ML17306A246

Forwards Response to Generic Ltr 91-06, Resolution of Generic Issue A-30, 'Adequacy of Safety-Related DC Power Supplies.'

ML17306A246
Person / Time
Site:	Palo Verde
Issue date:	10/25/1991
From:	Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-30, REF-GTECI-EL, TASK-A-30, TASK-OR 161-04240-WFC-G, 161-4240-WFC-G, GL-91-06, GL-91-6, NUDOCS 9111050104
Download: ML17306A246 (25)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9111050104 DOC.DATE: 91/10/25 NOTARIZED:

YES DOCKET FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528 STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi 05000530 AUTH.NAME AUTHOR AFFILIATION CONWAY,W.F.

Arizona Public Service Co.(formerly Arizona Nuclear Power RECIQ.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards response to Generic Ltr 91-06,"Resolution of Generic Issue A-30,'Adequacy of Safety-Related DC Power Supplies.'" DISTRIBUTION CODE: A001D COPIES RECEIVED:LTR ENCL SIZE: TITLE: OR Submittal:

General Distribution D NOTES: STANDARDIZED PLANT Standardized plant.Standardized plant.RECIPIENT ID CODE/NAME PD5 LA TRAMMELL, C INTERNAL: ACRS NRR/DET/ESGB NRR/DST 8E2 NRR/DST/SICB8H7 NUDOCS-ABSTRACT OGC/HDS1 RES/DSIR/EIB EXTERNAL: NRC PDR NOTES: COPIES LTTR ENCL 1 1 2 2 6 6 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 RECIPIENT ID CODE/NAME PD5 PD THOMPSON,M NRR/DET/ECMB 7D NRR/DOEA/OTS B 1 1 NRR/DST/SELB 7E NRR/DST/SRXB 8E OC F 01 NSIC COPIES LTTR ENCL 1 1 2 2 1 1 1 1 1 1 1 1 1 0 1 1 1 1 05000528 05000529 05000530 D D NOTE TO ALL"RIDS" RECIPIENTS:

D D PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!TOTAL NUMBER OF COPIES REQUIRED: LTTR 27 ENCL 25 P~

Arizona Public Service Company P.O.BOX 53999~PHOENIX, ARIZONA 85072<999 WILLIAM F.CONWAY EXECUTIVE VICE PRESIDENT NUCLEAR 161-04240-WFC/GAM October 25, 1991 Docket Nos.STN 50-528/529/530 U.S.Nuclear Regulatory Commission Attn: Document Control Desk Mail Station Pl-37 Washington, D.C.20555

Dear Sirs:

Sub)ect: Palo Verde Nuclear Generating.Station.(PVNGS)

Units 1, 2, and 3 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)" File: 91-010-026; 91-056-026 Enclosed with this letter is the Arizona Public Service Company (APS)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)." This response is being submitted to the NRC under oath or affirmation.

Should you have any questions regarding this submittal, please contact Michael E.Powell of my staff at (602)340-4981.Sincerely, WFC/GAM/gam Enclosure cc: J.B.Martin D.H.Coe A.C.Gehr A.H.Gutterman 9iii050104 9ii025 PDR ADOCK 05000528 P*PDR'I 1 ,~1 t I 161-04240-WFC/GAM Octobe" 251991 STATE OF ARIZONA))ss.COUNTY OF MARICOPA)I, W.F.Conway, represent that I am Executive Vice President Nuclear, that the foregoing document has been signed by me on behalf of Arizona Public Service Company with full authority to do so, that I have read such document and know its contents, and that to the best of my knowledge and belief, the statements made therein are true and correct.W..F.Conway Sworn To Before Me This 8 Dey Of C 1991."No.tary Public e Hy Commission Expires 0 3 C RESPONSE TO GENERIC LETTER 91-06 UESTION RESPONSE The following information is to be provided for each unit at each site: 1.Unit: PVNGS All three PVNGS units are essentially identical, and the Units 1,2&3 information provided herein is applicable to all three units.2.a.The number of independent redundant divisions of Class IE or safety-related DC power for this plant is: (Include any separate Class IE or safety-related DC, such as any DC dedicated to the diesel generators.)

Two There are two independent redundant divisions (load groups)of Class IE or safety-related DC power.Each load group is comprised of two subsystems.

The two DC load groups are identified in the PVNGS Technical Specifications, Table 3.8-1 as Trains A and B.This configuration is graphically shown in the PVNGS UFSAR Figure 8.3-4.b.The number of functional safety-related divisions of DC power necessary to attain safe shutdown for this unit is: One The PVNGS UFSAR, Section 8.3.2.2.1.3 describes that the complete loss of either of the DC subsystems (one per each DC load group)which supply control power for their respective Class IE AC load groups will not prevent the minimum safety functions from being performed.

