ML20206D514

Forwards Recommendations for Handling Insp of MSIV Springs, Per 860618 Telcon.Visual Insp of Inner & Outer Springs for Cracks for Operating Plants & Full Disassembly & Insp for Cracks for Plants Under Const Recommended

ML20206D514
Person / Time
Site:	Fermi
Issue date:	06/18/1986
From:	Dennison D GENERAL ELECTRIC CO.
To:	Vaughan L NRC
References
NUDOCS 8606200033
Download: ML20206D514 (3)

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.* FCOM SE 488 9257341 4.10.1t96 12:55 P. 3  ;

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.? MhEN STEAM ISOLATICAS VALVE EETERNAL SPRING FAILURES

'i During a e local leak rate test of the main steam isolation valves (MSIV) at'yes % it was discovered that three inner springs from one valve ians one inner spring from ancther valve cracked. The root cause ioC failure was identified as quench cracks in the

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springs. This'~ conclusion was independently confirmed by the spring manufacturer, an outside consultant for Detroit Edison, and GE. Atwood and Morrill ( A&M) considers all of their BWR and PWR MSIV's susceptible to this f ailure mode. It has recommended to the NRC in referenced letter (Copy attached) that all springs be

' inspected with a magnetic particle (MP) examination. It provided all the utilities who own plants using A&M MSIV's the spring manufacturer's MP procedure and acceptance criteria.

GE believes that a MP examination on hot rolled spring material will not accomplish the desired objective but will reveal many extraneous, indications. GE recommends the following actions:

1. For all' plants in operation including Oyster Creek, Nine Mile Point 1, Monticello, Pilgrim, Brown's Ferry, Peach Bottom, Hatch 1, Limerick 1, Susquehanna 1 and 2, and Grand Gulf-'

visually inspect the inner and outer springs for cracks o4 a scheduled outage. Valve disassembly is not necessary forg this inspection. If cracks are found, test all springs withy' a 5% overload test. Replace all cracked springs.

2. For Limerick 2, Hope Creek, Perry, Clinton and River Bend--

, disassemble and test 25% of the springs with a 5% overload test. Afterwards, verify visually the spring.s did not crack.

If cracks are detected, perform the overload test on all the remaining springs. Replace all cracked springs.

3. All newly purchased springs shall be subjected to the overload test prior to installation on valves.

Metallurgical study of the crack spring surface ind.4.ca.tes that the crack is not caused by fatigue. The spring material m.s fouad more brittle than expected for this material. Bri dle fracture is expected to occur early in spring life. Any spring that passas the overload test is expected to provide satisfactory service.

The springs in the operating plants have been subjected to the normal stress, and have been cycled approximately 4 to 5 timms between each refueling outage. If there is quench cracks in then, they would have failed. Hence if spring integrity can be verdflad via visual examination, they are not expected to havo generic failure potential. -

GE estimated that if the following conditions Uere to occur in on0 valves a failure of up to 3 out of 8 outer springs, or all 8 ir.n2r springs, the valve will take about one more second to cl:20, The effect on the closing time should be evaluated for each planc against their unique FSAR limits. If the FSAR limits for ths

- spring closure time is exceeded, additional calcalation can be 1 performed to determine if the offsite dosage limits are exceeded.

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e d *- ; The effect of an isolated spring failure on the leak tightness of a valve is negligible.

.The plants affected by this note are as followed:

Utility station Jersey Central oyster Creek Power and Light Niagara Mohawk Nine Mile Point 1 Power Corp.

.i 'Northern States Monticello

" Power Co.

. Boston Edison Pilgrim T.V.A. Brown's Ferry 1, 2, and 3 Philadelphia Elsc. Peach Bottom 2 and 3 Georgia Power Hatch 1 P.P.& L. Susquehanna 1 and 2 Philadelphia Elec. Limerick 1 and 2 Public Service Hope Creek Eleo and Gas Detroit Edison Enrico Fermi 2 Mississippi Power Grand Gulf and Light Cleveland Elec Perry i -Illuminating Illinois Power Clinton Gulf States Util. River Bend i

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