ML19246A763
| ML19246A763 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/22/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Cavanaugh W ARKANSAS POWER & LIGHT CO. |
| References | |
| NUDOCS 7907060325 | |
| Download: ML19246A763 (1) | |
Text
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611 RYAN PLA7.A DRIVE, SUITE 1000 L
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REGION IV 9, '
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%, V AR LINGTON, TEXAS 76012 May 22, 1979 Docket Nos. 50-313 50-368 Arkansas Power and Light Company ATTN:
Mr. William Cavanat.gh III Vice President of Generatior.
and Construction P. O. Box 551 Little Rock, Arkansas 72203 Gentlemen:
Enclosed is IE Bulletin No. 79-11 which requires action by you with regard co your power reactor facilities with an operating license or a construction pemit.
Should you have questions regarding this Bulletin or the actions required of you, please contact this office.
Sincerely, t
Karl V. Sey 1:
Director
Enclosures:
1.
List of IE Bulletins Issued in Last Twelve Months 300 225 cc:
James P. O'Hanlon, Plant Manager Arkansas Nuclear One P. O. Box 608 Russellville, Arkansas 72801 L. Alexander, QC Supervisor g gt)7 0 6 0 M b
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT IE Bulletin No. 79-11 Date:
May 22, 1979 Page 1 of 2 FAUI.TY OVERC'JfWIT TRIP DEVICE IN CIRCUIT BREAKERS FOR ENGINEERED SAFETY SYSTFMS Discussion:
We have received v I%n. tion fr m Westinghouse and an NRC licensee relating to the pc
' a l CC '_ 2 of circuit breaker in an engineered safety system,
of a nua'.ea,..< c.
-)] a ' t.
This ci cuit breaker had a oefect in one of its three time cetay eishpats which r, :lted in a reduced time delay for over-currer: p r a ts c r _ ' t. The defect was a small hairline crack in the end cap of the das' por.
Furt.1 av iuvest igation by this licensee disclosed that 7 out of 17 spate d
. t and caps and 2 non-engineered safety feature breakers also had similar dcfects.
The circuit breaker is a Westinghouse type DB-75.
Westinghou e.ype DC-50 breakers also use the same type of dashpot and end cap.
DB-50 and -75 breakers are used extensively in PWR's and some BWR's may also have the same breakers.
Similar make and model circuit breakers, when used for scram purposes, do not require'the overcurrent trip feature and thus are not of concern.
The end cap cra ck "2 defect, if severe enough, could result in premature tripping of the circuit breaker because cf insufficient time delay in overcurrent protection, i.e., the motor starting (inrush) current could cause the breaker to trip inadvertently and thus prevent the motor start.
The defects reporteu 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.
The subject of Bulletin 73-1 was end caps made of a black phenolic material. As a result of that Bulletin, the black end caps were replaced with a new type made of fiber-filled polye' ter material called " navy gray."
Prior to the April 1979 report, there have been no reports of suspect " navy gray" end caps either from scheduled testing or unusual 1,chavior in service. The manufacturer of the " navy gray" end caps believes the crack defects may be linked to a raw material batch problem.
That is, the molding ingredient materials used may have neared the end of their shelf life before use.
It is not believed the end caps, af ter fabrication, have a significant shelf life limit, due to the low residual stress and low crack propagation probabilities.
300 22D' Description of Event:
The following information was obta a '" ~
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~ '~- c April 12, 1979, and a subsequent m ' DUPLICATE DOCUMENT the licensee.
j Fntire document previously entered into system under:
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