Neutronics assessment of the shielding and breeding requirements for FNSF (standard aspect ratio)

This paper presents design and analysis results regarding key aspects of the neutronics for a standard aspect ratio fusion nuclear science facility (FNSF). Optimization of the inboard design is based on maximizing tritium production and minimizing radiation damage to the ohmic heating coil (OHC). The calculations show that the outboard tritium breeding blanket alone is not enough for achieving tritium self-sufficiency in the FNSF. Options to enhance tritium production in FNSF include the use of either a thin, specifically designed tritium breeding blanket or the use of only a multiplier in the highly space-constrained inboard region. Trade-offs between breeding, shielding to protect the magnets, and materials for the inboard region shows that an inboard thickness of 50cm is enough if a ceramic insulator is used. If an organic insulator is preferred, the inboard thickness has to be increased. Radiation-induced increase in the electrical resistivity of the copper has also been studied and its impact on the aforementioned optimization process for the blanket/shield thickness/material choice has been accounted for.