Effect of the β decay of metallic fission products on the chemical and phase compositions of the uranium–plutonium nitride nuclear fuel irradiated by fast neutrons

Abstract

Thermodynamic analysis of the chemical and phase compositions of uranium–plutonium nitride (U_0.8Pu_0.2)N_0.995 irradiated by fast neutrons to a burn-up fraction of 14% shows that a structure, which consists of a solid solution based on uranium and plutonium nitrides and containing some elements (americium, neptunium, zirconium, yttrium, lanthanides), individual condensed phases (U₂N₃, CeRu₂, Ba₃N₂, CsI, Sr₃N₂, LaSe), metallic molybdenum and technetium, and U(Ru, Rh, Pd)₃ intermetallics, forms due to the accumulation of metallic fission products. The contents and compositions of these phases are calculated. The change in the chemical and phase compositions of the irradiated uranium–plutonium nitride during the β decay of metallic radioactive fission products is studied. The kinetics of the transformations of ⁹⁵Nb₄₁N, ¹⁴³Pr₅₉N, ¹⁵¹Sm₆₂N, and ¹⁴⁷NdN into ⁹⁵Mo₄₂ + Ns.s., ¹⁴³Nd₆₀N, ¹⁵¹Eu₆₃N, and ¹⁴⁷SmN, respectively, is calculated.