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

• The 4S Toshiba Gen IV 10 MWe core design is used for a neutronic simulation with MCNP.
• Pin-cell and full-core simulations are carried out to obtain the neutron spectrum, k∞ and keff.
• The initial fuel inventory is determined for two absorber rods viz B4C and Hf.
• The maximum fuel rod radius is found to be 6 mm and 6.2 mm for 9 mm Hf and B4C rods.

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 keff with a central absorber control rod. Two absorber materials are considered viz boron carbide (B4C) 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 B4C. This work is of use for the core design of small multipurpose Gen-IV reactors.