Analysis of zirconium hydride moderator effect on the micro lead-based reactor

Abstract

As a crucial parameter for the design of micro reactors, the neutron spectrum directly impacts the k_eff, the critical size, burnup characteristics, reactivity temperature coefficients and so on. When considering the optimization of the reactor size, designs utilizing thermal neutron spectrum and fast neutron spectrum each present their unique advantages and challenges. To investigate the impact of energy spectrum on the reactor performance, a micro lead-based reactor with annular channel fuel elements is proposed and the study of the influence of varying the volume ratio of moderator and fuel (the M/F ratio) on the k_eff, the critical size, burnup characteristic and reactivity temperature coefficients by using the Reactor Monte Carlo code (RMC code) is conducted. The results show that for the micro lead-based reactor proposed, when the reactor energy output demand is greater than 350 MWt·years, the design with fast neutron spectrum (without moderator) exhibits the minimum size. While the reactor energy output demand is less than 350 MWt·years, the design with a thermal neutron spectrum (with moderator) achieves the minimum size. Moreover, to ensure the negative reactivity temperature effect, the M/F ratio should be maintained below 3.4. The insights presented in this paper will serve as valuable references for the design of the micro reactor.