Plutonium and other actinides behaviour in NEXT process

The behaviour of Pu and other actinides in some characteristic processes of the NEXT process, i.e. the crystallization process and the U–Pu–Np co-recovery process, was investigated with referring to the experimental results obtained in our experimental facility, CPF. In the crystallization process, the existence of Pu(VI) in the dissolver solution brought the co-crystallization of Pu(VI) with U, and low DFPu. Such co-crystallization could be prevented by adjusting the Pu valence to Pu(IV). In the crystallization with the dissolver solution containing Pu(IV), meanwhile, DFCs showed significant low values, which might be caused by the formation and crystallization of some kinds of Cs compounds with Pu(IV). In the U–Pu–Np co-recovery process which had high [HNO3] feed solution obtained from the crystallization process, it was confirmed experimentally that almost all the Np could be extracted with U and Pu in the extraction section. Some considerable parameters, e.g. temperature, acidity of stripping solution, were pointed out for preventing the leakage of U and Pu to the solvent and for avoiding the Pu polymer formation in the stripping section using only diluted HNO3 as the stripping solution. Under the appropriate stripping condition taking account of these parameters, the calculation and experimental results showed that these elements could be stripped efficiently.