Advanced multiple principal element alloys as structural material in ARC : neutronic and activation analysis

While the problem of global warming is becoming increasingly urgent, the geopolitical situation is underling the necessity of include in the Italian energetic mix sources other than oil and gas. Conversely, the public opinion is still frightened by fission technologies, forcing governments to invest in different solutions. Great efforts have been spent in nuclear fusion research and the availability of new technologies in these years (e.g. high temperature superconductive magnets) are making it appear as a credible medium-term solution. The ARC project, proposed by scientist of the MIT and PSFC is aiming to prove the feasibility of such a technology, with a grid connected reactor. The present Thesis, developed in collaboration with M.I.T., investigates new structural materials for TBR enhancement in ARC ( high entropy alloys) and activation studies. After the construction of a D-like model for a poloidal section of the torus, neutronic studies were conducted, using a classical Montecarlo approach; OpenMC, a tool developed at MIT, has been used for this purpose. The results are strongly encouraging, proving in theory the possibility of eliminating the Be layer from the layout thanks to the usage of innovative materials; a study on the impact of each element on the alloys performances have been conduced, to steer further investigations. The activation analysis that followed, conduced with the tool FISPACT-II, confirmed the superiority of high entropy alloys also in this regard, allowing a faster decay for irradiated material and the possibility of recycling in a time scale around 100 years. The last part of the thesis is devoted to a sensitivity analysis, to evaluate the different effects on activation of the most common and probable impurities, varying their concentration and simulating the effect on the dose.