Preliminary investigation of neutron shielding compounds for ARC-class tokamaks

Abstract

Radiation shielding design is a crucial step in the development of a nuclear fusion reactor. Superconducting magnets are indeed a highly engineered component whose properties are particularly sensitive to irradiation damage. In addition, novel magnet technologies, such as High Temperature Superconductors (HTS), and the attractiveness of compact tokamak designs (like Affordable Robust Compact - ARC - reactor), require an even higher precision in the shielding design. In this work most promising radiation shielding solutions for compact tokamaks are explored. The study applies a Monte Carlo particles transport technique assisted by the OpenMC code. A D-shaped model is built and ARC reactor core is considered as main case study. A detailed analysis of the radiation environment is carried out. The study then assesses the most promising compounds on the basis of most suitable cross sections, material shielding properties and space constraints. In addition, the work addresses the problem of energy deposition on the shield providing an analytical model for active cooling necessities. Results highlighted the necessity of heavy elements and high density compounds as a considerable photon flux is generated in neutron-material interactions. Tungsten borides (WxBy) ceramics seem to be particularly promising for shielding radiation in a compact configuration.