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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings 7 Evaluation of Radiation Ecology Status Around Russian Nuclear and Radiation Enterprises Based on Landscape-Geochemical Research* V. I. Velichkin, Ye. N. Borisenko, A. Yu. Miroshnikov, V. I. Myskin, N. V. Kuzmenkova, and I. I. Chudnyavtseva, Russian Academy of Sciences Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry INTRODUCTION Past experience in radiogeoecological work aimed at rehabilitating radiation-contaminated areas indicates that the effectiveness of such rehabilitation measures largely depends on the reliability and quality of the initial scientific foundations on which the measures were developed and based. The data traditionally presented as the basis for rehabilitation of contaminated areas include information on the composition, quantity, and distribution of contaminants and on the soil cover in which they are found. This information makes possible an overall assessment of the current radiochemical status of the environment at the sites being studied, but it is insufficient both to reveal the conditions and mechanisms of contaminant migration and concentration and to predict how the studied ecosystems will change over time and space. Since 1990, at the initiative and under the leadership of Academician N. P. Laverov, the Russian Academy of Sciences Institute of Geology of Ore Depos- * Translated from the Russian by Kelly Robbins.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings its, Petrography, Mineralogy, and Geochemistry (IGEM) has been conducting landscape-geochemical research scientifically based on the teachings of Professor A. I. Perelman and his students regarding geochemical landscapes and geochemical barriers. The techniques developed at IGEM especially for assessing the environmental impacts of nuclear and radiation facilities have been elaborated and applied in practice by specialists from the institute’s Laboratory of Radiogeology and Radiogeoecology. These techniques include the following: Detection and characterization of actual and potential radiation sources Identification and integrated study of the hierarchy of landscape geochemical systems as well as elementary landscapes and their transition zones Studies within each landscape type of the composition and geochemical parameters of soil, vegetation, substrate rocks, surface water and groundwater, and bottom sediments of swamps, lakes, rivers, and reservoirs Studies and assessments within each elementary landscape of distribution and availability modes of radioactive and stable contaminants in soil, vegetation, substrate horizons, river and lake water, and bottom sediments Integrated assessment of migration and accumulation conditions of radioactive and stable contaminants within landscape geochemical systems and elementary landscapes on the basis of their geomorphological, soil-lithological, geochemical, hydrogeological, and biological features Disclosure and studies of natural geochemical barriers and formation conditions of technogenic1 geochemical barriers Creation of landscape geochemical and ecological geochemical maps in various scales Cartography is an integral component of these techniques. Maps provide the necessary basis for detecting areal diversity of conditions for the distribution of radioactive substances, for assessing and predicting changes in the radioecological environment over space and time, and for supporting decisions on optimizing environmental management. This research methodology makes it possible to determine the characteristics of transfer and accumulation of radioactive and stable contaminants, and on this basis, to predict more reliably the ecological status and further changes in natural landscapes in regions where nuclear and radiation facilities are located. IGEM specialists are using this methodology to study a number of major nuclear and radiation sites in Russia located in various climatic zones. This paper focuses on results of the first stage of this research. 1 Technogenic is used to refer to phenomena arising as a result of the development or deployment of technology.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings SOURCES OF RADIATION AND CHEMICAL CONTAMINATION AT RUSSIAN NUCLEAR AND RADIATION ENTERPRISES This paper covers three groups of major Russian nuclear and radiation enterprises. The first includes the Mayak Production Association radiochemical complex, a multipurpose dual-use facility that in its initial phase of activity was oriented exclusively to work on defense-related nuclear programs, but was later converted to focus on eliminating the consequences of defense-related activities and addressing various problems associated with the nuclear power fuel cycle. The second group includes the Nerpa Ship Repair Plant, which is among the enterprises that carry out specific operations connected with eliminating nuclear weapons carriers. The third group includes facilities engaged in work on particular stages of