L.N. Gumilyov Eurasian National University, a dissertation defense for the degree of Doctor of Philosophy (PhD) by Aktayev Medet Ryskalievich on the topic «Geochemical migration of radionuclides after a thermonuclear explosion in well 1004 on the territory of the Semipalatinsk test site» in the educational program «8D05208 – Ecology and nature management».
The dissertation was carried out at the Department of «Management and Engineering in the sphere of environmental protection» of L.N. Gumilyov Eurasian National University.
The language of defense is russian
Official reviewers:
Baigazinov Zhanat Abylkanovich – Doctor of philosophy (PhD), chairman of the board of JSC “Park of Nuclear Technologies” (Kurchatov, Republic of Kazakhstan).
Tashekova Azhar Zhumanovna – Doctor of philosophy (PhD), professor of the department of applied biology at Alikhan Bokeikhan University (Semey, Republic of Kazakhstan).
Temporary members of the Dissertation Council:
Polivkina Elena Nikolayevna – candidate of biological sciences, head of the laboratory of radioecological and biogeochemical research of the branch of the Institute of radiation safety and ecology (Kurchatov, Republic of Kazakhstan).
Klivenko Alexey Nikolaevich – Doctor of philosophy (PhD), Head of the Scientific Center for Radioecological Research (Semey, Republic of Kazakhstan).
Tibor Kovacs – PhD, Hungarian institute of radiochemistry and radioecology, head of department (Veszprém, Hungary).
Scientific consultants:
Akbayeva Lyailya – Candidate of biological sciences, acting professor of the department “Management and Engineering in the Sphere of Environmental Protection” ENU named after L.N. Gumilyov (Astana, Republic of Kazakhstan).
Kuzmenkova Natalia – candidate of geographical sciences, leading researcher at the Department of Radiochemistry of the Moscow State University named after M.V. Lomonosov (Moscow, Russian Federation).
The defense will take place on April 24, 2025, at 10:00 AM in the Dissertation Council for the training direction «8D052 – Environment» in the educational program «8D05208 – Ecology and nature management» of L.N. Gumilyov Eurasian National University. Conducting a meeting of the dissertation council in a mixed (offline and online) format.
Link: https://surl.li/eijuch
Address: Astana, st. Kazhymukhan, 13, Educational building No. 3, room. No. 333.
Abstract (English): Relevance of the Research Topic. Between 1949 and 1989, nuclear tests were conducted at the Semipalatinsk Test Site (STS), leaving a significant mark on the history of Kazakhstan. Both surface and underground tests resulted in severe environmental damage and had adverse effects on human health. The closure of the site in 1991 was an essential step towards a world free of nuclear weapons; however, studying the consequences of nuclear tests remains necessary. Protecting the environment, particularly people, from residual and secondary radioactivity is a key aspect of addressing the issues associated with the test site. The importance of solving STS-related problems has been recognized by the international community. The United Nations General Assembly, acknowledging the seriousness of the situation, has adopted three resolutions regarding assistance to the region. A number of decisions have been made regarding the planned work to return radiation-contaminated areas to economic use, supported by the Security Council of Kazakhstan on April 6, 2009, and the Protocol Decision of the Interdepartmental Commission under the Security Council of Kazakhstan on May 7, 2009, as well as the Program for the Comprehensive Resolution of Issues of the Former Semipalatinsk Nuclear Test Site for 2005–2007. Moreover, on July 5, 2023, a new law on the Semipalatinsk Nuclear Safety Zone was adopted, aimed at rehabilitating the territory of the former test site. According to the legal acts of Kazakhstan, the entire territory of STS is currently classified as reserve land. Article 143 of the Land Code of Kazakhstan states that "Land plots where nuclear weapon tests were conducted may be granted by the Government of Kazakhstan for ownership or land use only after all measures for the elimination of nuclear test consequences and a comprehensive environmental assessment have been completed, with a positive conclusion from the state environmental expertise." According to available data, part of the test site's land meets hygiene standards and is therefore suitable for economic use. In this regard, studying the environmental safety of the test site is of great practical importance. The modern Semipalatinsk Test Site has transformed from a source of military threat into an object of scientific research, including studies on the geochemical migration of radionuclides in different media, the assessment of radiation risks for ecosystems and humans, and the development of predictive radiation impact models. Currently, several underexplored issues related to the geochemical migration of radionuclides from water bodies formed as a result of thermonuclear explosions at STS exist. Radionuclides can migrate as colloids, adsorbed on mineral particles or organic substances, significantly increasing their mobility and transport range. At the same time, geological formations can act as natural barriers, retaining radionuclides within specific horizons. At STS, the primary mechanisms of radionuclide migration from nuclear test sites are airborne and waterborne transport. One such site is a water body formed after the first Soviet