Core meltdown assessment in the GCFR

This paper discusses the chronological sequence of events and supporting analysis during a total loss of all coolant circulation in the GCFR with top supported core. Redundant and diverse cooling systems provided for decay heat removal reduce the probability of this postulated event below the range of plant design bases. It is nevertheless considered to investigate the potential for consequence mitigation and containment margin. Two distinct phases of the sequence are discussed: 1) the core response to a total loss of coolant circulation and 2) the capability of the PCRV to retain molten fuel debris. GCFR specific design features to prevent recriticality and fuel vaporization due to fuel slumping are under investigation. Analytical and experimental work is in progress to evaluate the feasibility of such early accident termination mechanisms. Several concepts for post accident fuel containment have been identified and appear technically feasible.