The raison d’être of the Initiative for Inert Matrix Fuel (IMF) is to contribute to Research and Development studies on inert matrix fuels that could be used to utilise, reduce and dispose both weapon- and light water reactor-grade plutonium excesses. In addition to plutonium, the amounts of minor actinides are also increasing. These actinides have to be consequently disposed in a safe, ecological and economical way. The promising strategy that consists of utilising plutonium and minor actinides using a once-through fuel approach within existing commercial nuclear power reactors e.g. US, European, Russian or Japanese Light Water Reactors (LWR), Canadian Pressured Heavy Water Reactors, or in future transmutation units, has been emphasised since the beginning of the initiative. The approach, which makes use of inert matrix fuel is now studied by several groups in the world [,]. This option has the advantage of reducing the plutonium amounts and potentially minor actinide contents prior to geological disposal. The second option is based on using a uranium-free fuel leachable for reprocessing and by following a multi-recycling strategy. In both cases, the advanced fuel material produces energy while consuming plutonium or the minor actinides. This material must, however, be robust. The selected material must be the result of a careful system study including inert matrix – burnable absorbent – fissile material as minimum components and with the addition of stabiliser. This yields a single-phase solid solution or more simply if this option is not selected a composite inert matrix–fissile component. In screening studies e.g. [,] pre-selected elements were identified as suitable. In the 90s an IMF once through strategy was adopted considering the following properties: