ML20082Q522

Responds to Generic Ltr 91-06, Resolution of Generic Issue A-40, 'Adequacy of Safety-Related DC Power Supplies,' Per 10CFR50.54(f)

ML20082Q522
Person / Time
Site:	Callaway
Issue date:	09/06/1991
From:	Schnell D UNION ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-40, REF-GTECI-SC, TASK-A-40, TASK-OR GL-91-06, GL-91-6, ULNRC-2479, NUDOCS 9109120214
Download: ML20082Q522 (7)

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33 September 6, 1941 ,

U.S.-Nuclear Regulatory Commission Attn:- Docus.ent Control Desk ,

Mail btation Pl-137 Washington, DC 20555

. Gentlemen:- ULNRC- 2479 DOCKET NO.-50-483

• CALIAWAY PLANT

. RESPONSE TO GENERIC' LETTER 91-06,

" RESOLUTION OF GENERIC: ISSUE A-30,

' ADEQUACY OF= SAFETY-RELATED-DC-POWER SUPPLIES,'

._ PURSUANT'TO 10 CFR 50.54(f)"

Attachment:

~ Responses to queGtions listed in Enclosure 1 of NRC Generic L6tter 91-06.

The subject.NRC_ Generic Letter requested additional _information regarding the adequacy of safety-related DC. power. supplies at the Callaway-Plant..

Union Electric Company's-responses to questions' listed in Enclosure 1 of'the subject =NRC Generic. Letter are attached.

Eased'on our responses.to these questions, no.

further action is required to resolve Generic Issue A-30

-for the callaway Plant.

If additional *information concerning this- ,

L Generic Letter'is required, please-contact us.

Very truly y urs, lL. 'f. fiZA2/che-h'w[

Donald F.-Schnell GAC/p1h '

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4 STATE OF MISSOURI )

) S S-CITY OF ST. LOUIS )

Alan C. Passwater, of. lawful age, being first duly sworn upon oath says that he is Manager, Licensing and Fuels (Nuclear) for Union Electric Company; that he has read the foregoing document and knows the content--thereof; that he has executed the same for and on behalf of said company with full power and authority to do so; and -

that the facts therein stated are true and correct to the best of his knowledge, information and belief.

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Alan C. Passwater Manager, Licensing and Fuels Nuclear SUBSCl3IBED and sworn to before me this _ [ ^ day of ./ m 7/ n'/ 4 -

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, 1991.

,.g . i. . .. at tA.

gy e ffAYY BARBARA J. PFAFF NOTARY PUBUC, STATE 08 Ml!5OURI Mf COMMISSION EXPlRES APRIL 22. 1993 ST. LOUIS COUNTY 1

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ce s. T. A. Baxter,-Esq.

Shaw,_Pittman, Potts.& Trowbridge 2300 N. Street, N.W.

Washington,-D.C. 20037 Dr. J. 0. Cermak CFA, Inc.

18225-A Flower 11111 Way ,

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.Gaithersburg, MD 20879-5334 R. C. Knop Chief, Reactor Project _ Branch l U,S. Nuclear Regulatory Commission Region III >

799' Roosevelt Road

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Glen Ellyn, Illinois 60137 Bruce Bartlett Callaway Besident Office

-U.S. Nuclear Regulatory Commission RR41 Steedman, Missouri 65077 IM. Dr Lynch (2)

-Office of Nuclear Reactor Regulation

-U.S. Nuclear-Regulatory Commission 1 White Flint,-North, Mail Stop 13E21 '

-11555 Rockville Pike

.-Rockville, MD 20852

' Manager,. Electric Department

' Missouri--Public Service Commission ,

P.O. Box 360 Jefferson City, MO 65102 P

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ULNRC-2479

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ENCLOSURE 1 10 CFR 50.54(f) REQUEST - GENERIC ISSUE (GI) A-30 " ADEQUACY OF SAFETY-RELATED DC POWER SUPPLIES"

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k ground 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 comon cause f ailures.

Risk analysis and past plant experience support conclusions that failure of the de power supplies could repre:;ent a significant contribution to the unreliability of shutdown cooling. Analysis indicates that intdequate maintenance and surveillance and failure to detect battery unavailability are the prime contributors to f ailure of the de power systems.

During the development of plans to resolve G1 A-30, it was observed that several previously issued regulatory notices (IENs), bulletins (IEBs) and letters (GLs) submitted to licensees include recomendations similar to those that have been identified to resolve G1 A-30. More specifically, it has been determined that recomendations contained in notifications IEN 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 recomendations and actions will have resolved 61 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.

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

1. Unit _ _callaway

2. a. The number of independent redundant divisions of Class 1E or safety-related de power for this plant is __ _ 2 . (Include any separate Class IE or safety-related de, such as any oc dedicated to the diesel generators.)

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

3. Does the control room at this unit have the following separate, independent 1.y annunciated alarms and_ indications for each division of de power?

a. alarms

1. Battery disconnect or circuit breaker open? yes

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

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4 Enclosure 1

3. de system ground? Yes

4. de bus undervoltage? Yes

5. de bus overvoltage? Yes

6. Battery charger f ailure? Yes

7. Batt cy discharge? Yes __

b. Indicatiens

1. Battery float charge current? _Yes

2. E 'tery circuit output current? __ Yes

3. Battery discharge? Yes

4. - Bus voltage? Yes

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

4. Does this unit have indication cf 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 from its ac power source during maintenance or testing? Yes

5. If the answer to any part of question 3 or 4 is no, then provide information justifying the existing design features of the'f acility's safety-related

, de 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 de division to be unavailable? _Yes _ and (2) do plant procedures prohibit maintenance or testing on redundant de divisions at the same time?  ;

Yes 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. ca11avev pi,nt 7,ckn4 m e ~ 4fications have D provisims equilvalent to bestinghouse standard technical specifications. l

7. Are maintenance, surveillance and test procedures regarding station t

batteries conducted routinely at this plant? Specifically:

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

1. Pilot cell electrolyte level?

. 2 ULNRC-2479 Enclosure 1

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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-surveillance requirements are the following verified to be within acceptable limits:

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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?l8 months are the following verified:

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

2. Physi _ cal 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 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 by performance discharge test,- if the battery shows signs of degradation or has reached 85% of the expected service life?

Lnclosure 1

-4

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

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

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

Yes

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

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.

• Note: For questions involving supporting type information (question numbers 5 and 9) instead of developing and supplying the information in response to this letter, you may ommit 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) Commit 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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