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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings 12 Experience in Rehabilitating Contaminated Land and Bodies of Water Around the Mayak Production Association* Yu. V. Glagolenko, Ye. G. Drozhko, and S. I. Rovny, Mayak Production Association THE CREATION OF ENVIRONMENTAL PROBLEMS AT THE MAYAK PRODUCTION ASSOCIATION Since the moment of its creation in the late 1940s, the enterprise known today as the Mayak Production Association—Federal State Unitary Enterprise has faced scientific-technical and industrial tasks of unprecedented complexity in connection with its work on building nuclear weapons. Over the course of decades, the achievement of military-political goals pushed environmental protection questions into the background, which ultimately led to serious radioecological problems. The current radioecological situation in the region where Mayak is located arose as a result of the following factors: Discharges of liquid radioactive wastes into the open hydrographic system of the Techa River (1949-1956) The 1957 accident at a liquid radioactive waste holding tank, which resulted in the creation of the East Urals Radioactive Trace * Translated from the Russian by Kelly Robbins.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings The use of the V-9 (Karachai) and V-17 (Staroye Boloto) reservoirs for the storage of medium-level liquid radioactive wastes The creation of the man-made reservoirs of the Techa Cascade for the storage of low-level liquid radioactive wastes Windborne dispersal of radioactive sediments from the exposed shoreline of the Karachai Reservoir (1967) The fundamental problems associated with Mayak’s ongoing activities are linked to the use for technical purposes of eight industrial reservoirs at the enterprise to store liquid radioactive wastes accumulated as a result of defense program operations (see Figure 12-1). To ensure that thorough and comprehensive measures are taken to make Mayak’s production activities environmentally safe, a comprehensive plan has been developed to address environmental problems associated with the enterprise’s current and past operations. The essence of this effort lies in implementing the following four-part program: Reducing and ultimately halting discharges of all liquid radioactive wastes into industrial reservoirs Eliminating the most radiologically hazardous reservoirs—Karachai (V-9) and Staroye Boloto (V-17) Ensuring the safe operation of the Techa Cascade of reservoirs Reducing the volume and radioactivity level of the high-level wastes stored in holding tanks Each of these problems merits separate consideration. The problem of the Techa Cascade is of the highest social significance. ENSURING THE SAFE OPERATION OF THE TECHA CASCADE Problems associated with reservoir safety, particularly for the reservoirs of the Techa Cascade, have been substantially exacerbated by changes in climate conditions in the region. Since the early 1980s, the region has experienced wetter conditions (disparity between annual precipitation and evaporation from bodies of water), and as a result, water levels in most of the reservoirs, including those of the Techa Cascade, have approached regulatory maximums. For example, an analysis of water balance components for Reservoir V-11, the final reservoir in the cascade, indicates that the primary reason for the rise in its level since 1980 is the change in meteorological conditions in the region (see Table 12-1). Whereas from 1950 until the 1980s, the average level of evaporation in the Mayak region exceeded precipitation by 100 mm per year, the situation
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings FIGURE 12-1 Water supply and discharge system at Mayak.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings TABLE 12-1 Water Balance in the Techa Cascade Reservoirs, 1993-2006 Water Balance Component Change in Volume Million m3 % Total volume, Techa Cascade reservoirs as of January 1, 1993 300.64 — as of January 1, 2007 330.81 — Change in volume 30.17 5.4 Inputs: atmospheric precipitation 439.2 79.1 household and industrial wastewater discharges, storm drain runoff 83.4 15.0 discharges of low-level wastes 4.5 0.8 underground and surface flows from drainage basin 28.0 5.0 Total inputs 555.1 100 Outputs: surface evaporation 327.8 59.1 seepage from Techa Cascade reservoirs 197.1 35.5 Total outputs 524.9 94.6 was reversed from 1980 to 2006, when precipitation exceeded evaporation by an average of 90 mm per year. The situation in the Techa Cascade became extremely critical in 1999-2000, when the water level in Reservoir V-11 rose 1.2 m in 1.5 years. The recurrence of such a situation in the future cannot be ruled out. In the next 50 years, plans call for two main periods of rehabilitation of the Techa Cascade in the course of its operations: During the first period, which will last 6 to 8 years, volumes of liquid waste discharges into the reservoirs will be reduced, and the water balance in the Techa Cascade will be stabilized. During the second period, conditions are to be created for the long-term, controlled, and safe storage of the liquid wastes that have accumulated in the Techa Cascade reservoirs, and technical solutions and projects will be implemented to reduce water levels to acceptable standards. The rise of the water level in Reservoir V-11 will lead to increased infiltration of strontium-90 into the canals and ultimately into the Techa River (see Figure 12-2). Several measures were taken in 1999-2006 to stabilize the water level in the reservoirs of the Techa Cascade and reduce the influx of radioactive substances from the cascade into the Techa River system: The northern borehole water extraction system was put into operation, making it possible to remove up to 1.5 million m3 of groundwater from the Techa Cascade.