ML20127K624
| ML20127K624 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 10/08/1973 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9211200454 | |
| Download: ML20127K624 (1) | |
Text
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NORTHERN 5TATES POWER COMPANY M I N N E A PO L.i s, M I N N E S OTA SSeot October 8, 1973 f)'\\
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Mr. J P 0' Leary, Director OCT 11 jg73 P-f
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T U S Atomic Energy Commission g/, -
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Dear Mr. O' Leary:
3,. g MONTICELLO NUCLEAR GENERATING PIR4T Docket No. 50-263 License No. DPR-22 Malfunction of the "B" SPGT System Heater A condition occurred at the Monticello Nuclear Generating Plant which we are reporting to your office in accordance with Section 6.7.B.1, Abnormal Occurrence Reports, of Appendix A, Technical Specifications, of Provisional Operating License DPR-22.
On September 29, 1973, while deinerting the primary containment during a scheduled reactor shutdoen, the "B" Standby Gas Treatment (SBGT) System LOW HEAT alarm was received and indication of low differential temperature was observed.
The redun-dant SBGT train was immediately placed in operation.
Subsequent investigation revealed failure of the 30 amp-600 volt fuse block assembly in the heater circuit.
It was determined that a loose fuse clip on the fuse block had created a high resistance path resulting in overheating of the assembly to the point of failure.
The fuse block assembly was replaced.
Physical inspection and electrical testing of the heater revealed it to be undam-aged. An operability test of the "B" SBGT System was satisfactorily performed on October 2,1973, prior to reactor startup.
This occurrence did not affect safe operation since the redundant train was fully operabic and within minutes the plant conditions were such that SBGT operability was not required.
No similar failures have occurred at Monticello. An inspection of the redundant SBGT train heater circuit was performed and no abnormal conditions noted.
It is felt that the measures tcken were sufficient to prevent repetition.
Yours very truly, N.0 o
u L 0 Mayer, PE Director of Nuclear Support Services 9211200454 731000 cc: J G Keppler PDR ADOCK 05000263 l
G Charnoff S
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Minnesota Pollution Control Agency gy l
Attn. Ken Dzugan l
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