Oxidation of powder and ceramic UO2 by KClO3 in molten (Li–Na–K)2CO3 eutectic

Abstract

The oxidation of UO₂ powder and ceramic has been studied in the (Li–Na–K)₂CO₃ eutectic melt containing added potassium chlorate between 723 and 873 K. Complete oxidation of the powder could be achieved at 723 K and with KClO₃:UO₂ mole ratios between 0.25 and 0.3. Potassium monouranate was formed in the reaction and no chlorine was liberated. Although 723 K is some 50 K above the starting temperature for decomposition of KClO₃ in air, tests showed that in the ternary carbonate eutectic less than 10% had decomposed in the first 30 min. Comparison with the oxidation of UO₂ by KNO₃, the previous best known oxidant under similar conditions, showed that the efficiency of KClO₃ as an oxidising agent for UO₂ powder was greater at 723 K. KClO₃ was also better than KNO₃ for the oxidation of ceramic UO₂ at 723 K, but the reaction was not complete at this temperature, even at KClO₃:UO₂ mole ratios up to 3.8. Attempts to achieve complete reaction by increasing the temperature were unsuccessful because the KClO₃ now decomposed too rapidly.