industrial excavation explosion in Borehole 1004, carried out in January 1965 to create an artificial reservoir in arid regions. This body of water was later informally named "Atomic Lake." Previous studies have shown significant differences in radionuclide concentrations in different parts of Atomic Lake. It is hypothesized that the sources of contamination are in the soils surrounding the crater, formed by the fragmentation of rock due to the thermonuclear explosion. Currently, the primary radionuclide contamination is concentrated in these soils around the crater. Additionally, contaminated groundwater inflows from other nuclear test boreholes in the "Balapan" area were suspected to contribute to the lake's contamination. Hypothesis. Modern radionuclide contamination of Atomic Lake may be due to two factors. The primary source of contamination is the leaching of anthropogenic radionuclides from atmospheric fallout in the crater soils surrounding Atomic Lake. A secondary contamination factor is the inflow of anthropogenic radionuclides into the lake via underground water through geological fault channels from the nearest nuclear test boreholes. Objective of the Study. The study aimed to investigate the processes of geochemical migration and distribution of radionuclides in the environment around Atomic Lake and to assess the radiation dose exposure. Research Tasks: 1. To study the distribution of anthropogenic radionuclides in environmental objects around Atomic Lake. 2. To investigate hydrochemical and hydrothermal factors affecting the distribution and migration of radionuclides in the reservoir. 3. To analyze the levels of contamination in groundwater adjacent to Atomic Lake and assess the potential for geochemical radionuclide migration. 4. To determine the source of water contamination in Atomic Lake. 5. To assess the radiation dose exposure in the study area. Novelty of the Research: A comprehensive study of the spatial distribution of anthropogenic radionuclides in areas of excavation thermonuclear tests at STS was conducted for the first time, expanding scientific knowledge on radionuclide distribution in environmental objects. The source of water contamination with radionuclides in the test area was identified and substantiated for the first time, along with the mechanisms of their distribution, including the role of water stratification. New data on the spatial distribution of radionuclides in the air around contaminated soils were obtained, revealing zonal heterogeneity in contamination levels, essential for radiation safety measures. For the first time, radiation dose calculations were conducted for the local population under elevated radiation exposure conditions, and recommendations for radiation safety were developed. Object of the Study: The object of the study, "Atomic Lake," is located in the "Balapan" area in the southeastern part of the Semipalatinsk Test Site. The geographical coordinates of the site are 49°56'07.13"N latitude and 79°00'30.34"E longitude. The absolute elevation above sea level is 298 meters. Currently, the lake has a depth of 80 meters, a crater diameter of 400 meters, and crest heights of soil formations ranging from 20 to 35 meters. The total volume of water in the inner reservoir is approximately 6,000,000 cubic meters. Scientific and Practical Significance. The significance of this research lies in the identification of patterns in the distribution of anthropogenic radionuclides in the environment resulting from a thermonuclear explosion. The obtained data on the spatial distribution of radionuclides will be used to refine and verify existing models of radionuclide migration in different media and to predict the long-term behavior of radionuclides in aquatic environments. The practical significance of the study is that the research results will be used to justify further decisions regarding the change in the status of "reserve land" ("Atomic Lake") and its withdrawal from public economic use. Radiation dose data are necessary for developing an access control system to the site, aimed at protecting public health and minimizing radiation exposure risks beyond permissible limits. Overall, the lake was originally created for economic purposes, including regulating the flow of the Shagan River. Therefore, assessing the radiation and chemical conditions of the study site is crucial for determining the possibility of further lake usage. Research Results: 1. The presence of radionuclides such as ³H and ⁹⁰Sr was detected in the lake water, with specific activities ranging from 160 to 20,000 Bq/kg and from 1 to 15 Bq/kg, respectively. The lowest radionuclide concentrations were always observed in the upper layers of the lake at depths of 10–20 meters, while maximum concentrations were recorded at depths of 60–80 meters. Anthropogenic radionuclides ²³⁹+²⁴⁰Pu, ²⁴¹Am, and ¹³⁷Cs were not detected in any investigated points at the lake's surface or bottom. Seasonal observations showed stable distributions of ³H and ⁹⁰Sr over time, which is attributed to the absence of water exchange below 20 meters. It was found that the impact of contaminated crater soils on air quality is significant up to a distance of 200 meters, where the specific activity of ²³⁹+²⁴⁰Pu exceeds the permissible volumetric activity for the population by a factor of two. 2. The primary mechanism influencing the depth distribution and seasonal stability of radionuclides is the stratification of the water column due to dissolved chemical compounds. Hydrochemical indicators between the upper and bottom layers of the lake differed by a factor of two, with minimum values of 10 g/L in the surface water layer at depths of 10–20 meters and maximum values of 20 g/L in the bottom layer. This contributed to the increased density of water with depth, leading to a stagnant lake regime. The hydrothermal regime of "Atomic Lake" is characterized by the presence of a thermocline zone at a depth of up to 20 meters, where external water exchange processes occur throughout the year due to thermal convection and wind mixing. Below this horizon, the lake is not subject to water circulation caused by external physical processes. 