Multiphysics analysis of the ARC liquid blanket

The Affordable Robust Compact (ARC) reactor is a conceptual design of a nuclear fusion reactor developed by MIT Plasma Science and Fusion Center; its main objective is to demonstrate the feasibility and the advantages of compact high magnetic fields - produced by REBCO high temperature superconducting tapes in demountable field coils - and of inboard radio frequency lower hybrid current drive launchers, ensuring a steady state condition for plasma and the consequent power generation. ARC includes a fully liquid blanket consisting of FLiBe: a molten salt made by a 2:1 LiF-BeF2 mixture, therefore serving, simultaneously, as tritium breeder, heat-transfer fluid and neutron shielding material. The design foresees a high efficiency Brayton cycle to extract heat from high temperature FLiBe (around 900 K) and produce electricity, operated by helium. With the aim of performing a multi-physics analysis of the Breeding Blanket (BB), a coupling procedure between two finite volume tools has been developed. On one side, the nemoFoam solver has been written, with the purpose of modelling the 3D neutronic behaviour of a given system solving the multi-group diffusion equations and, on the other, the official thermal hydraulic OpenFOAM solver for conjugate heat transfer problem in multiple regions has been slightly modified for the purposes of this work. Both codes are written in OpenFOAM environment, a free open source framework for developing executable applications. Being the involved physical phenomena strongly interdependent, performing a multiphysics analysis was the natural choice to resolve properly the effects of such connection. The conducted analysis presents the field of power deposited by neutrons, the steady state flow and temperature fields of the FLiBe inside the blanket tank, under nominal operating condition, as well as the temperature distribution across the solid layers between the plasma chamber and the BB.