Dissolution and chemical analysis of Zr-based lanthanide nitrides

Dissolution behavior of Zr-based lanthanide nitride solid solutions, which are surrogates of Zr-based transuranium nitrides, in nitric acid was examined. Powder sample of the matrix material, ZrN was completely dissolved with 7.4 mol/L HNO3 at 383 K in 20 hours or 7.7 mol/L HNO3 at room temperature in 134 days. LnN-ZrN solid solutions were completely dissolved with milder conditions; 0.25GdN-0.75ZrN was with 7.5 mol/L HNO3 in 6 days, and 0.40DyN-0.60ZrN was with 7.7 mol/L HNO3 in 1 day or 1.0 mol/L in 20 days at room temperature. These results suggest that it became easier to dissolve LnN-ZrN solid solution with increasing the contents of LnN. From chemical analysis of LnN-ZrN samples, a change of the metal compositions during pellet sample fabrication process was observed for 0.40DyN-0.60ZrN, though not for 0.25GdN-0.75ZrN. The change of the metal composition in 0.40DyN-0.60ZrN sample is considered to be due to vaporization of Dy during the heating process.