Extension and application of TRANSURANUS fuel performance code to the MYRRHA reactor in normal and transient conditions

The Belgian Nuclear Research Centre (SCK•CEN) is designing an innovative Accelerator Driven System (ADS) called MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications), embedded inside the European Sustainable Nuclear Industrial Initiative (ESNII) program. Objectives of this facility are to prove the feasibility of the ADS concept at a reasonable power level and to sustain the development of future Generation IV reactors making available a heavy metal-cooled core environment featured by a fast neutron spectrum. This work deals with MYRRHA fuel pin performance analysis employing the TRANSURANUS fuel performance code, with the aim of assessing the current design specifications in normal operating conditions and in the event of a particular design basis accident originating from a particle accelerator trip (i.e., a beam power jump, BPJ). For simulating in a thorough way the fuel pin response, the TRANSURANUS applicability is extended to the specific cladding material adopted for MYRRHA, contributing to its predictive capability enlargement by implementing five new correlations. The thermo-mechanical simulations are carried out considering a conservative fictitious hottest fuel pin and employing the most reliable set of input models suggested by the TRANSURANUS manual, relying upon fuel and cladding design limits for normal operating conditions and for the overpower accidental transient. A sensitivity analysis on phenomena/properties which most affect the scenario results is performed, with the purpose of facing the issue linked to model uncertainties in a deterministic way, providing a conservative assessment of the fuel pin design. The main outcome of this analysis is that the MYRRHA fuel pin performs well below the design limits in both normal operation and BPJ conditions. Considering the wide safety margins unveiled in the accidental scenarios, the linear power required to exceed the design limits is investigated, supplying a useful indication for licensing purposes or for devising a potential reactor power increment.