsening grid condition into account. 
An internal NRC expert panel convened to obtain short-term grid-related 
risk insights found that it is important to have effective NPP 
configuration risk management, as required by the Maintenance Rule, 
during periods when the grid is degraded. In particular, a potentially 
significant increase in NPP risk may occur if equipment required to 
prevent and mitigate station blackout is unavailable when the grid is 
degraded.
    Recent NRC studies have found that, since 1997, LOOP events have 
occurred more frequently during the summer (May-October), than before 
1997, the probability of a LOOP event due to a reactor trip has also 
increased during the summer months, and the durations of LOOP events 
have generally increased. The staff is concerned about extended 
maintenance activities scheduled for equipment required to prevent and 
mitigate station blackout during these months, especially in areas of 
the country that experience a high level of grid stress.
    The staff found a good deal of variability in the data collected in 
accordance with TI 2515/156 regarding grid reliability evaluations 
performed before taking risk-significant equipment out of service. Some 
NPPs communicate routinely with their TSOs once per shift to determine 
grid conditions, while others rely solely upon the TSOs to inform them 
of deteriorating grid conditions and do not inquire about grid 
conditions prior to taking risk-significant equipment out of service. 
Some do not consider the NPP post-trip switchyard voltages in their 
evaluations, and some do not coordinate risk-significant equipment 
maintenance with their TSOs.
    The NPP/TSO communication protocol is a useful tool to obtain the 
information necessary for the grid reliability evaluations performed as 
part of the maintenance risk assessment required by 10 CFR 50.65 before 
a risk-significant piece of equipment is removed from service. Such a 
protocol is also useful in conforming to the guidance in NUMARC 9301, 
Rev. 2 for reassessing plant risk in light of emergent conditions. As 
discussed under the previous topic, the RTCAs available to most TSOs 
give them the capability to determine the impact of various 
transmission system contingencies on the condition of the transmission 
system. It is important that the NPP operator know when the 
transmission system near the NPP cannot sustain a reasonable level of 
contingencies. The NPP operator should know the general condition of 
the NPP offsite power system before removing an SSC from service under 
the maintenance rule and for as long as the equipment remains out of 
service.

Offsite Power Restoration Procedures in Accordance With Section 2 of 
Regulatory Guide 1.155

    LOOP events can also have numerous unpredictable initiators, such 
as natural events, potential adversaries, human error, or design 
problems. Pursuant to 10 CFR 50.63, ``Loss of all alternating current 
power,'' the NRC requires that each NPP licensed to operate be able to 
withstand a station blackout (SBO) for a specified duration and recover 
from the SBO. NRC Regulatory Guide (RG) 1.155 provides NRC guidance for 
licensees to use in developing their approaches for complying with 10 
CFR 50.63. Section 2 of RG 1.155 provides guidance on the procedures 
necessary to restore offsite power, including losses following ``grid 
undervoltage and collapse.'' Section 2 states: ``Procedures should 
include the actions necessary to restore offsite power and use nearby 
power sources when offsite power is unavailable.''
    Preestablished agreements with NPP TSOs that identify local power 
sources and transmission paths that could be made available to resupply 
NPPs following a LOOP event help to minimize the durations of LOOP 
events, especially unpredictable LOOP events. Discussions with NPP 
licensees indicate that some licensees do not have such agreements in 
place, but instead attempt restoration of their EDGs following a 
potential SBO. RIS 2004-05 states that NPPs should have procedures 
available consistent with the guidance in Section 2 of RG 1.155 for 
restoration of offsite power following a LOOP or SBO event.

Losses of Offsite Power Caused by Grid Failures at a Frequency of >= 20 
Years in Accordance With Regulatory Guide 1.155

    The data collected in accordance with TI2515/156 indicate that some 
nuclear power plants have experienced grid-related LOOP events since 
the nuclear power plants were initially analyzed in accordance with the 
criteria in RG 1.155. The staff is concerned that these nuclear power 
plants have not been reanalyzed to determine whether their SBO coping 
durations remain consistent with the guidance in RG 1.155 subsequent to 
these LOOP events. The staff is also concerned that some plants may be 
inappropriately eliminating some of these grid events from their 
operating experience data base.
    In view of the above, power reactor licensees may depend on 
information obtained from their TSOs in order to make operability 
determinations for TS compliance; to perform risk assessments under the 
maintenance rule; and to assure compliance with the SBO rule.

