Analysis of variation of neutronic and kinetic parameters of a Heavy Water Zero Power Reactor caused by changes in the fuel lattice pitch using MCNPX code

Abstract

The Heavy Water Zero Power Reactor (HWZPR) is a 100‑W research reactor that uses natural uranium metallic fuel and heavy water as moderator. The HWZPR is designed for training and research in reactor physics fields. The main aim of this paper is to evaluate the variation of neutronic parameters of a HWZPR resulting from changes in the fuel lattice pitch using MCNPX code. In such a manner, neutronic parameters including effective multiplication factor (k_eff) for critical water level, effective delayed neutrons fraction (β_eff), prompt neutrons lifetime (l_p), and neutron flux distribution are investigated and benchmarked. The results illustrated that, as the lattice pitch is increased, more heavy water is needed for criticality condition according to the decrease in the number of fuel rods and fewer available fissile materials. Comparison of the results with the reactor Safety Analysis Report shows reasonable agreement.