05000298/LER-1979-020, Forwards LER 79-020/03L-0

Forwards LER 79-020/03L-0

ML19208D458
Person / Time
Site:	Cooper
Issue date:	09/05/1979
From:	Lessor L NEBRASKA PUBLIC POWER DISTRICT
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML19208D459	List: 05000298/LER-1979-020, Forwards LER 79-020/03L-0 05000298/LER-1979-020-03, /03L-0:on 790809,while Performing Surveillance Procedure on Relief Valve Bellows Monitoring Sys,Pressure Switch MS-PS-71G Failed to Actuate.Caused by Improper Assembly.Switch Was Replaced
References
CNSS790456, NUDOCS 7909280448
Download: ML19208D458 (2)

LER-1979-020, Forwards LER 79-020/03L-0

Event date:
Report date:
2981979020R00 - NRC Website

text

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COOPER NUCLEAR STATeoN P.O. box 98, B RoWNVILLE, NEBR AS6 18321 Nebraska Publ.ic Power Distr. t TELEmo~E mn.2sa.n ic CNSS790456 September 5, 1979 Mr. K. V. Seyfrit U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region IV 611 Ryan Plaza Suite 1000 Arlington, Texas 76011

Dear Sir:

This report is submitted in accordance with Section 6.7.2.B.2 of the Technical Specifications for Cooper Nuclear Station and discusses a reportable occurrence that was discovered on August 9, 1979. A licensee event report form is also enclosed.

Report No.:

50-298-79-20 Report Date:

September 5, 1979 Occurrence Date: August 9, 1979 Facility:

Cooper Nuclear Station Brownville, Nebraska 68321 Identification of Occurrence:

A ccndition which could have lead to operation in a degraded mode permitted by a limiting condition for operation established in pr.ragraph 3.6.D.2.a of the Technical Specifications.

Conditions Prior to Occurrence:

The reactor was in a cold shutdown condition due to a scram which occurred earlier in the day.

Description of Occurrence:

While performing Surveillance Procedure 6.2.2.2.5 to test the operability of the relief valve bellows monitoring system as re-quired by Technical Specifications 4.6.D.4 pressure switch MS-PS-71G failed to operate.

Designation of Apparent Cause of Occurrence:

Pressure switch MS-PS-71G was returned to the manufacturer (Pres-sure Controls, Inc.) for analysis. Pressure Controls' report stated the cause of the failure was due to the micro s" itch not setting sufficiently Llose to the piston stop. This prevented sufficient overtravel of the micro switch so that switching was dI#

intermittent.

YY w w 3

7909280 4

Mr. K. V. Seyfrit September 5, 1979 Page 2.

Analysis of Occurrence:

Pressure switch MS-PS-71G is a Model A 17-1 non-adjustable pressure switch manufactured by Pressure Controls, Inc.

It is factory set for 105 to 150 psig. This pressure switch was installed in May 1979, at that time the switch tested satisfactorily. The switch failed to activate during the first quarterly surveillance test after installation.

MS-PS-71G is part of the relief valve bellows monitoring system.

The pressure switch is used to indicate leakage past the bellows of the pilot operator for relief valve MS-RV-71G.

Had the bellows of the relief valve developed a leak the pressure switch would not have functioned and actuated an alarm in the control room indi-cating a bellows failure nor would the relief valve have functioned automatically. The manual and automatic depressurization modes of operation of the subject relief valve would have been operable in the event of a bellows failure. The redundent relief valves were ope rable, thus this occurrence presented no adverse consequences from the standpoint of public health and safety.

Corrective Action

The subject pressure switch was removed and sent to the manufac-turer for analysis and a failure report has been received and evaluated. The manufacturer stated that the failure mode of the switch was a unique occurrence. A new pressure switch was in-stalled and tested satisfactorily during the reactor startup.

Sincerely, L. C. Lessor Station Superintendent Cooper Nuclear Station LCL:cg Attach.

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