[[Page 19129]]

Accordingly, the NRC staff is requesting information on such matters 
from addresses. The NRC staff has not, however, identified any 
corrective actions that might be warranted.

Requested Information

    In accordance with 10 CFR 50.54(f), addressees are required to 
submit written responses to this generic letter within 60 days of its 
date.
    In their responses, addressees are requested to answer the 
following questions and provide the information to the NRC with respect 
to each of their NPPs:

Use of Nuclear Power Plant/transmission System Operator Protocols and 
Real Time Contingency Analysis Programs To Monitor Grid Conditions in 
Accordance With GDC 17 and To Determine Operability of Offsite Power 
Systems Under Plant Technical Specifications

    1. General Design Criterion (GDC) 17, ``Electric power systems,'' 
of Appendix A, ``General Design Criteria for Nuclear Power Plants,'' to 
Title 10, Part 50, of the Code of Federal Regulations (CFR) requires, 
in part, that licensees minimize the probability of the loss of power 
from the transmission network given a loss of power generated by the 
nuclear power unit. In order to determine if you have taken the 
necessary steps to minimize the probability of loss of offsite power 
(LOOP) following a reactor trip in accordance with GDC 17, describe 
what formal agreements you have for your transmission system operator 
(TSO) to promptly notify you when conditions of the surrounding grid 
are such that degraded voltage (i.e., below TS requirements) or LOOP 
could occur following a trip of the reactor unit. Would the low 
switchyard voltage initiate operation of plant degraded voltage 
protection?
    Specifically, what is the time period required for the 
notification? Do you have procedures to periodically check with the TSO 
to determine the grid condition and ascertain any conditions that would 
require a notification? Describe the grid conditions that would trigger 
a notification.
    If you do not have a formal agreement with your TSO, please 
describe why you believe you comply with the provisions of GDC 17 as 
stated above, or describe what actions you intend to take to establish 
the necessary formal agreement with your TSO.
    2. GDC 17 requires, in part, that licensees minimize the 
probability of the loss of power from the transmission network given a 
loss of power generated by the nuclear power unit. In order to 
determine if you have taken the necessary steps to minimize the 
probability of LOOP following a reactor trip in accordance with GDC 17, 
describe how you ensure that the offsite power system will remain 
operable following a trip of your NPP.
    We are particularly interested in information regarding whether 
your NPP's TSO uses a real-time contingency analysis (RTCA) program to 
determine grid conditions that would make the NPP offsite power system 
inoperable in the event of various contingencies? The type of 
information we are interested in includes the following: Does your 
NPP's TSO use the RTCA program as the basis for notifying the NPP when 
such a condition is identified? Would the RTCA program utilized by your 
TSO identify the condition where a trip of the NPP results in 
switchyard voltages (immediately and/or long-term) below the minimum TS 
requirements and operation of plant degraded voltage protection? How 
frequently does the RTCA program update? Provide details of RTCA-
identified contingency conditions that would trigger an NPP 
notification from the TSO. Is the NPP notified of periods when the RTCA 
program is unavailable to the TSO, and does the NPP conduct an offsite 
power system operability determination when such a notification is 
received? Subsequent to an unscheduled inadvertent trip of the NPP, are 