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: (BL001S)A-1 0 3%V*<P f RESPONSE TO GENERIC I EITER 91-06 UESTION RESPONSE 1.Battery disconnect or circuit breaker open?Yes On annunciator panels ESA-UA-2E and ESB-UA-2F (Procedures 41AI 1ES2A, 41AL-1ES2B, 42AI 2ES2A, 42AI 2ES2B, 43AL-3ES2A, and 43AI 3ES2B).2.Battery charger disconnect or circuit breaker open (both input AC and output DC)?No A separate independently annunciated alarm for an open charger disconnect or open input circuit breaker is not provided.However, these alarms are provided on the common charger trouble alarm for each charger, which provides annunciation, CRT display, and typewriter printout in the Control Room (Dwg 13-E-PKB-004).

3.DC system ground?No Independent annunciation is not provided, however, DC system ground is alarmed on a common alarm for each DC subsystem, which provides annunciation, CRT display, and typewriter printout in the Control Room (Dwgs 13-E-PKB-001 and 13-E-PKB-002).

4.DC bus undervoltage?

No Independent annunciation is not provided, however, DC system undervoltage is alarmed on a common alarm for each DC subsystem, which provides annunciation, CRT display, and typewriter printout in the Control Room (Dwgs 13-E-PKB-001 and 13-E-PKB-002).

5.DC bus overvoltage?

No Bus overvoltage is not provided, but overvoltage is alarmed as a part of the common alarm (the charger DC high voltage output relay is monitoring the DC bus potential).

The common alarm provides annunciation, CRT display, and typewriter printout in the Control Room (Dwgs 13-E-PKA-002, 13-E-PKA-004, 13-E-PKA-005, 13-E-PKA-007, and 13-E-PKB-004).(BLOOIS)A-2 0

RESPONSE TO GENERIC LEITER 91-06 UESTION RESPONSE 6.Battery charger failure?No Independent annunciation is not provided, however, battery charger failure is alarmed on a common alarm for each DC subsystem, which provides annunciation, CRT display, and typewriter printout in the Control Room (Dwgs 13-E-PKB-001 and 13-E-PKB-002).

7.Battery discharge?

No However, battery discharge is alarmed indirectly.

During normal operation, the 125 VDC load and battery charging current is supplied by the battery charger.Failure of the battery charger to supply those loads is alarmed.Charger output voltage is alarmed (charger undervoltage relay)at 120 volts DC.If the bus voltage drops to 112 volts, the DC bus undervoltage relay will actuate an additional alarm (Procedures 41AL-1RK1A, 42AL-2RK1A, 43AL-3RK1A).

b.Indications:

1.Battery float charge current?No Battery current indication does not read float charge current (it has 0-1500 amp scale).However, the control room has voltage indication that corresponds to charge/discharge.

Also, float charge current is verified during the 7-day surveillance (Procedure 32ST-9PK01).

2.Battery circuit output current?Yes Panel B01 (Dwgs 13-E-PKB-001 and 13-E-PKB-002).

3.Battery discharge?

No Battery discharge indicator is not provided;however, a weekly surveillance test is performed to obtain specific gravity and voltage of each designated pilot cell.This indicates the state of battery charge (Procedure 32ST-9PK01).

(8L001S)A-3 0'0 I RESPONSE TO GENERIC LEITER 91-06 UESTION 4.Bus voltage?Yes RESPONSE Panel B01 (Dwgs 13-E-PKA-002, 13-E-PKA-004, 13-E-PKA-005, 13-E-PEA-007).

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

Yes These procedures are: Procedures 41AL-1RK1A, 41AI 1ES2A, 41AL-1ES2B 42AL-2RK1A, 42AI 2ES2A, 42AI 2ES2B 43AL-3RK1A, 43AL-3ES2A, 43AL-3ES2B 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 DC bus and the battery charger from its AC power source during maintenance or testing?Yes Annunciation is provided when battery breakers are not in the closed operating position.Annunciation is provided when the charger AC power breaker is open or the DC disconnect is open, as discussed in question 3.a.2 response (Dwgs 13-E-PKB-001, 13-E-PKB-002, 13-E-PKB-004).

5.If the answer to any part of question 3 or 4 is no, then provide information justifying the existing design features of the facility's safety-related DC systems.*See note below.JustiGcation is provided in the Comments/JustiGcation section following each specific question with a"no" answer.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 unavailable?

and No Physical separation, electrical isolation, and redundancy are provided to prevent the occurrence of common mode failures.In addition, no provision exists for transferring loads between redundant 125 V-DC subsystems (UFSAR 8.3.2.2.1.3 and 8.3.2.2.1.16).(BL001S)A-4 k

RESPONSE TO GENERIC LETTER 91-06 UESTION RESPONSE (2)Do plant procedures prohibit maintenance or testing on redundant DC divisions at the same time?Yes This is addressed in Procedures 40AC-90P18, and 73AC-9ZZ04.

Also, Technical SpeciGcations 3.8.2.1 and 3.8.2.2 require at least one operable DC train in all modes.If the facility Technical SpeciGcations 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: The PVNGS Technical Specifications have provisions equivalent to those found in the Combustion Engineering Standard Technical Specifications for maintenance and surveillance; however, question 7 will be answered for veriGcation purposes.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 within acceptable limits: 1.Pilot cell electrolyte level?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK01.

2.Specific gravity or charging current?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK01.

3.Float voltage?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK01.

