Preliminary Neutronics and Thermal-Hydraulics Study on Thorium-Based HTR-PM With Outer Breeding Zone

In this work, a two-zone reactor core, which contains an inner driving zone and an outer ThO2 breeding zone, is designed under the framework of the HTR-PM. The main aim of this work is to investigate the feasibility of thorium utilization in the mature design of the HTR-PM with the inherent safety features. The neutronics and thermal-hydraulics characteristics are investigated to optimize the design parameters by using VSOP. The aim of optimization is to maximize the conversion of thorium to 233U in the breeding zone. The preliminary results indicate that the volume ratio of the breeding zone to the driving zone has significant influence on the power peaking factor and the maximum fuel temperature in normal operation and accidental conditions. On the other hand, the increase of reactor power will lead to increase of maximum fuel temperature after DLOFC accident. More heavy metal loading in the breeding zone will raise 233U yield, while the influence of fuel particle radius on the conversion ratio is negligible. An optimized 200 MWt two-zone reactor design is obtained with volume ratio of the driving zone to the breeding zone of 4:1, and 7 g and 30 g heavy metal per fuel sphere in the driving zone and the breeding zone, respectively.