ML20247D185

From kanterella
Jump to navigation Jump to search
Provides Addl Info Re Molded Case Circuit Breaker Replacement,Per Insp Repts 50-282/88-201 & 50-306/88-201. Util Has Concluded That Replacement Breakers from Bud Ferguson Co Suitable for safety-related Purposes
ML20247D185
Person / Time
Site: Prairie Island  Xcel Energy icon.png
Issue date: 07/12/1989
From: Larson C
NORTHERN STATES POWER CO.
To: Miller H
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-88-010, IEB-88-10, NUDOCS 8907250073
Download: ML20247D185 (2)


Text

-_ _ . _ . -.

_7_ -

Northem States Power Company 414 Nicollet Mall Minneapolis, Minnesota 554011927 Telephone (612) 3345500 July 12, 1989 H J Miller Division Direct)r of Reactor Safety U S Nuclear Regulatory Commission s.

799 Roosevelt Road Glen Ellyn, Illinois 60137 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 Licence Nos. DPR-42 50-306 DPR-60 Additional Information Concerning Molded Case Circuit Breaker Replacement NRC Inspection 50-282/88-201 and 50-306/88-201 Reference 1: Letter from C E Larson (NSP) to H J Miller (NRC) dated June- 30, 1989, titled: " Molded Case Circuit Breaker Replacement" In Reference 1, we committed to replace cable connectors supplied with the Bud Ferguson Company MCCBs that had been reused in the installation of some of the replacement MCCBs. These replacements were completed by July 7, 1989.

In Reference 1, we stated that all replacement breakers had been successfully tested per the test procedures specified in Prairie Island's Commercial Grade Procurement Dedication Evaluation for MCCBs. The basis of our acceptance should be clarified.

The breaker manufacturer recommended that terminal heat rise testing of ANSI /UL 489-1985 be performed in lieu of the contact resistance checks specified in NRC Bulletin 88 10. The condition of the breaker contacts is more accurately determined by the measurement of the heat rise at the breaker terminals. However, since contact resistance testing was specified in Bulletin 88-10, it was measured as a separate follow-on check. All eight breakers tested, successfully met our stipulated test acceptance criteria.

Four of the tested circuit breakers fell outside of the Bulletin 88-10 criteria that no pole contact resistance value could vary more than 50% from the lowest value (Section 2.2 of Attachment 1 to Bulletin 88-10). After further internal review of the entire set of test data and discussion with the breaker manufacturer, we concluded that the replacement breakers were suitable for safety related purposes.

8907250073 890712 PDR ADOCK 05000282 LD Q PDC kL 171gg gpf

t

.....t J Northem States Power Company l H J Miller July 12, 1989 Page 2 L.

Please contact us if you have any questions related to our resolution of this issue.

C E Larso Vice Presi ent Nuclear Generation c: Regional Administrator III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC G Charnoff 1

1

)

l l

l j

1 1

I j