05000369/LER-1981-185, Forwards LER 81-185/03L-0.Detailed Event Analysis Encl

Forwards LER 81-185/03L-0.Detailed Event Analysis Encl

ML20039D887
Person / Time
Site:	McGuire
Issue date:	12/23/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20039D888	List: 05000369/LER-1981-185, Forwards LER 81-185/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-185-03, /03L-0:on 811118,residual Heat Removal Loops Rendered Inoperable.Caused by Disconnecting Pressurizer Vapor Space Temp Sensor Signal Cable W/Resultant Closing of Inlet Isolation Valve.Work Associated W/Shutdown Request
References
NUDOCS 8201060311
Download: ML20039D887 (3)

LER-1981-185, Forwards LER 81-185/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981185R00 - NRC Website

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373-4083 Mr. J. P. O'Reilly, Regional Administrator U. S. Nuclear-Regulatory Commissiot.

Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: McGuire Nuclear' Station Unit 1 Docket No. 50-369

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/81-185. This report concerns Technical Specification 3.4.1.4, "Two Residual Heat' Removal (RHR) loops shall be operable and at least one RHR-loop.shall be in operation." This incident was considered to be of no significance with respect to the health and safety of the-public.

This report is being submitted three working days late. We apologize for any inconvenience-this may have caused.

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cc: Director Records Center Office of Management & Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C.

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s DUKE POWER COMPANY' MCGUIRE NUCLEAR STATION-REPORTABLE OCCURRENCE REPORT NO: 81-185 REPORT DATE: December 23, 1981 FACILITY: McGuire Unit 1, Cornelius, North Carolina IDENTIFICATION: Automatic Valve Closure Causing Loss of Shutdoun Decay Heat Removal

INTRODUCTION

On November 18 with Unit 1 in Mode 5, cold shutdown, both residual heat removal (ND) loops were rendered inoperable when an inlet isolation valve inadvertently shut. Concurrently, a pressurizer high temperature alarm was received. ND pump A was immediately stopped to protect the pump, and action to restore the system to operation was initiated. The valve was reopened and the system was

- operating after a twenty-two minute shutdown.

Investigation revealed that Construction personnel working in accordance with a shutdown request had disconnected the pressurizer vapor space temperature sensor signal cable. This signal is used as a diverse means of providing overpressure protection to-the ND system. By design, the pressurizer vapor space signal pro-vides an open-permissive' signal to the valve's actuator at 47SOF decreasing.. It also functions to automatically close the valve at 4750F increasing. When the signal lead was disconnected a fail-safe characteristic caused the valve actuator to close the. valve.

Since the on duty Shift Supervisor provided authorization to proceed with the work associated with the adequately documented shutdown request, this incident is attributed to personnel error.

EVALUATION:

When the alarms associated with the incident occurred the Shif t Supervisor' immediately realized the mistake and attempted to stop the work proceeding in the reactor building through the use of the site general announcing system. An operator was also dispatched to the scene. These efforts were effective in that

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the construction workers responded by reconnecting the leads, which cleared the problem.

The' controlling procedure at the time of. the incident was " draining the Reactor Coolant System." One step in the procedure requires that the valve operator power breakers be locked.open, rendering the two ND' suction valves inoperable.

Had the draining operation proceeded beyond'that step in the procedure the incident would not have occurred.

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.MCGUIRE NUCLEAR STATION Reportable Occurrence Report No.81-185 Page Two

CORRECTIVE ACTION

Operators have been cautioned about the possibilities of ND isolation due--

to actuation of protective-features.' Procedural' irsprovements are con-tinuously under study.

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