1er septembre 2013
Réduction de puissance d’une pompe de recirculation qui a entrainé une réduction de puissance du réacteur. Un accident de perte de réfrigérant primaire aurait pu survenir suite à un déséquilibre de flux entre les pompes supérieur aux limites prescrites.
Première divergence : septembre 1969 - Type BWR Mark 1 - Puissance 621 MWé
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Event Number : 49316 - Facility : MONTICELLO - State : MN - Unit : [1] RX Type : GE-3 -
Event Date : 09/01/2013 - Event Time : 16:10
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
Initial PWR : 100 % - Current PWR 98 %
Event Text
RECIRC PUMP RUNBACK AND POWER REDUCTION
"On September 1, 2013 at 1610 CST, Monticello Nuclear Generating Plant (MNGP) experienced a runback of ’A’ Recirc pump from 87% speed to 82% speed. Operators took action to lock ’A’ Recirc pump scoop tube. This runback resulted in a power reduction from 100% to 98% RTP [Rated Thermal Power]. Should a LOCA [Loss of Coolant Accident] occur with the resultant mismatch between total jet pump flows of the two loops greater than required limits, the core flow coastdown and resultant core response may not be bounded by the LOCA analyses. It has been determined that this is an unanalyzed condition as defined by 10CFR50.72(b)(3)(ii)(B).
"At 2123 CST on September 1, 2013, MNGP completed adjusting recirc flow speed on ’A’ and ’B’ Recirc pumps to match jet pump loop flows to within the required limits and is no longer in an unanalyzed condition. Both ’A’ and ’B’ Recirc scoop tubes remain locked pending investigation."
The licensee has notified the NRC Resident Inspector.
Source : https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2013/20130903en.html
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