Search

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]

Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO solution, respectively. Cs ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm were performed. The surface morphology and the relative atomic mole ratio of the specimen surface were investigated by SEM and EPMA. The order of Cs ion removal efficiency of laser was no-treatment < KOH < KNO during the 42 shots. From the investigation of XPS peaks around 532.7 and 292.9 eV, KNO on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that CsO particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and it changed into FeO. It was also suggested that CsO particulates were formed by the reaction between the reactive oxygen generated from the decomposition of KO and Cs ion on the metal surface.. [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]

Abstract: This work studied anodic dissolution characteristics of a SIMFUEL electrode at several potentials in carbonate solutions of a high concentration at several pHs. The electrolytic uranium dissolution of SIMFUEL was much affected by a corrosion product of UO2CO3 generated at the electrode during the dissolution in carbonate solution. The corrosion product distorted the voltammogram of SIMFUEL in the potential region of oxygen evolution and increased the overpotential of oxygen evolution at the electrode. The effective dissolution of the SIMFUEL electrode in a carbonate solution could be obtained at an applied potential such as +4V (vs SSE) or more which had an overpotential of oxygen evolution high enough to rupture the corrosion product on the electrode surface. The corrosion potential of SIMFUEL decreased with pH in the carbonate solution, and the dissolution rate and current efficiency of the SIMFUEL increased with a decrease of pH in the carbonate solution. [ABSTRACT FROM AUTHOR]