The interaction of caesium with sintered uranium-plutonium oxides

Post-irradiation analysis of mixed oxide fuel requires detailed information on the possible reaction products formed by fission product caesium with fuel materials. The results obtained by the reaction of caesium oxide with sintered UO2 and 30 wt% PuO2-UO2 solid solution are reported. These reactions proceed very slowly even in the presence of oxygen. However the rate of formation of the compounds could be enhanced if the air or oxygen is bubbled through water. Cs2(U,PU)2O7 is the only complex oxide phase that could be isolated. In all other cases, PuO2 is formed along with caesium uranates. The composition of the caesium uranate formed depends on the Cs/U ratio and the temperature. Reduction of Cs2U2O7 with hydrogen at 600deg C gave a new caesium uranate phase, the x-ray diffraction pattern of which could be indexed on an orthorhombic cell with a = 4.12A, b = 6.58 A and C = 5.83 A. (auth.)