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

High conversion Th-U233 fuel cycle implemented in existing reactors can potentially improve utilization of natural resources, through the exploitation of vast thorium resources and the reduction in natural uranium demand, since the Th-U233 fuel is theoretically capable of achieving a high conversion ratio in the thermal neutron spectrum. Recently, several studies on a high conversion Th-U233 fuel cycle for the current generation of PWRs have been performed. In [1] it was demonstrated that the self-sustainable Th-U233 fuel cycle can be achieved through the introduction of an advanced heterogeneous seed-blanket (SB) fuel assembly design. In [2] it was shown that the self-sustainable fuel cycle requirements can be met using heterogeneous SB configuration with standard fuel assembly dimensions, however the power density reduction from a typical 104 W/cm3 to about 30 W/cm3 was required in order to compensate for the high power peaking in the seed region. This paper presents the results of the neutronic optimization study of a high conversion Th-U233 SB fuel assembly that can be used in the current generation of PWRs without any changes in the core design. The main goal is to maximize the conversion ratio through the optimization of the fuel composition and moderate modification of the fuel pin dimensions while preserving standard PWR fuel assembly lattice pitch and outer dimensions as well as using ''typical'' oxide fuel. (orig.)