ML20003C401

AO 50-219/74/11:on 740215,four Torus to Drywell Vacuum Breakers Failed to Demonstrate Operability During Weekly Surveillance Testing.Caused by Excess Friction in Valve Hinge Pines.Valves Freed W/Opening & Closing Movements

ML20003C401
Person / Time
Site:	Oyster Creek
Issue date:	02/25/1974
From:	JERSEY CENTRAL POWER & LIGHT CO.
To:
References
AO-50-219-74-11, NUDOCS 8103030591
Download: ML20003C401 (2)

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t OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/11 qjD e

Report Date p

February 25, 1974

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C Occurrence Date r

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February 15, 1974

%jg Identification of Occurrence Violation of the Technical Specifications, paragraph 3.5. A.3, failure of four torus to drywell vacuum breakers to demonstrate operability during weekly surveillance testing. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15B.

Conditions Prior to Occurrence "Ihe plant was operating at steady state power.

The major plant parameters at the time of the event were as follows:

Power:

Core, 1904 MWt Electric, 670 MWe 4

Flow:

Recirculation,15.5 x 10 gpm Av 6 lb/hr I

Feedwater, 7.23 x 10 Stack Gas: 29,000 pCi/sec

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Description of Occurrence s

On Friday, February 15, 1974, at approximately 1500, while performing weekly surveillance testing on the fourteen torus to drywell vacuum breakers, it was found that four of the vacuum breakers (V-26-5, 6, 9, and 11) failed to demonstrate operability in that they failed to close without assistance for the last 1 inch of travel. This surveillance testing was being performed to satisfy the requirements of AEC letter (D. J. Skovholt to R. H. Sims dated January 30, 1974). This operability testing basically consisted of manually opening each valve to the fully open position and then allowing it to close without assistance. Any hanging up in the opening or closing motions was interpreted as non-operability. Valve V-26-5 was made operable immediately with the application of several successive opening and closing movements. Plant operation continued on the basis of the requirements of paragraph B.5 of the referenced letter, which allows continued operation if not more than 25*, of these vacuum breakers are 1GG MdEM[ _

e Abnormal Occurrence No. 50-219/74/11 Page 2 inoperabic. Maintenance on the remaining three inoperable vacuum breakers (V-26-6, 9, and 11) was complete at approximately 0100 on Feb ruary 16, 1974.

Apparent Cause of Occurrence Unusual service condition is a major factor contributing to the cause of this occurrence.

It is believed that these failures are attributed to excess friction in the valvo hinge pins. A similar failure was re-ported as Attachment IV to Jersey Central Power 6 Light Company's letter from Mr. Dcnald A. Ross to Mr. A. Giambusso dated January 17, 1973.

Analysis of Occurrence The drywell-torus vaceum breaker system is required to prevent water ose.11ation in the downcomers due to low steam flow rates in the down-comers and to provide protection against negative pressure conditions in the containment vessel. The significance of this event is minimal in that the bases of the Technical Specifications state that this condition has no deliterious effect on negative pressure protection since only about 25% of the available vacuum relief capacity is required for this protection.

Corrective Action Valves V-26-6 and 11 were freed with repetitive opening and closing movements. Valve V-26-9 was returned to an operable condition by removing two rings of packing from one side of the shaft, reducing the friction of the valve hinge pin. Corrective action being taken is as discussed in a letter to Mr. Robert J. Schemel from Mr. D. A. Ross dated October 8,1973.

In tha: letter, it was noted that an apparent " growing" characteristic has been experienced with the teflon bushings at several facilities including Oyster Creek. The bushing difficulty has been discussed with Atwood 6 Morrill Company and a long-term solution is under investigation in conjunction with.the General Electric Company.

Failure Data Basic valve data are as follows:

Manufacturer - Atwood 6 Morrill Company Type -

Butterfly Vent Area -

1.75 square feet per valve

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