the resultant switchyard voltages verified by procedure to be bounded 
by the voltages predicted by the RTCA?
    If a RTCA program is not available to the NPP's TSO, are there any 
plans for the TSO to obtain one? If so, on what schedule? If an RTCA 
program is not available, does your TSO perform periodic studies to 
verify that adequate offsite power capability, including adequate NPP 
post-trip switchyard voltages (immediate and/or long-term), will be 
available to the NPP over the projected time frame of the study? Are 
the key assumptions and parameters of these periodic studies translated 
into TSO guidance to ensure that the transmission system is operated 
within the bounds of the analyses? If the bounds of the analyses are 
exceeded, does this condition trigger the notification provisions 
discussed in question 1 above?
    If your TSO does not use, or you do not have access to the results 
of a RTCA program, or that your TSO does not perform and make available 
to you periodic studies that determine the adequacy of offsite power 
capability; please describe why you believe you comply with the 
provisions of GDC 17 as stated above, or describe what actions you 
intend to take to ensure that the offsite power system will be 
sufficiently reliable and remain operable with high probability 
following a trip of your NPP.
    3. GDC 17 requires, in part, that licensees minimize the 
probability of the loss of power from the transmission network given a 
loss of power generated by the nuclear power unit. NPP TS requirements 
also require that the plant's offsite power system be operable as part 
of the plant's limiting conditions of operation. In order to determine 
if you have taken the necessary steps to minimize the probability of 
LOOP following a reactor trip in accordance with GDC 17 and your plant 
TS, describe how you ensure that the NPP's offsite power system and 
safety-related components will remain operable when degraded switchyard 
voltages are present.
    Specifically, when the TSO notifies the NPP operator a trip of the 
NPP would result in switchyard voltages (immediately and/or long term) 
below TS minimum requirements and would result in operation of plant 
degraded voltage protection, is the NPP offsite power system declared 
inoperable under the plant TSs? If not, why not? If onsite safety-
related equipment (e.g., emergency diesel generators or safety-related 
motors) are lost and incapable of performing their required safety 
functions as a result of responding to an emergency actuation signal 
during this condition, are they declared inoperable as well? If not, 
why not? Do you evaluate onsite safety-related equipment to determine 
whether it will operate as designed during this condition? When the NPP 
is notified by the TSO of other grid conditions that may impair the 
capability or availability of offsite power, are any plant TS action 
statements entered? If so, please identify them. If you believe your 
plant TS does not require you to declare your offsite power system or 
safety-related equipment inoperable in any of the aforementioned 
scenarios, describe why you believe you comply with the provisions of 
GDC 17 and your plant TS as stated above, or describe what actions you 
intend to take to ensure that the offsite power system and safety-
related components will remain operable when degraded switchyard 
voltages are present.
    4. GDC 17 requires, in part, that licensees minimize the 
probability of the loss of power from the transmission network given a 
loss of power generated by the nuclear power unit. NPP TS requirements 
also require that the plant's offsite power system be operable as part 
of the plant's limiting conditions

