FLUNED

FLUNED is an open-source, mesh-based tool that reconstructs the time-dependent distribution of activation products in cooling circuits exposed to fusion-neutron irradiation. Starting from completed CFD run (OpenFOAM or ANSYS Fluent) and the neutron-induced activation data, it solves an advection–diffusion–decay problem and outputs concentration fields ready for dose-rate, shielding, or licensing analyses.

Key features

• CFD-agnostic input – import meshes and flow fields directly from OpenFOAM/Fluent results; no re-meshing or solver modification required.

• Fast parallel solver – C++ core built on OpenFOAM classes; scales to HPC clusters via native MPI decomposition.

• Simple workflow – fluned -t (template), fluned -i (pre-process), FLUNED-solver, and fluned-post streamline the full simulation loop.

• Peer-reviewed & validated – benchmarked against the 2019 FNG water-activation experiment and documented in (De Pietri et al., 2023).

• Quick install – one-step script (fluned-repo-install.sh) for Linux/WSL2, including all Python helper tools.

• GPL-3.0 License

• Installation
• Theory
  • Overview
  • Governing Conservation Equation
  • Reynolds Decomposition
  • Turbulent Closure - Gradient Diffusion Hypothesis
  • General Source Term
  • Simplified Source Term (Single-Step Transmutation + Decay)
  • Laminar-Flow Limit
• User’s Guide
  • Single Isotope workflow
  • Multiple Isotopes workflow
  • Input File Guide
    • Keyword List
• Validation
• Testing
• Publications
  • Description and Validation
  • Coupling