TEMPERATURE REACTIVITY CONTROL METHODOLOGY FOR HYDRIDE-MODERATED SMALL REACTOR WITH POISON NUCLIDES

摘要

A small nuclear reactor for isolated area requires light weight, passive safety, nuclear security, efficiency and autonomous control for powering without human control. A small calcium-hydride moderated reactor was proposed to satisfy these demands. However, the positive temperature reactivity of the hydride moderated reactor was reported in the previous study. Furthermore, the positive temperature reactivity was also observed in the proposed core. This positive temperature reactivity comes from the combination of spectrum shift by temperature change and energy distribution of the reaction cross section. The present temperature reactivity control method utilized ~(113)Cd and ~(151)Eu as poison nuclides which have resonance capture cross section at shifted thermal neutron peak energy. These poison nuclides increase neutron capture reaction; consequently, this method made temperature reactivity negative over the whole temperature range. This methodology will be utilized to design the hydride-moderated small reactor.