Evaluation of the consequences of containment bypass scenarios

Fission product transport and deposition in auxiliary and secondary containment buildings are important considerations in severe-accident analysis. Accordingly, a methodology has been developed that can be used to evaluate such fission product retention. Accident sequences considered include containment bypass scenarios and others that involve fission products being released from the containment into an adjacent building. The following were produced: (a) a list of plant-specific features that have a major influence of fission product retention; (b) a catalog of the pertinent auxiliary building/reactor building configurations sufficient to allow utilities to perform their own analyses; (c) a model for the building circulatory flows, both natural and forced, which allows arbitrary nodalization and has been experimentally verified; and (d) analyses of the sequences for the major variations in design. Fission product releases to the environment are principally governed by building response. Other important factors include the following: (1) auxiliary building size; (2) building compartmentalization and position of door jambs; (3) junction flow area to the environment; (4) operability of ventilation systems; (5) scrubbing through water pools covering the release point; (6) water sprays