[Federal Register Volume 76, Number 11 (Tuesday, January 18, 2011)]
[Notices]
[Pages 2924-2928]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-888]


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NUCLEAR REGULATORY COMMISSION

[NRC-2011-0013]


Proposed Generic Communications; Draft NRC Regulatory Issue 
Summary 2011-XX; Adequacy of Station Electric Distribution System 
Voltages

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC or the Commission) 
is issuing this Regulatory Issue Summary (RIS) to clarify the NRC 
staff's technical position on existing regulatory requirements and 
voltage studies necessary for Degraded Voltage Relay (second level 
undervoltage protection) setting bases and Transmission Network/
Offsite/Onsite station electric power system design bases. This RIS 
does not transmit any new requirements or staff positions. No specific 
action or written response is required.

DATES: Comment period expires 30 days after publication. 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.

ADDRESSES: You may submit comments by any one of the following methods. 
Please include Docket ID NRC-2011-0013 in the subject line of your 
comments. Comments submitted in writing or in electronic form will be 
posted on the NRC Web site and on the Federal Rulemaking Web site 
Regulations.gov. Because your comments will not be edited to remove any 
identifying or contact information, the NRC cautions you against 
including any information in your submission that you do not want to be 
publicly disclosed.
    The NRC requests that any party soliciting or aggregating comments 
received from other persons for submission to the NRC inform those 
persons that the NRC will not edit their comments to remove any 
identifying or contact information, and therefore, they should not 
include any information in their comments that they do not want 
publicly disclosed.
    Federal rulemaking Web site: Go to http://www.regulations.gov and 
search for documents filed under Docket ID NRC-2011-0013. Address 
questions about NRC dockets to Carol Gallagher, telephone: 301-492-
3668, e-mail: <a href="/cdn-cgi/l/email-protection#17547665787b3950767b7b76707f72655779657439707861"><span class="__cf_email__" data-cfemail="e1a280938e8dcfa6808d8d8086898493a18f9382cf868e97">[email protected]</span></a>.
    Mail comments to: Cindy Bladey, Chief, Rules, Announcements and 
Directives Branch (RADB), Division of Administrative Services, Office 
of Administration, Mail Stop: TWB-05-B01M, U.S. Nuclear Regulatory 
Commission, Washington, DC 20555-0001, or by fax to RADB at 301-492-
3446.

FOR FURTHER INFORMATION CONTACT: Kenn A. Miller, Office of Nuclear 
Reactor Regulation, Division of Engineer, U.S. Nuclear Regulatory 
Commission, Washington, DC 20555-0001, telephone: 301-415-3152, e-mail: 
<a href="/cdn-cgi/l/email-protection#dfb4bab1b1baabb7f1b2b6b3b3baaded9fb1adbcf1b8b0a9"><span class="__cf_email__" data-cfemail="8fe4eae1e1eafbe7a1e2e6e3e3eafdbdcfe1fdeca1e8e0f9">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: 

[[Page 2925]]

NRC Regulatory Issue Summary 2011-XX; Adequacy of Station Electric 
Distribution System Voltages

Addressees

    All holders of, or applicants for, a power reactor operating 
license or construction permit under Title 10 of the Code of Federal 
Regulations (10 CFR) Part 50, ``Domestic Licensing of Production and 
Utilization Facilities,'' except those who have permanently ceased 
operations and have certified that fuel has been permanently removed 
from the reactor vessel.
    All holders of, and applicants of design centers and combined 
operating licenses under 10 CFR Part 52, ``Licenses, Certificate and 
Approvals for Nuclear Power Plants.''

Intent

    The U.S. Nuclear Regulatory Commission (NRC or the Commission) is 
issuing this Regulatory Issue Summary (RIS) to clarify the NRC staff's 
technical position on existing regulatory requirements and voltage 
studies necessary for Degraded Voltage Relay (second level undervoltage 
protection) setting bases and Transmission Network/Offsite/Onsite 
station electric power system design bases. This RIS does not transmit 
any new requirements or staff positions. No specific action or written 
response is required.