the nuclear fuel cycle, such as uranium ore extraction and processing enterprises (the Priargunsk Mining and Chemical Production Association—PMCPA) and electricity producers (the Smolensk and Balakovo nuclear power plants) (see Figure 7-1). The bulk of the radionuclides contaminating the environment at the nuclear and radiation enterprises studied are technogenic in nature; that is, they were created in the course of processes occurring in nuclear reactors. Before the initiation of work in the nuclear energy field, most of these radioisotopes did not exist in nature. Naturally occurring radioactive elements are known ecosphere contaminants only at the PMCPA uranium mining complex, which is located in the eastern part of the Lake Baikal region. FIGURE 7-1 Locations of major Russian nuclear and radiation enterprises. 1—Nerpa Ship Repair Plant; 2—Smolensk Nuclear Power Plant; 3—Balakovo Nuclear Power Plant; 4—Mayak Producation Association; 5—Priargunsk Mining and Chemical Production Association.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings The contamination sources, their toxic substance content, and the mechanisms of their spread into the environment are characterized as follows at each of the nuclear and radiation enterprises studied. The Mayak Production Association, Russia’s oldest and largest radiochemical enterprise, has the largest number of known sources of radioactive contamination. In the course of Mayak’s 60 years of operations, two periods may be singled out during which there were various active sources of radiation contamination. In the initial period (the 1950s and early 1960s), there were uncontrolled gas-aerosol emissions of radioactive substances into the atmosphere and discharges of liquid wastes, including highly active wastes, into the Techa River. From 1949 through 1956, this river received discharges of liquid radioactive wastes with a total activity level of 2.5 million Ci, which led to intensive radiation contamination of silt deposits in the Techa River and of the soil layer in its valley. The same period experienced wide-scale environmental contamination due to accidents. First, a container of highly radioactive liquid wastes exploded, subsequently discharging into the atmosphere finely dispersed radionuclides with a total activity of about 2 million Ci. Later, the winds spread a radioactive cloud of drought-created dust from the shores of Lake Karachai, an accumulation reservoir for liquid radioactive wastes. These accidents resulted in the formation of the East Urals Radioactive Trace, which has an area of more than 1,500 km2. At present, the currently operating enterprises of the Mayak Production Association emit into the atmosphere a regulated quantity of radioactive aerosols that causes practically no environmental damage. Planned discharges of low-activity liquid radioactive wastes are also made into the reservoirs of the Techa Cascade and of medium-activity liquid wastes into Lake Karachai. These releases result in the radiation contamination of the groundwater lying beneath these bodies of surface water. The primary radionuclides in the discharged gas-aerosol fractions and liquid radioactive wastes are short-lived plutonium-106, zirconium-95 + niobium-95, cesium-144, cobalt-60, zinc-65, and tritium; medium-lived cesium-137 and strontium-90; and a significantly smaller quantity of long-lived uranium-238 and transuranic elements (plutonium, neptunium, americium, and curium). Except for the short-lived ones, all the remaining radionuclides are found in various quantities in previously contaminated soils, rock, and surface water and groundwater. At the Nerpa Ship Repair Plant, which dismantles decommissioned nuclear-powered submarines, the main operations include cutting up the submarine hulls and reprocessing their internal parts. These operations result in the formation of finely dispersed mechanical particulate clouds containing radioisotopes (cesium-137, strontium-90, and cobalt-60) and heavy metals (iron, copper, nickel, titanium, and others) that are spread by air currents into the environment. During their routine daily operations, the Smolensk and Balakovo nuclear power plants regularly carry out controlled air emissions containing radioactive inert gases and aerosols of the radionuclides cesium-137, cesium-134, strontium-