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings FIGURE 12-2 Correlation between total infiltration of strontium-90 into the surface levels of the Techa River and water level in Reservoir V-11. The water control capabilities of the Right Bank Canal were restored by ridding it of ash washed into the canal from the Argayash power plant. The volume of ash extracted from the canal totals 15,000-17,000 m3 annually. The existing system of upland canals (Left Bank and Right Bank) in the Techa Cascade facilitates the transfer of surface and groundwater in the cascade’s catchment basin. Plans have been developed and work has been initiated to create a primary and comprehensive sewerage system to transfer decontaminated water into the open hydrographic network. Creation of such a system is the most significant measure in stabilizing the water level in Reservoir V-11. Completion of the project will make it possible to reduce the level of water flowing into the Techa Cascade by 3 million m3 per year. Measures have been taken to reduce discharges of liquid radioactive wastes. Efforts to reduce the input side of the water balance may be of little effect if increasingly wet conditions continue. Therefore, a great deal of attention is being devoted to improving the stability of Dam P-11, which is a key element in the system of hydrotechnical structures in the Techa Cascade that ensure the safe operation of the entire reservoir system. Built in 1964 based on a design by the Kuibyshev Branch of the Hydropro-
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings ject Institute, the dam at Reservoir V-11 (P-11) is of a low-pressure earthen-fill type. Dam P-11 was rehabilitated in 1975 and 1991, which made it possible to operate it right up to the 217.32 m mark. Exploration and testing of the physical-mechanical properties of the soils making up the body of the dam indicated the presence of weakened zones in the upper part of the structure. It was decided to install an additional antiseepage element deep within the body of the dam. The most effective measure for preventing infiltration and developing suffusion processes in the body of the dam is the creation of an antiseepage curtain, a “wall in the soil.” An antiseepage lock will be created in the central part of the dam by driving a series of metallic plates (Larsen plates) into the ground. Work to sink the foreshaft and experimental work to construct the wall-in-the-soil structural element itself were successfully completed in 2006. This year (2007), plans call for completing work to create the antiseepage curtain in the body of Dam P-11. Constructing such antiseepage elements will make it possible to operate Dam P-11 more safely and bring it up to first-class level with regard to static, seismic, and infiltration stability parameters. Most importantly, this will improve its operating capacity, that is, its normal level of resistance. Fundamental resolution of the Techa Cascade problem may be achieved only by selecting and implementing a plan for artificially lowering the water level in Reservoir V-11. One option that has not been implemented would be to create a complex for water purification and transfer of processed water from Reservoir V-11 into the Left Bank Canal. The enterprise has adopted and tested a membrane-sorption water purification system for Reservoir V-11 that would make it possible to discharge the purified water into the open hydrographic system. This system has processed more than 300 m3 of real water (with strontium-90 activity of 1,500 Bq/L). The purification coefficient achieved was more than 300, which meets requirements and radiation safety standards adopted in the Russian Federation. THE KARACHAI RESERVOIR (V-9) Taking Reservoir V-9 out of operation requires the complete cessation of its use as a receiving basin for liquid radioactive wastes. Basic data on this reservoir are presented in Table 12-2. After the decision was made to eliminate Reservoir V-9 and experimental work was carried out, planned efforts have proceeded since 1986 to drain and fill in this body of water as part of projects for eliminating and decommissioning the reservoir in the first, second, and third stages. Work to eliminate (decommission) the Karachai Reservoir is being carried out by filling in the basin with rock. In areas where highly radioactive technogenic sludge is found, special solid concrete blocks in reinforced sections are also put in place using specialized radiation-shielded equipment.