Spinel inert matrix fuel testing at the Hfr Petten

Magnesium aluminate spinel is one of the most investigated inert matrix materials, due to its good physico-chemical stability, resistance against neutron irradiation, and its thermal conductivity comparable with conventional UO2 fuel. At the HFR in Petten various combinations of actinides and spinel have been tested within the EFTTRA programme, with the object to study the transmutation of americium. To study the incineration of plutonium in spinel in a once through mode, the OTTO irradiation was started, which is still being irradiated at the HFR. From the various irradiation tests it appears that MgAl2O4 spinel shows a chemical instability at high temperatures and a large volumetric swelling under the influence of high-energy fission products. These disadvantageous properties put severe restrictions on the use of spinel for the partitioning and transmutation of spent fuel. (author)