Investigation of FMI-based multi-fidelity simulation for nuclear cores: Application to ADS beam trips

This paper presents the use of the Functional Mock-up Interface (FMI) standard for multi-scale studies of nuclear reactors. GeN-Foam and OFFBEAT, two OpenFOAM-based solvers, are used for general nuclear reactor analysis and fuel behavior studies. In this work, these solvers have been embedded in Functional Mock-up Units and can communicate solely through the FMI standard. The methodology, developed for general nuclear reactor applications, is designed to handle fast transients using a semi-implicit coupling scheme between FMUs. Sensitivity analysis of the interpolation methods and the number of implicit iterations is performed to assess the robustness of the approach. The methodology is demonstrated through the simulation of beam trip events in a recent version of the Transmutex Accelerator-Driven System (ADS) design. A preliminary study investigates the effects of different beam trip durations on power evolution and fission gas release. Finally, a preliminary 5-year irradiation study of the hottest fuel pin is conducted, based on the results obtained from the methodology. The findings show that a low-reliability accelerator significantly increases fission gas release. Additionally, the low linear heat generation rate in the design prevents pellet-cladding contact, which provides margins for potential improvements in core performance.