Fission Product Release from Fuel Under Severe Accident Conditions

Recent advances in the understanding of fission product release from fuel under severe accident conditions in light water reactors are reviewed. In addition to the effects of temperature and time at temperature, recent results from in-pile and out-of-pile tests and the accident at Three Mile Island Unit 2 suggest that the effects of fuel morphology such as restructuring of the UO₂ microstructure, fuel liquefaction, molten pool formation, debris bed formation, and the effect of fuel chemistry have important influences on fission product release behavior under severe accident conditions. Consideration of these effects is required for complete models of fission product release during severe light water reactor accidents.