[en] A study was made on the dependence of the rate of Pu⁶⁺ macroconcentration reduction to Pu⁴⁺ (2-40 g/l) when bubbling mixture of gaseous nitrogen oxides (oxide and dioxide) on nitric acid concentration (3-8 mol/l, initial Pu⁶⁺ content (20-95 %) total plutonium concentration in processable solution temperature (50-80 deg C), the rate of gaseous nitrogen oxides and composition of the given gaseous mixture, as well as the presence of uranium (6) and stable isotopes of some fission products in processable solution. Empirical kinetic equation for the rate of studied process enabling to calculate the apparent rate constants of gas-chemical reduction of Pu⁶⁺ to Pu⁴⁺ using experimental data is suggested. Applicability of derived equation for decribing the studied process under steady conditions during regeneration of NPP spent fuel is shown