Transient simulation of the in-pile performance of a MA-bearing fuel pin

This document reports the performance evaluation of the hottest americium-bearing fuel pin irradiated in the in-pile test sections (IPS) sub-assembly of the MYRRHA research reactor (design revision 1.8) during the primary over-power transient scenario selected within the PATRICIA Project (Milestone MS5), namely the Beam Power Jump (BPJ). The simulations are performed with the TRANSURANUS thermo-mechanical fuel performance code coupled with the SCIANTIX physics-based module for inert gas behaviour, incorporating the propaedeutic advancements for transient simulations achieved within the scope of PATRICIA Work Package 5. These advancements include models for Am-fuel thermal properties (thermal conductivity, melting temperature, specific heat) developed in Task 5.1, a dedicated surrogate model for the helium production rate during MYRRHA irradiation accounting for the relevant contribution of the fuel americium enrichment in Task 5.2 and the multi-physics environment implemented in Task 5.4. The safety evaluation of the IPS fuel pin is performed on critical figures of merit (bulk temperature, fuel central temperature, gap width and equivalent von Mises stress) and reveals a good margin to the design limits.