ML17286B098

Responds to Generic Ltr 91-06, Adequacy of Safety-Related DC Power Supplies, Pursuant to 10CFR50.54(F).Provides Justification to Questions Listed W/No as Answer

ML17286B098
Person / Time
Site:	Columbia
Issue date:	10/18/1991
From:	Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-91-06, GL-91-6, GO2-91-191, NUDOCS 9110230052
Download: ML17286B098 (13)

Text

FORD, 1 REGULATO INFORMATION DISTRIBUTION YSTEM (RIDS)

ACCESSION NBR:9110230052 DOC.DATE: 91/10/18 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION SORENSEN,G.C. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Responds to generic ltr 91-06, "Adequacy of Safety-Related DC Power Supplies," pursuant to 10CFR50.54(F).Provides justification to questions listed w/no as answer.

DISTRIBUTION CODE: AOOID TITLE: OR COPIES RECEIVED:LTR Submittal: General Distribution

/ ENCL / SIZE: 7 NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 ENG,P.L. 2 2 INTERNAL: ACRS 6 6 NRR/DET/ECMB 7D 1 1 NRR/DET/ESGB 1 1 NRR/DOEA/OTSB11 1 1 C)

NRR/DST ,8E2 1 1 NRR/DST/SELB 7E 1 1 NRR/DST/SICB8H7

~l NRR/DST/SRXB 8E 1 1 1 1 NUDOCS-ABSTRACT 1 1 OC/LFMB 1 0 OGC/HDS1 1 0 REG FIL'E 1 1 RES/DSIR/EIB 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 24 ENCL 22

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 October 18, 1991 9ii0230052 9ii018 G02-91-191 PDR ADOCK 05000397 p PDR Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

NUCLEAR PLANT NO. 2, OPERATING LICENSE NPF-21 RESPONSE TO GENERIC LETTER 91-06, "ADEQUACY OF SAFETY-RELATED DC POWER SUPPLIES," PURSUANT TO 10CFR50.54(F)

The subject generic letter required written response to questions in its within 180 days. Attachment 1 contains the required response to those questions. In accordance with the instructions in Items 5 and 9, the following provides justifications to those questions with a "no" answer:

Justification for responses to question 3.a.7 Does the control room have the following separate, independently annunciated alarms and indications for each division of dc power? - Battery Discharge At WNP-2, battery discharge is indirectly annunciated by alarms indicating charger failure and bus undervoltage. This control room instrumentation is described in the FSAR 8.3.2.2. 1.2. Battery high discharge rate is not separately alarmed. In the absence of an electrical fault and with battery charger available, all normal and emergency steady state loads are carried by the battery charger. At 125% of its full load rating, the battery charger operates in a current-limiting mode and any overcurrent in excess is supplied by the battery. However, the feeder circuit fuses are sized to trip on overcurrents of this magnitude, thereby preventing battery high dis-charge current to continue to the point of degrading the system.

Annunciation of the isolated Class lE circuit is made for each connected load.

The WNP-2 SER, Rev 0, acknowledging no high discharge rate alarm in the control room, concluded the monitoring provided was acceptable and the addition of the high discharge rate alarm was not required.

Wage Two RESPONSE TO GENERIC LETTER 91-06, "ADEQUACY OF SAFETY-RELATED DC POWER SUPPLIES," PURSUANT TO 10CFR50.54(F)

Justification for response to question 7.b.6 Are maintenance, surveillance and test procedures regarding station batteries conducted routinely? Specifically:

At least once per 92 days, or within 7 days after a battery discharge, overcharge, or if the pilot cell readings are outside the 7-day surveil-lance requirements are the following verified to be within acceptable lim-its: Visually inspect or measure resistance of terminals and connectors (including the connectors at the dc bus)?

At WNP-2, an inspection for corrosion is performed at the battery terminals and connectors, where acid may be present. The connections at the DC bus are cable connections. Typical of other bus connections, they are not subjected to the conditions experienced by those at the battery. The inspection performed is in accordance with IEEE 450 and WNP-2 Technical Specifications Surveillance 4.8.2. l.b.

This justification for the current configuration is supported by NRC approval of the licensing basis documents, as discussed above.

Very truly yours, G. C. orensen, Manager Regulatory Programs ME/bk Attachments CC: JB Martin - NRC RV NS Reynolds - Winston 8 Strawn PL Eng - NRC DL Williams - BPA/399 NRC Site Inspector - 901A

STATE OF WASHINGTON )

Subject:

Response to Generic Letter 91-06

)

COUNTY OF BENTON )

I, G. C. SORENSEN, being duly sworn, subscribe to and say that I am the Manager, Regulatory Programs, for the WASHINGTON PUBLIC POWER SUPPLY SYSTEM, the applicant herein; that I have full authority to execute this oath; that I have reviewed the foregoing; and that to the best of my knowledge, information, and belief the statements made in it are true.

DATE: , 1991 G. C. Sorens n, Manager Regulatory Programs On this date personally appeared before me G. C. SORENSEN, to me known to be the individual who executed the foregoing instrument, and acknowledged that he signed the same as his free act and deed for the uses and purposes herein mentioned.

GIVEN under my hand and seal this / /+ day of 1991.

Notary Public in and for the STATE OF WASHINGTON My Commission Expires A ri12 1 5

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ENCLOSURE 1 10 CFR 50 ~ 54(f) RE(UEST GENERIC ISSUE (GI) A 30 "ADE(UACY OF SAFETY-RELATED DC POMER SUPPLIES" Back round The specific area of concern of GI A-30 "Adequacy of Safety-Related DC Power Supplies" is the adequacy of the safety-related dc power in operating nuclear power plants, particularly with regard to multiple and common cause failures.

