ML17252A199

Transmittal of Reportable Occurrence No. 50-249/1976-7

ML17252A199
Person / Time
Site:	Dresden
Issue date:	05/27/1976
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS Ltr. #412-76 50-249/1976-7
Download: ML17252A199 (3)

Text

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CommoClth Edison Dresden Nuclear Power Station R.R. #1 Morris, Illinois 60450 Telephone 81 SJJ/ ~~~,....

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~ u.-:llQ6..L BBS Ltr. 114 Mr. James Directorate of R Mail Soetit>ft Ood<ol tlcirlt U. S. Nuclear Regulate 799 Roosevelt Road Glen Ellyn, Illinois 60137 May 27, 1976 III Enclosed please find Reportable Occurrence number 50-249/1976-7.

This report is being submitted to your office in accordance with the Dresden Nuclear Power Station Technical Specifications, Sec,~ion 6. 6. B.

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~. St~phenson f v Station Superintendent Dresden Nuclear Power Station BBS:smp Enclosure cc:

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EVENT DESCRIPTION (continued) and reactor power was reduced to clear the alarms.

After the alarms had cleared, power was slowly increased until 0450 hours0.00521 days <br />0.125 hours <br />7.440476e-4 weeks <br />1.71225e-4 months <br />, when an apparent off-gas explosion occurred.

Reactor power was further reduced to approximately 360 MWe.

Standby steam jet air ejector (SJAE)

"3Awas placed in service.. However, further inv,estigation indicated that the rupture diaphr_agm in both SJAE' s had been damaged, and a unit shutdown was initiated and completed by 1038 hours0.012 days <br />0.288 hours <br />0.00172 weeks <br />3.94959e-4 months <br />.

Off-gas system explosions have occurred previously on both units 2 and 3.

Corrective action implemented was replacement.of the failed diaphragms

. and the "3B" off-gas filter.

(050-249/76-7)

. -CAUSE DESCRIPTION (continued)

The explosion apparently failed both SJAE diaphragms at the same time.

• • It "i:s** assumed that the pressure wave failed the rupture diaphragms in both the operating SJAE "3B" and the standby SJAE "3A" due to leakage through the discharge valve.

Although personnel on shift at_ the time reported hearing two explosions, no evidence could be found to support this theory.

The "3B" off-gas filter in service at the time of the explosion was damaged and subsequently replaced.

Prior to the unit startup, both filters were tested and off-gas system valve lineups were verified to be correct.

An investigation of this and other previous off-gas explosions has been initiated.* The investigation will address the origin and prevention of off-gas system explosions.