ML20245H532

Advises of Reclassification of Nine Circuit Breakers Previously Deemed Traceable Re NRC Bulletin 88-010

ML20245H532
Person / Time
Site:	Maine Yankee
Issue date:	06/19/1989
From:	Whittier G Maine Yankee
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GDW-89-212, GL-89-02, GL-89-2, IEB-88-010, IEB-88-10, IEIN-88-046, IEIN-88-46, MN-89-83, NUDOCS 8906290513
Download: ML20245H532 (3)

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p.y MaineYankee RELIABL' 9 ECTRICITY FOR MAINE $1NCE 1972 EDISON DRIVE . AUGUSTA, MAINE 04330 . (207) 622-4868 June 19, 1989 MN-89-83 GDH-89-212 Unit"ed States Nuclear Regulatory Commission

- Attention: Document Control Desk Hashington, DC 20555

References:

(a) License No. DPR-36 (Docket No. 50-309)

(b) NRC Bulletin No. 88-10: Non-Conforming Molded-Case Circuit Breakers, dated November 22, 1988 (c). NRC Information Notice No. 88-46: Licensee Repcet of Defective Molded-Case Circuit Breakers, dated July 8,1988 (d) NUMARC Letter to NUMARC Board of Directors, dated March 9, 1989, NRC Bulletin 88-10 (e) MYAPCo. Letter to USNRC, dated March 31, 1989 (MN-89-44)  ;

Subject:

IE Bulletin No. 88-10, Non-Conforming Molded-Case Circuit Breakers -

Supplemental desponse Gentlemen:

Maine. Yankee responded to IE Bulletin No. 88-10 with Reference (e). With that response we indicated we would conduct audits of Maine Yankee's intermediate suppliers of molded case circuit breakers to ensure their records were sufficient to provide reasonable assurance that the breakers were traceable to the original manufacturer. He completed these audits on May 30, 1989.

The results of one audit led Maine Yankee to reclassify nine circuit breakers which were previously deemed to be traceable by discussion and

' documentation attesting so by the vendor. This vendor was Nutherm International, Inc., of Mt. Vernon, Illinois. With Reference (e), Maine Yankee identified Nutherm as having supplied three molded case circuit breakers which were traceable to companies identified by the NRC in IE Information Notice 88-46 as having supplied suspect breakers. Nutherm claimed the remaining breakers were traceable to the manufacturer thre;Jh their HESCO supplier in St. Louis, and had packing slips and information D >m HESCO attesting so. Maine Yankee attempted to substantiate Nuthern, claim by conducting audits at both Nutherm and at HESCO. Maine Yankee found no evidence of tampering or wrong doing at either site, however, we were also unable to obtain the evidence we believe necessary to meet the new NRC expectations (Generic Letter 89-02) to substantiate Nutherm's claim that the breakers are traceable to the original manufacturer. These breakers are identical to those described in Maine Yankee's response to Action Item 1c of Reference (e).

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, MaineYankee United States Nuclear Regulatory Commission Page two Attention: ~ Document Control Desk MN-89-83 Reclassification of the nine circuit breakers results in Maine Yankee having less than eighty percent (78.61.) of the molded case circuit breakers in stock traceable to the original manufacturer. In accordance with the Bulletin, Maine Yankee has expanded our investigation to include all circuit  ;

breakers (CBs) purchased between August 1,1983 and August 1,1988 and '

installed in the plant. Thirty-two breakers fit this category. Of the thirty-two, twelve circuit breakers were installed in Class 1E applications.

Efforts to verify traceability of these units has just begun and should be completed by June 30, 1989. He will further supplement our response to IE l Bulletin 88-10 upon completion of these efforts.

Four of the twelve CBS installed were purchased from ilutherm on the same purchase orders as those hodited by Maine Yankee, and as such have been declared non-traceable. These breakers were installed (one each) on DC buses 1, 2, 3, and 4, between the bus and its associated battery charger. The  ;

breakers were installed in 1987 as par

• af an engineering design change to  ;

facilitate disconnecting the DC bus ftm its battery charger in crder to 4 conduct maintenance on the battery chargers. This maintenance is normally conducted while the plant is shut down and safeguards loads on the DC buses are minimal, Circuit breakers were installed in lieu of switches for this application in order to provide a second level overcurrent protection between the DC bus and its battery charger. The battery charger is also equipped with a circuit breaker which provides the first level fault protection. If the suspect breakers tripped prematurely, the DC bus would separate from its charger and load would shift to the batteries. If the breaker failed to trip on a fault, bus protection would be provided by tripping of the battery charger's circuit breaker. This is the same fault protection provided the DC buses for fifteen years of plant operation before installation of the subject circuit breakers. If the breakers were to develop high contact resistance, additional heat may develop within the DC distribution cabinet. This has not posed a problem with the CBs in over two years of operation, thus supporting our determination that these breakers have not been tampered with.

For the foregoing reasons, we conclude that operation with the four subject circuit breake* 3 installed does not compromise plant safety. Maine Yankee does not plan to replace these circuit breakers at this time. The breakers were installed to function as switches, and they were not ;ntended nor serve any necessary safety function. Any of the postulated failure modes for these CBs does not increase the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety; nor does it create possibility of an accident or malfunction different than previously evaluated. Therefore, operation with the subject circuit breakers installed does not constitute an unreviewed safety question and is justified.

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. MaineYankee United States Nuclear' Regulatory Corraission Page three Attention: Document Control Desk- HN-89-83' He trust this information is satisfactory. Maine Yankee does not plan to test the aforementioned circuit breakers in accordance with our understanding that testing is optional (see Final Clarification of NRC Bulletin 88-10 including staff comments of February 17, 1989 Enclosure 3 of Reference (d)).

The breakers in Stores will not be used in Class IE applications and will.be held on. site until April 1, 1990, should NRC require additional actions-for them.

Very truly yours, MAINE YANKEE

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G. D. Whittier, Manager

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1 c: Mr. Richard H. Hessman Mr. Hilliam T. Russell Mr. Cornelius F. Holden Mr. Patrick M. Sears ,

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