ML20137U132
| ML20137U132 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 01/31/1986 |
| From: | Mangan C NIAGARA MOHAWK POWER CORP. |
| To: | Starostecki R, Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| (55(E)-85-22), (NMP2L-0600), (NMP2L-600), NUDOCS 8602190059 | |
| Download: ML20137U132 (3) | |
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I M V NIAGARA RUMOHAWK NIAGARA MOHAWK POWER CORPORATION /300 ERlE BOULEVARD WEST, SYRACUSE, N.Y.13202/ TELEPHONE (315) 474-1511 January 31, 1986 (NMP2L 0600) l Mr. R. W. Starostecki,' Director U.S. Nuclear Regulatory Comission Region I Division of Reactor Projects 631 Park Avenue King of Prussia, PA 19406 Re: Nine Mile Point - Unit Docket No. 50-410
Dear Mr. Starostecki:
Enclosed is a final report in accordance with 10CFR50.55(e) for the problem concerning the Reliance Motor on Limitorque Motor Operator Model No. SB-3-150, DBE Qualification.
This problem was reported via tel-con to T. Silko of your staff on June 25, 1985, and an interim report was transmitted on July 26, 1985.
Please note that the model number addressed in all previous corres-pondence was SMB-3-150; the proper model number is SB-3-150 Very truly yours, C
Senior Vice President CVM/GG/cla (1412H) xc: Director of Inspection and Enforcement U.S. Nuclear Regulatory Comission Washington, DC 20555 R. A. Gram, NRC Senior Resident Inspector
!M Tea Paajho 9
I l
e NIAGARA M0 HAWK POWER CORPORATION NINE MILE POINT - UNIT 2 DOCKET NO. 50-410 Final Report for a Problem Concerning Reliance Motor on Limitorque Motor Operator, Model SB-3-150, DBE Qualification (55(e)85-22)
Description of the Problem Loss of torque was observed by Wyle Laboratories during the testing of a Limitorque motor-operated valve actuator with a Limitorque model SB-3-150 operator equipped with a Reliance Electric motor as part of the General Electric Environmental Qualification Program.
During the design basis testing of the valve actuator under elevated temperature and steam conditions, the motor exhibited loss of torque after 7 days of the 100-day test period.
A second identical motor exhibited the same loss of torque af ter 14 additional days due to motor rotor failure. A third motor failed after 43 days.
Underlying Cause The rotor used in the motor that failed is made of a magnesium alloy.
The rotor is used by Reliance when high motor torque is required.
When the rotor was subjected to a steam environment, the rotor bar at the interface with the end ring corroded which led to separation of the end ring from the conduction bars.
Analysis of Safety Implications Twenty motor operated valves at Nine Mile Point Unit #2 were identified by the vendor as having magnesium rotor design.
These motor operated valves were reviewed for their required post-accident operabili ty time, and it was determined that in a harsh environment 13 motor operated valves have a post-accident operability time of less than 1 day, and 5 motor operated valves have a post-accident operability time of 100 days. The remaining 2 motor operated valves are in a mild environment; therefore, a post-accident operability time is not applicable for these valves.
Similarly, the 13 valves with a one day post-accident operability time are not required to operate af ter one day and thus are acceptable as is.
The only valves with an environmental qualification problem are motor operated valves 2RHS*M0V24A, B, C, and 2CSL*MOV104 and 2CSH*MOV107 which are injection valves outside the containment for the emergency core cooling system.
If it were necessary to realign the valves after 7 days, realignment may not be possible af ter this failure.
A Loss of Coolant Accident inside the drywell would not result in conditions severe enough to affect operation of these valves.
Only a high-energy line break outside of primary containment is of concern since the valves are located in the secondary containment.
Failure of these valves could have rendered all three emergency core cooling systems inoperable.
Based on the above, it can be concluded that had this condition remained uncorrected, it could have adversely affected the safety of operations of the i
plant.
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Corrective Action General Electric has perfonned a review of valve functional requirements and provided the necessary valve alignments for safe pl ant operation during postulated design basis event beyond 7 days.
Stone & Webster has confirmed that the emergency core cooling system operation with this valve alignment is not adversely affectou by high-energy line breaks outside containment.
Therefore, the post accident operability time for the 5 emergency core cooling system motor operated valves outside containment will be revised.to 100 days following Loss of Coolant Accident inside containment and 7 days following a high-energy line break'outside containment.
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