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings 90, cobalt-60, manganese-54, carbon-14, and iodine-131, as well as transuranic elements. The concentrations of these emission components are substantially lower than maximum allowable levels. However, their progressive accumulations in soils could exceed allowable standards over time. Located near the city of Krasnokamensk in the eastern part of the Lake Baikal region, the PMCPA is the only enterprise in Russia that mines and processes molybdenum-uranium ores from the Streltsov Ore Field, which is unique in the size of its total uranium reserves. Here the environmental contaminants include natural radionuclides (uranium-238, uranium-235, and their decay products radium-226 and radon-222), thorium-232, potassium-40, and stable elements (molybdenum, manganese, arsenic, and beryllium), as well as sulfuric, nitric, and other acids. The contamination sources include tailings repositories for uranium ore processing and sulfuric acid production plants; dump sites for poor and unbalanced ores for heap leaching of uranium; an ash repository at the heating plant, which uses local hard coal; discharge sites for mine water; dump sites for unbalanced ores and worked rock; areas where uranium ores are strip mined; entrances to underground mines; and roads on which ore materials and worked rock are transported. Contaminants are transferred from the soil surface in the form of fine particle suspensions transported by surface water or atmospheric currents. In surface water the toxic substances migrate in suspended and solute form, while in groundwater they circulate in solutions and colloidal suspensions. GEOCHEMICAL LANDSCAPES AND THEIR RADIOECOLOGICAL STATUS IN REGIONS WHERE NUCLEAR AND RADIATION ENTERPRISES ARE LOCATED As further characterized below, regions with nuclear and radiation enterprises are located in all of the landscape-geochemical zones of Russia: tundra (the Nerpa Ship Repair Plant), forest (Smolensk Nuclear Power Plant), forest-steppe (Mayak Production Association), steppe (Balakovo Nuclear Power Plant), and dry steppe (PMCPA). This makes it possible to carry out a comparative analysis of conditions for the migration and concentration of natural and technogenic radionuclides in various landscape-geochemical settings. The Nerpa Ship Repair Plant specializes in dismantling decommissioned nuclear-powered submarines. This enterprise is located in the northern part of the Kola Peninsula, in the tundra landscape zone. The natural landscapes of this area, called “Murmansk-like,” formed on dense, poorly permeable, crystalline Precambrian rock, creating a topography of plains and folded rocky uplifts and depressions. On the basis of these rocks and because of their specific physical characteristics, primitive shallow soils were formed (to the depth of a few tens of centimeters). These soils may be characterized as mildly acidic, organogenic, highly peaty, hydromorphic formations with moderately restorative reactivity.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings They possess a heightened capacity for accumulating radioactive and stable contaminants. Water migration of dissolved forms of these elements is complicated in these soils. The contaminants are transferred mainly in a suspended particulate state in the atmosphere and in surface water flows. Autonomous and subsidiary elementary geochemical landscapes have been defined in the landscape-geochemical system around the Nerpa Ship Repair Plant.2 It has been established that in the soil layer of the autonomous landscapes, the highest average contents of radioactive cesium (97 and 77 Bq/kg) are found in soils at the industrial site and in the 15 km zone surrounding it. Meanwhile, these indicators reach only 39 Bq/kg in the 50 km zone around the plant. It is most likely that average cesium-137 content levels in the soils in this zone are due to global atmospheric fallout and may appropriately be viewed as background levels in the area of the Nerpa plant, as at the plant site and in the 15 km zone, in addition to background levels, there is the cesium-137 that, as previously noted, is carried by air currents from the site where the submarines are dismantled. Typically, from 79 to 92 percent of the total quantity of radioactive cesium accumulated in soils is concentrated in the top 3-6 cm layer, which is the most enriched with organic compounds. Increased concentrations of heavy metals have also been discovered in soils at the industrial site and in the 15 km zone. Thus, the environmental impact zone for the activities of the Nerpa Ship Repair Plant was determined in the course of the research. The increased levels of radioactive cesium and heavy metals found in the zone are significantly lower than maximum allowable concentrations. Nevertheless, the radioecological status of the environment around the Nerpa plant requires systematic monitoring. The Smolensk Nuclear Power Plant is located in the forest landscape zone of Central Russia. The forest and agricultural landscapes of this region formed on sandy-clay, weakly fractured rock from the old East European Platform, with topographic conditions characterized by gently sloping hills and plains. A significant part of the area is forested, with low-lying parts of the plains and riparian floodplains being swampy. Weakly mineralized with hydrocarbonates and calcium, the groundwater lies at a depth of 30 cm to up to 3 (and rarely 10) m. The soils are sod-podzolic and podzolic-gley in sands, loamy sands, light loams, and clays, as well as meadow, peat-gley, and peaty. Two types of geochemical landscapes may be singled out: (1) Polessk-type, which are flat, swampy, and forested plains on sands and loamy sands; and (2) Smolensk-type, which are hilly, lightly forested, raised plains and eroded uplifts on clay and clay-sand moraine deposits. Polessk-type landscapes are more hydromorphic. They are characterized by processes of leaching of radionuclides from the topmost soil layers, low sorption 2 Autonomous landscapes are parcels of the studied areas with a higher topographic elevation. Subsidiary landscapes are parcels with less elevated relief, which often contain river and stream channels or lake depressions.