SOME SAFETY STUDIES FOR CONCEPTUAL FUSION-FISSION HYBRID REACTORS.

The objective of this study was to make a preliminary examination of some potential safety questions for conceptual fusion-fission hybrid reactors. The study and subsequent analysis was largely based upon reference to one design, a conceptual mirror fusion-fission reactor, operating on the deuterium-tritium plasma fusion fuel cycle and the uranium-plutonium fission fuel cycle. The blanket is a fast-spectrum, uranium carbide, helium cooled, subcritical reactor, optimized for the production of fissile fuel. An attempt was made to generalize the results wherever possible. The major potential hazards were found to be: fission products, actinide elements, induced radioactivity, and tritium. Event trees were constructed for the following accidents: blanket loss-of-flow, blanket loss-of-coolant, steam ingress, and plasma density-temperature transient. Important phenomena studied were loss-of-coolant, steam ingress, and blanket criticality. As a result of these studies it appears that highly reliable and even redundant decay-heat removal must be provided. Refs.