ML20127L295
| ML20127L295 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/10/1973 |
| From: | NORTHERN STATES POWER CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9211230485 | |
| Download: ML20127L295 (1) | |
Text
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NORTHERN STATES POWER COMPANY MINN E A POLIS. MIN N E SOTA 88401
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Mr. J P 0'1cary, Director 6
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Dear Mr. O' Leary:
oQ MONTICELLO NUCLEAR GENERATING PLANT Doci.c t No. 50-263 License No. DPR-22 Slow Closure of a Main Steam Isolation Valve A condition occurred at the Monticello Nuclear Generating Plant which we are reporting to your office in accordance with Section 6. 7.B.1, Abnormal Occurrence Reports, of the Technical Specifications, of Provisional Opera ting License DPR-22 On August 1,1973, during routine surveillance testing, MSIV 2-80A closed in 6 seconds.
fication of 3-5 seconds closure.This closure was in excess of the allowable Technical was being slowed the last 107, of stroke due to frictional resistanceAn inv between the spring support yoke and the yoke rods.
pair of rollers attached to the top of the yoke were not riding on theIt was noted that t yoke rods, last portion of the valve closure stroke.thus allowing metal to metal contact p Corrective maintenance included rods, burnishing the galled areas on the yoke rods, and lu contact areas between the rollers and yoke rods.
During subsequent timing tests the valve operated smoothly and without interference, however, after several exercises the valve was noted t closing in less than 3 seconds.
o be low and the flow restrictor assembly air bound.The dashpot oil level was found to be The dashpot was filled and vented, allowing the MSIV to be satisfactorily tested at 4 seconds closure.
The inboard "A" MSIV oil dashpot is particularly difficult to fill and vent since the valve is canted from the vertical plane in such i
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