The reaction of sodium with urania-ceria solid solutions

Abstract A study of the reaction between sodium and urania-ceria solid solutions has been performed over the range of ceria concentrations in the solid solutions of 3 to 80 mol.% at temperatures up to 800°C. The reaction product formed in the quaternary system could not be identified as either of the compounds Na 3 UO 4 or NaCeO 2 , the phases in equilibrium with liquid sodium in the corresponding oxide ternary systems. It is suggested that compounds of the type Na 2− z MO 3 ( M = U 1− x Ce x ) are formed which are in equilibrium with sodium and a reduced oxide solid solution. The value of z increases with increasing Ce concentration and the Ce/(U + Ce) ratio in the product and reduced oxide phase is the same as in the original oxide solid solution. The threshold cerium valency for the reaction is the 3 + state.