Microstructure characterisation of irradiated Am-containing MgAl2O4 (EFTTRA-T4)

The first americium-containing inert matrix target (MgAl2O4) irradiation in the High Flux Reactor (Petten) in the EFTTRA-T4 experiment has demonstrated the feasibility of transmutation of minor actinides in a once through scenario in a epi-thermal neutron flux. The inert matrix itself showed rather poor behaviour under irradiation. A large swelling linked to a high porosity formation was observed. Scanning and transmission electron microscopy were used to investigate the radiation damage from the fission products and alpha-decay. It was observed that MgAl2O4 undergoes severe structural modifications such as amorphisation. Electron probe microanalysis revealed that the target was not stable from a chemical aspect implying that its use as a target for transmutation may need to be reconsidered.