ML20203M031
| ML20203M031 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/20/1986 |
| From: | Lempges T NIAGARA MOHAWK POWER CORP. |
| To: | Kane W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| (55(E)86-17), (NMP2L-0829), (NMP2L-829), NUDOCS 8609030298 | |
| Download: ML20203M031 (2) | |
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Y N!AGARA NuMOHAWK NIAGARA RIONAWII POWER CORPOAA790N/300 ERIE BOULEVARD WEST. SYRACUSE N Y.13202/ TELEPHONE (315) 4741511 i
i August 20, 1986 j
(NMP2L0829)
Mr. H. Kane, Director U.S. Nuclear Regulatory Commission Region I Division of Reactor Drojects j
631 Park Avenue j
King of Prussia, PA 19406 4
j Re: Nine Mlle Point - Unit 2 i
Docket No. 50-410
Dear Mr. Kane:
j l
Enclosed is a final report, in accordance with ICCFR50.55(e), for the problem concerning cracks in contact levers for Main Steam Isolation Valve limit switches (NAMCO EA180).
This problem was reported by means of tel-con to 4
G. Meyer of your staff on July 17, 1986.
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Very truly yours, 4
I T. E. Lempges Vice President Nuclear Generation TEL/GG:ar 1981G j
xc: Ofrector of Inspection and Enforcement U.S. Nuclear Regulatory Commission F
i Washington, DC 20555 H. A. Cook, NRC Senior Resident Inspector NMPC Project File (2) i I
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I y NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT - UNIT 2 DOCKET NO. 50-410 Final Report for a Problem Concerning Main Steam Isolation Valve Limit Switches (N#iC0 EA180)
Cracks in Contact Levers (55(e)86-17)
Descriptig of the Problem It was found that the plastic lever within the flain Steam Isolation Valve limit switch have cracks in the plastic where the contact assembly is secured to the lever.
The contacts are mounted to a thin netal bracket which is riveted to the lever on each end.
The problem apparently resul ted from excessive tonsion on the rivet which deformed the bracket and caused a crack to propagate from the rivet hole.
The fact that the rivet overlaps a ledge at the bottom of the plastic could have contributed to the cracking.
The problem was discovered by a Field Quality Control inspector while inspecting termination of the device side of a Conax environmental seal.
Engineering requested that Field Quality Control review all Category I
switches on the inheard Main Steam Isolation Valves which were to receive seals.
As a result of the initial and follow-up inspections, Unsatisfactory Inspection Reports E6A44557 and E6A44562 were generated identi fying 14 switches with single or multiple cracks out of 20 switches inspected for this Concern.
Analysis of Safety Implications These switches provido OPEN and CLOSLD valve position status as well as safety-related control function for the Main Steam Isolation Valves.
- Thus, failure of the switch could prevent closure of the Main Steam Isolation Valves and/or possible false or misleading information for variables which are monitored as part of the implementation of Regulatory Guide 1.97.
Had this condition remained uncorrected, it could have adversely affected the safety of operations of the plant, i
Corrective Action Visual inspection of the contact levern of all QA Category I NN4C0 EA170 series and EA180 series limit switches has been performed.
The inspection included all switches in stock inventories.
The contact levers were removed for inspection.
Cracked parts have been replaced in accordance with Engineering and Design Coordination Report No. C041120.
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