ML20003C724
| ML20003C724 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 03/15/1974 |
| From: | JERSEY CENTRAL POWER & LIGHT CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-50-219-74-16, NUDOCS 8103160389 | |
| Download: ML20003C724 (3) | |
Text
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OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/16 Report Date March 15, 1974 Occurrence Date March 7,1974 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 and D.
Conditions Prior to Occurrence The plant was operating at steady-state power.
The major plant parameters at the time of the event were as follows:
Power:
Core,1870 MWt Electric, 653 MWe 4
Flow:
Recirculation, 15.7 x 10 gpm 6 lb/hr Feedwater, 7.14 x 10 Stack Gas:
33,050 pCi/sec Description of Occurrence On Thursday, March 7,1974, at approximately 1000, while performing weekly surveillance testing on the fourteen torus to drywell vacuum breakers, it was found that four of the vacuum breakers (V-26-4, 5, 6, and 12) failed to demonstrate 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). This operability test-ing basically consisted of (1) checking each valve to be fully closed; (2) manually opening each valve to the fully open position; and (3) allowing it to close without assistance; and then (4) checking each valve to be fully closed.
V-26-4 was found to open freely; however, some hesitation in the valve movement was observed after the valve was released in the fully open position. Once the closing motion began, the valve flo31403&i
- Abnormal Occurrence No. 50-219/74/16 Page 2
. appeared to move freely to the fully seated position. Valves V-26-5, 6, and 12 all opened freely but required assistance in the closing movements. Plant shutdown commenced as soon as these discrepancies were identified since the requirements of paragraph 3.5. A.3 of the
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' Technical Specifications could not be satisfied. By approximately 1130, these valves were determined to again be operable following the
. application of successive manual actuations to each valve. However, based on the recent history of failures of the torus-drywell vacuum
. breaker valves, it was decided to continue with the plant shutdown and effect more permanent repairs on the valves following the shutdown.
It a
is noted here that Valve V-26-9 was locked in the closed position on February 28, 1974 following its failure to demonstrate operability.
This failure was reported as Abnormal Occurrence Report No. 50-219/74/15 dated. March 7, 1974.
J Apparent Cause of Occurrence Design is considered to be a major factor contributing to the cause of this occurrence.
It is believed that these failures are attributed to excess. friction in the valve hinge pins. Similar failures have been re-ported as Abnormal Occurrence Report No. 50-219/74/11 dated February 25, 1974; Abnormal Occurrence Report No. 50-219/74/14 dated March 1, 1974; and Abnormal Occurrence Report No. 50-219/74/15 dated March 7, 1974.
- Analys'is of Occurrence Re -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 con-
' dition has no deliterious effect on negative pressure protection, since only about 25% of the available vacuum relief capacity is required for this protection.
. De drywell-torus vacuum breaker valves ' are required to be closed during
- pipe, break accidents ' (particularly small breaks).to assure proper steam condensation and prevent torus overpressure. D ese valves would have
. performed this function if required.
. Corrective Action.
Following plant shutdown, Valves V-26-4,-5, 6, 9, 11, and 12.were inspected.and repaired. De repairs:may be summarized as follows:
1.c New bushings were. installed.in' four valves with shaft 43 hinge. pin, bushing clearances in the range of 15-20 mils,
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- per. vendor reconnendation.
In the other two vacuum breaker 1 -
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A
Abnormal Occurrence No. 50-219/74/16 Page 3 valves, the installed bushings were removed, machined for shaft hinge pin - bushing clearances in the range of 15-20 mils, and reinstalled.
2.
New packings were installed in three valves. The installed packing material in the other three valves was removed, cleaned, and reinstalled.
All fourteen torus to drywell vacuum breaker valves will be inspected
~ during the upcoming refueling outage for seating material condition, disc freedom, and general condition of valve internals.
In addition, all fourteen valves will be completely overhauled. Valve bushings not previously replaced will be replaced and new packing material will be installed in all valves, providing material is available.
Additional corrective action being taken to effect a satisfactory long-term solution is as discussed in a letter to Mr. Robert J. Schemel from Mr. D. A. Rocs 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 long-term solution is under investigation in conjunction with 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 i
_-a._