ML20086S972

SR-S1-74-01:on 740526,reactor Vessel Leakoff High Temp Alarm Received.Caused by Inadequacy of Packing Mfg by J Crane Co. Packing Will Be Replaced W/Grafoil Packing

ML20086S972
Person / Time
Site:	Surry
Issue date:	07/15/1974
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
SR-S1-74-01, SR-S1-74-1, NUDOCS 8403060062
Download: ML20086S972 (5)

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Mr. Normen C. Ifonolcy, Director Serial ITo. 192 Directort.to of Regulatory Operations P0&M/JTBac1w United States Atenic l'ncrgy Com:niacion -

Region II - Suite alt) Docket No. 50-280 230 reachtreo Street, Northwest License No. DPR-32 Atlanta, C:orgia 30303

Dear Mr. Moseley:

Attached for your infornstion in a special report, SR-SI-74-01, which describes the failure of the packing on a loop laolation valvo on Unit 1:o. I at oar Surry Power Station.

The substance of this report has been reviewed by the Station Hoc 3 car Uniety and Operating Cc nittaa and vill be placed on the aconda for the nort neeting of the System Nuclear Safety and Operating Cet=cictec.

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odiaal signed Cy C. M. STALLINGS C. M..Stallinga

.Vice Prcoident-Power Supply ,

and Production Operations Attactuaento .

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SPECIAL REPORT REPORT NO. SR-SI-74-01 FAILURE OF LOOP ISOLATION VALVE PACKING DOCKET NO. 50-280 LICENSE NO. DPR-32 JUNE 11, 1974 SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANY

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I. INTRODUCTION I

l This report describes an occurrence involving Icakage of reactor coolant caused by a reactor coolant loop isolation valve packing failure. The subject valve is a 30 inch motor operated gate valve manufactured by the Darling Valve and Manufacturing Company.

II.

SUMMARY

OF OCCURRENCE On May 26, 1974, Unit No. 1 was operating at approximately 50 per cent of rated power. At approximately 1035 hc,urs, a reacter vessel leakoff high temperature alarm was received. A reactor coolant system Icakage check revealed a leakage of approximately 30 gpm. An attempt was made to locate leakage by closing HCV-1544, reactor vessel flange Icakoff isolation valve. Leakage continued at approximately 30 gpm indicating that the source was other than the reactor vessel head flange. At 1054 hours0.0122 days <br />0.293 hours <br />0.00174 weeks <br />4.01047e-4 months <br />, a load reduction was initiated with reactor hot shutdown attained at 1257 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.782885e-4 months <br />. A containment entry was made and revealed a slight steam leak from the valve stem of loop "C" hot leg isolation valve. Following backsesting of this valve the reactor coolant system leakage rate declined to less than 1 gpm.

Due to the drop in Icakage rate following the backseating of loop "C" hot leg isolation valve, it was concluded that the reactor coolant system leakage was caused by the failure of the valve packing. Due to the effective prevention of further leakage by tighter backscating of the valve, no immediate corrective action is considered necessary. The valve remains operable and capable of performing its intended function.

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III . ANALYSIS OF OCCURRENCE The installed packing is the preformed type manufactured by John Crane Company (compound 1871): The inadequacy of this type of packing has been recognized for this and certain other applications.

Preformed Grafoil packing has proven to be superior to the present packing in similar applications. As a result, where operating conditions and materials availability permit, the John Crane packings are being replaced with Grafoil. Packings on Unir No. I loop isolation valves will be replaced with preformed Grafo11 when operating conditions and materials availability permits. In the

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interim, tighter backseating of the subject valves will prevent further leakage.

IV. ANALYSIS AND EVALUATION OF SAFETY IMPLICATIONS OF Tile OCCURRENCE The purpose of the loop isolation valves is to allow isolation of the loop from the reactor vessel. The loop "C" hot leg isolation valve, despite the degradation of the packing, remains capabic of performing its intended function. Tighter backseating of the valve has eliminated leakage. While Icakage would result from closing of the valve, the duration of the Icakage would be equal to the duration of the valve stroke and would result in a relatively minor loss of reactor coolant (less than 100 gallons) which would be confined within the drain system. Thus continued operation with the damaged packing will not present further pr>blems.

Because of previous experience, the reactor coolant system will not be cooled down with the valves backscated.

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. l V. CONCLUSIONS The reactor coolant system leakage was caused by the failure of the packing of the loop "C" hot leg isolation valve. The present packing has proven inadequate for this application and will be replaced with preformed Grafoil packing as operating conditions and materials availability permit. In the interim, tighter backscating when the coolant system is hot will prevent further leakage.