ML19317F938

Forwards RO-76-15.Provides Details

ML19317F938
Person / Time
Site:	Rancho Seco
Issue date:	11/22/1976
From:	Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML19317F939	List: ML19317F938 ML19317G016
References
FOIA-79-149 NUDOCS 8002210650
Download: ML19317F938 (2)

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- SACRAMENTO' MUNICIPAL' UTILITY DISTRICT C 1708 59th Street. Box 15830, Sacramento. California 95813; (916) 452 3211 du/ :

November-22,'1976 Mr..R. H. Engelken-

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Director of Regulatory Operations-j

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NRC. Ope' rations. Office, Region V

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2' 1990 N.. California Boulevard

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-Walnut Creek, California 94596

'f Re: ' Operating License DPR -

.... g Docket No. 50-312 Reportable Occurrence.76-15 7

Dear Mr. Engelken:

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N In accordance with Technical Specifications for Rancho Seco; Nuclear,

. Generating Station, Section 6.9.1, and Regulatory Guide 1.16, 'evision 4, Section C.2.a(5),- the Sacramento Municipal Utility District herchy submits a written follow-up report on Reportable Occurrence 76-15, initially sub-mitted to the.NRC_on November.12, 1976.

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An, attempt was made to cycle one of the valves providing suction to

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th'e Decay Heat Pumps from the Emergency Sump (HV-26106) on November 11, 1976,- in accordance with a surveillance program established in Reportable i

Occurrence 76-2.

Three attempts to cycle the valve on signal from the Control Room failed and attempts to cycle the redundant Emergency Samp J

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. valve (HV-26105).also failed. ' An operator manually turned each valve

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hand uheel after which they operated freely. They were cycled several-times withouts failing to operate. The unit was shut down, depressurizing from a hydrostatic test,when the incident occurred.

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A discussion with your office on November 11 brought up the topic of the settings on the bypass switches for the. torque limit switches of these valves.. Investigation revealed that one valve had the torque switch bypassed for only.one notor' rotation while the stem was rotating and the other for thirty rotations.

It is possibic that the bypass switches were-

~ dropping out prior to the disc clearing the seat, with the resulting torque

' stopping' movement. 'To preclude this' possibility the bypass switches were J

-lance' program will be instituted to test each valve once a~ week for a nonth.

~h reset-to allow more motor turns before dropping out.

An increased surveil-If'all; cycles are successful, each. valve will be cycled monthly until the end..of. core cycle ene. This is the first failure of IIV-26105, uhile IIV-26106 m

hasifailed to cycle on two previous occasions, as reported in R0 76-2 and i

A0 74-2.

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f Mr. R. H. Engelken

' November 22,=1976 i

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-HV-26105.and HV-26106 are 18" gate valves manufactured by Darling Valve a

- and Manufac'turirg' Company._ The operators are Limitorque Model SMB-0.

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There was.no plant transient associated with this event.

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Respectfully submitted, e

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J. J.. Mattir.:oe j'

Assistant General Manager l

and Chief Engineer r

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