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i PALISADES NUCLEAR POWER PLANT SER Supplement Docket No. 50-255
,CONTAINMENT OVERPRESSURIZATION POTENTIAL DUE TO AUXILIARY FEEDWATER RUN-OUT FLOW
- FOLLOWING A MAIN STEAM LINE BREAK By letter dated December 21, 1979, the staff requested the Consumers Power Company, the licensee for the Palisades Nuclear Plant, to provide certain additional infor-mati6n.
Specifically, the Consumers Power Company was to assess the potenti~l for containment overpressurization due to the anticipated continuous addition, at pump's run-out flow, of auxiliary feedwater to the affected steam generator follow-fng a postulated main steam line break (MSLB) accident.
The staff's interest in this issue resulted from the Part 21 report filed by the Virginia Electric and Power Company (VEPCO) dated September 4, 1979.
In that re-port, the NRC was infonned by VEPCO that overpressurization of the containment at North Anna, Units 3 and 4, could occur in the event of a postulated MSLB inside containment.
VEPCO indicated that, due to the anticipated continuous addition of
. auxiliary feedwater to the broken loop steam generator, at the pump's run-out flow condition, following a MSLB accident, the containment pressure will reach *the con-tainment design pressure in about 10 minutes.
In a letter dated January 21, 1980, the Consumers Power Company responded to the staff 1 s letter cited above and indicated ~hat the auxiliary feedwater sys tern uti 1-i zes run*~'out flow control equipment to limit flow.
The flow limit has not yet been determined, but will probably be set at less than 250 gpm to avoid water hammers in the feedwater 1 ine.
In the original MSLB analysis ~o consideration was given to auxiliary feedwater pump run-out.
Combustion Engineering has performed an analysis that demonstrates 8003250 6'1~
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f.. that the addition of auxiliary feedwater at the run-out flow condition (2250 gpm) wi11 not cause containment pressure to rise above the initial blowdown peak.
The staff concurs with the licensee's conclusion that the peak containment pressure will remain below the containment design pressure with the addition of auxiliary feedwater at the run-out flow rate.