FESTIM (Finite Element Simulation of Tritium In Materials) is an open-source finite element code developed in Python for simulating hydrogen transport in materials. Initially motivated by challenges in fusion energy, FESTIM has since been applied more broadly, including studies of hydride formation, hydrogen embrittlement, tritium permeation into coolants, and tritium inventory assessment. Built on the FEniCS framework, FESTIM enables multi-dimensional, multi-material simulations with multiphysics coupling capabilities (OpenFOAM for thermo-hydraulics and OpenMC for neutronics)
The FESTIM Workshop was created to introduce new users to the code through a hands-on tutorial, beginning with simple diffusion problems and advancing to permeation modeling and plasma-facing component studies. This tutorial demonstrates FESTIM’s flexibility through practical examples while providing guidance on how to set up and run simulations. This presentation gives an overview of the tutorial structure, highlights representative applications, and illustrates how FESTIM can be employed to investigate hydrogen transport phenomena across fusion and materials research. Particular emphasis will be placed on the new FESTIM 2.0 tutorials, which build upon the DOLFINx backend to further expand the code’s performance and capabilities.