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings capacity of geochemical barriers within the soil, and weak contaminant fixation, which on the whole promotes their vertical and lateral migration. However, because of the low contrast between the autonomous and superaqueous landscapes, this migration proceeds slowly. Radionuclides have accumulated primarily in the peripheral zones of swamps in the alkaline gley sorption geochemical barrier. Smolensk-type landscapes are less swampy. The leaching of radionuclides from the topmost layers of sod-podzolic, loamy, and clay soils is less pronounced than in the Polessk-type areas. The geochemical barriers within the soil have a higher sorption capacity and limit the vertical migration of radionuclides. These landscapes are also characterized by processes of sheet erosion and accumulation of radionuclides with soil particles less than 1 mm in diameter from the foothill slopes, eolian dispersal, and displacement of contaminants in the soil layer during tillage. It has been established that radionuclides generated by the Smolensk Nuclear Power Plant during normal, accident-free operations enter the environment in small quantities and are localized in soils very close to the plant. Radionuclides are absorbed by sediments at the bottom of the reservoir and by humus and peat layers in the soils and precipitate out on the periphery zones of swamps, which represent a complex geochemical barrier of absorbent gley and alkaline components. This is the most effective concentrator of substances in the landscape zones affected by the Smolensk plant. The research that has been conducted indicates that the overall radioecological situation in the area around the Smolensk Nuclear Power Plant meets current safety requirements. The radionuclides emitted by the plant during its normal operating regime are fully contained by the natural geochemical barriers that exist in the landscape. The Balakovo Nuclear Power Plant and a large portion of the 30 km zone around it are located in the steppe landscape zone of Central Russia (the Syrtovaya Plain of the Volga area around Saratov). The landscapes of the black-earth steppe that developed in this area were formed on carbonate-sand-gley weakly violated rock on the sedimentary mantle of the ancient East European Platform. The topography is predominantly marked by flat plains divided by a network of infrequent gullies into separate flat, steeply sloped uplifts where water exchange processes are greatly slowed. The autonomous and subsidiary landscapes exhibit little lithological and geochemical contrast. The soils are chernozems with high and medium humus content and varying degrees of carbonate content, lixiviation, and solonetz characteristics. They are characterized by calcium-class water migration, and groundwater reactivity is neutral, slightly alkaline, and rarely slightly acidic. Chernozem soils possess increased capacity for irreversible absorption of cesium-137. In essence, the top layer of chernozem soils is an active spatial geochemical barrier to radioactive cesium. At the same time, wind and mechanical transport processes are fairly widely developed. Analysis of the quantitative aspects of cesium-137 distribution in the soil
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings layer within the 30 km zone indicated that the overall level of cesium-137 content (no more than 40 Bq/kg) in the soils of the region studied is substantially lower than allowable standards. Furthermore, more than 90 percent of this radioisotope was concentrated in the top 3 cm of the soils, the layer most enriched with organic matter. The data gathered make it possible to conclude that small quantities of radionuclides deposited daily due to regular atmospheric emissions by the Balakovo Nuclear Power Plant are firmly fixed and progressively absorbed by the soils. This tendency means that regular monitoring observations must be conducted in the area around the Balakovo plant. The Mayak Production Association is located in a forest-steppe landscape zone and is geographically associated with the eastern slope of the southern segment of the Ural mountain range. The western part of the region lies in the Ural foothills, while the eastern part lies in the hilly plain of the West Siberian Platform plate. The forest-steppe landscapes of this area were formed on intensively dislocated mica shales (in the western part of the region), on sedimentary-volcanic andesite-basalt rock (in the central part), and sand-clay-carbonate