Abstract
The resource-renewable boiling water reactor (RBWR) is an innovative BWR which has a capability to breed and burn transuranium elements (TRUs) using a multi-recycling process. One of RBWR core designs RBWR-TB2 was designed to be a TRU burner similar to sodium fast reactors (SFRs). The RBWR-TB2 is intended to burn TRUs from light water reactor (LWR) spent fuels and is assumed to be applied for reducing the amount of TRUs to be managed in storage facilities. The RBWR-TB2 can fission TRUs at a rate more than twice the rate of TRU production by the advanced BWR (ABWR). It is important to develop reactor internals and fuel assemblies that ensure the feasibility of the RBWR-TB2. RBWR-TB2 reactor internals are developed based on existing proven ABWR technology which is already being used in commercially operating plants. The RBWR-TB2 system is almost the same as that of the ABWR except for the reactor core. The tight pitch fuel lattice and fuel rods are introduced to the reactor core of the RBWR-TB2 to burn TRUs more efficiently. We organized the issues associated with the reactor internals that need to be tackled in order to realize the RBWR-TB2. Consequently, we confirmed that the reactor internals and fuel assemblies could be designed as commercial products. We also proposed the reactor internals and fuel assemblies that were suitable for the RBWR-TB2 which has a closed packed core. We designed a fuel assembly which had lower flow-induced vibration of fuel rods than that in the ABWR. The seismic response estimation of fuel assemblies is one of the most important design tasks for ensuring the seismic safety of nuclear reactors. The resonant frequency of our designed fuel assembly was calculated by a finite element method. The resonant frequency of the RBWR fuel assembly was 11 Hz and more than that of the ABWR assemblies. The designed RBWR-TB2 fuel assembly has higher rigidity. We concluded that the core structure of the RBWR-TB2 was feasible from the viewpoint of vibration characteristics. The RBWR appears to be a promising candidate energy source for energy security, reducing greenhouse-gas emissions, and mitigating the negative environmental impact of TRUs.
