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This work studied a way to reclaim uranium from contaminated UO oxide scraps as a sinterable UO powder for UO fuel pellet fabrication, which included a dissolution of the uranium oxide scraps in a carbonate solution with hydrogen peroxide and a UO precipitation step. Dissolution characteristics of reduced and oxidized uranium oxides were evaluated in a carbonate solution with hydrogen peroxide, and the UO precipitation were confirmed by acidification of uranyl peroxo-carbonate complex solution. An agglomerated UO powder obtained by the dissolution and precipitation of uranium in the carbonate solution could not be pulverized into fine UO powder by the OREOX process, because of submicron-sized individual UO particles forming the agglomerated UO precipitate. The UO powder prepared from the UO precipitate could meet the UO powder specifications for UO fuel pellet fabrication by a series of steps such as dehydration of UO precipitate, reduction, and milling. The sinterability of the reclaimed UO powder for fuel pellet fabrication was improved by adding virgin UO powder in the reclaimed UO powder. A process to reclaim the contaminated uranium scraps as UO fuel powder using a carbonate solution was finally suggested. [ABSTRACT FROM AUTHOR]

Abstract: This work studied a process to recover uranium from contaminated (U,Gd)O2 scraps generated from nuclear fuel fabrication processes by using the dissolution of (U,Gd)O2 scraps in a carbonate with H2O2 and the precipitation of the dissolved uranium as UO4. The dissolution characteristics of uranium, Gd, and impurity metal oxides were tested, and the behaviors of UO4 precipitation and Gd solubility were evaluated with changes of the pH of the solution. A little Gd was entrained in the UO4 precipitate to contaminate the uranium precipitate. Below a pH of 3, the uranium dissolved in the form of uranyl peroxo-carbonato complex ions in the carbonate solution was precipitated as UO4 with a high precipitation yield, and the Gd had a very high solubility. Using these characteristics, the Gd-contaminated UO4 could be purified using dissolution in a 1-M HNO3 solution with heating and re-precipitation upon addition of H2O2 to the solution. Finally, an environmentally friendly and economical process to recover pure uranium from contaminated (U,Gd)O2 scraps was suggested. [Copyright &y& Elsevier]

Abstract: The dynamic precipitation characteristics of UO4 in different solution conditions (pH, ionic strength, uranium and H2O2 concentrations) were characterized by measuring changes in the absorbance of the precipitation solution and by monitoring the change of particle size in a circulating particle size analyzer. The precipitation solution conditions affected the precipitation characteristics such as the induction time, precipitation rate, overall precipitation time, and particle size in a complex manner. With increases in both pH and ionic strength, the induction time was prolonged, and the individual particle size decreased, but the individual particles tended to grow by aggregation to form larger precipitates. The uranium concentration and the ionic strength of the solution affected the induction time and precipitation rate to the greatest extent. [Copyright &y& Elsevier]