Benchmarking of the FLUKA Monte Carlo code against the SINBAD FNG dose experiment for Shutdown Dose Rates in D-T Fusion Applications

The assessment of shutdown dose rates in fusion facilities is crucial for ensuring safe operation, particularly for worker access to critical areas. Accurate prediction of radiation levels is therefore essential, but technically challenging. The FNG dose benchmark, included in the SINBAD database, is a well-known experiment widely used to validate novel workflows for residual dose rate assessments. In this work, the FNG dose benchmark was implemented for use with the FLUKA Monte Carlo code (version 4-5.0) and quantitatively compared with the available experimental data. FLUKA built-in options enabled one-step simulations that automatically accounted for the time evolution of the full radionuclide inventory, using the internal database to eventually evaluate dose rates at shutdown. Furthermore, examples were provided to illustrate the code’s ability to generate informative outputs. The implementation also involved replicating the literature FNG source routine in FLUKA, with potential applicability to other SINBAD FNG cases. Comparison to literature and the agreement of results with experimental data was generally within a factor of two, demonstrating the reliability and flexibility of the code for reproducing complex fusion benchmarks.