Analysis of structural response of Monju reactor vessel under HCDAs using the PISCES-2DELK Code (II); Parametric study

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Two groups of the parametric studies were performed using the PISCES-2DELK Code to examine the problems in the detailed assessment of the structural integrity of the reactor primary system under hypothetical core disruptive accidents (HCDAs) in the prototype fast reactor "Monju". The results were integrated and discussed in the present report. The first group of the studies was performed to examine the sensitivities of uncertainties in input data and modeling employed in the analyses. In the second group of the studies, several important structures were selected to discuss their effects on the structural response of the reactor vessel to HCDA loads. The results of the studies were discussed based on the point of view of an energy flow from an expanding core. It was found that there were general relationships in this energy flow. The relationships were then integrated into simple correlations among: the expansion work of the HCDA bubble; the kinetic energy of the coolant slug upon impact with the plug head; the energy absorbed by the crushable structures under the plug head; the internal energy increase due to the deformation of the reactor vessel upon coolant slug impact; the maximum hoop strain of the reactor vessel. The correlations thus developed have been very useful not only to interprete the result of each parametric case in detail, but also to extrapolate or interpolate the results to cases with different initial and/or boundary conditions without re-running PISCES-2DELK Code.