New thorium core loading patterns for high temperature gas cooled nuclear microreactors

Ten different 50:50 vol ratio thorium core loading configurations for a chosen HTGR microreactor were compared with original uranium core loading from neutronics point of view. 2.72 x 109 individual TRISO particles except for homogeneous fuel configuration were modeled. The best configuration was achieved when fuel channels with three layer axial ThCO-UCO-ThCO seed/blanket were placed in the core as radial seed/blanket configuration with ThCO filled fuel channels. With thorium loading, initial criticality was reduced from 1.301 to 1.2619 and EFPD from 3500 days to 1775 days but power generation, power peaking factor, and maximum axial power peaking factor in the highest power producing fuel channel were increased therefore the burnable poison distribution optimization was performed to reduce these parameters. When compared with 20.35 kW, 2.13, and 1.3 values for aforementioned parameters for uranium configuration, 20.70 kW, 2.17 and 1.70 values for thorium core loading are acceptable.