Background

    The events at Millstone and Arkansas Nuclear One (ANO) that led to 
the NRC staff's position requiring degraded voltage protection for 
nuclear power plant Class 1E (or safety related) electrical safety 
buses and expectations for voltage calculations for the plant offsite/
onsite electric power system interface, are discussed below as a 
reminder of past operating experience.

Millstone Unit 2

    Electrical grid events at the Millstone Station, in July of 1976, 
have shown that when the Class 1E buses are supplied by the offsite 
power system, sustained degraded voltage conditions on the grid can 
cause adverse effects on the operation of Class 1E loads. These 
degraded voltage conditions will not be detected by the Loss-of-Voltage 
Relays (LVRs) which are designed to detect loss of power to the bus 
from the offsite circuit. The LVR's low voltage dropout setting is 
generally in the range of 0.7 per unit voltage or less, with a time 
delay of about 2 seconds.
    As a result of further evaluation of the Millstone events, it was 
also determined that improper voltage protection logic can also cause 
adverse effects on the Class 1E systems and equipment, such as spurious 
load shedding of Class 1E loads from the standby diesel generators and 
spurious separation of Class 1E systems from offsite power due to 
normal motor starting transients. See ADAMS Accession No. ML093521388 
for more information regarding this event.
    As a result of these Millstone events, the NRC required all 
licensees to implement degraded voltage protection under Generic Action 
(Multi-plant Action B-23) to ensure automatic protection of safety 
buses and loads. Since degradation of the offsite power system can lead 
to or cause the failure of redundant Class 1E safety related electrical 
equipment, the NRC required licensees to install degraded voltage 
protection schemes (second level of voltage protection (Degraded 
Voltage Relays (DVRs)) for the onsite power system) as described in NRC 
Letters dated June 2 & 3, 1977, ``Statement of Staff Positions Relative 
to Emergency Power Systems for Operating Reactors,'' which were sent to 
all licensees of all operating nuclear power plants. As an example, see 
the NRC letter dated June 2, 1977, ADAMS Accession No. ML100610489, 
sent to the licensee for Peach Bottom Atomic Power Station. These DVRs 
were to satisfy the following criteria:
    (a) The selection of voltage and time delay setpoints shall be 
determined from an analysis of the operating voltage requirements of 
the safety related loads at all onsite system distribution levels;
    (b) The voltage protection shall include coincidence logic to 
preclude spurious trips of the offsite power source;
    (c) The time delay selected shall be based on the following 
conditions:
    (1) The allowable time delay, including margin shall not exceed the 
maximum time delay that is assumed in the FSAR accident analyses;
    (2) The time delay shall override the effect of expected short 
duration grid disturbances, preserving availability of the offsite 
power source(s): and
    (3) The allowable time duration of a degraded voltage condition at 
all distribution system levels shall not result in failure of safety 
related systems or components;
    (d) The voltage monitors (or DVRs as defined above) shall 
automatically initiate the disconnection of offsite power sources 
whenever the voltage and time delay limits have been exceeded; and
    (e) The voltage monitors (DVRs) shall be designed to satisfy the 
requirements of IEEE Standard 279-1971, ``Criteria for Protection 
Systems for Nuclear Power Generating Stations''; and
    (f) The Technical Specifications shall include limiting conditions 
for operation, surveillance requirements, trip setpoints with minimum 
and maximum limits, and allowable values for second-level voltage 
protection DVRs.
    The NRC outlined the purpose of the degraded voltage relays to 
protect Class 1E safety related buses from sustained degraded voltage 
conditions on the offsite power system under accident and non-accident 
conditions in Branch Technical Position (BTP) of the Standard Review 
Plan (SRP/NUREG-0800), PSB-1, Revision 0, ``Adequacy of Station 
Electric Distribution System Voltages,'' dated July 1981 (ADAMS 
Accession No. ML052350520), and in the current BTP 8-6 of the SRP, 
Revision 3, ``Adequacy of Station Electric Distribution System 
Voltages,'' dated March 2007, (ADAMS Accession No. ML070710478).

