Fuel element pre-design
A mixed plutonium-uranium oxide fuel (MOX) was selected as the main candidate since the beginning of the MYRRHA project, taking into account a large experience in the MOX production in Europe and its better neutronic properties, compared to uranium dioxide, in the fast neutron spectrum. Based on past experience within the fast reactor programme in Europe, enrichment of 30 to 35 % of plutonium is envisaged.
For the first cores of MYRRHA, the well-known ASS of 15-15 Ti class (such as AIM1 in France, DIN 1.4970 in Germany, D9 in the USA) will be used for the fuel cladding. Advanced ferritic-martensitic steel (FMS) T91 is chosen as the candidate material for future fuel loadings, once qualification will be completed.
Fuel assembly pre-design
Since a high fast neutron flux is targeted in MYRRHA, the high density triangular lattice of fuel rods has been chosen for the pre-design of the fuel assembly.
A number of the fuel rods within the hexagonal bundle were set to 90 plus one dummy rod in the centre for instrumentation and monitoring.
The positions of fuel assemblies within the sub-critical core will regularly be changed and 'fresh' assemblies will be loaded to compensate the reactivity loss.
More information: R&D programme > Fuel qualification