'Risk analysis and past plant experience support conclusions that failure of the dc power supplies could represent a significant contribution to the unreliability of shutdown cooling. Analysis indicates that inadequate maintenance and surveillance and failure to detect battery unavailability are the prime contributors to failure of the dc power systems.

During the development of plans to resolve GI A-30 it was observed that several previously issued regulatory notices (1ENsf, bulletins (IEBs) and letters (GLs) submitted to licensees include recommendations similar to those that have been identified to resolve GI A-30. Nore specifically, it has been determined that recommendations contained in notifications IEH 85-74, "Station.

Battery Problems", IEB 79-27, "Loss of Non-Class 1E Instrumentation and Control Power System Bus during Operation," and separate actions being taken to resolve GI 49,

" Interlocks and LCOs for Class 1E Tie Breakers" include the elements necessary to resolve GI A-30. It is therefore concluded that licensees that have implemented these recommendations and actions will have resolved GI A-30.

The response to the questions that follow. is necessary to provide the staff with information to determine whether any further action is required for your fac i i ty.

1 Ouestions The following information is to be provided for each unit at each site:

1. Unit LUNP- R

2. a. of independent redundant divisions of Class 1E or safety-The number related dc 1

power for this plant is lE f y. 1 THIEF+,'.

d~t yNddi d (Include any p

the diesel generators.) 4, <,g;,~@~~

b. The number of functional safety-related divisions of dc power necessary to attain safe shutdown for this unit is ~

3. Does the control room at this unit have the following separate, independently annunciated alarms and indications for each division of dc power?.

a. alarms

1. Battery disconnect or circuit b> eaker open?

2. Battery charger disconnect or circuit breaker open (both input ac and output dc)? MEK

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3. dc system ground?

4. dc bus undervoltage?

5. dc bus overvoltage?

6. Battery charger failure?

y. Btt yg 1 1 Indications

1. Battery float charge current?

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circuit output current?

c. Does the unit have written procedures for response to the above alarms and indications?

4. Does this unit have indication of bypassed and inoperable status of circuit breakers or other devices that can be used to disconnect the

'attery and battery charger from its dc bus and the battery charger from 1 1 g t 1 t g.

5. If the answer to any part of question 3 or 4 is no, then provide informacion justifying the existing design features of the facility's safety-related dc systems. *See note below.

6. (1) Have you conducted a review of maintenance and testing activities to minimize the potential for human error causing more than one dc division to be unavai lab le? and (2) do plant procedures prohibit maintenance or testing on re un ant dc divisions at the same time?

If the facility Technical Specifications have provisions equivalent to those found in the Mestinghouse and Combustion Engineering Standard Technical Specificat',on.

for maintenance and surveillance, then question 7 may be skipped and a statement to that effect may be inserted here.

7. Are maintenance, surveillance and test procedures regarding station batteries conducted routinely at this plant? Specifically:

a. At least once per 7 days are the following verified to be wi.hin acceptable limits:

1. Pilot cell electrolyte level?

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2. "Specific gravity or charging current?

3. Float voltage?

4. Total bus voltage on float charge?

5. Physical condition of all cells?

b. At least once per 92 days, or within 7 days after a battery discharge, overcharge, or if the pilot cell readings are outside the 7-day sulvei llance requirements are the following verified to be within acceptable limits:

1. Electrolyte level of each cell? YES

2. The average specific gravity of all cells? YES

3. The specific gravity of each cell? Y'ES

4. The average ele'ctrolyte temperature of a representative

5. The float voltage of each cell?

6. Visually inspect or measure resistance of terminals and connectors (including the connectors at the dc bus)?

C. At least every 18 months are the following verified:

1. 1 I f 1 I (by )'. ~gd

2. Physical condition of the battery?

3. Battery charger capability to deliver rated ampere tbt<<h 8 b*'. ~gg

4. The capability of the battery to deliver its design duty y1 t h 8 8 I ~88

5. Each individual cell voltage is within acceptable limits d I g h

d. At least every 60 months, is capacity of each battery verified by 8 1 f 8 I g

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e. At least annually, is the battery capacity verified by performance discharge test, if the battery shows signs of degradation or has hdbtg f h. b d I Iffy y8 (qP hh>;

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8. Does this plant have operational features such that following loss of one safety-related dc power supply or bus:

a. Capability is maintained for ensuring continued and adequate t ll g.

b. Reactor coolant system integrity and isolation capability are maintain~d?

c. Operating procedures, instrumentation (including indicators and control functions are adequate to initiate annunciators),

g tland d l dg dig'.

9. If the answer to any part of question 6, 7 or 8 is no, then provide your basis'or not performing the maintenance, surveillance and test procedures described and/or the bases for not including the operational features cited. *See note below.

• Note: for questions involving supporting type information (question numbers 5 and 9) instead of develdoping and supplying the information in response to this letter, you may coomit to further evaluate the need for such provisions during the performance of your individual plant examination for severe accident vulnerabilities (IPE). If you select this option, you are required to:

'(1) So state in response to these questions, and (2) Coranit to explicitly address questions 5 and 9 in your IPE submittal per the guidelines outlined in NUREG-1335 (Section 2.1.6, Subitem 7),

"Individual Plant Examination: Submittal Guidance."

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