In the Federal Republic of Germany (FRG), the reprocessing of spent fuel assemblies and the recycling of the recovered plutonium are essential for the final disposal of high-level nuclear waste. In addition, the recycling of uranium and plutonium is an effective measure to avoid proliferation of plutonium for weapons and to reduce the needs of uranium. Therefore, the technology of recycling has been developed in the FRG since 1966. In the prototype boiling water reactor (BWR) of Kahl, in the BWR nuclear power plant at Gundremmingen, and the pressurized water reactor plant at Obrigheim mixed-oxide fuel (MOX) assemblies have been operated with good success. Also, the experience gained at Alkem’s MOX fuel fabrication plant is very positive. Reprocessing tests of spent MOX fuel rods have indicated that a nearly homogeneous mixture of PuO2 and UO2 should be used to achieve a good solubility of MOX fuel in nitric acid. In all, very important experience in safeguarding plutonium and MOX fuel material was gained.