ML20245D968
| ML20245D968 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 04/17/1989 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8905010250 | |
| Download: ML20245D968 (15) | |
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PHILADELPHIA ELECTRIC COMPANY j
2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA. PA.19101 (215)841-4000 April 17,'1989
,R Docket Nos. 50-352 50-353 License No. NPF-39 Construction Permit No. CPPR-107 U.S.' Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555:
SUBJECT:
' Limerick Generating Station, Units 1 and 2 Response to 10CFR50.63, " Loss of All Alternating Current Power"
Dear Sir:
On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regulations in 10CFR50. A new section, 50.63'was added which requires that each light-water-cooled nuclear power plant be able to withstand and recover from a station blackout (SBO)-of a specified duration. Utilities are expected to have the baseline assumptions, analyses, and related information used in their coping evaluation available for NRC review.
It'also identifies the factors that must be
-considered in'specifying the station blackout duration. Section'10CFR50.63 requires that, for the' station blackout duration, the plant be capable of maintaining core r'
cooling and appropriate containment integrity. 10CFR50.63 further requires that each licensee submit the:following information.
~
1.
A proposed station blackout duration, including a justification for its selection based on the redundancy and reliability of the on-site 1
emergency alternating current (AC) power sources, the expected frequency of loss of off-site power, and the probable time needed to-restore off-site power; R
2.
A description of the procedures that will be implemented for station blackout events for the duration (as determined in 1 above) and for recovery therefrom; and 3.
A list and proposed schedule for any needed modifications to equipment
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and associated procedures necessary for the specified station blackout duration.
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Doc ment Control Desk April 17, 1989 Page 2
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The NRC has issued Regulatory Guide 1.155, " Station Blackout " which describes a means acceptable to the NRC Staff for meeting the requirements of 10CFR50.63. Regulatory Guide (RG) 1.155 states that the NRC Staff has determined that the document issued by the Nuclear Utility Management and Resources Council, NUMARC 87-00, " Guidelines and Technical Based for NUMARC Initiatives Addressing Station Blackout At Light Water Reactors," also provides guidance that is in large part identical to the RG 1.155 guidance and is acceptable to the NRC Staff for meeting the requirements of 10CFR50.63. Table 1 to RG 1.155 provides a cross-reference between RG 1.155 and NUMARC 87-00 and notes where the RG takes precedence.
l i
Philadelphia Electric Company (PECo) has evaluated the Limerick Generating
)
Station (LGS), Units 1 and 2, in accordance with the requirements of the SB0 rule 1
using guidance from NUMARC 87-00, except where RG 1.155 takes precedence. The i
results of this evaluation are detailed below.
(Applicable NUMARC 87-00 sections are l
shown in parentheses.)
A.
Proposed Station Blackout Duration j
NUMARC 87-00, Section 3, was used to determine a required coping duration category of four hours.
The following plant factors were identified in determining the proposed station blackout duration as per NUMARC 87-00.
1.
AC Power Design Characteristic Group is P2 based on the following.
a.
Expected frequency of grid-related loss of off-site power (LOOP) events does not exceed once per 20 years (Section 3.2.1, Part 1A,
- p. 3-3);
b.
Estimated frequency of LOOP events due to extremely severe weather (ESW) placed the plant in ESW Group 3 (Section 3.2.1, Part 13, p.
l 3-4);
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l c.
Estimated frequency of LOOP events due to severe weather (SW) l places the plant in SW Group 2 (Section 3.2.1 Part IC, p. 3-7);
)
and i
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d.
The off-site power system is in the 11/2 Group (Section 3.2.1, l
Part 10, p. 3-10).
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I 2.
The emergency AC (EAC) power configuration group is A based on the following (Section 3.2.2, Part 2C, p. 3-13).
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DocbmentControlDesk I
April 17, 1989 Pagt 3 l
a.
There are three EAC power supplies not credited as alternate AC power sources per unit (Section 3.2.2, Part 2A, p. 3-15); and b.
One EAC power supply is necessary to operate safe shutdown equipment following a loss of off-site power per unit (Section 3.2.2, Part 2B, p. 3-15).
I NOTE:
A limited amount of operator actions are credited to initiate cross-ties between electrical power sources in order to justify a one out of three EAC configuration.
3.
The target Emergency Diesel Generator (EDG) reliability is 0.95.
a.
NUMARC 87-00, Section 3.2.5, provides the following criteria for determining the target EDG reliability based on demand sample size.
If the EAC Group is A, B, or C, and any of the following criteria are met, then the nuclear unit may select an EDG reliability target of either 0.95 or 0.975.
lAST 20 DEMANDS > 0.90 RELIABILITY LAST 50 DEMANDS > 0.94 RELIABILITY LAST 100 DEMANDS > 0.95 RELIABILITY A target EDG reliability of 0.95 is justified based on having a nuclear unit average EDG reliability for the last 100 demands greater thsn 0.95, consistent with NUMARC 87-00, Section 3.2.4.
4.
An alternate AC (AAC) power source will be utilized at the LGS which meets the criteria specified in Appendix B to NUMARC 87-00. The AAC source is a Class 1E EAC power source which meets the assumptions in Section 2.3.1 of NUMARC 87-00.
The AAC power source is available within one hour of the onset of the station blackout event and has sufficient capacity and capability to operate systems necessary for coping with a station blackout for the required SB0 duration of four hours to bring and maintain the plant in safe shutdown. An AC independent coping analysis was performed for the one hour required to bring the AAC power source on line.
