FESTIM: An open-source code for hydrogen transport simulations

FESTIM (Finite Element Simulation of Tritium In Materials), is a versatile open-source finite element code developed in Python for simulating hydrogen transport in materials. FESTIM addresses limitations observed in existing codes by enabling multi -dimensional, multi -material simulations, leveraging the flexible finite element method and the open-source FEniCS library. Use cases illustrating FESTIM's applicability and efficacy are presented: reproduction of thermo-desorption experiments, modelling plasma-facing components (divertor monoblocks), and modelling breeding blankets. A comparative analysis with two other numerical tools (TMAP8 and COMSOL (R) ) is then performed. FESTIM is in very good agreement with these codes and shows similar (or better) computing performances. Finally, the thorough validation and verification (using the method of manufactured solutions) of the code is described, highlighting the code's reliability.