ML19289D743

LER 79-001/01T-0 on 790219:w/unit off-line & at 10% Steam Flow,A&B Main Steam Stop Valves Failed to Close.Caused by Deposits on Valve Shafts or Hardening of Gland Packing. Valves Were Exercised & Packing Adjusted

ML19289D743
Person / Time
Site:	Point Beach
Issue date:	02/23/1979
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19289D742	List: ML19289D741 ML19289D743
References
LER-79-001-01T, LER-79-1-1T, NUDOCS 7903140313
Download: ML19289D743 (3)

Text

NRC fop.M 3G6 . U. S. NUCLEAR REGULATORY COMMISSION J7-77)

, LICENSEE EVENT REPORT CONTROL DLOCK: l 1

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h l o l 2 l l During a staf f review on 2-19-79, it was determined that the followino I o 3 was reportable. At 1152 hours0.0133 days <br />0.32 hours <br />0.0019 weeks <br />4.38336e-4 months <br />, 12-9-78, with the unit off line and I o 4 lapproximately 10% steam flow, both "A" and "B" main steam stop valves o s (failed to close. The valves were closed with mechanical assistance at 1 0 6 [1215 hours 12-9-78. Past experience indicates that the reverse type i o 7 l check valves would have closed in high steam flow conditions; therefore,l O s lthe public health and safety was not affected. I C DE C DE SUBC E COMPONENT CODE SUBC DE SU ODE lol9l 8

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47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i O lThe Atwood-Morrill reverse swing check valves failed to close due to l l,gi;l buildup of deposits on the valve shafts and/or hardening of the aland

, .,  ; packing. The valves were exercised and the packing was adjusted.

g3;3; lDifferent packing types and valve operator modifications are being g,g,, investigated. l 7 8 9 80 STA S  % POWER OTHER STATUS DISCO RY DISCOVERY DESCRIPTION i 5 l Gl@ l 0 1l 0 l@l N/A l l A l@l Operator observation ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE i

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80 LOSS OF OR DAVAGE TO FACILITY TYPE DESCniPTION Ii I 9 I LZj@l N/A 7 8 9 10 80 PUB LICITY r NRC USE ONLY ISSUE D DE SC RIPTION 790314o3fg l l l l *g 7

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68 69 l lll 80 5 NAME OF PREPARER Sol Burstein pgoye: 414/277-2121

r ATTACHMENT TO LICENSEE EVENT REPORT NO. 79-001/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 2 Docket No. 50-301 At 1152 hours0.0133 days <br />0.32 hours <br />0.0019 weeks <br />4.38336e-4 months <br /> on December 9, 1978, with Unit 2 off line for moisture separator reheater tube plugging, the reactor shutdown in hot standby, steam generator pressure at 830 psig, two condenser steam dump valves fully open and two partially open, and approximately 10% steam flow, both "A" and "B" main steam stop valves (CV-2017 and CV-2018) failed to leave the full open position upon the receipt of a close signal.

At 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br />, the valves were closed with mechanical assistance. The "A" main steam stop valve closed completely upon a tap with a pipe. The "B" main steam stop valve closed to approximately the 25% open position with a sharp rap using the pipe, but considerably more force (approximately 700 ft. lbs.) was required to close it completely.

Both valves were exercised several times to assure proper operation. The "A" valve had to be assisted open several times, but then cycled and functioned satisfactorily without assistance. The "B" valve opened, but required help in reclosing the last 25% of the stroke on several more occasions.

Maintenance loosened and lubricated the packing. The valve then functioned satisfactorily, but remained somewhat tight during the last 25% of the stroke.

The subsequent proper functioning of the valve is attributed mostly to the exercising of the valve rather than the packing adjustment and lubrication. It is believed that the long steaming period (233 days) permitted deposits to buildup between the shafts and the stuffing box bushing, this increasing the friction coefficient of the sliding surfaces.

During the subsequent staff review of the event, it was the consensus of opinion that realistically the 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 6 lbs./ hour steam flow even without receiving a closing signal.

The staff has concluded, however, that lengthy success-ful runs of the unit with the attendant possibility of build-up of deposits on the shafts and/or hardening of the gland packing may require further attention and possible modifications to preclude this type of sticky valve operation

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upon plant shutdown. Investigations into a different type of gland packing (Lubrite) is in progress and consideration to giving air assist to the closing action of the valves is being studied.

This event was originally written up as an in-plant significant operating event; however, in later discussions with the plant's chief NRC inspector, it was mutually agreed that the event was more properly reportable under Technical Specification licensee event reporting criteria.