(810018)

RESPONSE TO GENERIC LEITER 91-06 UESTION RESPONSE 4.Total bus voltage on fioat charge?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK01.

5.Physical condition of all cells?Yes Procedure 32ST-9PK01.

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: Technical Specification 4.8.2.1.b specifies these surveillance requirements be performed at least once per 92 days and within 7 days after a battery discharge with a battery terminal voltage below 105 volts, or battery overcharge with a battery terminal voltage above 145 volts.Technical specification Table 4.8-2, footnote (1)specifies that if any category A parameter (including pilot cell specific gravity or battery charging current less than two amps on charge)is outside the 7 day surveillance requirement, all category B measurements (including those parameters in Question 7.b, 1 through 6 of this response below)must be taken and found within their allowable values.1.Electrolyte level of each cell?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK02.

2.The average specific gravity of all cells?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK02.

3.The specific gravity of each cell?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK02.

4.The average electrolyte temperature of a representative number of cells?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK02.(BL0018)A-6 I'

RESPONSE TO GENERIC L5WHER 91-06 UESTION RESPONSE 5.The float voltage of each cell?Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK02.

6.Visually inspect or measure resistance of terminals and connectors (including the connectors at the DC bus)?No Technical Specification Surveillance Requirement 4.8.2.1 and Procedure 32ST-9PK02 require visual inspection or resistance measurement of battery terminals and connectors during the 92 day surveillance test of station batteries.

However, the DC bus connector visual inspection is done as part of the inspection and testing of the DC motor control center, scheduled every third refueling outage.Increased periodicity of the DC bus connector visual inspection is not considered necessary because these connectors are not in close proximity to the battery cells, and therefore are not subject to the potentially corrosive environment of the battery.c.At least every 18 months are the following verified: 1.Low resistance of each connection (by test)?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK03.

2.Physical condition of the battery?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK03.

3.Battery charger capability to deliver rated ampere output to the DC bus?Yes Technical Specification Surveillance Requirement 4.8.2.1;Procedure 32ST-9ZZ34.(BL001S)A-7 0

I RESPONSE TO GENERIC LEITER 91-06 UESTION RESPONSE 4.The capability of the battery to deliver its design duty cycle to the DC bus?Yes Technical SpeciGcation Surveillance Requirement 4.8.2.1;Procedure 32ST-9PK03.

5.Each individual cell voltage is within acceptable limits during the service test?Yes Procedure 32ST-9PK03 requires that each cell voltage be monitored during the 18 month battery service discharge test, so that the test can be suspended when any cell voltage drops below acceptable limits.d.At least every 60 months, is capacity of each battery veriGed by performance of a discharge test?Yes Technical Specification Surveillance Requirement 4.8.2.1.e.At least annually, is the battery capacity veriGed by performance discharge test, if the battery shows signs of degradation or has reached 85%of the expected service life?Yes Technical SpeciGcation Surveillance Requirement 4.8.2.1.8.Does this plant have operational features such that following loss of one safety-related DC power supply or bus: (BU$1S)A-8 E

RESPONSE TO GENERIC LETTER 91-06 UESTION RESPONSE a.Capability is maintained for ensuring continued and adequate reactor cooling?Yes The PVNGS UFSAR, Section 8.3.2.2.1.13 discusses how each unit has separate and independent DC electric systems capable of supplying minimum ESF loads and loads required for attaining a safe and orderly cold shutdown of the unit assuming a single failure.Procedures 41AO-1ZZ17, 42AO-2ZZ17 and 43AO-3ZZ17 provide guidance to the operators for actions following loss of 125 VDC Class IE electrical power and address the capability to ensure that continued and adequate core cooling is maintained.

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

Yes The PVNGS UFSAR, Section 8.3.2.2.1.13 discusses how each unit has separate and independent DC electric systems capable of supplying minimum ESF loads and loads required for attaining a safe and orderly cold shutdown of the unit assuming a single failure.Procedures 41AO-1ZZ17, 42AO-2ZZ17 and 43AO-3ZZ17 provide guidance to the operators for actions following loss of 125 VDC Class IE electrical power and address maintaining reactor coolant system integrity and isolation capability.

c.Operating procedures, instrumentation (including indicators and annunciators), and control functions are adequate to initiate systems as required to maintain adequate core cooling?Yes Procedures 41AO-1ZZ17, 42AO-2ZZ17, 43AO-3ZZ17, provide guidance to the operators for actions following loss of 125 VDC Class IE electrical power.These procedures describe the indicators and annunciators and control functions to initiate systems as required to maintain adequate core cooling.(BM01S)A-9 RESPONSE TO GENERIC LEITER 91-06 UESTION RESPONSE 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.The basis for the"no" answers to questions 6(1)and 7.b.6 are provided in the Response section for those questions.

All other parts to question 6, 7 and 8 are answered"yes".*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 commit 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: The supporting information and justiGcation for any"no" responses has been provided in this submittal.

No further evaluation of the need for the provisions with"no" responses is planned.(2)So state in response to these questions, and 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." (BL001S)A-10 f't 1 A 4 I l I