Thermodynamic analysis of the gas phase composition over uranium-plutonium carbonitride irradiated with fast neutrons

A thermodynamic analysis of the gas phase composition over uranium-plutonium carbonitride U0.8Pu0.2(C0.5N0.5)0.995 irradiated with fast neutrons was carried out with respect to temperature and burnout. In the temperature range of 900–2500 K, accumulation of fission products in fuel resulted in the formation of a multicomponent gas phase containing the following basic elements and compounds: volatile (Cs, Sr, Ba, Se, Te, I, Pd, CsI, Cs2I2, BaI, SrI, BaI2, SrI2, LaSe, TeSe, and LaTe), nitrogen-containing components (N2, N, CN, CN2, C2N2, UN, UN2, PuN2, CsN, CeN, LaN, YN, MoN, and ZrN), carbon-containing components (C, UC, UC2, UC4, PuC, PuC2, PuC4, ZrC, ZrC2, YC2, CeC2, LaC2, and NdC2), and hardly volatile metals (U, Pu, Ru, Rh, Pd, Y, Ce, La, Nd, Tc, Mo, and Zr). The partial pressures of the said gas phase components over carbonitride fuel were calculated with respect to temperature and burnout (up to 18%).