Transmutation of Np-237 in the First Cycle of AP1000 Core

The spent fuel generated by nuclear power plants contains large quantities of radionuclides, including long-lived fission products (LLFP) and minor actinides (MA). These nuclides decay to no harm through thousands of years. Partitioning and transmutation technology (P&T) is to separate these nuclides from the spent fuel into specific device for neutron irradiation, making it into a low-level radioactive nuclides or stable nuclides. As a major MA nuclide, neptunium (Np) has a high productivity and long half-time. In this paper, MCNP code is used to build the AP1000 reactor core model, and neptunium dioxide (NpO2) transmutation rod is introduced to design 10 schemes where transmutation material is putted into the first cycle core. By calculation and comparing the effective multiplication factor (keff), the added quality of neptunium dioxide and the changing extent to make the core reach the critical again, the result shows that the scheme where neptunium dioxide coating is putted in the fuel enrichment 4.45% of the core has advantages. This paper analyzes the scheme and optimized.