Vaporization behavior of uranium-plutonium mixed nitride

The vaporization behavior of UN, PuN and uranium-plutonium mixed nitride, (U, Pu)N, was observed by a Knudsen-effusion mass spectrometry. The mixed nitride samples with the wide PuN composition range were prepared by the homogenization of the mixtures of UN and PuN synthesized by the carbothermic reduction. The results of evaporation for UN and PuN agree reasonably with those reported previously. The partial pressures of U and Pu over mixed nitride were depressed by the formation of the solid solution of UN and PuN. The estimation of the activaties and activity coefficents of UN and PuN in mixed nitride revealed that mixed nitride does not behave as an ideal solution. It is also suggested that mixed nitride evaporates congruently in the temperature range of the present study without the formation of any molten phase in a condition of Knudsen effusion. (orig.)