High conversion Th–U233 fuel for current generation of PWRs: Part II – 3D full core analysis

Abstract

This study explores a possibility of designing a high conversion (HC) Th–U233 core for current generation of pressurized water reactors (PWRs). Increasing the conversion ratio in existing PWRs can potentially improve the utilization of natural resources, through the exploitation of vast thorium reserves and reduction in natural uranium demand.HC can be achieved through the use of heterogeneous seed-blanket (SB) Th–U233 fuel assembly design, where the supercritical seed works as a neutron supplier, while the subcritical blanket acts as U233 breeder. One of the main challenges associated with the heterogeneous SB fuel assembly designs is significant power imbalance between the seed and blanket regions caused by the high concentration of fissile material in the seed region and consequently requiring a substantial reduction in the core average power density.The main objectives of the current work are: (1) to design a high conversion SB Th–U233 fuel assembly which is directly retrofittable into existing PWRs without introducing significant modifications into the core and plant design; (2) to estimate the reasonably achievable core power density level at which reactor safety is not compromised by performing 3D coupled neutronic and thermal–hydraulic (T–H) analysis of a typical PWR core fully loaded with HC Th–U233 SB fuel.Part II of the two-part paper reports on the steady-state whole core analysis of 100% Th–U233 fueled PWR. The results of this study demonstrate the feasibility in principle of achieving conversion ratio close to unity for a Th–U233 PWR core operating at power density of 60W/cc, in three-batch annual fuel cycle and without exceeding the main safety limits.