ML20086D751

AO 73-12:on 730507:valve RHR-25A Failed to Open When Control Switch Placed in Open Position.Valve Manually Opened to Mid Position.Motor on RHR-25A Replaced & Valve Operability Demonstrated

ML20086D751
Person / Time
Site:	Vermont Yankee
Issue date:	05/14/1973
From:	Riley B VERMONT YANKEE NUCLEAR POWER CORP.
To:	US ATOMIC ENERGY COMMISSION (AEC)
References
AO-73-12, VYV-2673, NUDOCS 8312050074
Download: ML20086D751 (4)

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VERMONT YANKEE NUCLEAR POWER CORPORATION l [

SEVENTY SEVEN OROVE STRECT RUTLAND, VERF10NT 05701

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P.O. BOX 157 VERNON. VERMONT 05354 May 14,1973 7 , ,..

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Director Q( ul i l

Directorate of Licensing U.S. Atomic Energy Commission MAY 211973 t- 3 Washington, D.C. 20545 ~\ sa *

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REFERENCE:

Operating License DPR-28 b td 28

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Docket No. 50-271 Abnormal Occurrence No. A0-73-12

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Dear Sir:

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T7 Nuclear Power Station, Section 6.7.B d, we are reporting the following j ': Abnormal Occurrence as A0-73-12.

\ ,h1 / At approximately 2225 on May 7,1973, while performing routine

', surveillance on the LPCI system, valve RilR-25A failed to open when the control switch was placed in the open position. This constitutes a failure of a safety system component and is thereby an abnormal occurrence

[ ,' ' p* per Technical Specification Section 1.0. A.4. The valve was manually ,

g opened to its mid position and the control switch was once again placed 1lj in the open position. This time the valve traveled to its full open position. The reactor was at approximately 75% power at the time of this .

incident.

Valve RHR-27A was then closed. Since this valve will open in response to a LPCl initiation signal, the LPCI subsystem was considered operable.

Surveillance testing was then completed on the LPCI subsystem. The motor on RHR-25A was replaced and valve operability demonstrated by 1400 May 8,1973.

8312050074 730514 A PDR ADOCK 05000271 <-

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VERMONT NKEE NUCLEAR POWER CORPORATIOW r

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Directorate of Licensing May 14, 1973 Page 2

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The Plant Operations Review Committee reviewed the reported incident and concluded that the motor f ailure was due to high differential pressure across the valve disc which exceeded the design capability of the valve operator. This differential' pressure resulted f rom leakage past the RHR testabic check vglve and the f act that during surveillance testing system pressure is J much higher than would exist under the accident condition for which LPCI is designed. Therefore, had accident conditions existed at q the time of the incident, no valve motor failure would have - '

• occurred and the system would have operated as designed. To_ preclude l

repetition of this incident, plant operating procedures have been

! modified to require depressurization of the piping between the check valves RHR-46A/B and the injection valves RHR-25A/B prior to conducting valve operability surveillance of RHR-25A/B. These remedial actions  ; "

• were deemed adequate to prevent recurrence.

Very truly yours; VERMONT YANKEE NUCLEAR POWER CORPORATION B.U. Riley .} '

Plant Superintendent g ..

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• Licensce: Vermont Yankqe__ Nuclear Power Corp.

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- ' II . D. Thornburg, ~o .tr Docket No.: 30-271

- Chief, FS6EB Abnomal Occurrence: 73-12

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.RO:1!Q (5)

Dn Central Files (1) oart The attached report from the subject licensee is Regulatory Standards :3)

Dir. of Licensing (13 i forwarded in accordance with RO Manual Chapter 1000.

t o m. .. . o -..o -tas at.anas The action taken by the licensee is considered

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eut appropriate. Follovup will be performed during the next inspection n's appropriate . Confes of a sa ma m.m. .no ..o .....<s the report have been forwarded to the PDR, Local

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f. / / t' *!! / e PDR, NSIC, ITTIE and State representatives. The u.

R. T. Carlson, RO:I licensee vill submit a 10 day written report to PeeJett ser1 Datt 5/9/73 Licensing.

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