ML20064F279

/03X-1 on 780527:during Unit Startup,B S/G Code Safety Valve Lifted Causing Tavg to Drop Below 541 Degrees F in Violaion of T/S3.1.1.5.Caused by Broken Lower Adjusting Ring Locking Pin.Valve Was Replaced

ML20064F279
Person / Time
Site:	Farley
Issue date:	11/20/1978
From:	ALABAMA POWER CO.
To:
Shared Package
ML20064F267	List: ML20064F266 ML20064F271 ML20064F274 ML20064F279
References
LER-78-038-03X, LER-78-38-3X, NUDOCS 7811280348
Download: ML20064F279 (3)

Text

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LICENSEE EVENT REPORT Update Report Previous Report Date 6/26/78

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63 ft DOCK E T isuuBER 61 69 EVENT OATE 14 76 HEPORT DATE 80 tvENT DESCRIPTION ANO PROB A0LE CONSEQUENCES h

[o g l l At 0400, during a unit startup, B S/G code safety valve lif ted, causing Tavn to drop i gny3j ; below 541 F. T/S 3.1.1.5 requires that RCS lowest operating loop temp Tavg be greater l lnI.:1 [ than/ equal to 541 F. Tavg was restored to within T/S limits at 0405. The code safety l g n i s ; ; valve f ailed to resent af ter the unit was brought on line, and an attempt was made to l 1 c 16 I I gag the valve to rescat it. T/S 3.7.1.1 requires all main steam line code safety valvbs l0l7i [ be operable. At 0538 unit tripped (high S/C level) and was cooled down to replace l g .i g valve. T/S requirements were met. Health / safety of public not affected. l 7 9 80 1"STEY C A'.:SE CAUSE COMP. VALVE COCE COCE SubCODE CoVPONENT CODE SUSCODE SU8 CODE 10101 l cl cl@ Lt_J@ La_J G I V l ^ I t I V l E l X lh LXJh [pj h 7 8 9 10 11 12 13 is 19 20

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i ALABAMA POKER COMPAh"i JOSEPil M. FARLEY NUCLEAR PLANT DOCKET NO. 50-343 ATTACliMENT TO LER 78-038/03X-1 Facility: Joseph M. Farley Unit 1 Report Date: (Update Report - Previous Report Date 6/26/78) ~ -[

Event Date: 5/27/78

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js Identification of Event

Tavg decreased below technical specification limit of 541F; main steam line code safety valve failed to reseat af ter lif ting.

Conditions Prior to Event:

1 The unit was in Mode 1 at approximately 8% of full power. A routine startup operation was in progress. The unit was not on-line.

Description of Event:

, At 0400 on 5/27/78, while transferring from turbine throttle valve control to governor valve control during a unit startup, a pressure transier.t caused one main steam line code safety valve (Q2N11V011A) associated with the B steam generator to lift. The effective increase in load resulted in the Tavg decreasing below 541F. Technical Specification

. 3.1.1.5 requires that the reactor coolant system lowest operating loop temperature Tavg be greater than or equal to 541F. The Tavg was returned to within the technical specification limits at 0405.

After lif ting, the code safety valve failed to reseat. The Emergency Director was notified, and plant personnel were prepared to take the 4

necessary emergency action if plant conditions required. The unit was brought on line and the load increased to approximately 20% in order to decrease main steam pressure enough to cause the valve to shut, and also to prevent an uncontrolled cooldown. When this attempt failed, it was decided to gag the valve. Plant conditions were being maintained at 20%

power while gagging the valve when a steam generator level transient resulted in a high-high steam generator level turbine trip-reactor trip.

The unit was cooled down and placed in Mode 5 in order to replace the

valve.

The valve was replaced, the valve setpoint was verified, and the unit was returned on-line at 0231 on 5/30/78.

Designation of Apparent Cause:

Decrease in Tavg was due to lif ting of main steam line code safety valve. Failure of code safety valve to rescat was due to broken lower adjusting ring locking pin. This allowed the lower adjusting ring to move upward and prevent the valve from reseating. The pin was subsequently determined to have failed due to fatigue. The vendor has stated that it l

I

5 78-038/03X-1 is highly probable that localized stresses were created during machining of the pin which were not apparent during the surface inspection of the pin subsequent to machining. These stresses greatly multiplied the effects of the relatively low applied stresses on the pin during valve operation, and eventually resulted in failure of the pin.

Analysis of Event:

I The Tavg was returned to within its limit within the time period specified in Technical Specification 3.1.1.5.

The code safety valve lifted at its set pressure, 1075 psig + 1%. The requirements of Technical Specification 3.7.1.1 were complied with.

The vendor considers the failure of'the pin to be a random failure peculiar'only to the Farley Plant and that there is an extremely low probability of a similar failure occerring. Should a similar failure occur, it would not affect the setpoint or the ability of the valve to lift and relieve overpressure. There is a potential for the valve not to seat (similar to the failure which occurred).

This occurrence did not affect the health and safety of the public. ,

f Effect on plant:

) This occurrence resulted in a unit shutlown. The unit was off-line for approximately 69 hours7.986111e-4 days <br />0.0192 hours <br />1.140873e-4 weeks <br />2.62545e-5 months <br />.

Corrective Action:

Reactor power was increased to increase Tavg.

When.the code safety valve could not be seated, the unit _was cooled

. down, and the valve was replaced. -

j The vendor has modified his inspection procedure to preclude the possibility of a similar failure. The vendor feels that the probability that other pins installed at Farley have similar stresses is extremely remote; however, the existing ring pins will be replaced during the refueling outage.

Failure Data:

Q2N11V011A is a type 3707RA-RT22, 6 inch safety valve manufactured by the Dresser Industrial Valve and Instrument Division. Dresser has stated that this is the first failure of.a ring pin on a 3700 Series W1w.

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