Neutronic Assessment of Candidate Materials for TF Coils Shielding in a DEMO Fusion Reactor Based on a DCLL Blanket

Under the Spanish Breeding Blanket Technology Program TECNO_FUS, a conceptual design of a dual-coolant lithium-lead (DCLL) blanket for DEMO is being revisited. In this work, different shielding candidate materials are assessed in their ability to satisfy the radiation load requirements that must be fulfilled in the toroidal field (TF) coils: absorbed dose in the insulator (Epoxy), peak fast neutron fluence in the superconductor (Nb₃Sn), peak nuclear heating in the winding pack and maximum neutron fluence in the cooper stabilizer. Furthermore, the impact of the material choice on waste management requirements of both shielding and vacuum vessel (VV) materials is evaluated, and the performance of candidate materials is examined in terms of the helium production in the VV SS316LN material and its implications in reweldability. Materials discussed for the High Temperature Shield are Eurofer, graphite, B₄C, WC and WB₄C, while the metal hydrides ZrH₂, Zr(BH₄)₄, and TiH₂ are discussed for the Low Temperature Shield. In the case of DEMO irradiation scenario, all the analyzed material combinations fulfill the design requirements for the waste management of the shield and VV, He production in the VV wall and TF coils radiation loads requirements.