Radiolytic and chemical transformation of solvents used in nuclear fuel reprocessing

Extractant-diluent systems used in the Purex-process were degraded radiolytically to study the influence of radiolytic and chemical changes on the extractive properties of the systems studied. Radiolytic degradation of TBP-diluents-nitric acid systems was studied using gas chromatography, thin-layer radiochromatography, IR- and UV-spectra and paramagnetic resonance methods. The influence of the dose-rate, the nature of diluent of TBP as well as of nitric acid concentration on extraction of uranium as well as retention of uranium and zirconium by degraded Purex-solvents has been established. Radiolysis of the systems studied was compared with thermal degradation and main differences between both processes have been shown. It was established that the present methods of solvents clean-up are not effective for heavily degraded solvents. (author)