The effect of irradiation on the thermal stability of the levextrel dibenzo-21-crown-7 applying to the high-level waste fractionation processes

– The thermal decomposition of the solid extractant based on dibenzo-21-crown-7 (levextrel DB21C7, also known as TVEX-DB21C7 in Russia) in contact with nitric acid solutions and nitrates of cesium and strontium and irradiation to a dose of 500 kGy was investigated. For the initial levextrel DB21C7 samples, there are no processes with the heat release in the temperature range of 50–600 °C in argon inert atmosphere. In air oxidizing atmosphere, exothermic processes are observed at the temperatures of 200–580 °C with the heat release of 8770 ± 140 J/g. Partial radiolytical degradation of the levextrel DB21C7 was noted, which is confirmed by infrared (IR) spectrometry. In the IR spectra of the samples, the decrease in the intensity of the absorption bands 1100–1400 cm −1 was found, as well as the appearance of the peak in the area of 1650–1750 cm −1 . For the samples in contact with 6,2 mol/l nitric acid, the thermal effects with the value of 360 ± 20 J/g in inert atmosphere and 8900 ± 170 J/g in oxidizing atmosphere were determined. The defined gaseous products (2-methyl-1,3-dioxolane, 1,4-benzodioxin, 2,3-dihydro-, and a number of benzene derivatives) of thermolysis and radiolysis of the levextrel resin are flammable and are capable of ignition in the presence of an oxidizer and an ignition source.