A Comparison of Design Study between Critical and Subcritical Systems for TRU Transmutation: Focused on the Safety Point of View

Currently, two systems for TRU (transuranics) transmutation, the critical and the subcritical reactor systems, are being investigated by many research groups. Both systems have their own advantages and disadvantages. In this study, the comparative analyses of nuclear characteristics between both systems were performed. The fuel loaded into a TRU transmutation reactor includes few fertile nuclides, which contribute to stability and safety of the nuclear reactor. Thus, this study was focused on the intrinsic difference in the dynamic parameters between both systems. At the same time, the neutronic effects of the external source and the neutron absorber on the nuclear characteristics were also analyzed for the subcritical and the critical systems, respectively. Neutron flux spectrum, fuel temperature coefficient, coolant temperature coefficient, delayed neutron fraction, and neutron generation time were considered for comparative analyses. Based on the obtained results, some conclusions and proposals could be derived with relation to TRU transmutation reactor design.