PUREX Process and Recent Developments

Decladding/dissolution of spent fuel in concentrated nitric acid 

As a consequence, whereas NaN02 was employed for feed adjustment of the reprocessing solution in the earlier plants, N204 is being used increasingly for this purpose today. Similarly, in the partitioning cycle, U(IV) has replaced ferrous sulfamate. The 

Ban et al. reviewed the reduction properties of several salt-free reagents for Np(VI) and Pu(IV) to choose selective reductants that reduce only Np(VI) to Np(V) for separating Np from U and Pu in TBP by reductive back-extraction (165). Allylhydrazine was proposed as a candidate for selective Np(VI) reduction, and it was confirmed by a batch experiment that allylhydrazine reduced almost all Np(VI) to Np(V) and back-extracted Np from the organic phase (30% TBP/n-dodecane) to the aqueous phase (3 M HN03) within 10 minutes. A continuous countercurrent experiment using a miniature mixer-settler was carried out with allylhydrazine at room temperature. At least 91% of Np(VI) fed to the mixer-settler was selectively reduced to Np(V) and separated from U and Pu. 

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