Outline of nuclear fuel cycle

Ojima, Hisao

The mined uranium ore is refined and becomes a "yellow cake" in which the uranium content is about 60%. Then the yellow cake is converted into UF that is the raw material of uranium enrichment. The content of U is enriched usually by means of the centrifuge separation. The enriched uranium is converted into UO and is used for pellet fabrication. Finally, the uranium is used in the LWR plant as nuclear fuel. The uranium and plutonium are recovered from the spent fuel in the reprocessing plan and they are used as nuclear fuel again. As for the method of the reprocessing, the PUREX process using TBP as extractant is a main stream because of its stability and safety in operation. The preprocessing process consists of a head-end process including a shearing process, a dissolution process, and a clarification process, and a chemical process including a solvent extraction process, a concentration process, a denitration process and mixed conversion process. The nitric acid and the solvent are recycled in the plant and high level liquid waste is vitrified into glass form, finally. In Japan, through the experience of the Tokai Reprocessing Plant, the first commercial reprocessing plant, Rokkasho Reprocessing Plant, will start its operation in 2008. The spent fuel from FBR can be reprocessed by the PUREX method taking into account of its characteristics such as high plutonium content rate, high burn-up, and the structure of fuel assembly. Currently, the adoption of a new technology is examined aiming for further economy improvement and the achievement of the reduction of the waste load. The safeguards is the activity to prevent the diversion of nuclear material.