Flowsheet Study of U-Pu Co-Crystallization Reprocessing System

• Published in: Journal of nuclear science and technology 2008-01, Vol.45 (6), p.510-517
• Main Authors: HOMMA, Shunji, ISHII, Jun-ichi, KIKUCHI, Toshiaki, CHIKAZAWA, Takahiro, SHIBATA, Atsuhiro, KOYAMA, Tomozo, KOGA, Jiro, MATSUMOTO, Shiro
• Format: Article
• Language: eng ; jpn
• Subjects: Fuels; Light water reactors; Nitrates; Plutonium; Recycling; Reprocessing; Spent fuels; Uranium
• ISSN: 0022-3131; 1881-1248
• DOI: 10.3327/jnst.45.510

A U-Pu co-crystallization reprocessing system is proposed for light water reactor fuels and its flowsheet study is carried out. This reprocessing system is based on experimental evidence indicating that Pu(VI) in a nitric acid solution is co-crystallized with uranyl nitrate, whereas it is not crystallized when uranyl nitrate is not present in the solution. The system consists of five steps: dissolution of spent fuel, Pu oxidation, U-Pu co-crystallization, re-dissolution of the crystals, and U re-crystallization. The proposed system does not require the use of organic solvents, resulting in a relative increase in safety and cost-effectiveness. The system requires recycling of the mother liquor from the U-Pu co-crystallization step to recover almost the entire amount of U and Pu at this step. The appropriate recycling ratio is determined, such that satisfactory decontamination is achieved. A consistent ratio of Pu to U in the mother liquor from the U re-crystallization is maintained by regulating the temperature, suggesting that the quality of the liquor, which can be a source of mixed oxide fuels, can be controlled despite differences in the composition of the spent fuel. The size of a plant utilizing the proposed system is estimated to be about 30% less than that of the PUREX system.