Redox behavior of $${\text{VO}}^{2 + } / {\text{VO}}_{2}^{ + }$$ VO 2 + / VO 2 + as a simulant of $${\text{NpO}}_{2}^{ + } / {\text{NpO}}_{2}^{2 + }$$ NpO 2 + / NpO 2 2 + in boiling nitric acid solution

To evaluate the redox behavior of $${\text{VO}}^{2 + } / {\text{VO}}_{2}^{ + }$$ as a simulant of $${\text{NpO}}_{2}^{ + } / {\text{NpO}}_{2}^{2 + }$$ in boiling nitric acid solution, i.e., typical operating conditions for nuclear fuel reprocessing plants, oxidation rate measurements for VO2+ in boiling and non-boiling nitric acid solutions, thermodynamic calculations, and kinetic calculations were performed. The results indicated that the apparent oxidation rate of VO2+ to $${\text{VO}}_{2}^{ + }$$ is accelerated by a decrease in $${\text{NO}}_{2}^{ - }$$ and HNO2 concentrations owing to the boiling phenomena of nitric acid solution.