ML20083D862

Responds to Request for Info Re safety-related Dc Power Supplies

ML20083D862
Person / Time
Site:	Vallecitos Nuclear Center
Issue date:	09/20/1991
From:	Darmitzel R GENERAL ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9110010301
Download: ML20083D862 (5)

Text

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GE Nuclear Energy

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September 20, 1991 4

U.S. Nuclear Regulatory Commission

' Washington, D. C. 20555 i l

Attention: Document Control Desk j

References:

1) License R-33, Docket 50-73.

2) Letter with enclosures, J. G. Partlow to All Holders of Operating Licenses; April 29, 1991.

t Gentlemen:

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This letter is in respense to your request for information concerning safety-related de power supplies (Ref. 2).

To the best of my knowledge and belief, the information

, contained in the attached document is accurate.-

Very truly yours, 9 (L4ndC F. W. Darmitzel, Manager

.i Environmental Programs

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Att.

, Submitted and sworn before me this 25 M day of SEPTEm8EE ,

1991, foYY 4Ed % ' , Notary Public, in and for the County of Alameda, St te of California, ws%u g) OFFICIAL SEAL

.g CHRISTINE AR!!ZUMi y jf PJOTwrrueuc.c,uppa,,a

/ ALAMEDA COUNTY

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. ENCLOSURE 1-10 CFR 50.54(f) REQUEST - GENERIC ISSUE (GI) A-30 " ADEQUACY OF SATETY-RELATED DC POWER SUPPLIES" B,a c kg roun_d -

The specific area of concern of GI A-30 " Adequacy of Safety-Related DC Power Supplies" is the adequacy of the safety-related de- 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 de 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 de power systems.

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

_ . Battery Problems", IEB 79-27, t' Loss of Non-Class IE 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 it;ments 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 facility.

-Ouest_ ions The following information is to be provided for each unit at each site:

1. Unit CE-Nuclear Test Reactor _

2. a. The number of independent redundant divisions of Class IE or safety-related de power for this plant is _ _ _ None . (Include _ any separate Class IE or safety-related dc, such as any dc dedicated to the diese1' generators.)

b. The number of functional safety-related divisions of_ de power necessary to attain safe shutdown for this unit is None __.

3. Does. the control room at _ this unit have the following separate, independently annunciated alarms and indications for each division of de power? N/A a.- alarms

1. Battery disconnect or circuit breaker open?

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

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3. de system ground? __

4. de bus undervoltage? _ _ _

5. de bus overvoltage? ,

6. Battery charger failure? __ _

7. Battery discharge? _ , , _

b. Indications

1. Battery 'loat charge current? _ _

2. Battery circuit output current?

3. Battery discharge?

4. Bus voltage?

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 cisconnect the battery and battery charger from its de bus and the battery charger from its ac power source during maintenance or testing? N/A ,_

5. If the answer to any part of question 3 or 4 is no, then provide information justifying de systems.

the existing design features of the facility's safety-related

• See note beloW. N/A

6. (1) Have you conducted a reylew of maintenance and testing activities to minimize the potential for human error causing more than one de division to be unavailable? Ng and(2)doplantproceduresprohibit maintenance or testing on redundant dc divisions at the same time? S/A If the facility Technical Specifications have provisions equivalent to those found in the Westinghouse and Combustion Engineering Standard Technical Specifications 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: N/A

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

1. Pilot cell electrolyte level? _ _ _ _

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3. de system ground? __

4 de bus undervoltage? ___

5. de bus overvoltage? _ .

6. Battery charger failure?

7. Battery discharge? ___ _ __

b. Indications

1. Battery float charge current?

2. Battery circuit output current? -

3. Battery discharge? _ _

4. Bus voltage? __

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

' battery and battery charger from its de bus and the battery charger f rom its ac power source during maintenance or testing? _ N/A

5. If the answer to any part of question 3 or 4 is no, then provide infonaation justifying de systems.the existing design features of the facility's safety-related

'See note below. N/A

6. (1) Have you conducted a review of maintenance and testing activities to minimize the potential for human error causir.g more than one de division to be unavailable? N/A and (2) do plant procedures prohibit maintenance or testing on redundant de divisions at the same time? N/A If the facility Technical Specifications have provisions equivalent to those found in the Westinghouse and Conbustion Engineerir.g Standard Technical Specifications 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 reoarding station batteries conducted routinely at this plant? Specifically: s/A

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

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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 af ter a battery discharge, overcharge, or if the pilot cell readings are outside the 7-day surveillance requirements are the following verified to be within acceptable limits:

1. Electrolyte level of each cell?

2. The average specific gravity of all cells?

3. The specific gravity of each cell?

4. The average electrolyte temperature of a representative number of cells?

5. The float voltage of each cell?

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

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

1. Low resistance of each connection (by test)?

2. Physical condition of the battery?

3. Battery charger capability to deliver rated ampere output to the de bus?

4. The capability of the battery to deliver its design duty r cycle to the de bus?

5. Each individual cell voltage is within acceptable limits during the service test?

d. At least every 60 months, is capacity of each battery verified by performance of a discharge test?

e. At least annually, is the battery capacity verified b) performance discharge test, if the battery shows signs of degradation or has l

reached 85% of the expected service life?

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

.a. Capability is maintained for ensuring continued and adequate

-reactor cooling?

b. Reactor. coolant system integrity and isolation capability are maintained?

- c. . Operating procedures, instrumentation (including indicators and annunciators), and control functions are adequate to initiate systems as required.to maintain adequate core cooling?

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

• Note: For-questions involving supporting type information (question numbers 5 and 9) instead of developing and su) plying the information in response to this letter, you may commit to furtier 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) Commit.to explicitly _ address questions 5 and 9 in your IPE submittal

' per the guidelines outlined in NUPEG-1335 (Sc:tici, 2.1.6, Subitem /),

" Individual Plant Excmination: Submittal Guidance."

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

N/A

a. Capability is maintained for ensuring continued and adequate reactor cooling? ,

b. Reactor coolant system integrity and isolation capability are maintained?

c. Operating procedures, instrumentation (including indicators and annunciators), and control functions are adequate to initiate systems as required to maintain adequate core cooling?

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

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

'(1) So state in response to these questions, and (2) Comit to explicitly address questions 5 and 9 in your IPE submittal per the guidelines outlined in NUREG-1335 (Section 2.1.5, Subitem 7),

" Individual Plant Examination: Submittal Guidance."

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