ML20003C395
| ML20003C395 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 03/07/1974 |
| From: | JERSEY CENTRAL POWER & LIGHT CO. |
| To: | |
| References | |
| AO-50-219-74-15, NUDOCS 8103030508 | |
| Download: ML20003C395 (2) | |
Text
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I OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/15 c> vad d
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q% @ 1:A~2 Occurrence Date February 28, 1974 Identification of Occurrence Failure of one torus to drywell vacuum breaker to demonstrate operability during weekly surveillance testing. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15D.
Conditions Prior to Occurrence The plant was operating at steady-state power.
The major plant parameters at the cime of the event were as follows:
Power:
Core, 1870 MWt Electric, 650 MWe N
Flow:
Recirculation,14.9 x 10 gpm 6
Feedwater, 6.95 x 10 lb/hr Stack Gas:
27,700 pCi/sec Description of Occurrence On Thursday, February 28, 1974, at approximately 0945, while performing
-weekly surveillance testing on the fourteen torus to drywell vacuum breakers, it was found that one vacuum breaker (V-26-9) failed to demon-strate operability. This surveillance testing was being performed to satisfy the requirements of AEC letter (D. J. Skovholt to R. H. Sims dated January -30,1974). The operability testing basically consisted of:
Verifying that each valve was seated prior to testing.
1.
2.
Manually opening each valve to the fully open position and then allowing it-to close without assistance.
- 3.. Verifying that each valve was seated after testing.
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Abnormal Occurrence No. 50-219/74/15 Page 2 V-26-9 was found to be seated prior to testing and opened freely; however, it did not close freely and manual assistance was required to seat the valve after testing.
Apparent Cause of Occurrence Design is considered to be a major factor contributing to the cause of this occurrence.
It is believed that this failure is attributed to excess friction in the valve hinge pins. Similar failures were reported as Abnormal Occurrence Report No. 50-219/74/11 dated February 25, 1974 and Abnormal Occurrence Report No. 50-219/74/14 dated March 1, 1974.
Analysis of Occurrence The drywell-torus vacuum breaker system is required to prevent water oscillation 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.
The drywell-torus vacuum breaker valves are required to be closed during pipe break accidents (particularly small breaks) to ensure proper steam condensation and prevent torus overpressuring. This valve would have performed this function, if required.
Corrective Action Based on the recent history of failures of V-26-9, it was decided to lock this valve in the closed position pending implementation of a sat-isfactory long-term solution. This locking was in compliance with the requirements of paragraph B.4 of the AEC letter (D. J. Skovholt to R. H. Sims dated January 30, 1974).
Other 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 that 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 '.ong-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
- Check Valve Vent Area
- 1.75 square feet per valve