Effect of carbon impurity in irradiated mixed uranium–plutonium nitride on the phase composition upon β−-decay of fission products

Abstract

As shown by thermodynamic modeling, accumulation of fission products in the course of irradiation of mixed uranium–plutonium nitride containing 0.25 wt % C impurity leads to the formation of a multicomponent carbonitride solid solution containing U, Pu, Am, Np, Zr, Y, lanthanides, and also separate carbide (UMoC₂, U₂RuC₂, URu₃C_0,7, BaC₂, SrC₂) and nitride (U₂N₃) phases and intermetallic compounds U(Ru, Rh, Pd)₃. The β⁻-decay of metallic radionuclides in separate carbide phases of spent nuclear fuel leads to changes in their chemical compositions. The transformation kinetics of separate dicarbide (⁸⁹SrC₂ → ⁸⁹YC₂, ⁹⁰SrC₂ → ⁹⁰YC₂ → ⁹⁰ZrC + C, ¹⁴⁰BaC₂ → ¹⁴⁰LaC₂ → ¹⁴⁰CeC₂) and complex carbide (U⁹⁹MoC₂ → UC₂ + ⁹⁹Tc) phases was calculated.