PNO-III-97-085, on 971009,licensee Identified Gas While Venting Unit 1 Safety Injection Sys Discharge Piping During Monthly Venting Surveillance Test.On 971010,unit 2 Reactor Tripped as Result of Degraded Voltage on Power Supply

PNO-III-97-085:on 971009,licensee Identified Gas While Venting Unit 1 Safety Injection Sys Discharge Piping During Monthly Venting Surveillance Test.On 971010,unit 2 Reactor Tripped as Result of Degraded Voltage on Power Supply

ML20206R304
Person / Time
Site:	Byron
Issue date:	10/14/1997
From:	Lanksbury R, Tongue T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-97-085, PNO-III-97-85, NUDOCS 9901190236
Download: ML20206R304 (2)

--- ._~- ~-- --_ . . - _ ~ _ . _ -- . - . ~ . - , - . . . _ . . -

r.

l October 14, 1997 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-III-97-085 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 Region III staff (Lisle, Illinois) on this date.

Facility Licensee Emergency Classification Commonwealth Edison Co. Notification of Unusual Event l Byron 1 2 Alert 1 Byron, Illinois Site Area Emergency Dockets: 50-454,50-455 General Emergency X Not Applicable

Subject:

UNIT 1 REACTOR SHUT DOWN TO REPAIR CHECK VALVE IN SAFETY j INJECTION SYSTEM; UNIT 2 REACTOR SUBSEQUENTLY TRIPS FOR UNRELATE On October 9, 1997, the licensee identified gas while venting the Unit 1 safety injection system discharge piping during a monthly venting surveillance test. This gas was traced to dissolved nitrogen from a safety injection accumulator which,was back leaking through a check valve in the cold leg piping of the safety injection system. The water leakage through the check valve was calculated to be 5 gallons per minute, which exceeded the Technical Specification limit of 1 gallon per minute.

When the valve could not be repaired within the 4-hour limiting condition for operation, the licensee began a reactor shutdown, as required.  ;

The length of the Unit 1 outage has not been determined.

At about 11:15 a.m. on October 10, 1997, the Unit 2 reactor tripped as a result of degraded voltage on a power supply for the control rod system.

There are two parallel power supplies. The licensee was replacing one of the power supplies when the voltage on the operating power supply dropped below a 13-volt setpoint, causing one bank of control rods to drop into ,

the reactor. This control rod insertion, in turn, caused the reactor i trip.

Unit 2 had been scheduled to begin a maintenance outage on October 11, 1997, to. repair a leaking steam extraction line in the main condenser.

l The resident inspectors will monitor the licensee's outage and repair activities.

The State of Illinois will be notified. The information in this preliminary notification has been reviewed with licensee management.

~ ~

9901190236 971014 PDR I&E $

PNO-III-97-085 PDR i

c; d

r.*

l PAGE 2 i I PN-397085 f . .

The licensee notified the NRC Operations Center of the safety injection surveillance test results at 12:43 p.m. on October 9, 1997. Additional information was subsequently provided. Region III (Chicago) was notified of the Unit 2 reactor trip about 11:30 a.m. on October 10, 1997. The information in this preliminary notification is current as of 2:30 p.m.

on October 10, 1997.

Contact:

THOMAS TONGUE ROGER LANKSBURY (630)829-9613 (630)829-9631 l

l l

l i