ML19209D123

LER 79-007/01T-0:on 790929,main Steam Line B Isolation Valve Failed to Close During 20% Steam Flow,W/Unit Off Line.Caused Not Stated.Packing Was Loosened & Atwood Morrill Reverse Swing Check Valve Closed

ML19209D123
Person / Time
Site:	Point Beach
Issue date:	10/10/1979
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19209D113	List: ML19209D112 ML19209D123
References
LER-79-007-01T-01, LER-79-7-1T-1, NUDOCS 7910190429
Download: ML19209D123 (2)

Text

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NRC FORM 366 U. S. NUCLEAR REGULATORY COMMISSION (7-77)

LICENSEE EVENT REPORT CONTROL BLOCK: l 1

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) o 1 W l LICENSEE IlPlB l H l 214 l@l15 0 l 0 l - 10 l LICENSE 0 l 0 NUMBER0l0 -

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EVENT DATE 14 'S REPORT DATE 80 EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h o 2 lAt 0520 hours0.00602 days <br />0.144 hours <br />8.597884e-4 weeks <br />1.9786e-4 months <br />, 9-29-79, with the unit off line and accroximately 20 per I o a icent ste. y flow, the "B" main steam isolation valve (2-CV-2017) failed

4 to close. Past experience indicates that the reverse tvoe check valve  !

O 5 lwould have closed in high steam flow conditions. Therefore, the valve I o 6 Eould have performed its safety function had it been required to do so. 1 0 71 lThis event is reportable per T. S. 15.6.9.2.A.9 and was similar to LER l O s l79-001/01T-0. I SY S T E M CAUSE CAUSE COMP. VALVE CCCE CODE SLBCODE COMPONENT CODE SUBCODE SU8 CODE O 9 lC D l@ l El@ l B l@ V l A l Ll V l E l 18X l@ l19 C l@ (_D_] h 7 8 9 10 11 12 13 20

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35 36 40 44 42 43 44 CAUSE DESCRIPTION AND COPRECTIVE ACTIONS i o lThe packing was loosened and the Atwood-Morrill reverse swina check i i valve closed with steam flow at 0533 hours0.00617 days <br />0.148 hours <br />8.812831e-4 weeks <br />2.028065e-4 months <br />, 9-29-79. I i >

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ATTACHMENT TO LICENSEE EVENT REPORT NO. 79-007/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 2 Docket No. 50-301 At 0120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> on September 29, 1979, with Unit 2 off line for secondary side plant maintenance, four condenser steam dump valves were opened (approximately 20% steam flow) during the closing operation of the main steam isolation valves. The "B" main steam valve (2-CV-2017) failed to leave the full open position upon the receipt of a close signal. The "A" main steam isolation (2-CV-2018) valve closed fully.

The "B" valve partially closed with some mechanical assistance. The valve was then reopened and with both mechanical assistance and steam flow, it swung to a position one inch short of the fully closed position. The valve was again reopened and the gland stuffing ? x packing was loosened. Steam flow was initiated, the close signal given and the valve fully closed at 0533 hours0.00617 days <br />0.148 hours <br />8.812831e-4 weeks <br />2.028065e-4 months <br />, September 29, 1979.

After a recent similar event (see Licensee Event Report No. 79-001/0lT-0), the plant staff concluded that the main steam isolation valves would have functioned in the unlikely event of a steam line break and the resulting high steam flow since the valve discs hang at three degrees into the steam flow and have closed on several instances in the past at 4 X 10 8 lbs./hr. (6.6 X 10 6 lbs./hr. corresponds to 100% power) steam flow even without receiving a close signal. Therefore, it is concluded that the valve would have performed its safety function had it been required to do so.

Recognizing the repetitiveness of this type of valve failure to fully close at zero or low flow condition without mechanical assistance or the slacking off of the gland packing, plant staff involvement in investigation of solutions to this problem will continue.

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