A neutronic pin cell and full-core design analysis of the 4S reactor

Abstract The 4S (Super-safe small, and simple reactor) core, based on the Toshiba Gen-IV 10 MWe fast reactor design, is modeled and simulated with the Monte Carlo code MCNP to obtain useful neutronics design information. This paper carries out a preliminary pin-cell simulation to obtain the neutron spectrum, the infinite multiplication k ∞ and the effect of temperature and moderator density followed by a full-core simulation for the effective multiplication factor k eff with a central absorber control rod. Two absorber materials are considered viz boron carbide (B 4 C) and hafnium (Hf) to determine the fuel inventory to balance the beginning of cycle (BOC) excess reactivity. It is found that for a single central absorber rod of radius 9 cm, the maximum fuel rod radius is 6 mm for hafnium and 6.2 mm for B 4 C. This work is of use for the core design of small multipurpose Gen-IV reactors.