Most analytical and experimental approaches to the evaluation of fluid-structure interaction (FSI) effects in the General Electric Mark I BWR pressure suppression system treat the torus shell as rigid when the shell in real systems is flexible. This report describes linear three-dimensional finite-element analyses of one torus bay that investigated the qualitative effect of torus wall flexibility on hydrodynamic loads induced by a nominal safety relief valve (SRV) discharge. The results of these analyses support the general conclusion drawn from earlier two-dimensional analyses. The report also discusses finite-element analyses of a 3-D representation of the earlier 2-D plane-strain model of the torus shell.

This report describes a series of extended analyses requested by the US Nuclear Regulatory Commission to provide qualified understanding of possible fluid/structure interaction (FSI) effects for SRV teequencher test results. Three input pulses with total impulses varying by up to a factor of five are applied to two-dimensional finite-element models of the Mark I torus with shell diameter-to-thickness ratios of 0, 300, and 600. The results of these analyses support earlier conclusions that increased wall flexibility enhances attenuation of hydrodynamic loads and furthermore indicate that the magnitude of the attenuation is only weakly affected by the total impulse of the bubble pressure time-history.