platform deposits (in the eastern part). The special characteristics of the topography mean that the region is divided into strongly predominant (about 75 percent of the area) autonomous (alluvial) landscapes in the elevated sections and the subsidiary (superaqueous) landscapes, which occupy a substantially smaller part of the region, covering the low-lying areas and lake and river valleys. The forest-steppe landscapes of the region around the Mayak Production Association are distinguished by the great diversity of their soil cover. The widely encountered forest (dark gray, gray, and light gray), chernozem (meadow, leached, and solonetz-like), meadow-swamp, solonetz, and solodic soils are differentiated by their soil profiles and geochemical parameters. The physical-chemical conditions in the soils vary from weakly acidic oxidizing (in forest soils) to weakly alkaline and alkaline oxidizing-restorative and restorative (in chernozem and saline soils). During the more than 50-year operating history of the Mayak Production Association, the natural landscapes in the area where the enterprise is located have been subjected to complex radiation and chemical contamination. Analysis of the available data indicates that most of the contamination occurred in the early stage of Mayak’s operations, as a result of the above-mentioned radiation accidents in 1957 and 1968, violations of procedures for the safe management of liquid radioactive wastes, and uncontrolled discharges of radioactive wastes into the atmosphere and the lake and river network. The current regulated atmospheric emissions have practically no effect on the environmental radiation situation. Meanwhile, continuing planned discharges of low-level liquid wastes into the reservoirs of the Techa Cascade and medium-level wastes into Lake Karachai are progressively contaminating the rock and groundwater beneath the reservoirs. Thus, radiation contamination of the soil cover in the natural landscapes
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings and of the bottom sediments in the reservoir-accumulators for liquid radioactive wastes occurred during the initial stage of activities at Mayak’s enterprises. The areas affected by radionuclide contamination of the soil may be categorized as follows: The East Urals Radioactive Trace, which was created as a result of accidental emissions of radionuclides, occupies a broad territory in the central and northwestern parts of the region being studied. The area’s boundary is defined at the 1 Ci/km2 level on a contour map of strontium-90 activity. In the center of the area, strontium-90 contamination reaches the hundreds of curies per square kilometer. Solid radioactive waste storage sites on the Mayak grounds Radionuclide anomalies in the Techa River watershed (the Asanov Swamps) Fairly limited tendencies have been identified for the spread of previously accumulated radionuclides under the physical-chemical conditions prevalent in the forest-steppe landscapes in the Mayak region. Horizontal migration has been noted in the soils of the autonomous landscapes, but since the appearance of radioactive anomalies, this migration has not led to a noticeable change in their initial contours. Vertical migration has been more clearly manifested in these landscapes; nevertheless, most of the radionuclides in vertical soil profiles are attached at geochemical barriers (of the sorption, leaching, or organomineral types) at a depth of 15-20 cm. In superaqueous landscapes, the radionuclides are fixed at deeper levels (up to 50 cm). In contaminated superaqueous landscapes in river valleys affected by seasonal flooding, lateral migration of radionuclides is also noted. This is due to the contaminants being washed out of the soils by floodwaters and carried into the transitory river systems. The Priargunsk Mining and Chemical Production Association. The deposits of the Streltsov molybdenum-uranium ore field with its extensive and unique uranium reserves are located in the dry steppe zone in the southeastern part of the Lake Baikal region. The PMCPA, which processes these deposits, is Russia’s only enterprise that mines and processes molybdenum-uranium ores. The environmental pollutants here include natural radionuclides (uranium-238, uranium-235, and their decay products radium-226 and radon-222), thorium-232, potassium-40, and stable elements (molybdenum, manganese, arsenic, and beryllium), as well as sulfuric, nitric, and other acids. The area around the enterprise is divided into two major landscape-geochemical systems—the Argunsk (dry mountain steppe) and the Urulyungui (broad intermountain valleys). The terrain in the Argunsk area represents both a source and a transit pathway for flows of substances. They are characterized by a near-neutral, weakly alkaline geochemical environment (pH > 6) and weakly evident vertical and lateral geochemical barriers.