ML20127G588

RO:721208,stack Gas Monitoring Sys Was out-of-svc for Nearly 2 Hr & Tripped Due to Motor Overload.Caused by Freezing Moisture in Return Line.Sample Return Line Wrapped W/Heat Tape & Insulated

ML20127G588
Person / Time
Site:	Monticello
Issue date:	12/15/1972
From:	Mayer L NORTHERN STATES POWER CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9211170386
Download: ML20127G588 (2)

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• NSAs NORTHERN STATES POWER COMPANY M $ N N E A POLI S. MIN N E SOTA 58d01 ,,

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December 15, 1972 S c3

< d 9 t Mr. A Giambusso Deputy Director for Beactor Projects 2%

g'r , gj United States Atomic Energy Commission 9 ~,, hgQW ./

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Washington, DC 20545 &

Dear Mr. Giambusso:

'Q b ~4 M/ [f Co MONTICELIO NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 Loss of Stack Gas Monitoring System A condition occurred at the Monticello Nuclear Generating Plant which we are reporting to your office in accordance with the provisions of Section 6.6.B.3 of Appendix A, Technical Specifications of the Provisional Operating License DPR-22. On December 8,1972, the Stack Gas Monitoring System was out of service for nearly two hours. Continuous operation of this system is required by Technical Specification 3.8. A. The Begion III Compliance Office has been notified of the occurrence.

l At approximately OW1 on December 8,1972, the Stack Gas Fbnitoring System l Sample Pump tripped due to motor overload. An attempt was made to start the alternate pump but it tripped also. The resultant investigation re-vealed that the return line from the sampling system to the stack was l plugged due to the freezing moisture in the line. An orderly shutdown of

! the plant was initiated when the sampling system could not be made opera-l ble within one hour. At 0635, the Stack Gas Monitoring System was back in service and the plant was returned to full power.

l While the sampling system was inoperable, all other plant monitoring in-I strumentation including the air ejector monitors were observed and indicated l no enange in activity levels or release rates. (The stack gas monitors pro-vide only alarm functions; the air ejector monitors provide the automatic actions if high off-gas activities occur.)

To prevent a recurrence of the sampling system freeze-up due to condensation of moisture in the system, the sample return line was wrapped with heat tape and insulated; the sample suction line, which was already wrapped with heat tape, was also insulated. _

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Mr. A Giambusco December 15, 1972 Tage &

An Abnormal Occarrence T<eport will be available at the plant for review by the Begion III Compliance Inspector.

Yours very truly, cK o.

L 0 bhyer, P.E.

Director of Nuclear Support Services LOM/CEL/br cc: B H Grier

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