[[Page 19130]]

of operation. In order to determine if you have taken the necessary 
steps to minimize the probability of LOOP following a reactor trip in 
accordance with GDC 17 and your plant TS, describe how you ensure that 
the offsite power system will remain operable following a trip of your 
NPP.
    Specifically, do the NPP operators have any guidance in plant TS 
Bases sections, the Final Safety Analysis Report, or plant procedures 
regarding situations where the condition of plant-controlled or -
monitored equipment (e.g., voltage regulators, auto tap changing 
transformers, capacitors, static VAR compensators, main generator 
voltage regulators, etc.) can adversely affect the operability of the 
NPP offsite power system? If your TS Bases sections, the Final Safety 
Analysis Report, or plant procedures do not provide guidance regarding 
situations where the condition of plant-controlled or -monitored 
equipment can adversely affect the operability of the NPP offsite power 
system, describe why you believe you comply with the provisions of GDC 
17 and the plant TS as stated above, or describe what actions you 
intend to take to ensure that guidance exists to address situations 
where the condition of plant-controlled or -monitored equipment can 
adversely affect the operability of the NPP offsite power system.

Use of Nuclear Power Plant/Transmission System Operator Protocols To 
Monitor Grid Conditions for Consideration in Maintenance Risk 
Assessments Required by 10 CFR 50.65

    5. 10 CFR 50.65(a)(4) requires that licensees assess and manage the 
increase in risk that may result from proposed maintenance activities 
before performing the maintenance activities. As set forth above, grid 
reliability evaluations should be performed as part of the maintenance 
risk assessment required by 10 CFR 50.65 before taking a risk-
significant piece of equipment (including but not limited to an EDG, a 
battery, a steam-driven pump, an alternate AC power source, etc.) out 
of service to do maintenance activities, including surveillances, post-
maintenance testing, and corrective and preventive maintenance. In 
order to determine if you have taken the necessary steps to assess and 
manage the increase in risk that may result from proposed maintenance 
activities before performing the maintenance activities, please 
describe how you perform the grid reliability evaluations as part of 
the maintenance risk assessment required by 10 CFR 50.65.
    Specifically, is a grid reliability evaluation performed at your 
NPP as part of the maintenance risk assessment required by 10 CFR 
50.65, before taking a risk-significant piece of equipment (including 
an EDG, a battery, a steam-driven pump, an alternate AC power source, 
etc.) out of service to do maintenance activities, including 
surveillances, post-maintenance testing, and corrective and preventive 
maintenance? Are seasonal variations in the probability of a LOOP at 
your plant site considered in the evaluation? Is the summer (May-
October) a period of peak stress on the grid surrounding your NPP site? 
Do you contact the TSO to determine current and anticipated grid 
conditions as part of the grid reliability evaluation performed prior 
to taking risk-significant equipment out of service? Do you use a 
formal agreement or use formal procedures with your TSO, or do you 
contact the TSO periodically over the course of the out-of-service 
condition to check for a worsening grid condition that could emerge 
during a maintenance activity in progress? Is the TSO expected to 
notify the NPP of such a condition?
    If a grid reliability evaluation that includes consideration of 
seasonal variations in LOOP probability is not performed as part of the 
maintenance risk assessment required by 10 CFR 50.65, and a formal 
agreement with the TSO or formal procedures to aid in the communication 
between the NPP and TSO are nonexistent (i.e., not part of the 
maintenance risk assessment required by 10 CFR 50.65), describe why you 
believe you comply with the provisions of 10 CFR 50.65(a)(4) as stated 
above; or describe what actions you intend to take to ensure that the 
increase in risk that may result from proposed maintenance activities 
is assessed and managed in accordance with 10 CFR 50.65(a)(4).
    6. 10 CFR 50.65(a)(4) requires that licensees assess and manage the 
increase in risk that may result from proposed maintenance activities 
before performing the maintenance activities. As set forth above, grid 
reliability evaluations should be performed as part of the maintenance 
risk assessment required by 10 CFR 50.65 before taking a risk-
significant piece of equipment out of service to do maintenance 
activities, including surveillances, post-maintenance testing, and 
corrective and preventive maintenance. In order to determine if you 
have taken the necessary steps to assess and manage the increase in 
risk that may result from proposed maintenance activities before 
performing the maintenance activities, please describe how you perform 
the grid reliability evaluations as part of the maintenance risk 
assessment required by 10 CFR 50.65.
    Specifically, does the TSO coordinate transmission system 
maintenance activities that can have an impact on the NPP operation 
with the NPP operator? Does the NPP operator coordinate NPP maintenance 
activities that can have an impact on the transmission system with the 
TSO? How are these matters accomplished?
    If there is no coordination between the NPP operator and the TSO 
regarding transmission system maintenance or NPP maintenance 
activities, describe why you believe you comply with the provisions of 
10 CFR 50.65(a)(4) as stated above, or describe what actions you intend 
to take to ensure that the increase in risk that may result from 
proposed maintenance activities is assessed and managed in accordance 
with 10 CFR 50.65(a)(4).

