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 U_0.8Pu_0.2(C_0.5N_0.5)_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%).