ML20058K546
| ML20058K546 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/28/1972 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102120470 | |
| Download: ML20058K546 (1) | |
Text
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NSID NORTHERN STATES POWER COMPANY Minneapolis, Minnesota 55401 4/ N.
D August 28, 1972 O
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United States Atomic Energy Commission
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Dear Mr. Giambusso:
fe0flTlCELLO NUCLEAR GENERAT ITO PLAfR Docket No. 50-263 Li cense No. DPR-22 Failure of Main Steamline Drain Valve to Close A condition occurred at the Monticello Nuclear Generating Plant recently which we are reporting to yo ar office in accordance with Section 6.6.C.1 of Appendix A, Technical Specifications, of Provisional Operating License DPR-22.
On July 28, 1972, with the reactor in the cold shutdown condition, the Reactor mode switch was inadvertently turned into the RUN position while attempting to place it in STARlUP to perform a Rod Worth Vinimizer and Manual Control Checklist.
This properly resulted in a Group I I sol at i on.
Following the isolation it was observed that the outboard main steam line drain isolation valve, f 0 2037, had not closed. The control room operator at tempted to close the valve using the control room ma,ual switch but the valve remained open.
An inspection of the valve operater motor control center (LCC) revealed several loose munting screws on the 125 V DC auxiliary contactor. The loose mounting prevented the contactor from closing and picking up the 250 V DC valve operator contactor. The mounting screws were tightened and the valve was successfully stroked several times.
An inspection of all DC fEC's was immediately initiated.
All contactors were checked and the mounting screws tightened as necessary. Twelve contactors were found to have loose screws. Each mounting screw is provided with a lockwasher which will prevent movement, provided the screw is properly tightened.
Apparently these screws had not been sufficiently tightened during initial manufacture.
No recurrence of this problem is expected.
A Signi ficant Operating Event report will be available at the site for the Regulatory Operations inspectors.
Yours very truly, h.
L. O. Mayer, P. E.
Di rector of Nuclear Support Services
'N3 6
LOWkik cc:
Boyce Grier 9102120470 720828.
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