Comparative Analysis of the Phase Composition of Irradiated Uranium-Plutonium Nitride under Joint Influence of Carbon and Oxygen Impurities and β-Decomposition of Some Fission Products

Thermodynamic simulation demonstrated that the accumulation of fission products in irradiation of a uranium-plutonium nitride with admixture of carbon and oxygen (U0.8Pu0.2)(N0.9475O0.02625C0.02625) results in that a multicomponent oxycarbonitride solid solution is formed. This solid solution contains U, Pu,Am, Np, Zr, Y, and lanthanides as well as separate oxide (BaUO3, SrPuO3), carbide (URu3C0.7, Mo2C), and nitride (U2N3) phases and intermetallides U(Rh,Pd)3. The β– decay of metallic radionuclides in separate oxide and carbide phases of spent nuclear fuel changes their chemical and phase compositions, The transformation kinetics of separate phases 99Mo2C → 1/399Tc6C + 2/3 C, 140BaUO3 →1/2140Ce2UO6 + 1/2U was calculated.