Neutronics parameters optimization of the improved dual-cooled waste transmutation blanket for FDS

The neutronic analyses of the improved dual-cooled waste transmutation blanket (I-DWTB) for the fusion-driven sub-critical system (FDS) with a neutron wall loading of 0.5 MW/cm² are preformed on the basis of 3-D transport calculations with MCNP and 1-D burnup calculations with home-developed code BUS and the multi-group (175 neutron groups - 42 Gamma groups coupled) data library originated from the IAEA FENDL-2 (Fusion Evaluated Nuclear Data Library, Version 2) and the US ENDF/B-VI. The neutronic optimization are presented as the following: 1) through change tritium breeder fraction and the sizes of the corresponding zones, keep tritium self-sustainment (tritium breeding ratio TBR∼1.05) to fit the requirement of fusion source, 2) improve the U-zone materials fractions and dimensions to generate as many plutonium inventory as possible, 3) adjust the compositions and configurations of different isotopes of long-lived minor actinides (MA), fission products (FP) and other additive nuclides. The major purpose is to increase transmutation rates and to reduce waste inventory of long-lived spent fuels from fission reactor under the assumed constraints of the allowable maximum thermal power density (100 MW/m³), the maximum tritium breeding ratio TBR and the effective neutron multiplication Keff < 1. In addition, based on the consideration of safety, the influence between burn-up depth and the eigenvalue Keff is deducted and analyzed preliminarily.