ML17304A555

Suppl to Special Rept 1-SR-85-010:on 850509,emergency Diesel Generators a & B Failed to Attain Required Voltage,Frequency & Speed.Caused by Inadequate Design of Heater Control Sys. Mod to Replace Temp Control Valves Implemented

ML17304A555
Person / Time
Site:	Palo Verde
Issue date:	09/12/1988
From:	Haynes J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
1-SR-85-010, 1-SR-85-10, 192-00409-JGH-T, 192-409-JGH-T, NUDOCS 8809260264
Download: ML17304A555 (8)

Text

OSI'RIBUTION DEMON&ATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCE SSION NBR:8809260264 DOC.DATE: 88/09/12 NOTARIZED: NO 'OCKET FACIL.STN 50 528 Palo Verde Nuclear Station, Unit 1, Ari'z o n a Pu bli 05000528 AUTH. NAME AUTHOR AFFILIATION HAYNES,J.G. Arizona Nuclear Power Project (formerly Arizona Public Se v RECIP.NP4!E RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Suppl to Special Rept 1-SR-85-010:on 850509,re failure of diesel generators A.:& B to attain required voltage.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR / ENCL / SIZE: 3 TITLE: 50.73 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:Standardized plant. 05000528 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ZD CODE/NAME LTTR ENCL PDS LA 1 1 PD5 PD 1 1 CHAN,T 1 1 DAVIS,M 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB , 1 1 DEDRO 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ZCSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB NRR/DREP/RPB 10 ll 1 2

1 2

NRR/DREP/RAB NRR +IS/SIB 10 9A 1

1 1

1 NUDOCS-ABSTRACT 1 1 EG FI4 02 1 1 RES TELFORD,J 1 1 RES DSZR DEPY 1 1 RES/DSIR/EZB 1 1 RGN5 FIL'E 01 1 1 EXTERNAL: EG&G WILLIAMSgS 4 4 FORD BLDG HOYiA 1 1 H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC HARRIS,J 1 1 NSIC MAYS i G 1 1 NOTES 1 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 48 ENCL 47

Arizona Nuclear Power Project P.O. BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 192-00409-JGH/TDS/JEM September 12, 1988 U.S. Nuclear Regulatory Commission NRC Document Control Desk Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station Unit 1 Docket No. STN 50-528 (License NPF-41)

Supplement to Special Report 1-SR-85-010 File: 88-020-404 Attached please find Supplement 1 to Special Report 1-SR-85-010 prepared and submitted pursuant to Technical Specification 4.8. 1. 1.3 and 6.9.2. This report is submitted to provide updated information from the original report.

If you have any questions, please contact T. D. Shriver, Compliance Manager at (602) 393-2521.

Very tru y yours, J. G. Haynes Vice President Nuclear Production JGH/TDS/JEM/kj Attachment cc: D. B. Karner (all w/a)

E. E. Van Brunt, Jr.

T. J. Polich M. Davis A. C. Gehr INPO Records Center 8809260264 880912 PDR ADOCK 05000528 S PNU

PALO VERDE NUCLEAR GENERATING STATION UNIT 1 Supplement to Special Report 1-SR-85-010 Nonvalid Diesel Generator. Test Docket No. STN 50-528 License No. NPF-41 This supplement to Special Report 1-SR-85-010 provides updated information of the events of Hay 9, 1985, in which Emergency Diesel Generators (EDG) "A" and "B" failed to attain the required voltage, frequency and speed within ten (10) seconds. This report is written in accordance with Regulatory Position C.3.b of Regulatory Guide 1. 108, Revision 1, August, 1977.

At approximately 1418 HST on Hay 9, 1985 Palo Verde Unit 1 was in Node 3 (HOT STANDBY) when the "B" EDG failed to attain the required voltage, frequency and speed within ten (10) seconds on three (3) successive start attempts. As a result of the EDG "B" start failures, the EDG was declared inoperable.

Pursuant to Technical Specifications, which require that an EDG be demonstrated operable when the other becomes inoperable, an attempt was made to start EDG "A". However, EDG "A" failed to attain the required voltage, frequency and speed within ten (10) seconds. As a result of this start failure, EDG "A" was also declared inoperable.

Failure of the DGs to start within 10 seconds has been traced to inadequate design of the Heater Control System for the intake air header (turbocharger manifold). The purpose of the Heater Control System is to help ensure quick starting and smooth acceleration of the EDGs.

Heater Control of the intake air header is performed by heat exchanger coils in the heater/intercooler. When the temperature of the air into the heater/intercooler is less than 105'F, the heater temperature control valve opens allowing warm engine jacket water to heat the intake air header.

The heater temperature control valve is an air operated valve. To fully modulate, the temperature control valve may require 20 minutes. However, it is possible for the temperature control valve to modulate indefinitely in an intermediate position. During the time that the temperature control valve is in an intermediate position, it vents air continuously to the atmosphere.

Continuous venting of the temperature control valve results in a degraded control air pressure.

The air supply to the temperature control valve also supplies air to the pneumatic fuel rack control valves. The fuel racks allow fuel to be delivered to the EDG. As a result of the continuous venting of the temperature control valve, inadequate air pressure was available to quickly actuate the pneumatic fuel rack control valves. The slow actuation of the pnuematic fuel rack control valves resulted in the slow EDG start times.

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J

Supplement to Special Report 1-85-010 Page 2 The pneumatic fuel rack control valves are bypassed in the emergency operating mode. In actual emergency mode operation the fuel rack is controlled by 125 VDC solenoid operated valves. Since the pneumatic -,fuel rack control valves are bypassed in the emergency operating mode, these failed starts have been reclassified as nonvalid tests. This is in accordance with Position C.2.e(2) of Regulatory Guide 1. 108, Revision 1, August 1977.

As immediate corrective action the air lines to the temperature control valves were plugged to eliminate degraded control air pressure and slow EDG start times due to venting heater control valves. A modification to replace the temperature control valves has now been implemented in all three Units. The new valves do not vent to atmosphere as they change 'position; therefore, control air pressure remains constant.

At the time of this event there had been one (1) valid EDG failure in previous 12 valid tests for Palo Verde Unit 1 EDGs. However, a test interval of 14 days had been implemented due to the improper classification of these EDG start attempts as valid failures.

EDG "B" was returned to service at approximately 2023 HST on Hay 9, 1985. EDG "B" was unavailable for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and 5 minutes. EDG "A" was returned to service at approximately 1942 NST on May ll, 1984. EDG "A" was unavailable for 49 hours5.671296e-4 days <br />0.0136 hours <br />8.101852e-5 weeks <br />1.86445e-5 months <br /> and 55 minutes.