ARC reactor: Preliminary evaluation of tritium storage technologies and related safety issues

The fusion reactor ARC proposed by MIT is a concept of high-magnetic field reactor, using high temperature superconductors (HTS), with an innovative liquid breeding blanket (BB) made of a molten salt (FLiBe). The plasma chamber and the vacuum vessel are contained in the liquid blanket and the FLiBe is used also for the cooling of the vacuum vessel and of the divertor. The lithium (isotopically enriched with 90% 6Li) contained in the molten salt has the aim of producing tritium after the interaction with the neutrons released by the fusion reactions. FLiBe is then extracted from the breeding blanket and sent to a heat exchanger to finally produce electricity with a traditional thermodynamic cycle. The presence of high-magnetic field allows to reduce the dimensions of the reactor, with possible benefits on the capital cost. The aim of this work is to analyze the tritium breeding ratio to achieve self-sustaining fusion reactors and study the excess tritium production that need to be stored in particular structures to be later sold for new fusion reactors that require fuel to start-up. Depending on the design parameters of the reactor, the amount of tritium produced and stored can vary significantly. At the same time, tritium is a serious hazard for a fusion power plant. The smaller the tritium inventory in the whole plant, the lower the risk related to tritium accidental releases. Hence, a trade-off between economics and safety must be found. After calculating the quantity of tritium produced, it will be necessary to analyze the two main storage technologies currently on the market, namely the Zr-Co beds and those of U, to try to decide which is the best one to adopt for the specific case of the analysis. By a technical analysis of the environmental impact of a possible tritium release, subsequently, with the help of two software, res-rad and hot-spot, this analysis will be carried out on a particular case study of the possible accidental release of tritium from containment systems. Up to the final goal of calculating the dose received by the population surrounding the affected area.