PNO-IV-89-030A, on 890419,freeze Seal Failed on 6-inch Standby Svc Water Line.Caused by Flooding Portions of Auxiliary Bldg.Svc Water Sys Isolated & RHR Restarted

PNO-IV-89-030A:on 890419,freeze Seal Failed on 6-inch Standby Svc Water Line.Caused by Flooding Portions of Auxiliary Bldg.Svc Water Sys Isolated & RHR Restarted

ML20245F331
Person / Time
Site:	River Bend
Issue date:	04/24/1989
From:	Constable G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
References
PNO-IV-89-030A, PNO-IV-89-30A, NUDOCS 8905020343
Download: ML20245F331 (2)

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April 24,1989 m PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PN0-IV-89-30A i

- This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region IV' staff on this date.

FACILITY: Gulf States Utilities Licensee Emergency Classification:

River Bend Station Notification of Unusual Event Docket 50-458 Alert Site Area Emergency General Emergency 1

~ T ~~ Not Applicable  !

SUBJECT:

AIT COMPLETES INSFECTION AT RIVER BEND STATION This PN update provides clarification for the event reported on April 20, 1989, at River Bend Station (RBS).

The NRC Augmented Inspection Team (AIT) arrived on site on April 21, 1989. Prior to that time, the NRC Senior Resident Inspector (SRI) monitored the licensee's preliminary response to the event. The AIT was composed of a materials engineer, an electrical engineer, an SRI, a Region IV reactor inspector, and a team leader assisted by the NRR Project Manager and the NRC Senior Resident Inspector stationed at RBS.

At about 11:50 p.m. on April 19, 1989, a freeze seal failed on a 6-inch standby service water line. The freeze seal had been established to allow inspection and repair work on manual isolation valves to a safety-related auxiliary building cooler. The bonnet of the manually operated valve was off the valve and the service water system was in operation at the time of the event. The failure of the freeze seal resulted in flooding portions of the Auxiliary Building. Approximately 15,000 gallons of service water was  :

discharged through the disassembled valve covering portions of the 141-foot level of the Auxiliary Building floor with about 4 inches of water. A portion of the water flowed through holes in the floor under safety-related 480 Vac motor control centers (MCC) onto nonsafety-related cabinets on the 114-foot level containing 13.8 kV disconnect links and a 13.8 kV/480 Vac transformer.

The cabinets were not designed to shed the water leading to an electrical fireball that damaged the cabinet and components. A 13.8 kV breaker opened, deenergizing that cabinet and two others causing the loss of the residual heat removal (RHR) system, normal spent fuel pool cooling and normal lighting in l' the auxiliary building and the reactor building. The operators isolated the service water system in 15 minutes and restarted RHR in about 17 minutes. No appreciable increase in reactor coolant temperature was observed. Backup spent fuel cooling (service water) was available but was not immediately "

needed. Temperature in the spent fuel pool rose to 123'F at which time normal cooling water was restored and temperature was returned to normal.

The AIT reviewed the event, inspected the affected equipment, and interviewed various managers, operators, engineers, and technicians involved. The preliminary team findings indicate:

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1 Licensee control of freeze seal activities may not have been adequate.

Operator response to this event under the circumstances was satisfactory.

The electrical system performed as expected under the circumstances. No damage to safety-related electrical equipment has been identified.

Licensee engineering personnel are reviewing the potential for damage to individual safety-related components in redundant divisions by similar flooding events.

The AIT inspection was completed earlier today. A meeting with licensee management is scheduled for this afternoon. The preliminary AIT findings will be discussed. The AIT findings will be documented in NRC Inspection Report 50-458/89-20, which will be published in the near future.

The NRC issued a press release on April 21, 1989. The licensee and NRC are responding to media inquiries and there has been local media coverage.

The state of Louisiana has been informed. ,

Region IV received this updated information by fax from the AIT team leader on site.

This information has been confirmed with a licensee representative.

CONTACT: G. L. Constable, 728-8151 DISTRIBUTION:

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Com. Rogers GPA 01 INP0 egions & HQ)

Conn. Curtiss PA SLITP H-St PDR ACRS EDO OE TDT NSAC EW-W RRI ASLAP NRC Ops Ctr Licensee (Reactor)

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