Neutronic comparison of liquid breeders for ARC-like reactor blankets

The proposed blanket for Affordable Robust Compact (ARC) reactor is one of the simplest blanket concepts. It is a bulk tank filled with a lithium and beryllium fluorides molten salt. The fluid effectively works as tritium breeder, vessel coolant and neutron moderator and shield. However, despite the simplicity of the concept, the compactness of the reactor constitutes a novelty in the fusion field. It is thus necessary to evaluate all the possible solutions for an effective blanket component. This work analyses different liquid blanket identifying the most suitable for a compact fusion reactor. More specifically, the study addresses the capability of breeding tritium in a compact solution, actively shielding the coils and reducing the radioactive waste. Findings are that FLiBe optimizes the most the system in terms of applicability, tritium breeding, compactness and activation. Nonetheless, there is no lack of backup choices. For instance, there are hints that lithium-zirconium fluoride salts could accomplish the blanket main tasks in a compact reactor too. Leaving PbLi as inefficient, but cheap and still virtually viable solution

ARC reactor – Neutron irradiation analysis

Neutron irradiation is one of the most concerning issues to design plasma facing components and reactor inner structures in fusion devices, especially for high power density ones, like ARC reactor. This study addresses the main aspects of neutron irradiation on solid materials of ARC reactor. In particular it deeply analizes the effect of neutron induced activation proposing low activation structures, like vanadium alloys and different optimization methods like isotopic tailoring, detritiation and impurity control. Furthermore, irradiation damage issues and their dependence on the energy spectrum are highlighted. It resulted that V-Cr-Ti alloys dramatically reduce the radioactive inventory of ARC with respect to its baseline configuration, which proposes the application of Inconel 718. Such alloy is also optimizable through the tailoring of titanium isotopes and is virtually capable of hitting recycle limits in a couple of decades. Lastly, it shows a relatively growth of gas during irradiation. However, it is highlighted how experiments on neutron damage featuring fission neutrons risk to be able to tell very little about the behavior of the same materials under fusion neutrons, as damaging mechanisms seem to be different

Most advanced technological innovation as a part of simple solutions for the world energy problem

Energy studies are today interdisciplinary studies. They involve not just technical aspects, but also environmental, social and politic aspects. In this framework, an interdisciplinary approach to help solve energy issue through advanced technological innovations as a part of simple solution for the energy problem is considered. Two case studies were reported: the role of the fusion energy as new energy source and the methods to degrade polychlorinated biphenyls, synthetic compounds used in energy field, to reduce its environmental impact

FUSION ENERGY AND THE ARC PROJECT

The recent progress in fields such as High Temperature Superconductors (HTS), Additive manufacturing, new diagnostics, and innovative materials, has led to new scenarios and to a second generation of Nuclear Fusion Reactor designs. The new Affordable Robust Compact (ARC) Fusion Reactor is described in the paper. ARC could be not only the base-load but also a load-following reactor, capable to cover peak requests and other plant shutdowns. In order to investigate this interesting ability of ARC, its more sensitive component has been analyzed: ARC vacuum vessel

Preliminary investigation of neutron shielding compounds for ARC-class tokamaks

Radiation shielding design is a crucial step in the development of a nuclear fusion reactor. Superconducting magnets are indeed a highly engineered component whose properties are particularly sensitive to irradiation damage. In addition, novel magnet technologies, such as High Temperature Superconductors (HTS), and the attractiveness of compact tokamak designs (like Affordable Robust Compact - ARC - reactor), require an even higher precision in the shielding design. In this work most promising radiation shielding solutions for compact tokamaks are explored. The study applies a Monte Carlo particles transport technique assisted by the OpenMC code. A D-shaped model is built and ARC reactor core is considered as main case study. A detailed analysis of the radiation environment is carried out. The study then assesses the most promising compounds on the basis of most suitable cross sections, material shielding properties and space constraints. In addition, the work addresses the problem of energy deposition on the shield providing an analytical model for active cooling necessities. Results highlighted the necessity of heavy elements and high density compounds as a considerable photon flux is generated in neutron-material interactions. Tungsten borides (WxBy) ceramics seem to be particularly promising for shielding radiation in a compact configuration

DETECTION OF RADON EMISSIONS DURING 2016/2017 EARTHQUAKES IN ABRUZZO (ITALY)

«Aracne» is an Italian monitoring network, part of the «Tellus» project, for the real-time detection of radon emissions from Earth’s subsoil. The Aracne network was launched in August 2015, with the first multi-parameter station in Pizzoli, in central Italy, followed in December 2016 by the one of Cagnano Amiterno and finally the station of Capitignano, which will be installed by early 2018. The stations provide data at 10-minute intervals, together with all meteorological values outside the station and at the exact measuring point, such as humidity and temperature measured at about 20 cm from the radonometer that is being used. The stations are identical both for instrumentation and for measuring place characteristics, designed in such a way to maintain constant temperature and humidity. This project makes the stations of the Aracne network unique in the world as far as detection methodology is concerned. The Pizzoli station provided very interesting data during the seismic crisis that hit central Italy on 24 August 2016, 30 October 2016 and 18 January 2017 with three earthquakes of Mw 6.0, Mw 6.5, Mw 5.5 respectively

Optimization of tritium breeding ratio in ARC reactor

Affordable Robust Compact reactor is a conceptual design for a Tokamak conceived by Massachusetts Institute of Technology (MIT) researchers. The design of this tokamak is under development and update. One of the key parameters for fusion reactor power plants is the tritium breeding ratio (TBR), which has to guarantee the tritium self-sufficiency. The tritium inventory circulating in a fusion power plant must be minimized. In the meantime, to enhance plant's economics, the amount of tritium generated and stored should be maximized, since it would be used to startup new reactors. Both of the aforementioned trends meet their best in a TBR as high as possible. In this work, ARC tritium breeding ratio is studied and optimized. Taking advantage of Monte Carlo neutron transport codes, several configurations of ARC's blanket and vacuum vessel have been analyzed in order to find the most effective one for a high TBR. The study takes into account different materials for the structure, such as Inconel718, V-15Cr-5Ti and Eurofer97. Moreover, it scans different width of coolant's channels and evaluates the effect of lithium-6 enrichment in the blanket looking for the best configuration in terms of TBR