ML18024A538

RO#50-296/7822 on 780822:during Startup at 3% Thermal Pwr, MSRV 1-4 Opened & Did Not Reclose Completely,Resulting in Excessive Vessel Cooldown Rate,Due Apparently to Excessive Pilot & second-stage Leakage in the Valves

ML18024A538
Person / Time
Site:	Browns Ferry
Issue date:	11/08/1978
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18024A537	List: IR 05000296/1978022 ML18024A536 ML18024A538
References
NUDOCS 7811160104
Download: ML18024A538 (2)

Text

,ER SUPPLEMENTAL INFORMATION BFRO-50-296/7822 Technical Specification Involved: 3.6.A.l Reported under Technical Specification:

6.a.'(2)Date of Occurrence:

August 22, 1978 Time of Occurrence:

9:23 a.m.Unit: 3 Identification and Descri tion of Occurrence During startup at 3-percent thermal power, MSRV 1-4 opened and did not completely reclose resulting in excessive cooldown rate of the vessel.i The torus temperature 0 reached approximately 128 F.Conditions Prior to Occurrence Reactor at approximately 3-percent MWt.A arent Cause of Occurrence Excessive pilot and second-stage leakage.MSRV 1-4 exhibited steam cuts on the pilot and second-stage seats and discs.This condition was similar to conditions found on valves that have experienced the same type of failure.Anal sis of Occurrence It was determined that the transient was less severe than the design blowdown transient.

The fatigue usage factors are as follows: Feedwater nozzles Rx vessel, at waterline Closure studs 0.00091 0.000033 0.000667 Corrective Action The topworks,were replaced on this valve.The blowdown was analyzed in accordance with standard heatup/cooldown analysis techniques and fatigue usage factors assigned.

LER SUPPLE".KNTAL I'AFORIATIOY BFPiO-50-296/7822 Corrective Action (Continued)

Lonp;range corrective action consists of increasing the simmer marpin of the valve.Additionally, 2-stage topworks have been procured and will he installed subsequent to evaluation by the Division of Fngineering Design.A ri cent revision to the technical speci.fications which lowered the setpoint for the reactor water level isolation of the main steam lines should minimis<.the operation of the safety relief valves.Failure Data 926/788 and 296/7821 JGD: JAH 10/4/73