OpenFOAM-informed TRANSURANUS simulations for assessing the fuel pin performance in the MYRRHA in-pile test section

In continuation of previous examinations of the MYRRHA fuel pin performance conducted by Magni et al. (2023) and Luzzi et al. (2024), the present work aims to investigate the impact of the beam power jump (BPJ) transient scenario on the thermo-mechanical response of homogeneous Am-bearing fuel pin (0.49 wt.% - 5 wt.%) irradiated in the in-pile test section (IPS) of the MYRRHA research reactor (core design revision 1.8). The approach pursued in the current work consists of carrying out the pin performance analysis employing the TRANSURANUS fuel performance code informed by more specific and reliable thermo-hydraulic boundary conditions evaluated via the fluid dynamics code OpenFOAM. After illustrating the differences between the conventional approach with TRANSURANUS stand-alone and the approach adopted in this paper, compliance with safety-related limits is discussed with a focus on the transient pin behaviour. The results confirm that Am-MOX fuel options for MYRRHA are suitable and safe, even during the BPJ transient, with wide margins. The adopted approach (namely, complementing the fuel performance code thermo-mechanical analysis with high-fidelity thermo-hydraulic tools) is herein applied to a specific reactor design and irradiation scenario, but it is suitable for the assessment and safety analysis of other/future reactor concepts.