3. It was determined that the geological and lithological conditions of the study area include low-permeability impermeable clays, as well as clay shales and siltstones, which prevent the inflow of contaminated groundwater from underground nuclear test areas in the "Balapan" region. Groundwater from "Balapan" does not contribute to the level of ³H contamination in "Atomic Lake." It was established that the leaching and geochemical migration of ³H from contaminated crater soils occurs not only through surface water but also through groundwater. Groundwater outflows from the contaminated crater soils significantly impact Shagan River contamination at a distance of 2 km downstream. 4. A comparative analysis of stable isotope ratios δ¹⁸O/δ²H in "Atomic Lake" and groundwater from the "Balapan" site ruled out the hypothesis that "Atomic Lake" receives water from contaminated underground sources from "Balapan." Experimental leaching studies confirmed that the primary and sole source of contamination in "Atomic Lake" is the contaminated crater soil. 5. Radiation dose calculations indicated that permanent residence in the study area is not feasible, as it leads to exceeding the hygienic standard for the annual effective dose of radiation exposure to the population. The primary source of radiation exposure is external exposure to ¹³⁷Cs. Ingestion of radionuclides through water consumption in the study area results in exceeding the established annual effective radiation dose for the population. Compliance with Scientific Priorities and Government Programs. The study aligns with priority scientific directions related to environmental safety, radiation protection, and environmental conservation. The research results can be used within the framework of Kazakhstan's national programs for monitoring and rehabilitating radioactively contaminated areas, as well as for developing strategies to manage radiation contamination risks. Personal Contribution of the Candidate. The candidate conducted the dissertation research at the Water Resources Laboratory under the Department of Environmental Engineering and Ecology at L.N. Gumilyov Eurasian National University from 2022 to 2024. The candidate actively participated in developing the research methodology, conducting field and laboratory work, analyzing data, and preparing scientific publications. Validation of Research. Selected results have been published in scientific journals: 1. Characterization of geological and lithological features in the area proximal to tritium-contaminated groundwater at the Semipalatinsk test site // PLOS ONE. – 2023. - 8 February; 2024 – 6 March; 2024 - 22 March. 2. Research on the Conditions of Water Formation in radiation-hazardous sites of the Semipalatinsk test point // News of the National Academy of Sciences of the Republic of Kazakhstan Series of Geology and Technical Sciences. – 2023. – Vol. 5, No. 461. – P. 35-44. 3. Tritium distribution in the "water-soil-air" system in the Semipalatinsk Test Site // PLOS ONE. – 2023 - 16 July; 2023 - 26 December. 4. The character of radionuclide contamination of natural lakes at the territory of the Semipalatinsk test site // Journal of Environmental Radioactivity. 5. Research into the current radiological state of air and monitoring observations on STS and the adjacent territory // Journal of Environmental Radioactivity. – 2023. – Vol. 264. – P. 107199. 6. Assessment of Radiation Doses for Different Behavioral Scenarios in the "Atomic Lake" Area // Bulletin of NNC RK. – 2023. - No. 1. – P. 55-60. 7. Radiation Monitoring of Surface and Groundwater at the Semipalatinsk Test Site // Radiobiology and Environmental Safety -2022: Proc. of the Int. Conf. (Minsk, 2022 - 26-27 May). 8. Monitoring of Tritium Contamination in the Shagan River Waters // Proceedings of the Institute of Radiation Safety and Ecology, NNC RK, 2023 – Vol. 7. 9. Optimization of Monitoring Observations in Radiation-Hazardous Sites of STS Using Isotope Hydrology // Proceedings of the Institute of Radiation Safety and Ecology, NNC RK, 2023 – Vol. 7. Publications. The dissertation findings are reflected in nine publications: 5 in Scopus-indexed journals, 1 in journals recommended by the Committee for Quality Assurance in Education and Science of the Ministry of Education and Science of Kazakhstan, 1 in conference proceedings, and 2 in collected works. Structure and Volume of the Dissertation. The dissertation includes normative references, abbreviations, an introduction, a literature review, research materials and methods, results, conclusions, and a bibliography of 208 sources. The study consists of 122 pages, containing 14 tables and supported by 54 figures.
Conclusion of the Research Ethics Committee
Defense of the dissertation: https://youtu.be/eN7I6rG9Dhs
