High conversion Th-U233 fuel cycle for current generation of PWRs

This paper assesses the basic possibility of achieving a high conversion Th-233U fuel cycle that can be used for the current generation of Pressurized Water Reactors. The main fuel assembly design, describe in this paper, follows the RTF SBU design. A 17 x 17 heterogeneous PWR fuel assembly, which can ensure high conversion, was considered. Such heterogeneous fuel assembly geometry consists of central 233U based seed region and a large 232Th based blanket region. The fuel pins in the seed region has a standard PWR pins dimensions. However, the fuel pins in the blanket region was enlarged in order to reduce the moderation to fuel ratio and facilitated the resonance neutron absorption in blanket. This paper describes the 2D neutronics analysis of the proposed fuel assembly. The main analysis was performed with the deterministic lattice transport code HELIOS. The obtained results were conformed using the continuous-energy Monte-Carlo code Serpent. The fuel cycle length was evaluated by applying Non-Linear Reactivity Model to the results of fuel assembly burnup calculations. The 233U content was adjusted to achieve fuel cycle length of 18 months and maximum fissile inventory ratio (FIR). The results of the analysis have been shown that for the heterogeneous seed-blanket (SB) fuel assembly, a FIR of about 0.94 can be achieved.