ML20111B117
| ML20111B117 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 12/12/1984 |
| From: | Mangan C NIAGARA MOHAWK POWER CORP. |
| To: | Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| (55(E)-84-34), (NMP2L-0290), (NMP2L-290), NUDOCS 8501080481 | |
| Download: ML20111B117 (2) | |
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NUMOHAWK Y NIAGARA NIAGARA MOHAWK POWER ConPORATION/300 ERIE BOULEVARD WEST. SYRACUSE. N.Y.13202/ TELEPHONE (315) 474-1511 December 12, 1984 (NMP2L 0290)
Mr. R. W. Starostecki, Director U. S. Nuclear Regulatory Comission Region I Division of Project and Resident Programs 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point - Unit 2 Docket No. 50-410
Dear Mr. Starostecki:
Enclosed is a final report in accordance with 10CFR50.55(e) for the problem concerni ng Rosemount master trip units.
This problem was reported to S.
Collins of your staff on August 28, 1984. An interim report was submitted via our letter dated September 27, 1984.
Very truly yours, C
Vice President Nuclear Engineering and Licensing CVM/GG:csb (0582H) xc: Director of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, DC 20555 R. A. Gram, NRC Resident Inspector Project File (2) hhh
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NIAGARA MOHAWK POWER CORPORATION
-NINE MILE POINT - UNIT 2 DOCKET NO. 50-410 r
' Final Report for a Problem Concerning
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Rosemount Master Trip Units
- (55(e)-84-34 )
l Description of the Problem
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=The concern is that some control room mounted Rosemount 51000 trip units, which are used in. safety-related systems supplied by General Electric, have operated in an erratic fashion during adjustment of the safety trip point at
-Nine Mile Point Unit.2. The trip-units have a trip point adjustment l
potentiometer which is supplied with either a silver or gold flat part of the
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rotating shaft along with silver wiper contacts. Those units in which the flat part of.the' shaft is made of. silver can be affected by oxidation. This t
oxidation is responsfable for the observed erratic adjustment bahavior, e
Analysis >of-Safety Implications-The erratic adjustment behavior represents a calibration / maintenance procedure inconvenience, not.a safety concern.. General Electric has confirmed that once
-the trip point is set, the action of oxidation will not be detrimental to the t accuracy of-the safety trip point. -Therefore, this condition could not have adversely affected the safety of operations of-the plant-and the criteria-for r
.reportability have not been met.
It should be noted that we-intend to replace
{the potentiometers.in question in order to improve calibration and maintenance of the trip units.
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