Arkansas Nuclear One

    Another degraded voltage event, in September of 1978, at Arkansas 
Nuclear One (ANO) station demonstrated that degraded voltage conditions 
could exist on the Class 1E buses even with normal grid voltages, due 
to deficiencies in equipment between the grid and the Class 1E buses or 
by the starting transients experienced during certain accident events 
not originally considered in the sizing of these circuits. Information 
Notice No. 79-04, ``Degradation of Engineered Safety Features,'' (ADAMS 
Accession No. ML0311801180) provides additional information regarding 
this event.
    The NRC staff issued Generic Letter 79-36, August 8, 1979, 
``Adequacy of Station Electric Distribution Systems voltages'' (ADAMS 
Legacy No. 7908230155), expanding its generic review of the adequacy of 
electric power systems for operating nuclear power plants. 
Specifically, the NRC required all licensees to review the electric 
power systems at each of their nuclear power plants to determine 
analytically if, assuming all onsite sources of AC power are not 
available, the offsite power system and the onsite distribution system 
is of sufficient capacity and capability to automatically start as well 
as operate all required safety related loads.

Recent Inspection Findings

    Despite lessons learned from past events, and the generic 
communications on degraded voltage protection and adequate station 
voltages, NRC inspectors have identified incorrect

[[Page 2926]]

implementation of degraded voltage protection schemes by the licensees 
at various plants during inspections. Specifically, the existing 
degraded voltage setpoints at some plants were not adequate to protect 
the safety related components during degraded voltage conditions for 
accident and non-accident conditions. In some cases the voltage 
conditions were too low to power the safety related equipment but high 
enough to prevent transferring of safety loads to the standby power 
source. In addition, the time delays provided for the degraded voltage 
protection relays were not consistent with the accident analysis 
assumptions for those plants. Although the licensees' analyses were 
site specific, the NRC staff is concerned that other licensees might 
not have adequately implemented the staff positions and guidance issued 
previously to address the adequacy of station electrical distribution 
system voltages. Examples of inspection findings recently identified by 
the inspectors include the following:

DC Cook Units 1 and 2

    During the safety system design and performance capability biennial 
baseline inspection (NRC Inspection Report No. 50-315/03-07(DRS); 50-
316/03-07(DRS) (ADAMS Accession No. ML032260201) at the D.C. Cook 
Nuclear Power Plant in July of 2003, NRC inspectors identified that the 
degraded voltage protection scheme was bypassed whenever the 4160V 
buses were not being supplied through the reserve auxiliary 
transformers (RATs). This resulted in a lack of automatic degraded 
voltage protection during normal operation and for the first 30 seconds 
of an accident when engineered safety feature (ESF) loads were being 
sequenced onto the safety buses. This condition did not meet the staff 
position described in BTP PSB-1 and the electrical scheme is contrary 
to the design criteria for degraded voltage protection stated in an NRC 
letter to the licensee (a version of a letter sent to all licensees) 
dated June 3, 1977. This issue was reviewed by the NRR technical staff 
under Task Interface Agreement, TIA 2004-02 (ADAMS Accession No. 
ML042460579), and the staff concluded that the degraded voltage 
protection design at D.C. Cook was inadequate and as such should be 
modified to include degraded voltage protection during normal operation 
as well. Because the NRC staff had approved D.C. Cook's degraded 
voltage protection design in 1980, the staff's 2005 determination that 
the design was inadequate constituted a change in position and was 
subject to a backfit analysis. By letter dated November 9, 2005 (ADAMS 
Accession No. ML050680057), the NRC imposed a facility-specific 
compliance backfit on D.C. Cook Nuclear Plant, Units 1 and 2 to bring 
the facility into compliance with its license, the rules and orders of 
the Commission, and the licensee's written commitments. The licensee 
implemented a plant modification to the degraded voltage relaying 
circuit to make it functional during normal operation (See ADAMS 
Accession No. ML060530405) addressing the backfit issue.

