In recent years, extensive thermal-hydraulic experimental tests have been performed on the LBE-cooled, wire-wrapped fuel assembly of MYRRHA. These thermal-hydraulic tests were performed using fuel assembly mock-ups, in large-scale LBE experimental test facilities at SCK•CEN (Belgium), ENEA (Italy) and KIT (Germany). The fuel assembly pressure drop characteristics and flow induced vibration characteristics were tested with a full-scale 127-pin mock-up test section. The existing pressure drop correlations of Rehme and Cheng and Todreas (simplified model) predict the experimental pressure drop data very well and are considered suitable for use in the design and safety analysis of the MYRRHA system. Flow induced vibrations are very limited in the wire-wrapped bundle and fuel pin fatigue damage from vibration during operation is not expected. Further analysis and testing is required to determine if damage from fretting corrosion could be expected.

Heat transfer characteristics of the fuel assembly were investigated experimentally in two separate 19-pin heated rod test sections, cooled by LBE. The existing Kazimi-Carelli correlation predicts the global average Nusselt numbers very well, but the correlation is not developed to capture local hot-spots. For the fuel assembly safety analysis, a hot-spot factor is defined and analysed to determine the hot-spot temperature penalty, to further determine operational safety margins.