Using autoclave digestion to extract technogenic radionuclides from soil cover of Semipalatinsk test site

Tests of nuclear weapons, various radiation accidents have led to a significant contamination of the natural environment with technogenic radionuclides and an increase in the radiation load on humans and biota. The soil cover is a kind of depot that accumulates technogenic radionuclides, from where they can enter the body of animals and humans in various ways. The migratory abilities of radionuclides and their inclusion in biological chains are determined by the properties of the radionuclides themselves, the properties of the soil, as well as the mechanism of formation of radioactive contamination. A large number of nuclear tests and experiments of various types and capacities carried out at the Semipalatinsk Test Site (STS) led to the formation of various radioactive contaminated sites that differ from each other in nature, levels and isotopic composition. One of the most studied, from the point of view of studying the forms of presence, the solubility of radioactive particles, is the territory of the 'Experimental Field' testing ground, where ground and air tests were carried out. The specifics of the experiments, namely the interaction of the soil with the high-temperature explosion zone, led to the formation of slag surfaces and vitrified particles containing technogenic radionuclides, including ^239+240Pu and ⁹⁰Sr isotopes. Information on the presence of such sparingly soluble forms of radionuclides on the territory of other testing grounds of STS is extremely scarce. The resistance of radioactive particles to leaching by mineral acids can lead to an underestimation of the content in the soil cover of hazardous radionuclides, including ^239+240Pu and ⁹⁰Sr. Ultimately, this will lead to an underestimation of the radiation hazard for the population engaged in economic activities on the territory of the landfill (grazing, haymaking and mining) or living outside it. Chemical preparation of analyzed samples is one of the most time-consuming and critical stages, which limits the performance of the entire analysis as a whole, since even the highest performance measuring instruments cannot be realized with a lot of time spent on this procedure. Decomposition of samples in autoclaves is one of the alternative methods of sample preparation, but practically devoid of the disadvantages inherent in decomposition in open systems. The advantage of using autoclaves over decomposition in open systems is that the decomposition occurs in a closed volume of the reaction chamber at elevated pressure, which increases the boiling point of liquids and, accordingly, accelerates the decomposition of particles. Thus, sample digestion occurs in a shorter time, with fewer reagents and minimal analyte loss. The last factor, along with the completeness of the decomposition, is the main indicator that affects the quality of the analysis. In this paper, we consider the method of autoclave decomposition in the determination of technogenic radionuclides in soils of STS.