LOPWAT2: An Improved Thermohydraulic Code for LOPWA Analysis for a SES-10 Reactor

Abstract

An improved computer program, LOPWAT2, has been developed for the thermohydraulic analysis of a highly improbable accident sequence in a 10 MWth SES reactor in which total loss of pool water results in complete uncovery of the core. The maximum fuel sheath temperatures predicted by LOPWAT2 are in very good agreement with those predicted by the earlier version of the program. Thus, the earlier conclusion that there would most probably be insignificant fuel and fuel sheath damage in such an accident sequence, and hence an insignificant release of fission products, is reinforced. Preliminary results of an experimental program using an electrically heated simulation of the core indicate that a conservative assumption concerning the extent of the heat sink may be relaxed which would result in even lower predicted peak maximum fuel sheath temperatures.