Safety considerations in fast reactor fuel development

The role that Core-Disruptive Accidents play in the overall safety evaluation of fast reactors has not always been well defined or universally agreed upon. They have, however, become a traditional consideration in LMFBR safety. Reactors are carefully designed to minimize the potential for serious malfunctions and to incorporate automatic protective features which will terminate the effects of identifiable malfunctions within defined acceptable limits. The approach that is being followed in the United States is to also provide consequence-limiting features which will protect the public against the effects of an excursion beyond the capacity of the normal protective systems. These have been previously described as the four lines of assurance: prevention of accidents, limitation of core damage, containment of accidents in primary system and attenuation of radiological products. Typically, the response and adequacy of these consequence-limiting features are determined by evaluating the response of parts of the reactor system to a spectrum of simulated core-disruptive accidents. Similar considerations are applied to other parts of the fuel cycle. Theoretical and experimental studies of potential initiators for core disruption and the subsequent reactor bahaviour are discussed. The methods used to analyze and predict the course of core-disruptive accidents from initiating events to complete core disruption, and its effect on reactor structures are described, as are the experimental bases for the analyses. Specific developments in the technology and experimentation that support these analyses are discussed, including extensive experimentation in TREAT with fresh and preirradiated fuel pins prototypic of FFTF and CRBR