ATWS analysis for Browns Ferry Nuclear Plant Unit 1

Analyses of postulated anticipated transients without scram (ATWS) were performed at the Idaho National Engineering Laboratory. The Browns Ferry Nuclear Plant Unit 1 was selected as the subject of this work because of the cooperation of the Tennessee Valley Authority. The work is part of the Severe Accident Sequence Analysis Program of the US Nuclear Regulatory Commission. A main steamline isolation valve closure served as the transient initiator for these analyses, which preceded a complete failure to scram. Results from the analyses indicate that operator mitigative actions are required to prevent overpressurization of the primary containment. Uncertainties remain concerning the effectiveness of key mitigative actions. The effectiveness of level control as a power reduction procedure is limited. Power levels resulting from level control only reduce the pressure suppression pool heatup rate from 6 to 40F/min