ML20056B707
| ML20056B707 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/28/1972 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102080396 | |
| Download: ML20056B707 (3) | |
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NORTHERH STA E5 POWER COMPANY
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S REGULATORY t \\ >N g
Mall SECTION Dr. Peter A Marris to g
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DOCKET CLERK
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Dear Dr. Morris:
MONTICELLO NUCLEAR GEERATING PIANT Docket No. 50-263 License No. DPR-22 Reporting of Malfunction of Core Spray Injection Valve A condition occurred at the Monticello Nuclear Generating Plant recently which we are reporting to your office in accordance with provisions of Section 6.6.B.2 of Appendix A, Technical Specifications, of the Pmvision-T al Operating License DPR-22.
The Region III Compliance office has been notified of the occurrence.
During the procedure for filling and pressurizing the core spray piping in preparation for a reactor startup on January 20, 1972, it was found that the core spray injection valve, MO-1753, did not open. A cutaway view of the operator is attached.
The operator motor turns the vorm gear drive which in turn rotates the drive sleeve.
The stem nut which sits inside the drive sleeve is threaded internally to mesh with the valve stem; the stem nut is splined such that ic cannot rotate within the drive sleeve. A jam nut screws into the drive sleeve to hold the stem nut in place as the drive sleeve turns.
The threads are staked to keep the jam nut from unscrewing. On investigation of MO-1753, it was found that the jam nut had unscrewed completely, allowing the stem nut to ride up the valve stem as the drive s?eeve m tated. Position indication is fmm switches in the motor operator; "open" and "close" indication was ob-served without the valve opening.
The immediate solution to correct MO-1753 was to replace the jam nut and drill and tap a vertical hole through the mating drive sleeve and jam nut threads; a set screw was then inserted to keep the jam nut from turning.
All other motor operated valves of tle same type were inspected. Out of 51 additional valve operators, no otler jam nuts were found completely unscrewed fmm the drive sleeve. Nine jam nuts were found to have turned slightly. Five of these were fixed by inserting a roll pin between the jam nut and the drive =>1eeve.
The other four were smaller valve operators; 9102000396 720128 hh CF ADOCK 05000263; 4h CF
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N HERN STATES POWER MPANY d,
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j Dr. P A Morris January 28, 1972 i
1 they were fixed in place by restaking the threads.
Each motor operated valve i
-vith this type of operator has been staked. All valves were confirmed to func-
. tion properly by personnel stationed at the valve.
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A Significant Operating Event report will be available at the plant for the Compliance Inspector.
Yours very truly, L 0 Mayer, P.E.
Director of Raclear Support Services LOM/MHV/br Attachment i
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