ML20086E081

Updated AO 73-21:on 730711,microswitch Installed in DPIS-2-129B Failed to Actuate at Required Setpoint.Vendor Contacted to Reiterate Need for Improving Design of Actuating Arm Bearing.Actuating Arm Realigned

ML20086E081
Person / Time
Site:	Vermont Yankee
Issue date:	07/19/1973
From:	George Thomas VERMONT YANKEE NUCLEAR POWER CORP.
To:	US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086E085	List: ML20086E081 ML20086E101
References
AO-73-21, VYV-2893, NUDOCS 8312060041
Download: ML20086E081 (2)

Text

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VERMONT YANICICE NucLEAu Powicu Con POR ATION scVE:N TY GeVcN of tOVc GTHecT lluTi.Axn, h &tONT OG701 MF PLY Tui VYV-2893 e. o. nox is7 VERNON, VEllMONT 03354 July 19,1973 Director @ g Directorate of Licens Lug [C[ g 43 U.S. Atomic Energy Commission y k'ashington , D.C. 20545  ; qJ UL g 19 3d

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REFERENCE:

Operating License DPR-28 d'u Docket No. 50-271 p[e,) f q Abnormal Occurrence No. A0-73-21 N f'u

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Dear Sir:

As defined by Technical Specifications for the Vermont Yankee

u. . ,. i n e r o n. ,o v (:eneton qnctinn ( 7.R.1 we are renorting the following swno t i;ta t vecuttenme o nu s a- A t nua uvu t a uaum um - l r I ~a- - - - - I - --

with your office.

At approximately 1100 on July 11, 1973, while performing routine quarterly surveillance on the LPCI break detection logic, a microswitch installed in DPIS-2-129B f ailed to actuate at the required setpoint of 1 (+.5) psid as specified in Tabic 3.2.1 of Technical Specifications.

The microswitch actuating arm was mechanically bound and failed to drop into the cam vailey at its requi red setpoint. Functionally, this switch, 2-129B, operates in conjunction with switch 2-129D to actuate a relay in their respective string to close Loop B LPC1 valves and actuate Loop A recirculation valves. The reactor was operating at approximately 75% power at the time of this incident.

The channel was promptly made operable by realigning the actuating arm, and rechecking tbc trip point actuat ton repeatedly ten times. The i setpoint of the switch had not drifted from its required trip setting.

The channel was declared operable by 1115 on July 11, 1973. .

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. VERMONT KEE NUCLEAR POWER CORPORATIOS Directorate of Licenstag July 19, 1973 Page 2 The Plant Operations Review Committee reviewed this incident and noted the same Bartan suitch and actuating arm had failed previously during a surveillance test on April 10, 1973. This was reported as A0-7 3-09, and at that time the committee recommended the surveillance f requency be increased f rom quarterly to monthly. The vendor was also contacted and made aware of the problem. Operation of the switch and actuating arm during the period April 10 to July 11, 1973, on monthly test was normal. The comm!ttee now recommends that the vendor again be contacted to reiterate the need for improving the design of the actuating arm bearing, and requested to provide a resolutien to this recurring problem.

Vecy truly yours.

VERMONT YANKEE NUCLEAR POWER CORPORATION c -Ome Georb . Thomas Assistant Plant Superintendent nun n.i.2

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