ИСТИНА

The utilization of high level waste (HLW) after the reprocessing of spent nuclear fuel is one of the main problems of the rapidly developing nuclear power industry. It is possible to reduce their amount by extracting actinides and long-lived products from SNF using extraction processes, in which not only the extractant that selectively extracts dangerous nuclides is important, but also a properly selected diluent that is resistant to high radiation doses. Due to the high acidity during the technological process of the reprocessing, in the extraction systems undesirable products can be formed that reduce the fire and explosion safety of the processes. In the presented study, a qualitative and quantitative analysis of samples of the products of an extraction system was carried out with a promising extractant TODGA in Isopar-M diluent with the addition of 1-decanol or 1-nonanol, with saturation by 8 mol/L HNO3 and without it. Irradiation was carried out up to 500 kGy. For irradiated samples, unsaturated with nitric acid, the pattern of IR-spectra varies slightly with respect to similar non-irradiated samples. IR-spectroscopy was used to determine the formation of the main classes of products after radiation exposure: RCOOH, RCOR1, RCOOR. The presence of ketones, carboxylic acids and esters was proved by the coincidence of absorption bands by adding appropriate standards to irradiated samples, in a similar way the presence of organic nitrates (area 1646-1625 cm-1) and nitro compounds (1569-1539 cm-1) for samples, saturated with HNO3, was confirmed. The results of chromatographic analyzes of irradiated samples did not reveal a significant increase in low-boiling products for both systems saturated with nitric acid and unsaturated samples. When ionizing radiation is applied to the extraction system based on 1-decanol, Isopar-M undergoes more destruction, and in the system with 1-nonanol disintegrates the alcohol itself. 1-Decanol is more resistant to ionizing radiation. According to the results of IR-spectroscopy, the radiation yields of nitro compounds, ketones and carboxylic acids were determined. While conducting a quantitative analysis, we used the standard procedure for constructing the calibration dependences of the light absorption on a sample of standards (the area of compliance with the Bouguer-Lambert-Beer law). By the method of potentiometric titration, we determined that the concentration of nitric acid in the extraction system with 1-decanol is lower than with 1-nonanol, both “before” irradiation and “after”, which is consistent with the data on radiation yields. Thus, preliminary conclusions can be made, that extraction systems with 1-decanol showed themselves better at key stages of the analysis than systems with 1-nonanol. The most important is that 1-decanol is more resistant to ionizing radiation. The main products, formed by radiation exposure, were established. Fire and explosion-proof characteristics of the systems "Isopar-M - TODGA" with the addition of both alcohols during the tests do not significantly change. Acknowledgments: This study was supported by the Russian Science Foundation (project 16-19-00191).