| 摘要 |
<p>PURPOSE:To enable specified product specifications to be attained even if an amount of reducing agent to be added is reduced and the number of distribution stages of a multi-stage extraction device to be reduced by adding the reducing agent to diluted nitric acid in a specific range of a reducing agent ratio and performing distribution temperature in a specific range. CONSTITUTION:A co-decontamination process for extracting U and Pu to an organic phase is carried out by bring a nitric acid solution of a spent fuel into contact with a 30% TBP organic phase, and a distribution process is carried out by bringing the organic phase into contact with a Pu back extraction liquid which consists of a diluted nitric acid for back extraction of Pu to nitric acid water to keep U in the organic phase. In this case, a reducing agent is added to a diluted nitric acid which is a Pu back extraction liquid within a range of 0.02 to 1 in terms of the reducing agent ratio (amount of reducing agent/amount of Pu) with a distribution temperature being 10-30 deg.C. A distribution coefficient ratio of U to Pu can be increased and a large amount of Pu can be back-extracted to a nitric acid water phase in non-reduced state for separation from U, thus enabling an amount of added reducing agent to be reduced drastically. Also, by adding a small amount of reducing agent, Pu which stays within the organic phase can be readily and back-extracted in short distribution steps.</p> |
