ML20205G453

Ro:On 850927,MSIVs Failed to Fast Close.Caused by disc-to-seat Sticking of Asco Double Solenoid Valves. Solenoid Valves Replaced W/Valves Having Viton Seals.Other Asco Valves Inspected

ML20205G453
Person / Time
Site:	Brunswick
Issue date:	10/09/1985
From:	Howe P CAROLINA POWER & LIGHT CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
BSEP-85-1801, NUDOCS 8511130250
Download: ML20205G453 (2)

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Brunswick Steam Electric Plant P. O. Box 10429 Southport, NC 28461-0429 October 9, 1985 FILE: B09-13510A SERIAL: BSEP/85-1801 Dr. J. Nelson Grace, Administrator U.S. Nuclear Regulatory Commission Suite 2900 101 Marietta Street hV Atlanta, GA 30323 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 DOCKET NOS. 50-325 AND 50-324 LICENSE Ic DPR-71 AND UPR-62 FAILURE OF ASCO MODEL 8323A36E DOUBLE SOLENOID VALVES

Dear Dr. Grace:

During surveillance testing on September 27, 1985, main steam isolation valves (MSIVs) 2-B21-F028A, F028C, and F022C failed to fast close. The failures were determined to be caused by disc-to-seat sticking of ASCO Model 8323A36E double solenoid valves. Failure analysis is currently underway at the Harris Energy &

Environmental Center (HE&EC) Metallurgical Laboratory.

A review of Brunswick maintenance history, available literature and industry experience, including NOTEPAD, NPRDS, vendors, - other utilities, and preliminary failure results, has shown the following:

1. The seat material in the failed valves--ethylene prophylene (EP)--swells and changes its characteristics when exposed to hydrocarbons. One such change is a possible lowering of its melting point.

2. Hydrocarbons were found in the valve body.

3. The failed seat material (EP) showed evidence of being heated to the melting point.

4. The failed disk' seat material had become lodged in the exhaust ports of the failed solenoid valves.

5. Based upon the above, the failure mechanism appears to be a combination I of hydrocarbon contamination, temperature, and internal valve geometry.  !

8511130250 851009 PDR S ADOCR 05000324-pg 10

Dr. J. Nelson Grace 6. Viton, another seat material, is impervious to hydrocarbons and has a higher temperature rating than EP. However, Viton is more susceptible to radiation effects. Viton has a recommended changeout of 3.3 years, whereas EP has approximately a 4.2 year changeout.

7. Viton is recommended for use in systems that are not " oil-free."

As a result of these findings, Brunswick has taken the following actions to prevent recurrence of this failure:

1. The MSIV double solenoid valves on both units have been replaced with valves having Viton seals.

2. Other ASCO solenoid valves have been inspected. No deterioration of the seals was identified.

3. Continued failure analysis is being conducted at the HE&EC laboratories.

HE&E has reproduced the failure by applying heat (> 600') to the material; however, this material should not see that high a temperature during operation. Other factors are being tested / analyzed to more completely define the failure mode.

4. A monthly test of the double solenoid valves on each MSIV will be implemented on both units until the failure analysis is complete or until adequate operating history on the Viton seals is accumulated to show that the increased testing is no longer necessary.

5. The valves will be replaced at approximately three-year intervals due to the radiation susceptibility of Viton.

The use of Viton seals is consistent with the literature and the industry experience. It provides reasonable assurance that this failure mode has been eliminated.

Additional information will be provided in LER 2-85-008, scheduled to be submitted on October 25, 1985.

Very truly yours, dg b F. W. Howe, Vice President drunswick Nuclear Project RMP/rla Enclosure cc: NRC Document Control Desk

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