Searching for managing the reactivity and increasing the fuel cycle life in the PWR by an untraditional method

•Managing the excess reactivity and increase the fuel cycle in the PWR.•The BS assembly reduces the excess reactivity at the beginning of cycle.•Reducing the concentration of the most radioactive fission products.•Using 232Th achieve a high conversion ratio in the BS design. This study aims to find an economic method to decrease the excess reactivity and increase the fuel cycle length. The neutronic feasibility to replace the 238U with 232Th and the traditional assembly with Blanket-Seed assembly was analyzed. MCNPX code version 2.7 was used to design a three-dimension model of PWR to simulate the neutronic characteristics of the investigated fuel types and designs. The radial thermal neutron flux and the radial thermal power distribution through the assembly have been studied. The radial thermal neutron flux and thermal power distribution provide an insight view about the proposed fuel types and designs. The effect of the proposed fuel types and design on the infinity multiplication factor (Kinf), the breeding fissile concentration, the reactor-grade plutonium (rgPu), the minor actinides (MAs), conversion ratio (CR) and the concentration of the most radioactive fission products have been analyzed and compared with that of the standard fuel. From the neutronic point of view, the results showed the economic feasibility of using 232Th in regulating the initial excess reactivity.