ML20090E481

AO 50-237/75-45:on 750929,HPCI Turbine Failed to Trip at Designated Reactor Coolant Level.Caused by Open Circuit in Turbine Trip Solenoid Valve Coil Due to Failure of Cold Solder Joint within Coil.Hpci Trip Solenoid Valve Replaced

ML20090E481
Person / Time
Site:	Dresden, 05002377
Issue date:	10/09/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
11936, 669-75, A-50-237-75-45, A0-50-237-75-45, NUDOCS 8303310689
Download: ML20090E481 (2)

Text

'Comm ealth Edison ('#

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- * . g.;7 Addr:ss Reply 1::: Post Offica Box 767 Chicago, Illinois 60690 BBS Ltr. #669-75 Dresden Nuclear Power Station R. R. #1 4 to N Morris, Illinois 60450 d(O'.s October 9, 1975 P A r

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Mr. James G. Esppler, Regional Director (~ ,

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Directorate of -Reculatory Opera *,ien-Region III \\' /

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U. S. Hu: lear Regulatory Corticcion '

N 799 Roosevelt Road '

Glen Ellyn, Illinois 60137 'N/ syn _(f SUEJECT: R:"0RT OF AFM0?fuL 00CURRE!CE PER SECTICN 6.6.A OF'THE OECENICAL SPECIFIC?CIC:3 EPCI TUlGI'!E FAILURE TO TRIP

References:

1) Regulatory Guide 1.16 Rev. 1 App'endix A IE FILE COPY

2) Notification of Region III cf U. S. Nuclear. Regulatory'Co:=ission Telephone: l'r. Johncon,1150 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.37575e-4 months <br /> on' September.29,1975

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Telegra=: Keppler,1305 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.965525e-4 months <br /> on September 29, 1975

3) Drawing Nu-Joer 12E2533 Report number: 50-237/75 45 Report Date: October 9, 1975 Occurrence Date: Septe=ber 29, 1975 Facility: Dresden Nuclear . Power Station, Moiris, Illinois 60450 IDiiCIFICATION OF CCC.URRE"CE

'The Unit-2 HPCI turbine failed to trip at the designed reactor coolant level of g+ 48". .

CCNDITIONS PRIOR TO 000URRE* ICE .

The Unit-2 reactor modo cwitch was in the shutdown position. A scram precipitated by high drywell tressure had occurred on Unit-2 cpproximately 50 minutes earlier.

The HICI tebine was operating in response to low reactor coolant level ( <+46") and high drywell pressure signals.

8303310689 751009 -

PDR ADOCK 05000237 S PDR

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Mr. Jams G. K:pplcr Octob:r 9, 1975

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DESCRIPTION OF CCCURRE!CE At 0524 hours0.00606 days <br />0.146 hours <br />8.664021e-4 weeks <br />1.99382e-4 months <br /> en Septenter 29,1975, Unit-2 scra:i=ed on high drywell pressure.

(see report no. 50-237/75 h6). The HPCI turbine automatically initiated as -

designed, tripping after vessel coolant level reached +48". khile attempting to maintain rcteter coolant level by regulating feedvattr flow, the operator inadvertently allowed the coolant level to fall below +48". Because a high drywell pressure signal was still present, the HPCI turbine re-started.

At approximately 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, when reactor coolant level again reached +48",

the HPCI turbine failed to trip.

DESICATICU OF AFFA'EC CAUIE CF CCCUi!REIE (Equipment Failure) ,

An inspection of the turcine tripping circuitry revealed an open circuit in the turbine trip solenoid valve coil. The opened circuit apparently resulted from a cold solder joint failure within the coil.

ANALYSIS OF OCCURRE"CE '

The HFCI turbine trip valve solenoid rust be energized to initiato a trip.

Failure of the solenoid in the de-energized mode will prevent automatic or remote manual tu'bine trins, but will not inhibit any automatic actuation of the HFCI system. Since the continued operation of the HPC.I system merely resulted in even more conservative core protection, the health and safety'of the general public were never jcopardized by this occurrcnce.

CORRFCTIVE ACTICH Irrmediate corrective action was to set the turbine speed controller to minimum.

With the. vessel coolant level exceeding +48", HPCI discharge valve NO-2301-8 began to close as designed. The.' resultant low flow condition- caused minimu~.

flow valve MC-2331-14 to open. Pump suction was transferred from the storage tanks to the torus, allowing closed-cycle HPCI pump aperation.

At 0915 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.481575e-4 months <br /> on September 29, relay 2330-124 was jumpered, simulating reactor lou pressure which caused HTCI to automatically isolate. Ey 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br /> on September 30, the HFCI trip solenoid valve had been replaced, and the system was then trip-checked satisfactorily.

FAILURE DATA .

The failed valve is a Earksdale 3-vay solenoid valve. A similar failuse of this valve model occurred on Unit-3 May 19, 1972. The failure was also attributed to an open-circuited coil. .

,/w B. B. Stephenson

, Superintendent

! EES: GAR: cmp File /KRC