ML19256B389
| ML19256B389 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 05/22/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Davidson D CLEVELAND ELECTRIC ILLUMINATING CO. |
| References | |
| NUDOCS 7906130090 | |
| Download: ML19256B389 (1) | |
Text
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,8, cten ettvs. ettisois soi37 NAY 2 21979 Docket No. 50-440 Docket No. 50-441 The Cleveland Electric Illuminating Company ATTN:
Mr. Dalwyn R. Davidson Vice President - Engineering P. O. Box 5000 Cleveland, OH 44101 Gentlemen:
Enclosed is IE Bulletin No. 79-11 which requires action by you with regard to your power r-actor facilities with an operating license or a construction permit.
Should you have questions regarding this Bulletin or the actions required of you, please contact this office.
Sincerely, 64 James G. Keppler Director
Enclosure:
IE Bulletin No. 79-11 cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Harold W. Kohn, Power Siting Commission Mr. Daniel D. Wilt, Attorney 7906130090
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCDIENT REGION III m y 22, 1979 IE Bulletin No. 79-11 FAULTY OVERCURRENT TRIP DEVICE IN CIRCUIT BREAKERS FOR EN SAFETY SYSTEMS Discussion:
We have received information from Westinghouse and an NRC licensee relating to the potential failure of a circuit breaker in an engineered safety system This circuit breaker had a defect in one of its of a nuclect power plant.
three time delay dashpots which resulted in a reduced time delay for over-The defect was a small hairline crack in the end cap current protection.Further investigation by this licensee disclosed that 7 out of 17 g.are dashpot end caps and 2 non-engineered safety feature breakers also the dashpot.
The circuit breaker is a Westinghouse type DB-75.
had similar defects.
Westinghouse type DB-50 breakers also use the sa=e type cap.
may also have the same breakers.
Similar make and model circuit breakers, when used for scram purposes, A not The s cap require the overcurrent trip feature and thus are not of concern.
crack defect, if severe enough, could result in premature tripping cf tho circuit breaker because of insufficient time delay in overcurrent protect on, i.e., the motor starting (inrush) current could cause the breaker to trip inadvertently 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 The subject of Bulletin 73-1 was end caps made of a black phenolic As a result of that Bulletin, the black end caps were replaced with 73-1.
a new type made of fibre-filled polyester material called " navy-gray".
Prior material.
to the April 1979 report, there have been no reports of suspect " navy-gray The end caps either from scheduled testing or unusual behavior in service.
manufacturer of the " navy-gray" end caps believes the crack defects may be That is, the molding ingredient linked to a raw material batch problem.
It is materials used may have neared the end of their shelf life before use.
not believed the end caps, after fabrication, have a significant shelf life limit
<he to the low residual DUPLICATE DOCUMENT Entire document previously entered into system under:
!b ANO No. of pages: _ h