ML19261E378
| ML19261E378 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/22/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Woolever E DUQUESNE LIGHT CO. |
| References | |
| NUDOCS 7907060381 | |
| Download: ML19261E378 (1) | |
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,A UNITED STATES (% [;s,( j NUCLEAR REGULATORY COMMISSION ..: C REGION I k%'1 3i g 631 PARK AVENUE 0, ' ,o# KING OF PRUSSIA, PENNSYLVANIA 19406 %, ' %/ May 22, 1979 Docket No. 50-412 Duquesne Light Company ATTN: Mr. E. J. Woolever Vice President 43S Sixth Avenue Pittsburgh, Pennsylvania 15219 Gentlemen: Ecclosed is IE Bulletin 79-11 which requires action by you aith regard to your powar reactor facility (ies) with an operating license or a construction permit. Should you hr.ve questions regarding this Bulletin or the actions required by you, please contact this office. Sincerely, w e, Jf.-{ ? ?
- Wm_
Boyce H. Grier ' Director
Enclosures:
1. IE Bulletin No. 79-11 2. List of IE Bulletins Issued in Last Twelve Months cc w/encls: R. J. Washabaugh, Quality Assurance Managar
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790706038'(
3 UNITED STMES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 IE Bulletin No. 79-11 Date: May 22,1979 Page 1 of 3 FAJLTY OVERCURRENT TRIP DEVICE IN CIRCUIT BREAKERS FOR E Otscussior: '..e have received information frcm Westinghouse and an NRC licensee relating to the potential failure of a circuit breaker in an engineered safety system nuclear pcwer plant. de ay dashpots which resulted in a reduc'.d time delay for overcurrent protection. the end cap of the dashpot. Further l The defect was a small hairline crack ir investigation oy this licensee disclosed that 7 out of 17 spare dashpot end caps The and 2 non-enr,ineered safety feature breakers also had similar defects. circuit treaker is a Westinghouse type 08-75. Westinghouse type DB-50 breakers also use the same type of dashpot and end cap. extensively in SWR's, and some BWR:s may also have the same breakers. o not Similar make and model circuit breakers, when used for scram purposes. ~ cap require the overcurrent trip feature and thus are not of concern. t crack defect, if severe enough, could result in premature tripping r breaker because o f insufficient time delay in overcurrent protection. motor starting (inrush) current could cause the breaker to trip ina' f and thus prevent the motor start. The defects reported by the licensee in April 1979, occurred in the replacement end caps which were provided to solve the problem described in IE Bulletin 73-1. k The subject of Sulletin 73-1 was end caps made of a black Prior to the April 1979 of fibre-filled polyester material called " navy-gray". report, there have been no reports of suspect " navy-gray" end caps either frcm The manufacturer of the scheduleo testing or unusual behavior in service. " navy-gray" end caps believes the crack defects may be linked to a raw material That is, the molding ingredient materials used may have neared batch problem. It is not believed the end caps, after the end of their shelf life before use. fabrication, have a significant shelf life limit, due to the low residual stress and low crack p opagation probabilit%__ _ p DUPLICATE DOCUMENT l Entire document previously entered 11nto system under: OfoOfnOfhh' ANO No. of pages: 2 4 l. i il}}