Dynamic stresses in spherical containments with pressure suppression system during steam condensation

Different physical phenomena which control the structural integrity of the containment shell in case of a postulated failure of the primary coolant system are discussed. Detailed analyses are carried through for the chugging phase, where steam will be blown into the water pool of the pressure suppression system. As reference geometry a German boiling water reactor type 69 is used. The fluid dynamics of the water pool is described by a boundary integral equation method. For the structural dynamics of the thin spherical containment shell analytical solutions of Fluegge's shell equations are obtained. The feedback of structural deformations on the fluid-dynamic loadings, i.e., the effect of fluid-structure interaction is considered. It increases the loadings significantly in comparison to calculations without this effect. The steam condensation in the water pool is treated as a parameter. As results upper limit steam condensation scenarios are presented where the resulting stresses reach the admissible values. If these upper limit scenarios cover all the steam condensation events which may occur, the dimensions of the containment shell are adequate to steam condensation loadings. (According to many experiments the upper limit scenarios cover indeed the expected condensation events.) The computer programs used in this work are carefully checked by comparisons with other analysis methods and relevant experimental findings. (orig.)