Nuclear material input accountancy with a representative sampling method

•A method for establishing input accountancy for a used oxide fuel is proposed.•The method is based on obtaining a representative sample.•A sufficient sample quantity for satisfying a sampling error requirement is derived. The method of input accountancy for a used oxide fuel reprocessing plant has been based on the sampling of a homogenized liquid stream of dissolved used oxide fuel. This article presents an alternative sampling strategy where samples are taken directly from solid oxides. The strategy is to obtain a representative sample while not requiring the homogenization of the input materials. A theoretical derivation is given to determine the sample quantity for satisfying the sampling error requirement.