The decomposition of the levextrel tributyl phosphate in nitric acid solutions under isochoric conditions

•The thermal effects occurring during the heating of the levextrel TBP are studied.•The kinetics parameters describing the exothermic processes are estimated.•The gaseous products of the complete decomposition of the levextrel TBP are studied.•The safety limits of the sorption-type column are estimated by modeling. Solid extractants based on tributyl phosphate (levextrel TBP) are of interest for the additional extraction of uranium and plutonium from high level waste during the processing of spent nuclear fuel. To assess the possibility of application of the levextrel TBP, considering its potential fire and explosion hazard, the method of differential scanning calorimetry was used to determine the exothermic effects occurring during the heating of the levextrel TBP saturated with nitric acid solutions. It was found that at 37 % concentration of nitric acid solution containing a number of metal nitrates, the heating is accompanied by the exothermic thermal effect of 1034 ± 178 J/g, which is the average value for the heating rates from 1 to 5 K/min. The value of the heat release makes it possible to potentially classify the levextrel TBP as a class of self-decomposing substances and mixtures. The kinetic parameters of the multistage reaction describing the thermal decomposition of the levextrel TBP are estimated by mathematical optimization. Using computer modeling, the critical conditions for the occurrence of a thermal explosion in the sorption-type column for the additional extraction of radionuclides from high level waste are estimated, namely, the maximum permissible values of: the temperature of the core of the material inside the column; the radius of the column; additional heat generation of non-reactive origin inside the column.