Phase and Chemical Transformations of the β–Radioactive Intermetallics in Fast-Neutron-Irradiated Uranium–Plutonium Nitride

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 shows that a complex structure forms in it. It consists of a solid solution containing uranium, plutonium, americium, neptunium, zirconium, yttrium, and lanthanide nitrides and individual condensed phases (U₂N₃, CeRu₂, Ba₃N₂, CsI, Sr₃N₂, LaSe, (Mo + Tc), U(Ru, Rh, Pd)₃. The contents and compositions of these phases are calculated at a temperature of 900 K and a burn-up fraction up to 14%. The β^– decay of the metallic radionuclides is found to change the phase and chemical compositions of the irradiated (U_0.8Pu_0.2)N_0.995 nitride. The kinetics of the transformations of the radioactive intermetallics U¹⁰⁹Pd₃ → U + 3¹⁰⁹Ag, ¹⁴¹Ce¹⁰³Ru₂ → ¹⁴¹Pr¹⁰³Rh₂, and ¹⁴⁴Ce¹⁰⁶Ru₂ → ¹⁴⁴Nd¹⁰⁶Pd₂ is calculated.