A composition filled with actinide powder, comprising an organic matrix and an actinide powder or a mixture of actinide powders, comprises at least: a plasticizer comprising an alkane whose longest radical chain comprises at least a few tens of carbon atoms and is in a volume content of between 20% and 70% of the total volume of the organic compounds alone; a binder comprising at least one polyolefinic polymer and which is in a volume content of between 20% and 50% of the total volume of the organic compounds alone; a dispersant comprising a carboxylic acid or salts thereof, the volume content of which is less than 10% of the total volume of the organic compounds alone; said actinide powder or said mixture of actinide powders represent between 40% and 65% of the volume of the filled matrix.