Fermi Unit 2

    In May of 2008, NRC inspectors determined that the time delay 
settings of the degraded voltage relays for both divisions I and II of 
the Class 1E electrical distribution system were inadequate. The time 
delays could impact the emergency core cooling system (ECCS) injection 
timing requirements of the licensee's Title 10 of the Code of Federal 
Regulations (10 CFR) 50.46 loss-of-coolant accident (LOCA) analysis 
during a degraded voltage condition. The licensee's degraded voltage 
protection scheme could result in the voltage being too low to 
adequately power the ECCS equipment but high enough to prevent the 
emergency diesel generators (EDGs) from connecting to the safety 
related buses in a timely manner. This issue was reviewed by the NRR 
technical staff under TIA 2007-03 (ADAMS Accession No. ML080420435). 
The staff determined that the current degraded voltage protection 
scheme was inadequate, in that, the time delay relay settings for the 
degraded voltage relays for both divisions could impact the emergency 
core cooling system injection timing requirements. Additionally, for a 
short period of time under degraded voltage conditions, voltage could 
be too low for the proper operation of safety related motors but high 
enough to prevent emergency diesel generator start. Because the NRC 
staff had approved Fermi's degraded voltage protection design in 1981, 
the staff's 2008 determination that the design was inadequate 
constituted a change in position and was subject to a backfit analysis. 
The staff determined that the provisions of 10 CFR 50.109(a)(4), were 
applicable, and that a modification was necessary to bring the facility 
into compliance with the rules and orders of the Commission. See NRC 
Inspection Report 05000341/2008008 (ADAMS Accession No. ML081720585) 
for additional details. The NRC approved the plant modification in 
License Amendment No. 183 (ADAMS Accession No. ML102770382).

Peach Bottom Atomic Power Station Units 2 and 3

    Exelon did not use the safety related degraded grid relay trip 
setpoint specified in the Technical Specifications (TS) as a design 
input in calculations to ensure adequate voltage was available to all 
safety related components required to respond to a design basis loss-
of-coolant accident (LOCA). Instead, Exelon used the results from a 
Voltage Regulation Study to establish the voltage level for system 
operability. The study credited the use of non safety related equipment 
(load tap changers) to raise the voltage level. This allowed higher 
voltages to be used in the design calculations for components than 
would be allowed by the TS setpoint. The NRR technical staff reviewed 
the issue in TIA 2009-07 (ADAMS Accession No. ML102710178). The staff 
concluded that the licensee must demonstrate that the existing degraded 
voltage trip setpoints, including allowable values and time delays 
shown in the licensee's TS Table 3.3.8.1, are adequate to protect and 
provide the required minimum voltage to all safety related equipment. 
Since the load tap changers are not safety related and are subject to 
operational limitations and credible failures, they cannot be relied on 
to establish degraded voltage relay setpoints and time delay input for 
design basis calculations. For additional details, see NRC Inspection 
Report 05000277/2010004 and 05000278/2010004 (ADAMS Accession No. 
ML103140643). The licensee subsequently issued Licensee Event Report 
(LER) 2-10-04 (ADAMS Accession No. ML103280505) based on the 
determination that certain plant equipment could be degraded as a 
result of lower voltages that may exist during a postulated design 
basis loss-of-coolant event coupled with certain degraded voltage 
conditions.

