Neutronic Analysis for Feasibility of Fusion-Driven Subcritical System with Constant Fusion Power by Online Feeding of Molten Salt Fuel

To enhance the practical application of a fusion-driven subcritical reactor, a system with constant fusion power by online feeding of molten salt fuel was designed. The system satisfies multiple purposes including waste transmutation, tritium breeding (TB), and energy multiplication (EM) through constant fusion power. All neutronic calculations were performed by SERPENT2.1.29 with the ENDF/B-VII.0 neutron cross-section library in order to simulate the online-feeding process.

A constant k-eff is maintained by the amount of the feeding being larger than the amount of the removed fission products. However, system performance is significantly improved by just reducting the reactivity swing with the feeding. Compared to a once-through cycle (OTC), the performance of TB and EM is significantly improved as the feeding rate increases. However, there is no deep burning effect like the OTC for waste transmutation.

The performance of waste transmutation is changed in the feeding scenarios. For the scenario with a high plutonium ratio, transmutation with plutonium is increased. On the other hand, for the feeding scenario with a high minor actinide ratio, transuranic waste is burned. However, the transmutation performance is degraded due to a low fission-to-capture ratio.