Offsite Power Restoration Procedures in Accordance With 10 CFR 50.63 as 
Developed in Section 2 of Regulatory Guide 1.155

    7. Pursuant to 10 CFR 50.63, the NRC requires that each NPP 
licensed to operate be able to withstand a SBO for a specified duration 
and recover from the SBO. NRC Regulatory Guide (RG) 1.155 provides 
guidance for licensees to use in developing their approach for 
complying with 10 CFR 50.63. In order to determine if your current 
practices are consistent with the SBO requirements of 10 CFR 50.63 as 
developed in RG 1.155 please address the following:
    Consistent with the recommendations in Section 2 of RG 1.155, it is 
expected that you have established an agreement with your plant's TSO 
that identify local power sources and transmission paths that could be 
made available to resupply your plant following a LOOP event. Briefly 
describe any agreement made with the TSO.
    If you have not established an agreement with your plant's TSO that 
identifies local power sources and transmission paths that could be 
made available to resupply your plant following a LOOP event, describe 
why you believe you comply with the provisions of 10 CFR 50.63 as 
developed in RG 1.155, or describe what actions you intend to take to 
establish such an agreement with your plant's TSO.

Losses of Offsite Power Caused by Grid Failures at a Frequency of >=20 
Years in Accordance With 10 CFR 50.63 as Developed in Table 4 of 
Regulatory Guide 1.155

    8. Pursuant to 10 CFR 50.63, the NRC requires that each NPP 
licensed to operate be able to withstand a SBO for a specified duration 
and recover from

[[Page 19131]]

the SBO. NRC Regulatory Guide (RG) 1.155 provides guidance for 
licensees to use in developing their approach for complying with 10 CFR 
50.63. In order to determine if your current practices are consistent 
with the SBO requirements of 10 CFR 50.63, describe how your NPP 
maintains its SBO coping capabilities in accordance with 10 CFR 50.63.
    Specifically, has your NPP site experienced a grid-related total 
loss of offsite power since its coping duration under 10 CFR 50.63 was 
initially determined? If so, has the NPP been reevaluated using the 
guidance in Table 4 of RG 1.155 to determine if it should be assigned 
to the P3 offsite power design characteristic group? What were the 
results of this reevaluation, and was the initially determined coping 
duration for the NPP adjusted?
    If your NPP site experienced a grid-related total LOOP since the 
coping duration under 10 CFR 50.63 was initially determined and has not 
been reevaluated using the guidance in Table 4 of RG 1.155, describe 
why you believe you comply with the provisions of 10 CFR 50.63 as 
stated above, or describe what actions you intend to take to ensure 
that the NPP maintains its SBO coping capabilities in accordance with 
10 CFR 50.63.

Actions To Ensure Compliance

    9. If you determine that any action is warranted to bring your NPP 
into compliance with NRC regulatory requirements, including TS, GDC 17, 
10 CFR 50.65(a)(4), or 10 CFR 50.53, describe the schedule for 
implementing it.
    The required written response should be addressed to the U.S. 
Nuclear Regulatory Commission, ATTN: Document Control Desk, 11555 
Rockville Pike, Rockville, Maryland 20852, under oath or affirmation 
under the provisions of Section 182a of the Atomic Energy Act of 1954, 
as amended, and 10 CFR 50.54(f). In addition, a copy of the response 
should be sent to the appropriate regional administrator.
    Addressees may request extension of the time in which a response to 
this generic letter is required in writing within 30 days of the date 
of this generic letter. The NRC will not grant such an extension except 
for good cause shown.
    An addressee should consult SECY-04-0191, ``Withholding Sensitive 
Unclassified Information Concerning Nuclear Power Reactors From Public 
Disclosure,'' dated October 19, 2004, to determine if its response 
contains sensitive unclassified (nonsafeguards) information and should 
be withheld from public disclosure. SECY-04-0191 is available on the 
NRC public Web site.

Reasons for Information Request

    This generic letter requests addressees to submit information. The 
requested information will enable the NRC staff to determine whether 
applicable requirements (plant TSs in conjunction with 10 CFR Part 50, 
Appendix A, General Design Criteria 17; 10 CFR 50.65(a)(4); and 10 CFR 
50.63) are being met in regard to the grid topics addressed.

