05000369/LER-1981-072, Forwards LER 81-072/03L-0.Detailed Event Analysis Encl

Forwards LER 81-072/03L-0.Detailed Event Analysis Encl

ML20009F681
Person / Time
Site:	McGuire
Issue date:	05/27/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20009F683	List: 05000369/LER-1981-072, Forwards LER 81-072/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-072-03, /03L-0:on 810427,RHR Sys Discovered Isolated from RCS During Mod of Train a Solid State Protection Sys to Include Reactor on Turbine Trip.Caused by de-energized Relay in Logic,Closing Isolation Valve
References
NUDOCS 8107310404
Download: ML20009F681 (2)

LER-1981-072, Forwards LER 81-072/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981072R00 - NRC Website

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'g Mr. James P. O'Reilly, Director

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101 Marietta Street, Suite 3100 t-Atlanta, Georgia 30303 (5

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Dear Mr. O'Rtilly:

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Pleas.: find attached Reportable Occurrence Report R0-369/81-72.

This report concerns the RRR system being inadvertently isolated from the RCS. This in-cident was considered to be of no significance hith respec' to the health and safety of the public.

Vefy truly yours, c %.,N is.!un

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g, William O. Parker, Jr q RWO:pw Attachment cc: Director Mr. Bill Lavallee Office of Management & Program Analysis Nuclear Safety Analysis Center U.S. Nuclear Regulatory Commission P. O. Box 10412 Washington, D. C.

20555 Palo Alto, CA 94303 Ms. M. J. Graham Resident Inspector - NRC McGuire Nuclear Station

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e McGUIRE NUCLEAR STATION INCIDENT REPORT Report Number:

81-72 Reoort Date:

May 27, 1981 Occurrence Date: April 27, 1981 Facility: McGuire Unit 1,'Cornelius, N. C.

Identification of Occurrence: Residual Heat Removal System (ND) was isolated from the Reactor Coolant System (NC) for about fifteen minutes on April 27, 1981.

Condition Prior to Occurrence:

'4^de 5, Initial fuel loading Description of Occurrence:

The train A Solid State Protection System (SSPS) logic was being modified to include reactor trip on turbine trip. When the tuses from the SSPS output cabinet were removed, a r.armally energized output relay went to its de-energized position closing valve IND2A (NC Loop 3 Disch.

to ND System Containment Isc. Inside).

Apparent Cause: A normally energized relay in the SSPS logic was inadvertently de-energized closing valve IND2A and isolating the Reactor Coolant System from the Residual Heat Removal System.

Analysis of Occurrence:

It was not realized that work on the A train SSPS cabi-nets would affect 3 train operation of ND.

A and B trains of ND share a common suction from the Reactor Coolant System with two suction isolation valves in series (one train A powered and the othe; crain B powered). Closing either valve isolates the Reactor Coolant System from the ND system.

As soon as IND2A (NC Loop 3 Disch. to ND System Containment Iso. Inside) closed, an operator was sent to de-energize the valve and open it manually.

Safety Analysis

At the time of the incident only new fuel was in the core so no decay heat load existed.

No boron concentration changes were in progress so no mixing was required.

For these reasons and because ND flow was restored so rapidly, the health and the safety of the public were wat affected by this in-cident.

If a similar incident were to occur when ND was needed for mixing or cooling, the operators have shown that the flow path could be restored quickly.

Corrective Action

The ND suction from NC flow path was reestablished by manually opening the A train isolation valve.

IND2A was prevented from reclosing by re-moving the power.

The personnel involved have been cautioned to thoroughly in-vestigate the results of their actions when working in unusual conditions such as special modification projects.