A recriticality-free fast reactor core concept

An outline is given of simple evaluation models for a recriticality in an a ttempt to construct a fast reactor core that has high potential to terminat e an accident and prevent its progression, under postulated core-damage con ditions, into further disruption of the degraded core and into possible rec riticality leading to an energetic power excursion. The basic idea to preve nt recriticality events is to remove a certain amount of fuel material out of the core in order to keep the core subcritical. Based on the simplified models, general guidelines are given that minimize the amount of fuel remov al necessary to avoid recriticality events. Multigroup two-dimensional diff usion calculations are also performed to ascertain the tendency obtained by the simple model for the reactivity insertion due to a core collapse. In t he sense of controlled material relocation, the fraction of core materials is identified that should be preferentially removed out of the core to elim inate the recriticality potential.