PNO-V-89-004, on 890106,reactor Trip & Safety Injection Actuation Occurred.Caused by Failure of non-1E Power Supply Due to Ground Jumper.Jumper Removed & Steam Generator Level Sensing Lines Blown Down for Sludge Accumulation
| ML13316A460 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/09/1989 |
| From: | Andrew Hon, Johnson P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| References | |
| PNO-V-89-004, PNO-V-89-4, NUDOCS 8901200095 | |
| Download: ML13316A460 (2) | |
ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULAT*
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ACCESSION NBR:8901200095 DOC.DATE: 89/01/09 NOTARIZED: NO DOCKET #
FACIL:50-362 San Onofre Nuclear Station, Unit 3, Southern Californ 05000362 AUTH.NAME AUTHOR AFFILIATION JOHNSON,P.
Region 5, Ofc of the Director HON,A.
Region 5, Ofc of.the Director RECIP.NAME RECIPIENT AFFILIATION
SUBJECT:
PNO-V-89-004 on 890106,reactor trip & safety injection R
actuation occurred.Caused by power supply failure.
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PRELIMINARY NOTIFICATION OF E T OR UNUSUAL OCCURRENCE--PNO-V -04 Date 01/09/89 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance.
The information presented is as initially received without verification or evaluation and is basically all that is known by Region V staff on this date.
FACILITY:
SOUTHERN CALIFORNIA EDISON Emergency Classification SONGS UNIT 3 Notification of Unusual Event DOCKET NO. 50-362 Alert SAN CLEMENTE, CA Site Area Emergency General Emergency X
Not Applicable
SUBJECT:
REACTOR TRIP AND SAFETY INJECTION ACTUATION San Onofre Unit 3 experienced a reactor trip and safety injection (SI) actuation at 11:35 p.m. PST on Friday, January 6, 1989. The cause of the event was failure of a non-1E uninterruptible power supply (UPS), which caused a perturbation in the feedwater control system. The initiating sional for the reactor trip was low level in steam generator E-089, which resulted from the feedwater control perturbation. Main steam bypass valve control was in manual at the time of the trip (set at 900 psig) in support of routine surveillance testino on the turbine governor valves. This resulted in a faster cooldown of the reactor coolant system (RCS) and caused RCS pressure to drop below the SI actuation setpoint; however, the lowest pressure reached was 1720 psig, and no SI flow occurred. Other safety features functioned as required, and plant operators established stable plant conditions without difficulty.
The licensee concluded that the UPS inverter failed because of a ground jumper which was installed during the last refueling outage (to reduce interference while a temporary power supply was in use) but was not subsequently removed. This jumper appears to have also caused or contributed to failure of two other transformers in the non-1E UPS in July and October 1988. The jumper has now been removed by the licensee.
One steam generator low level trip also exceeded its required response time (1.3 vs.
0.9 seconds); the licensee blew down all steam generator level sensing lines to remove any possible sludge accumulation. Upon completion of a post-trip review, the reactor was taken critical at 1:37 a.m. PST on Monday, January 9, 1989 with the non-1E instruments powered from their backup power supply (UPS repair still in progress).
The unit entered Mode 1 at 5:25 a.m. and was synchronized with the grid at 9:54 a.m.
This information ip current as of 11:00 a.m..PST on January 9, 1989.
Contact:
P. Jo n
A. Hon (FTS) 63-3745 (714) 492-2641 DISTRIBUTION BY 5520:
FAX TO:
Date Time Date Time Chairman Zech EDO RI INPO Comm. Roberts AEOD RII NSAC Comm. Carr PAO RIII LICENSEE Comm. Rogers SLITP RIV RESIDENT INSPECTOR Comm. Curtiss NRR HQS. OPERATIONS OFFICER SECY NMSS PDR ARM MAIL TO:
ACRS OIA DOT:(Trans. Only, Applicable State)
GPA RES CA RV FORM 211 Revised: 8/19/87 8901200095 890109 PDR 18tE PNU PNO-V-89 0 0 4