The AAC power source utilized at the LGS is one of the black-out unit's four EAC power sources combined with three out of the four EDGs from the non-blacked out unit. After appropriate safeguard electrical division cross-ties are completed, the AAC source will power all the necessary safe shutdown systems. A one-line diagram of the LGS AC power system is displayed in Figures 1 through 9.
k)ocmentControlDesk April 17, 1989 Page 4 B.
Procedure Description Plant procedures have been reviewed and will be revised, if necessary, to meet the guidelines in NUMRC 87-00, Section 4, in the following areas.
1.
Off-site AC power restoration per NUMRC 87-00, Section 4.2.2:
a.
System Operation Division Procedure
" System Restoration Following Complete Shutdown."
b.
Procedure E-1
" Station Blackout."
2.
Severe weather per NUMRC 87-00, Section 4.2.3:
a.
Procedure SE-9 "High Wind."
Plant procedures have been reviewed and changes necessary to meet NU MRC 87-00 will be implemented in the following areas.
1.
Station blackout response per NUMRC 87-00, Section 4.2.1:
a.
Procedure E-1
" Station Blackout Procedure."
b.
Procedure T-250
" Containment Isolation."
Procedure changes are required to utilize the AAC power supply by cross-tieing EAC power divisions.
C.
Proposed Modifications and Schedule The AAC power source has the capacity and capability to power the equipment necessary to cope with a SB0 in accordance with NUMRC 87-00, Section 7 for the required coping duration determined in accordance with NUMRC 87-00, Section i
3.2.5.
j 1.
Condensate Inventory For Decay Heat Removal (Section 7.2.1)
We have determined from Section 7.2.1 of NUMRC 87-00 that 92,041 gallons of 1
water are required for decay heat removal, accounting for system leakage, J
for four hours. The minimum permissible condensate storage tank (CST) level provides 135,000 gallons of water, which exceeds the required quantity for coping with a four-hour station blackout. A low level alarm will sound in the control room if the CST water level decreases below 135,000.
The following procedure change is needed to utilize these water sources.
The station blackout procedure (E-1) will be revised so that the operators will be no longer be directed to shift Reactor Core Isolation Cooling (RCIC) pump suction to the suppression pool during an SB0 event.
1 L
Doc ment Control Desk April 17, 1989 L
P:ge 5
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2.
Class IE Battery Capacity (Section 7.2.2)
A battery capacity calculation has been perfonned pursuant to NUMARC 87-00, Section 7.2.2, to verify that the Class 1E batteries have sufficient capat.ity to meet station blackout loads for one hour.
3.
Compressed Air (Section 7.2.3)
Air-operated valves relied upon to cope with an 580 for one hour can either be operated manually or have sufficient backup sources independent of the preferred and blacked out unit's Class IE power supply. Valves requiring manual operation or that need backup sources will be identified in station procedures.
4.
Effects of Loss of Ventilation (Section 7.2.4) a.
The steady-state ambient air temperature has been calculated for the following dominant areas of concern.
AREA TEMPERATURE 0
RCIC Pump Room 139 F 0
Auxiliary Equipment Room 141 F The High Pressure Coolant Injection (HPCI) Pump Room and the Main Steam Tunnel are not dominant areas of concern since they do not contain station blackout equipment. The HPCI system will not be needed during a station blackout, and the valves located in the Main Steam Tunnel will either not need to be actuated or will be actuated within the first ten minutes of the event.
b.
Control Room The assumption in NgMARC 87-00, Section 2.7.1, that the control room will not exceed 120 F during an SB0 has been assessed.
ThecontrolroomattheLGShasbeencalgulatedtoreachasteadystate ambient air temperature in excess of 120 during an SBO. However, actionswillbetakentoprovidesupplementalgoolingtoensurethe control room temperature will remain below 120 F.
These operator actions will be reflected in the station blackout procedure (E-1).
Therefore, the control room will not be a dominant of concern.
Reasonable assurance of operability of station blackout response l
equipment in the above dominant areas of concern has been assessed i
using Appendix F to NUMARC 87-00 and the Appendix F Topical Report. No i
modifications are required to provide reasonable assurance for l
equipment operability.
l l
S.
Containment Isolation (Section 7.2.5)
The plant list of containment isolation valves has been reviewed to verify that the valves which must be capable of being closed or that must be
K.
,a-L Document Control Desk April 17, 1989 Pcg2 6
. operater' (cycled) under SB0 conditions can be positioned (with indication) independent of the preferred and blacked-out unit's Class 1E power supplies.
The following procedure change is required to ensure that appropriate containment integrity can be provided under station blackout conditions.
a.
T-250 Containment Isolation Procedure This procedure will be revised to provide the operator with guidai.ce regarding which valves may need to manually actuated depending upon which electrical power divisions are energized.
Containment isolation is not expected to be necessary as a result of a station blackout. However, once this procedure is revised, the capability to close necessary containment isolation valves will be assured.
b.
E-1 Station Blackout This procedure will be revised to direct operators to cross-tie the AAC power source to the electrical divisions that power containment isolation valves.
- 6. -
Reactor Coolant Inventory (Section 2.5)
The AAC source powers the necessary make-up systems to maintain adequate reactor coolant system inventory to ensure that the core is cooled for the required coping duration.
The associated procedure t.hanges identified in Parts A B, and C above will be completed one year after the notification provided by the Director, Office of
. Nuclear Reactor Regulation in accordance with 10 CFR 50.63(c)(3).
Very truly yours, G. A.
unger, Jr.
Director Licensing Section Nuclear Support Division Attachment cc:
W. T. Russell Administrator, Region I USNRC T. J. Kenny, USNRC Senior Resident Inspector, LGS
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