Estimation of the neutron-activated waste from decommissioning of NuScale's Power Module and evaluation of its suitability for the Swedish waste management system

Recently, several countries, including Sweden, have begun investigating the deployment of Small Modular Reactors. Licensing documentation for new reactors must include (preliminary) waste management and decommissioning plans. For light water reactors, the majority of the long-lived radioactive waste from their decommissioning consists of neutron-activated metallic components in the core region, the reactor internals and the reactor pressure vessel. Usually, this waste is planned to be disposed of in geological repositories, and the long-term safety after closure of Sweden's operating and planned repositories is mainly determined by their inventory of the long-lived radioisotopes C-14, Ni-59, and Ni-63. In this study, a three-dimensional model of NuScale's Power ModuleTM, a light-water small modular reactor, was created using Serpent 2, a multi-purpose three-dimensional continuous-energy neutron and photon transport code. The model consists of the nuclear core and surrounding metallic components. Based on burn-up calculations, the neutron flux in the equilibrium core was obtained. From the neutron flux, the cumulative concentrations for a range of relevant short- and long-lived radioisotopes were calculated in the metallic structures in the core region after 60 years of operation. The average specific activity of the selected radionuclides in the different components of the NuScale Power Module was calculated and compared to the activities in existing or anticipated decommissioning waste from Swedish reactors to evaluate the suitability of the Power Module's decommissioning waste for the Swedish waste management system. This study indicates that a single NuScale Power ModuleTM could generate between 1.08 and 2.13 m3 metallic LL-ILW/ GWel-year, i.e., radiologically suitable for disposal in the planned Swedish geological repository for long-lived, intermediated-level radioactive waste. These energy-equivalent volumes are estimated to be somewhat larger than those antic
QC 20240912