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings TABLE 12-2 Basic Parameters of Reservoir V-9 Parameter Value Area, km2 0.11 Volume, million m3 0.4 Activity level, million Cia 120 Distribution of activity, % Water 5 Sediments 95 aActivity due to strontium-90 and cesium-137. The first stage of work entailed filling in the northeastern part of the reservoir and building a series of dams to divide the body of water into sections. Filling in the northeastern section made it possible to localize most of the radioactive technogenic sludge that had formed in the reservoir, which contained the bulk of the accumulated radioactivity. Completing this stage was the most complex part of the entire project, inasmuch as it involved working in conditions of extremely high levels of radiation with sediments constantly coming to the surface as dam fill was being laid. The successful filling of the northeastern section of the reservoir fundamentally improved the radiation situation in the area surrounding Reservoir V-9 and the radiochemical plant. This stage was successfully completed in 1990. As a result of this work, about 60 percent of mobile sediments by volume were locally contained, along with 70 percent of all radionuclides accumulated in the reservoir. Completion of work in the first phase of the project to eliminate Reservoir V-9 proved that all technical solutions adopted were well founded, demonstrated that the task in general could realistically be completed, and made it possible to move forward on efforts to fill in the entire reservoir. At present, hydrological conditions in the Karachai Reservoir basin have changed as a result of changes in meteorological conditions and the increased water levels of recent years. This situation has required the correction of design solutions and the development of a third phase in the project to decommission Reservoir V-9. These plans were completed by the All-Russian Design and Scientific-Research Institute of Comprehensive Energy Technology in 2004. The plans call for filling in the remaining part of the reservoir while simultaneously gradually stopping discharges of liquid radioactive wastes. This work should result in elimination of the reservoir and recultivation of the land, but long-term monitoring, control, and maintenance will be needed. From the standpoint of the Karachai Reservoir’s impact on the environment, groundwater contamination remains a rather pressing problem. Forecasts of how the situation may develop over a fairly long period (300 years) indicate that in the future there will be practically no radiologically significant discharge of contaminated groundwater into the open hydrographic network.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings STAROYE BOLOTO RESERVOIR (V-17) Eliminating the Staroye Boloto Reservoir (V-17, described in Table 12-3) will involve use of the fill-in technology tested and used in the closure of Reservoir V-9. Furthermore, experimental work on covering over sediments was carried out at Reservoir V-17 in 2004-2005, which made it possible to confirm basic technical solutions involved in reservoir decommissioning. After the completion of work to fill in the reservoir, the existing radioactive waste storage site will be operated as a near-surface solid radioactive waste burial site. TABLE 12-3 Basic Parameters of Reservoir V-17 Parameter Value Area, km2 0.13 Volume, million m3 0.36 Activity level, million Cia 1.2 Distribution of activity, % Water 0.5 Sediments 99.5 aActivity due to strontium-90 and cesium-137. REDUCING DISCHARGES INTO INDUSTRIAL RESERVOIRS THROUGH ORGANIZATIONAL-TECHNICAL MEASURES AND WATER USE OPTIMIZATION With the aim of gradually reducing discharges, organizational-technical measures were carried out before the unit for cleaning and solidifying liquid radioactive wastes began operation. These measures made it possible to reduce discharges of medium-level radioactive wastes into Reservoirs V-9 and V-17 by 2,260 m3, of low-level technological wastes into the Techa Cascade by 73,000 m3, and of low-level nontechnological wastes by 410,000 m3. Further discharge reductions are possible only by optimizing technological processes at the enterprise. To achieve this goal, plans call for modernizing certain process stages and equipment and partially replacing the outdated technology. As a result of a number of scientific-practical and experimental design efforts, the two most promising technological plans were selected for optimizing spent fuel reprocessing. The plans chosen do not contradict the existing technology, but take into account its geography and the existing equipment and technological linkages among the various production divisions at the plant. They also make it possible to reduce the volume of medium-level radioactive waste created during spent fuel reprocessing by about half.