Palo Verde Nuclear Generating Station Units 1, 2, and 3

    In July of 2009, an NRC inspection team questioned the calculations 
that demonstrate adequate voltage to safety related loads during worst 
case loading conditions and the adequacy of a time delay of 35 seconds 
for transfer of safety buses to the onsite power supplies should an 
actual degraded voltage condition occur. The licensee's calculation 
assumed a voltage above the degraded bus setpoint to demonstrate 
adequate voltage at the terminals of the safety related loads rather 
than the degraded voltage dropout setpoint value. The licensee 
maintains that a degraded voltage condition concurrent

[[Page 2927]]

with a design basis accident is not credible. See NRC Inspection Report 
05000528; -529; and -530/2009008, ADAMS Accession No. ML093240524 
regarding the inspection finding. The NRR technical staff reviewed the 
issue in TIA 2010-05 (ADAMS Accession No. ML102800340). The staff 
concluded that the licensee's calculation must demonstrate that the 
trip setpoint adequately protects the Class 1E equipment powered by the 
safety related bus from a potentially damaging degraded voltage 
condition, and the time delay to transfer from a degraded offsite 
source to the standby power source to support the emergency core 
cooling equipment operation must be consistent with accident analysis 
time assumptions, as required by BTP PSB-1 (NUREG 0800).

Discussion

    Because the NRC continues to identify inspection findings 
associated with degraded voltage, the NRC is providing clarifying 
information on two issues related to the need for two sets of 
calculations for the design of the electric power systems of a nuclear 
power plant and its interface with the transmission network as defined 
in 10 CFR Part 50, General Design Criteria 17. The two issues are (1) 
Degraded Voltage Relaying Design Calculations, and (2) Offsite/Onsite 
Design Interface Calculations. The Degraded Voltage Relaying Design 
Calculations establish the necessary settings of the DVRs to ensure 
that required safety related components are provided adequate voltage 
based on the design of the Class 1E distribution system in the plant 
and its most limiting operating configuration. The Offsite/Onsite 
Design Interface Calculations specify the voltage operating parameters 
of the plant electrical distribution system based on the transmission 
system (Offsite) operating parameters. This interface calculation 
establishes operating voltage bands for all plant electrical buses, 
which ensures that all plant components and systems (Class 1E and Non 
Safety Related) have proper voltage for starting and running in all 
operational configurations (expected operational and accident 
conditions). Therefore, based on normal grid operation, the degraded 
voltage relays will not operate, maintaining the offsite power supply 
to the plant electrical distribution system.

1. Degraded Voltage Relaying Design Calculations

    Proper design of a degraded voltage relaying scheme is needed to 
ensure that safety related systems are supplied with adequate voltages. 
The purpose of the NRC developed Branch Technical Position (BTP) PSB-1 
(revised later to become BTP 8-6), is to protect Class 1E safety 
related buses and components from sustained degraded voltage conditions 
on the offsite power system coincident with an accident as well as 
during non-accident conditions. The Class 1E buses should separate from 
the offsite power system within a few seconds if an accident occurs 
coincident with sustained degraded voltage conditions. During normal 
plant operation, the Class 1E safety related buses should automatically 
separate from the power supply within a short interval (typically less 
than 60 seconds) if sustained degraded voltage conditions are detected. 
The time delay chosen should be optimized to ensure that permanently 
connected Class 1E loads are not damaged under sustained degraded 
voltage conditions (such as sustained degraded voltage just above the 
LVR voltage setting for the duration of the DVR time delay setting). 
The staff considers degraded voltage conditions coincident with a 
postulated design basis accident to be a credible event. DVRs should be 
set to protect the safety related equipment from sustained degraded 
voltage conditions.
DVR Setting Design Calculations
    Licensee voltage calculations should provide the basis for their 
DVR settings, ensuring safety related equipment is supplied with 
adequate operating voltage (typically a minimum of 0.9 per unit voltage 
at the terminals of the safety related equipment per equipment 
manufacturers requirements), based on bounding conditions for the most 
limiting safety related load (in terms of voltage) in the plant. These 
voltage calculations should model the plant safety related electrical 
distribution system such that the limiting voltage at the bus monitored 
by the DVR can be calculated in terms of the voltage at the terminals 
of the most limiting safety related component in the plant. These 
models would allow calculation of voltages at terminals or contacts of 
all safety related equipment with the voltage at the DVR monitored bus 
at the DVR dropout setting, providing the necessary design basis for 
the DVR voltage settings. In this manner, the DVR ensures adequate 
operational (starting and running) voltage to all safety related 
equipment, independent of voltage controlling equipment external to the 
plant safety related electrical distribution system. For the purposes 
of this calculation, no credit should be taken for voltage controlling 
equipment external to the Class 1E distribution system such as 
automatic load tap changers and capacitor banks. Voltage-time settings 
for DVRs should be selected so as to avoid spurious separation of 
safety buses from the offsite power system during unit startup, normal 
operation and shutdown. These DVRs should disconnect the Class 1E buses 
from any power source other than the emergency diesel generators 
(onsite sources) if the degraded voltage condition exists for a time 
interval that could prevent the Class 1E safety related loads from 
achieving their safety function. The DVRs should also protect the Class 
1E safety related loads from prolonged operation below sustained 
degraded voltage which could result in equipment damage.
    The licensees should demonstrate that the existing DVR settings 
including allowable values and time delays are adequate to protect and 
provide the required minimum voltage to all safety related equipment. 
The time-delay(s) chosen for DVRs during accident conditions should 
meet the accident analyses assumptions and allow for proper starting of 
all Class 1E safety related equipment. Also, the time delay chosen for 
DVRs during non-accident condition must not cause any degradation of 
the safety related components, including actuation of their protective 
devices.

