Reprocessing of fuel elements is a sequence of procedures that separates out various components of the spent fuel. Spent fuel is a mixture of around 4 percent highly active fission products, 95 percent uranium (with just 1 percent fissile uranium-235) and 1 percent plutonium. The uranium and plutonium can be used to manufacture new fuel elements and the fission products are treated as high-level waste. They are immobilised in a low-solubility glass matrix, making them suitable for transport and storage. After reprocessing abroad, the separated wastes have to be taken back by Switzerland.
Up to 2005, around 1200 tonnes of spent fuel were transported for reprocessing in France and the UK. There is currently a moratorium on reprocessing until 2016 and no more fuel elements are being transported abroad.