Related Generic Communications

    NRC Regulatory Issue Summary 2004-05, ``Grid Reliability and the 
Impact on Plant Risk and the Operability of Offsite Power,'' dated 
April 15, 2004 (ADAMS Accession No. ML040990550).

Backfit Discussion

    Under the provisions of Section 182a of the Atomic Energy Act of 
1954, as amended, and 10 CFR 50.54(f), this generic letter transmits an 
information request for the purpose of verifying compliance with 
applicable existing requirements. Specifically, the requested 
information will enable the NRC staff to determine whether applicable 
requirements (plant TSs in conjunction with 10 CFR Part 50, Appendix A, 
General Design Criteria 17; 10 CFR 50.65(a)(4); and 10 CFR 50.63) are 
being met in regard to the grid topics addressed. No backfit is either 
intended or approved in the context of issuance of this generic letter. 
Therefore, the staff has not performed a backfit analysis.

Federal Register Notification

    A notice of opportunity for public comment on this generic letter 
was published in the Federal Register (xx FR xxxxx) on {date{time} . 
[Comments were received from {indicate the number of commentors by 
type{time} . The staff considered all comments that were received. The 
staff's evaluation of the comments is publicly available through the 
NRC's Agencywide Documents Access and Management System (ADAMS) under 
Accession No. ML05xxxxxxx.]

Small Business Regulatory Enforcement Fairness Act

    The NRC has determined that this action is not subject to the Small 
Business Regulatory Enforcement Fairness Act of 1996.

Paperwork Reduction Act Statement

    This generic letter contains information collection requirements 
that are subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 
et seq.). These information collections were approved by the Office of 
Management and Budget, approval number 3150-0011, which expires on 
February 28, 2007.
    The burden to the public for these mandatory information 
collections is estimated to average 60 hours per response, including 
the time for reviewing instructions, searching existing data sources, 
gathering and maintaining the data needed, and completing and reviewing 
the information collection. Send comments regarding this burden 
estimate or any other aspect of these information collections, 
including suggestions for reducing the burden, to the Records and FOIA/
Privacy Services Branch (T-5 F52), U.S. Nuclear Regulatory Commission, 
Washington, DC 20555-0001, or by Internet electronic mail to 
INFOCOLLECTS@NRC.GOV; and to the Desk Officer, Office of Information 
and Regulatory Affairs, NEOB-10202, (3150-0011), Office of Management 
and Budget, Washington, DC 20503.

Public Protection Notification

    The NRC may not conduct or sponsor, and a person is not required to 
respond to, a request for information or an information collection 
requirement unless the requesting document displays a currently valid 
OMB control number.

Contact

    Please direct any questions about this matter to the technical 
contact(s) or the Lead Project Manager listed below, or to the 
appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Bruce A. Boger, Director, Division of Inspection Program Management, 
Office of Nuclear Reactor Regulation.

    Technical Contact: James Lazevnick, NRR, 301-415-2782.
    Lead Project Manager: John Lamb, NRR, 301-415-1446.

End of Draft Generic Letter

    Documents may be examined, and/or copied for a fee, at the NRC's 
Public Document Room at One White Flint North, 11555 Rockville Pike 
(first floor), Rockville, Maryland. Publicly available records will be 
accessible electronically from the Agencywide Documents Access and 
Management System (ADAMS) Public Electronic Reading Room on the 
Internet at the NRC Web site, https://www.nrc.gov/NRC/ADAMS/. 
If you do not have access to ADAMS or if you have problems in accessing 
the documents in ADAMS, contact the NRC Public Document Room

[[Page 19132]]

(PDR) reference staff at 1-800-397-4209 or 301-415-4737 or by e-mail to 
pdr@nrc.gov.

    Dated at Rockville, Maryland, this 6th day of April 2005.

    For the Nuclear Regulatory Commission.
Patrick H. Hiland,
Chief, Reactor Operations Branch, Division of Inspection Program 
Management, Office of Nuclear Reactor Regulation.
[FR Doc. E5-1674 Filed 4-11-05; 8:45 am]
BILLING CODE 7590-01-P