2. Offsite/Onsite Design Interface Calculations

    The offsite power source is the preferred source of power to safely 
shut down the plant during design basis accidents, abnormal operational 
occurrence, and reactor trips. The licensee's voltage calculations 
should provide the basis for proper operation of the plant safety 
related electrical distribution system, when supplied from the offsite 
circuit (from the transmission network). These calculations should 
demonstrate that the voltage requirements (both starting and 
operational voltages) of all plant safety related systems and 
components are satisfied based on operation of the transmission system 
and the plant onsite electric power system during all operating 
configurations of transmission network and plant systems. In this way, 
all safety related systems and components will function as designed 
with proper starting and running voltages during all plant conditions 
and the DVRs will not actuate (separating the transmission network 
supply). Following are guidelines for voltage drop calculations derived 
from Generic Letter 79-36, which have been supplemented to add 
clarifying

[[Page 2928]]

information. They do not represent new NRC staff positions.
Guidelines for Voltage Drop Calculations
    (a) The plant voltage analysis, while supplied from the 
transmission network, should be based on the operating voltage range of 
the transmission network connection. This transmission owner/operator 
supplied voltage range should address all transmission network and 
plant system operating configurations and should also include voltage 
drop due to the bounding worst case transmission system contingency 
(transmission system contingencies include trip of the nuclear power 
unit).
    (b) Separate analyses should be performed assuming the power source 
to the safety buses is (1) the unit auxiliary transformer; (2) the 
startup transformer; and (3) other available connections (e.g., from 
all available connections) to the offsite network one by one assuming 
the need for electric power is initiated by (1) an anticipated 
transient such as a unit trip (e.g., anticipated operational 
occurrence), or (2) an accident, whichever presents the bounding load 
demand on the power source.
    (c) For multi-unit stations, a separate analysis should be 
performed for each unit assuming (1) an accident in the unit being 
analyzed and simultaneous shutdown of all other units at the station; 
or (2) an anticipated transient (anticipated operational occurrence) in 
the unit being analyzed (e.g., unit trip) and simultaneous shutdown of 
all other units at that station, whichever presents the largest load 
situation.
    (d) All actions the electric power system is designed to 
automatically initiate should be assumed to occur as designed (e.g., 
automatic bulk or sequential loading or automatic transfers of bulk 
loads from one transformer to another and automatic starts of 
components). All non safety related plant auxiliary loads should be 
included, as applicable, in the plant loading studies.
    (e) Manual load shedding should not be assumed.
    (f) For each event analyzed, the maximum load necessitated by the 
event and the mode of operation of the unit at the time of the event 
should be assumed in addition to all loads caused by expected automatic 
actions and manual actions permitted by administrative procedures.
    (g) The voltage analysis should include documentation for each 
condition analyzed, of the voltage at the input and output of each 
transformer and at each intermediate bus between the connection of the 
offsite circuit and the terminals of each safety related load.
    (h) The calculated voltages at the terminals of each safety related 
load should be compared with the required voltage range for normal 
operation and starting of that load calculated in Item (a) above. Any 
identified inadequacies of calculated voltage should require immediate 
remedial action.
    (i) For each case evaluated, the calculated voltages on each safety 
bus should demonstrate adequate voltage at the component level without 
separation from the offsite circuit due to DVR actuation.
    (j) To provide assurance that actions taken to assure adequate 
voltage levels for safety related loads do not result in excessive 
voltages, assuming the maximum expected value of voltage at the 
connection to the offsite circuit, a determination should be made of 
the maximum voltage expected at the terminals of all safety related 
equipment and their starting circuits (if applicable). If this voltage 
exceeds the maximum voltage rating of any safety related equipment, 
immediate remedial action should be taken.
    (k) Analysis documentation should include a statement of the 
assumptions for each case analyzed.