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings The Urulyungui zone is an area where substances coming down from the mountain massifs accumulate, with some passing through in transit and some being accumulated. Substantial differentiation is noted in the geochemical conditions for migration in both the vertical and the lateral directions, leading to the formation of a wide spectrum of highly absorbent geochemical barriers (restorative hydrogen sulfide and gley types, as well as evaporative and biogeochemical). The mountainous part of the area is the site of numerous mining industry facilities that are sources of environmental contamination in varying degrees. From an environmental standpoint, the most hazardous among them is the system of tailings repositories at the ore processing complex, which is located in a mountain valley in the northeastern part of the ore field. The repositories contain 30 million metric tons of accumulated solid wastes and 12 million cubic meters of liquid phase wastes, with both varieties containing uranium and its decay products as well as a number of toxic chemical substances. These contaminants move into the surrounding landscape as they are carried by the wind from the repository surface and as liquid wastes components leak through the bottom of their holding vessels. Anomalous multielement concentrations of the contaminants have been found in the landscapes surrounding the tailings repositories. In contrast, in cases where pollutants have found their way into groundwater, they have formed plumes of contamination affecting significantly larger areas. The main pathway by which contaminants are transferred by groundwater runs away from the tailings repositories and toward the Sukhoi Urulyungui Valley. Therefore, there is a real threat of radiation and chemical contamination of groundwater in the Urulyungui Valley, the source of drinking water for the city of Krasnokamensk. The developing situation requires that the appropriate environmental protection measures be taken. CONCLUSION In carrying out radioecological studies in regions where Russia’s major nuclear and radiation facilities are located, IGEM specialists for the first time used a new landscape-geochemical method for environmental research developed at IGEM. The studies conducted using this method in the zones affected by five major nuclear and radiation enterprises produced the following results in the first stage of research: Detailed studies were made of the morphological, soil-geochemical, and physical-chemical characteristics of the natural landscapes in the areas where the enterprises are located, including in the tundra, forest, forest-steppe, and steppe landscape zones of Russia. Elementary geochemical landscapes were also identified and characterized in each region.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings The primary types of lateral and vertical migration of natural and technogenic radionuclides were identified and studied in each of the types of geochemical landscapes studied. The main natural and technogenic geochemical barriers hindering the spread of technogenic contamination were determined. An evaluation was made of the degree to which radioactive and stable contaminants arising in the course of operations by nuclear and radiation enterprises affect the environment in the areas where these enterprises are located. Methods were developed for small-, medium-, and large-scale radio-ecological mapping applicable to various landscape-geochemical and geological-geomorphological situations. By analyzing the results obtained, it is possible to draw the general conclusion that the radiation ecology situation in the regions where the Nerpa Ship Repair Plant and the Smolensk and Balakovo nuclear power plants operate meets current safety requirements. Meanwhile, in the regions where the PMCPA and the Mayak Production Association are located, there are areas where the natural landscapes have been subjected to radiation and chemical contamination. In the area around the Priargunsk facility, the greatest radioecological danger is presented by the repository for the liquid and solid wastes produced by the operations of the molybdenum-uranium ore processing plant and the sulfuric acid production plant. The toxic substances included in these wastes have contaminated the soils, subsoil rock, surface water, and groundwater in the zone affected by the repository. Migration of the water threatens the radiation and chemical contamination of underground sources from which drinking water is drawn. The wide-ranging plumes of intensive radioactive contamination of the soil cover in the Mayak area (the East Urals Radioactive Trace and the Techa River Valley) were formed in the early stage of activities at the enterprise. During the existence of the East Urals Trace, the contours of this radioactive anomaly have undergone substantial changes. At the same time, lateral migration of radionuclides has been observed in the Techa River Valley caused by the washing out of contaminants from the soil and bottom sediments by flood waters, which have carried the toxic substances into the transitory river systems.