ASSESSMENT OF 2 BWR ACCIDENT MANAGEMENT STRATEGIES

Candidate mitigative strategies for the management of in-vessel events during the late phase (after-core degradation has occurred) of postul ated boiling water reactor (BWR) severe accidents were considered at O ak Ridge National Laboratory (ORNL) during 1990. The identification of new strategies was subject to the constraint that they should, to the maximum extent possible, make use of the existing equipment and water resources of the BWR facilities, and not require major equipment modi fications or additions. As a result of this effort, two of these candi date strategies were recommended for further assessment. The first was a strategy for containment flooding to maintain the core and structur al debris within the reactor vessel in the event that vessel injection cannot be restored to terminate a severe accident sequence. The secon d strategy pertained to the opposite case, for which vessel injection would be restored after control blade melting had begun; its purpose w as to provide an injection source of borated water at the concentratio n necessary to preclude criticality upon recovering a damaged BWR core . Assessments of these two strategies were performed during 1991 and t his paper provides a discussion of the motivation for and purpose of t hese strategies, and the potential for their success.