Reflector Effect on Pulse Behavior of Uranium Zirconium-hydride Reactor

For compact uranium zirconium-hydride reactor which reflectors make considerable contribution to the reactivity, the effect of reflectors on pulse kinetics behaviors should not be ignored. In order to characterize this particular effect, a two-point pulse model based on Cohn’s two-point kinetics model was proposed. According to calculations for specific cases, this two-point model was compared with the ordinary one-point pulse model and the one-point pulse model with the correction of effective lifetime of prompt neutrons. Among all three models, the ordinary one-point pulse model should only be used for extreme cases where reflectors are exceedingly thin, otherwise there would be significant differences between this model and others. Results of corrective one-point pulse model are close to those of two-point pulse model for most cases. For specific cases with relatively thick reflectors and large initial reactivity insertions, the result of corrective one-point pulse model differs obviously from that of two-point pulse model, since the asynchrony of neutrons in cores and reflectors is not considered in corrective one-point pulse model. The two-point pulse model is able to distinguish neutrons in cores and reflectors, thus it shall be used in analyses of pulse behaviors of compact uranium zirconium-hydride reactors and severe accidents with significantly large positive reactivity insertions.