Peculiarities of radioactive soil contamination in places of underground nuclear tests in the Semipalatinsk test site

The article highlights the results of a radioecological survey of the surface areas of combat boreholes at the Sary-Uzen site located on the territory of the Semipalatinsk Test Site (STS), where underground nuclear tests in these boreholes were conducted earlier. The surface areas of boreholes were examined the levels of radioactive contamination of the soil were determined. A total of 2 main groups were identified. The first group includes boreholes with radioactive contamination of the soil on the surface area. The second group includes boreholes with no radioactive contamination of the surface soil layer. The first group can be divided into boreholes with a deformation of the ground surface and without it. For each variety, depending on the specifics of the nuclear test, the characteristic features of radioactive contamination were determined. Based on the results of the survey, the ranges of specific activity values were established.

The excretion of 241Am and 137Cs from the broilers organs after long-term application

Data, despite being crucial for internal dose assessment, is lacking on the transfer of artificial radionuclides from the environment to the food supply. Expanding the available information on these factors is important for the improvement of dose models for specific scenarios. This paper describes the results of a 70 day field experiment with broiler chickens on the dynamics of excretion of ¹³⁷Cs and ²⁴¹Am from the muscle, liver and bone of broilers after a 30 day application of contaminated feed. The radionuclide concentrations in the feed and the thigh muscle, thigh bone and liver of 54 chickens divided between grass meal and soil contaminated feed groups were evaluated by gamma spectrometry for ²⁴¹Am and ¹³⁷Cs. The obtained results confirm previous data on the dynamics of the excretion of cesium from organs, which can be described with a fast and a slow exponential curve of excretion. On the 70th day, following the 30-days application, 2-8% of the first-day activity concentrations of ¹³⁷Cs in organs (muscle, liver, bone) were detected. In the first two days, activity concentration of ²⁴¹Am decreases twofold in both liver and bone. 35% of the maximum activity concentration of ²⁴¹Am remained in bone and 15% in liver on the last day of the experiment.

The transfer of 241Am and 137Cs to the tissues of broilers' organs

Data on the transfer of artificial radionuclides from the environment to the food supply is necessary for internal dose assessment. There is a necessity for expanding and improving the available information on these factors in order to make better dose models for specific scenarios. This paper describes the results of a field experiment with broiler chickens on the transfer factor (Ff) and concentration ratio (CR) for the long-term intake of 241Am and 137Cs with grass meal and soil. The broilers were divided into two groups, each group had nine subgroups and each subgroup had three broilers. The radionuclide concentrations in the feed and the thigh muscle, thigh bone, and liver of 54 broilers divided between the grass meal and soil groups were evaluated by gamma spectrometry for 241Am and 137Cs. The duration of feeding with "contaminated" sources ranged between 1-70 days. The equilibrium stage of 241Am in muscle and bone occurs on the 1st and 40th day, respectively; for 137Cs in muscle- 30th days of intake and for liver and bone- 7th days. For 241Am, the liver did not reach equilibrium stage during the 70 days of intake. Ff of 137Cs in the "forage-muscle" and "soil-muscle" systems were determined as 1.9±0.3 and 0.18±0.05; Ff of 241Am in the "soil-muscle" system was-7.5×10-5.

Transfer of radionuclides to plants of natural ecosystems at the Semipalatinsk Test Site

A systematic study devoted to ¹³⁷Cs, ⁹⁰Sr, ²⁴¹Am, ^239+240Pu radionuclides in vegetation cover from several spots of the Semipalatinsk test site (STS) is summarised in this paper, highlighting the main findings obtained. The analysed spots are characterized by various types of radioactive contamination. Transfer factors (Tf) required for the quantitative description of the radionuclides transition from the soil to aboveground plant parts were determined, being found that, on average, the minimum Tf for all the radionuclides concerned were determined on the "Experimental Field" ground, followed by the determined ones in the "plumes" of radioactive fallout and in the conditionally "background" territories analysed. The highest transfer factors were characteristic of zones of radioactive streamflows and places of warfare radioactive agent (WRA) tests. On the other hand, ordering the radionuclide transferring factors in descending order, the following sequence was obtained: ⁹⁰Sr Tf > Cs Tf > ^239+240Pu Tf > ²⁴¹Am Tf, with the ⁹⁰Sr Tf, on the average, exceeding the ¹³⁷Cs Tf by 8 times and exceeding the ^239+240Pu Tf by up 16 times. ^239+240Pu Tf values were up to 3 times higher than the ²⁴¹Am Tf. The exception to the indicated radionuclide Tf descending order corresponded to places of WRA tests where Tf of radionuclides of interest by plants follows the sequence ⁹⁰Sr > ^239+240Pu > ¹³⁷Cs.

Distribution of artificial radionuclides in particle-size fractions of soil on fallout plumes of nuclear explosions

In this paper are analyzed the artificial radionuclide distributions (¹³⁷Cs, ⁹⁰Sr, ²⁴¹Am, ^239+240Pu) in particle-size fractions of soils from two radioactive fallout plumes at the Semipalatinsk Test Site. These plumes were generated by a low-yield surface nuclear test and a surface non-nuclear experiment with insignificant nuclear energy release, respectively, and their lengths are approximately 3 and 0,65 km. In contrast with the great majority of similar studies performed in areas affected mainly by global fallout where adsorbing radionuclides such as Pu are mainly associated with the finest soil fractions, in this study it was observed that along both analyzed plumes the highest activity concentrations are concentrated in the coarse soil fractions. At the plume generated by the surface nuclear test, the radionuclides are concentrated mainly in the 1000-500 μm soil fraction (enrichment factor values ranging from 1.2 to 3.8), while at the plume corresponding to the surface non-nuclear test is the 500-250 μm soil fraction the enriched one by technogenic radionuclides (enrichment factor values ranging from 1.1 to 5.1). In addition, the activity concentration distributions among the different soil size fractions are similar for all radionuclides in both plumes. All the obtained data are in agreement with the hypothesis indicating that enrichment observed in the coarse fractions is caused by the presence of radioactive particles resulted from the indicated nuclear tests.

Nature of radioactive contamination of components of ecosystems of streamflows from tunnels of Degelen massif

The paper provides data on environmental contamination due to radionuclides' migration with water. As a result of investigations there was obtained data on character of contamination of soil cover, surface water and underflow from tunnels of Degelen massif. Character of radionuclides' spatial distribution in environment was also shown. Mobility ranges of radionuclides' vertical and horizontal movements have been established in soils both across and along the stream flow. There was also shown a possibility to forecast radionuclides' concentration in soil by specific activity of these radionuclides in water. Different concentrations of radionuclides in associated components of the ecosystem (surface waters - ground waters - soils) have shown disequilibrium of their condition in this system. Generalization of investigation results for tunnel water streams' with water inflows, chosen as investigation objects in this work, allows to forecast radionuclides' behavior in meadow soils and other ecosystems of water streams from tunnels of Degelen test site. Based on analysis of curves, describing radionuclides' behavior in horizontal direction, we can forecast, that at this stage (137)Cs and (239+240)Pu would not be distributed more than 1.5 km from the access to the daylight surface, (90)Sr - not more than 2 km.