ML20133G436

Ro:On 851007,reactor Trip Occurred.Caused by Loss of Power from Offsite Sources.Plant Stabilized Using Natural Circulation to Remove Decay Heat Via Steam Generators.Ler Will Be Submitted within 30 Days

ML20133G436
Person / Time
Site:	Palo Verde
Issue date:	10/08/1985
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
ANPP-33678-EEVB, NUDOCS 8510150464
Download: ML20133G436 (2)

Text

-- . _ _

Arizona Nuclear Power Project P.O. BOX $2034 e PHOENIX, ARIZONA 85072-2034 October 8, 1985 ANPP-33678-EEVB/GEC U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555

Subject:

Palo Verde Nuclear Generatin.; Station (PVNGS)

Unit 1 Docket No. STN 50-528, License No. NPF-41 Report of Notification of Unusual Event - Reactor Trip File: 85-056-026; G.I.01.10 Gentlemen:

Attached please find a report describing a Notification of Unusual Event at the Palo Verde Nuclear Generating Station on October 7, 1985. This report addresses a reactor trip resulting from a loss of power to the unit from offsite sources.

This report is prepared and submitted pursuant to Table 5.3-1 of the PVNGS Emergency Plan. By copy of thic letter we are also forwarding a copy of the report to the Regional Administrator of the Region V Office and other offsite authorities.

If you have any questions or concerns, please contact me. ,

Very truly yours, Sw E. E. Van Brunt, Jr.

Executive Vice President Project Director EEVB/GEC/alh Attachment cc: J. B. Martin (all w/a) 1 R. P. Zimmerman R. F. Fish, Jr.

E. A. Licitra R. A. Colson, ADES C. E. Tedford, ARRA R. E. Bluhm, MCDCD&ES R. G. Godbebere, MCSO f

R. T. Milstead, DPS p ,

IMP 0 Records Center 8510150464 851008 l .

PDR ADOCK 05000528 I S PDR l

o .

PALO VERDE NUCLEAR GENERATING STATION UNIT 1 NOTIFICATION OF UNUSUAL EVENT OF OCTOBER 7, 1985 Docket No. 50-528 License No. NPF-41 At 2017 MST on October 7, 1985, the NRC Operations Center was notified, via the Emergency Notification System, of the declaration of a NOTIFICA-TION OF UNUSUAL EVENT for Unit 1 of the Palo Verde Nuclear Generating Station. The NOTIFICATION OF UNUSUAL EVENT was declared pursuant to Emergency Plan Implementing Procedure - 02, which requires the reporting of a reactor trip which is complicated by concurrent or subsequent events or conditions.

At approximately 1958, the plant was in Mode 3, with pressure of 2250 psi and temperature of 565 degrees F, when a loss of power to the unit from offsite sources caused a reactor trip. The part length and shutdown Control Element Assemblies were withdrawn in preparation for startup.

The exact cause of the loss of power is under investigation at this time.

The loss of power caused all four of the reactor coolant pumps to lose power. The reactor protection system detected an imminent loss of forced circulation, and initiated a reactor trip. The reactor coolant system was cooled via natural circulation following the loss of forced circu-lation.

]

In response to the loss of of fsite power to the essential power buses, both diesel generators started and loaded as designed. The transient also caused the initiation of Control Room Essential Filtration, Fuel Building Essential Ventilation, and Containment Purge Isolation.

All safety systems performed as designed, and in a conservative manner.

At 2003, the Shift Supervisor declared a NOTIFICATION OF UNUSUAL EVENT, and made the appropriate notifications.

The plant was stabilized using natural circulation to remove decay heat via the steam generators. There was not sufficient decay heat to require the use of steam bypass or atmospheric dump valves. The transient did not result in any challenges to the fission product barriers, or result in any releases of radioactive materials.

Offsite power was restored to the unit at approximately 2011, and a re-actor coolant pump restored to service at about 2042, restoring forced circulation. The NOTIFICATION OF UNUSUAL EVENT was terminated at 2044 The event continues to be evaluated, and a Licensee Event Report will be submitted within 30 days to further describe this occurrence.