Backfit Discussion

    The NRC has evaluated this RIS against the criteria of Title 10 of 
the Code of Federal Regulations (10 CFR) Section 50.109, 10 CFR Part 50 
Appendix A General Design Criteria 17, NRC Letter dated June 2, 1977 
``Statement of Staff Positions Relative to Emergency Power Systems for 
Operating Reactors,'' Branch Technical Position BTP-1 and later BTP 8-6 
(both of NUREG 0800) and Generic Letter 79-36 and determined that it 
does not represent a backfit. Specifically, NRC Staff technical 
positions outlined in this RIS are consistent with the aforementioned 
regulations and generic communications, while providing more detailed 
discussion concerning the necessary voltage calculations supporting DVR 
settings based only on voltage requirements of Class 1E components and 
the Class 1E distribution system design. Under section 50.109, a 
backfit can be defined as a proposed action that is a modification of 
the procedures required to operate a facility and may result from the 
imposition of a regulatory staff position that is either new or 
different from a previously applicable staff position.

Federal Register Notification

    To be done after the public comment period.

Congressional Review Act

    This RIS is not a rule as designated by the Congressional Review 
Act (5 U.S.C. 801-886) and therefore, is not subject to the Act.

Paperwork Reduction Act Statement

    This RIS does not contain any information collections and, 
therefore, is not subject to the requirements of the Paperwork 
Reduction Act of 1995 (44 U.S.C. 3501 et seq.).

Contact

    Kenn A. Miller, Office of Nuclear Reactor Regulation, Division of 
Engineering, U.S. Nuclear Regulatory Commission, Washington, DC 20555-
0001, telephone: 301-415-3152, e-mail: <a href="/cdn-cgi/l/email-protection#fc97999292998894d291959090998ecebc928e9fd29b938a"><span class="__cf_email__" data-cfemail="94fff1fafaf1e0fcbaf9fdf8f8f1e6a6d4fae6f7baf3fbe2">[email protected]</span></a>.

End of Draft Regulatory Issue Summary

    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, http://www.nrc.gov/NRC/ADAMS/index.html. 
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 (PDR) 
reference staff at 1-800-397-4209 or 301-415-4737 or by e-mail to 
<a href="/cdn-cgi/l/email-protection#32425640725c40511c555d44"><span class="__cf_email__" data-cfemail="b5c5d1c7f5dbc7d69bd2dac3">[email protected]</span></a>.

    Dated at Rockville, Maryland this 11th day of January 2011.

    For the Nuclear Regulatory Commission.

Roy Mathew,
Acting Chief, Division of Engineering, Office of Nuclear Reactor 
Regulation.
[FR Doc. 2011-888 Filed 1-14-11; 8:45 am]
BILLING CODE 7590-01-P


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