ML19256B441
| ML19256B441 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 05/22/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Clayton F ALABAMA POWER CO. |
| References | |
| NUDOCS 7907110080 | |
| Download: ML19256B441 (2) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION y ', ',', ( ( 'g 6
REGION 11 s
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,y 101 MARIETT A ST., N.W., SUITE 3100 AT LANT A, GEORGI A 30303 g'
MAY 2 21979 In Reply Refer To:
RII:JP0 QO-348; Alabama Power Company Attn:
Mr. F. L. Clayton, Jr.
Senior Vice President Post Office Box 2641 Birmingham, Alabama 35291 Gentlemen:
Enclosed is IE Bulletin 79-11 which requires action by you with regard to your power reactor f acility(ies) 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,
')
4 ames P. O'Reilly J
Director
Enclosures:
1.
List of IE Bulletins Issued in Last Pielve Months 836 123 700711 0 80
MAY 2' G7 ~!
Alabama Power Company -
cc w/ enc 1.
A. R. Barton Executive Vice President Post Office Box 2641 Birmingham, Alabama 35291 C. Biddinger, Jr.
Manager-Corporate Quality Assurcote Post Offic Box 2641 Birmingham, Alabama 35'91 H. O. Thrash Manager-Nuclear Generation Post Office Box 2641 Birmingham, Alabama 35291 H. G. Hairston, III Plant Manager Drawer 470 Ashford, Alabama 36312 R. E. Hollands, Jr.
QA Supervisor Post Office Box U Ashfor.', Alabama 36312 836 124
t UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 May 22, 1979 IE Bulletin No. 79-11 FAULTY OVERCURRENT TRIP DEVICE IN CIRCUIT BREAKERS FOR ENGINEERED SAFETY SYSTEMS Discussion:
We have received information from Westinghouse and en NRC licensee relating to the potential failure of a circuit breaker in an engineered safety system of a nuclear power plant. This circuit breaker had a defect in one of its three time delay dashpots which resulted in a reduced time delay for over-The defect was a small hairline crack in the eni cap of current protectior..
Further investigation by this licensee disclosed that 7 out of the dashpot.
17 spare dashpot end caps and 2 noc-engineered safety feature breakers also had similar defects. The circuit breaker ie a Westinghouse type DB-75.
Westinghouse type DB-50 breakers also use the same type of dashpot and end DB-50 and -75 breakers are used extensively in PWR's, and some BWR's cap.
may also have the same breakers.
Similar make and model circuit breakers, when used for se am purposes, do not The end cap require the overcurrent trip feature and thus are not of concern.
crack defect, if severe enough, could result in premature tripping of the circuit breaker because of insufficient time delay in overcurrent protection, i.e., the w tor 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 73-1.
As a result of that Bulletin, the black end caps were replaced with materisi.
a new type made of fibre-filled polyester material called " navy-gray".
Prior there have been no reports of suspect " navy-gray" to the April 1979 report, 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 linked to a raw material betch problem. That is, the molding ingredientIt 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, due to the low residual stress and low crack oropagation orobabilities.
IDUPLI r
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