ML20096H502
| ML20096H502 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/22/1984 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| F0577A, F577A, SD-50, NUDOCS 8409110430 | |
| Download: ML20096H502 (2) | |
Text
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General Offices
- Selden Street. Berlin Connecticut N
rts5[rac cca, P.O. BOX 270
.aro.e. cia.oara cwaa HARTFORD. CONNECTICUT 00141-0~70 J [',*"',[C,$~.~
(203) 66s-s000 L
L August 22,1984 Docket No. 50-423 F0577A Dr. Thomas E. Murley Regional Administrator Region I U. S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
References:
(1)
W. G. Counsil to T. E. Murley, F0467A, dated February 15, 1984.
(2)
W. G. Counsil to T. E. Murley, F0493A, dated March 23,1984.
(3)
W. G. Counsil to T. E. Murley, F0529A, dated June 20,1984.
Gentlemen:
Millstone Nuclear Power Station, Unit No. 3 Reporting of Potential Significant Deficiencies In Design and Construction:
Phase-to-Phase Electric Fault in a Motor Control Center (SD-50)
In a January 16, 1984 telephone conservation between the NRC Resident Inspector, Mr. T. Rebelowski and our Mr. D. B. Vail, Northeast Nuclear Energy Company (NNECO) reported a potential significant deficiency in the construction of Millstone Unit No. 3 as required by 10CFR50.55(e).
Subsequently, this was followed up with another telephone conversation with your Mr. T. Elsasser on January 17, 1984. The potential significant deficiency involves a phase-to-phase electrical fault which occurred in a motor control center (MCC) supplied by Gould, Inc. while a technician was testing with a clamp-on ammeter.
The fault occurred between adjacent phases of the uninsulated cable adapters used to terminate oversized cables to MCC circuit breakers and starters and was due to excessive flexibility of cable termination extension tabs on MCC breakers and starters which may have permitted shorting between phases.
The Category I MCCs, breakers and starters were seismically qualified by vendor testing. Initial testing, however, did not include the extension tabs. Subsequent seismic testing and analysis by Gould has verified the seismic integrity of the extension tabs. Gould has certified that the subject power cable extensions meet the specific seismic requirements and has amended the applicable seismic report accordingly.
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. However, since a short circuit occurred while placing a clamp-on ammeter on a non-safety related MCC cable and the fact that a similiar fault could occur on a
. safety-related MCC cable, we consider this matter to be reportable as ~ a significant deficiency.
In order to eliminate any susceptibility to similar tests resulting in maintenance induced disturbances, extension tabs are being removed and direct connection to motor control center breakers and starters is being utilized except on large (250A) MCC breakers in which the tabs are more rigid and have larger clearances.
We consider this to be.our final report closing out SD-50. We trust that the above information satisfactorily responds to your concerns.
Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY
'rfL W. G."Counsil '
Senior Vice President cc:
Mr. R. C. DeYoung, Director Division of Inspection and Enforcement U.S. Nuclear Regulatory Commission Phillips Building 7920 Norfolk Avenue Bethesda, MD 20014
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