Plutonium Behavior under the Condition of Uranium Crystallization from Dissolver Solution

Yano, Kimihiko ; Shibata, Atsuhiro  ; Nomura, Kazunori  ; Koizumi, Tsutomu; Koyama, Tomozo; Miyake, Chie

JNC has been developed uranium crystallization process as a component of advanced aqueous reprocessing system, NEXT (New Extraction System for TRU Recovery). In this process the greater part of uranium is separated from dissolver solution by crystallization as uranyl nitrate hexahydrate (UNH). Two types of experiments were carried out to clarify the plutonium behavior under the condition of uranium crystallization from dissolver solution. The results indicated that hexavalent plutonium is co-crystallized with uranium under the condition of uranium crystallization from dissolver solution, although plutonium concentration is lower than its solubility, and tetravalent plutonium is not. Therefore, the adjustment of plutonium valence at tetravalent is needed in order to avoid co-crystallization of plutonium and uranium.