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings LIQUID RADIOACTIVE WASTE REPROCESSING Completely eliminating discharges into special reservoir-repositories as part of plant modernization requires creating a unit to reprocess liquid wastes. Management of High-Level Radioactive Wastes Since 1987, Mayak has reprocessed high-level radioactive wastes in direct electric heating furnaces using a technology that turns the wastes into sodium aluminum phosphate glass using an EP-500–type furnace. While the complex has been in operation, it has reprocessed 20,000 m3 of high-level wastes with a total activity of more than 460 million Ci of β-emitting radionuclides, and more than 4,000 metric tons of glass has been produced. The storage facility is 59 percent full. The complex is processing a wide range of wastes from current production operations as well as some that accumulated previously. Waste processing volumes are presented in Table 12-4. TABLE 12-4 Quantity of Wastes Reprocessed Volume of Liquid Wastes Processed, m3 Quantity of Radionuclides Processed, kCi Quantity of Glass Produced, metric tons α Emitters β Emitters 20,000 5,830 458,400 4,139 Before the creation of new-generation remote furnaces, the primary method of reprocessing and solidifying high-level wastes remains their vitrification in direct heating EP-500–type furnaces. In 2006, construction was completed on the EP-500/4 furnace and the unit was put into operation. The expected service life of the furnace will end in 2009; therefore, to ensure that the technological process for high-level waste reprocessing is uninterrupted and to provide for the storage of the vitrified wastes, appropriate plans have been made to create the next in the series of electric furnaces. Management of Medium-Level Wastes At present, medium-level radioactive wastes that are created are discharged into industrial reservoirs V-9 and V-17; therefore, the problem of taking the reservoirs out of operation and decommissioning them is directly linked with the problem of halting the discharge of medium-level wastes into them. In 2006 the All-Russian Design and Scientific-Research Institute of Comprehensive Energy Technology developed the design for a medium-level radioactive waste cementing complex at the radiochemical plant (“Creation of a Complex for
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings Cementing Liquid and Heterogeneous Medium-Level Wastes”). The design plans identify a technological setup for medium-level waste reprocessing, including a standardization of the entire range of medium-level wastes, single-stage steaming of solutions, and cementing and burial in a near-surface–type repository using sectional-poured concrete technology. Management of Accumulated High-Level Wastes During the years of operation of Mayak’s radiochemical plants, more than 29,000 m3 of high-level liquid wastes with a total activity of 366 million Ci were accumulated in repository vessels. These wastes included the following: Aluminum, chromium, and iron hydroxide pulps and nickel ferrocyanide created after the purification of alkaline decantates in the acetate precipitation technology for the separation of weapons-grade plutonium Complex salt nitrate solutions, primarily refined products formed as a result of extraction processing of weapons-grade plutonium The storage of highly active suspensions and solutions in steel storage vessels is seen as one stage in waste reprocessing that reduces their activity as a result of the radioactive decay of short-lived radionuclides. The wastes can be subsequently reprocessed at reduced cost and effort. The duration of storage is determined by the expected service life of the storage vessels. For the first vessels, which were put into use in 1968, this period ends in 2018, which means that these wastes need to be moved into safer conditions. Currently existing high-level waste management practices at the enterprise’s radiochemical plant RT-1 involve vitrifying a mixture of radionuclides and accompanying stable chemical additives and then holding the glass blocks for temporary controlled storage in a special repository. However, such an approach is ineffective for accumulated high-level wastes, inasmuch as it is substantially complicated by well-known shortcomings in the direct vitrification method for the following reasons: Large volumes of ballast material (salts) are subject to vitrification along with radionuclides. The number of macrocomponents in the accumulated high-level wastes has a negative impact on the parameters of the vitrification process. These shortcomings may be eliminated by implementing a promising method for high-level waste reprocessing that calls for the preliminary separation of certain fractions of active components from the ballast mass of the radioactive wastes, which makes it possible to solidify the latter using cheaper methods such as cementing.
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Cleaning Up Sites Contaminated with Radioactive Materials: International Workshop Proceedings In summary, following are the enterprise’s top priority problems in resolving environmental problems: Ensuring safe operation of the special industrial reservoirs Reducing water balance inputs at the special industrial reservoirs Improving the stability of Dam P-11 Modernizing the radiochemical plant to reduce the amount of liquid radioactive wastes that it creates Creating a new phase of the high-level waste vitrification complex Creating a complex for cementing medium-level wastes so that discharges of medium-level liquid wastes into reservoirs V-9 and V-17 may be completely halted Carrying out work to remove reservoirs V-9 and V-17 from operation and rehabilitate their sites Developing technology to put previously accumulated high-level wastes into a form safe for long-term storage Accomplishing these objectives will facilitate a significant reduction in the environmental impact of Mayak’s ongoing production operations and will minimize the effect of factors created by the enterprise’s previous activities.