Application of chemical processes to separate the valuable substances - the still existing uranium and the newly generated fissile material plutonium - from the fission products, the radioactive waste in the spent nuclear fuel after its use in the reactor. The →PUREX process for reprocessing underwent several years of large-scale trial. A spent fuel element has, apart form the structure material, approximately the following composition: 96% uranium, 3% fission products (waste), 1% plutonium and small shares of →transuranium elements. The recovered uranium and the plutonium can be reused as fuel in a nuclear power plant following corresponding chemical treatment. The nuclear fuel recoverable in a reprocessing plant with an annual throughput of 350 t corresponds in the case of use in the today common light water reactors to an energy quantity of approx. 10 million t hard coal. In the reprocessing the high active waste (fission products) is separated and by →vitrification brought into a form ensuring safe ultimate disposal.