FIG. 9.29. Density contours of 137Cs on the bottom sediments of the Kiev reservoir: (a) before a flood; (b) after an average flood; and (c) after a high flood (contour of ‘1’ corresponds to 37 kBq/m2 or 10–6 Ci/m2).
9.4.URANIUM PROCESSING SITES IN UKRAINE
Uranium ores have been processed in Ukraine for over 50 years. Estimates of the quantity of waste generated from these activities vary (because of mixing of radioactive and non-radioactive waste at some sites); however, the latest official figure [9.40] is that there are 65.5 × 106 t of uranium tailings with a total activity of 4.4 PBq (120 000 Ci). The total area of tailings impoundments is 542 ha.
An overview of uranium mining and ore processing in Ukraine with an emphasis on radiological and environmental impacts is presented in
Section 6. There are two main processing sites, the Prydniprovsky chemical plant at Dniprodzerzhinsk, which was shut down in 1991, and the hydrometallurgical plant at Zhovti Vody, which is still in operation. In addition, there are several mining sites where ores were or are being mined.
In the early years of uranium mining and ore processing, little attention was paid to the environmental impact of operations or the management of tailings. Consequently, tailings were often deposited in inappropriate locations and were not properly rehabilitated upon closure of the site.
Recently, guidance has been provided by the IAEA on the management of radioactive waste
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FIG. 9.30. Lateral–longitudinal distribution of 137Cs (pCi/L) in solution in the upper layer of the Kiev reservoir (a) and vertical– longitudinal distribution of 137Cs (pCi/L) on suspended sediments during peak discharge (Q = 3000 m3/s) of an average flood
(b). (Note: 1 pCi/L = 0.037 Bq/L.)
FIG. 9.31. Lateral–longitudinal distribution of 137Cs (pCi/L) in solution in the upper layer of the Kiev reservoir (a) and vertical– longitudinal distribution of 137Cs (pCi/L) on suspended sediments during peak discharge (Q = 9000 m3/s) of a high flood (b). (Note: 1 pCi/L = 0.037 Bq/L.)
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from the mining and milling of ores [9.41]. The guide applies primarily to new facilities, although review of existing facilities against the guidelines is recommended:
(a)The strategy for management of waste should be consistent with the principles of radioactive waste management [9.2]. Two of these principles are the most appropriate to long lived radioactive waste such as uranium tailings. These are Principle 4 (Protection of Future Generations) and Principle 5 (Burden on Future Generations).
(b)Access to and dispersion of tailings needs to be restricted for long periods into the future. For this reason, tailings structures should have high stability against floods, erosion and earthquakes.
(c)Disposal of waste below ground level generally provides a higher degree of protection against surface erosion and human intrusion and requires less maintenance.
(d)Engineering controls may fail because of natural processes such as erosion. Such events are probabilistic in nature. Due attention needs to be given to the probability of the event occurring and to its likely impact on the integrity of the disposal system.
(e)Financial mechanisms should ideally be put in place so that the requirements for closure and post-closure monitoring can be met.
(f)Waste management structures should be closed when they are no longer needed, and to the maximum extent possible while operations are still continuing.
(g)Safety assessments should be carried out to cover the operational, closure and postclosure phases of the facility. These assessments should consider all significant scenarios and pathways by which workers, the public and the environment may be subject to radiological and non-radiological hazards.
(h)Radiological protection should be optimized so that doses are ALARA.
The project team visited the Prydniprovsky chemical plant and inspected several of the tailings sites in the area. Discussions were also held with technical experts on both operational and administrative aspects of the operations. No visits were made to Zhovti Vody or the uranium mines and so, for these sites, reliance was placed on information available in the open literature.
There appears to be only very limited information on the radionuclide levels in the environment in the vicinity of the Prydniprovsky chemical plant or the industrial sites at Zhovti Vody. Some information is presented in Section 6 on elevated levels of some radionuclides in the seepage, runoff and local rivers. Levels in rivers are generally below the maximum permissible levels in drinking water. Section 8 gives a few estimates of dose based on a limited consideration of pathways. Clearly there is a need for a comprehensive analysis based on more extensive monitoring data and consideration of all pathways, including airborne exposures (radon and daughters), foodstuffs (especially fish), drinking water and external radiation.
The Prydniprovsky chemical plant is part of a very large chemical complex that consists of chemical, nuclear and metallurgical plants bordering on the shores of the Dnieper River (see Section 6, Fig. 6.3). Some of the plants are still in operation, while others have closed down, leaving the equipment and other facilities in a state of neglect. The Prydniprovsky chemical plant site needs to be assessed holistically in order to understand the respective contributions of the facilities to pollution of the Dnieper River basin and the effects of interactions between the major waste storage areas. Essentially there needs to be an overall plan for the site, which will include rehabilitation of sites along with possible further industrial development.
At Zhovti Vody, countermeasures have been carried out at some mines and tailings impoundment sites. The large KBZh tailings site, which contains 19 × 106 t of radioactive waste, has been partly rehabilitated, but restoration is still incomplete because of financial problems.
The project team considers that tailings are the main problem at the Dniprodzerzhinsk and Zhovti Vody sites due to the potential for environmental and human health impacts over many generations. The main radionuclides in the tailings, 230Th (half-life 80 000 years) and 226Ra (half-life 1600 years), affect the overall radioactivity in the tailings. Consequently, there will be little decline in radioactivity for thousands of years. Although remedial works have been carried out at a few locations, most of the tailings are in an unsatisfactory condition.
Tailings are deposited at a number of unsatisfactory locations within the Prydniprovsky chemical plant. The most substantial waste pile is at the
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tailings D site, which contains about 1.5 PBq of radionuclides. The tailings are covered with phosphogypsum, a fine powdery waste from the fertilizer industry, to variable thicknesses (see Fig. 9.32). The banks of the tailings D pile are steep and on two sides drop away to the Konoplyanka River, which is a small waterway that flows into the Dnieper River (see Section 6, Figs 6.3 and 6.4). Preliminary estimates were given in Section 6 of releases of radionuclides to the Konoplyanka River via surface and seepage, but such estimates need to be refined by more specialized studies. The potential for erosion of this tailings pile over time appears high and needs to be assessed further.
Recent assessments of the Sukachevskoe tailings C site (see Fig. 6.3 for location) and, in particular, its dried up beaches, suggest that this site could be a significant source of secondary contamination because of dispersion of contaminated phosphogypsum by wind. The Ecological Inspection of the Dnipropetrovsk region has reported contamination of agricultural products grown on the surrounding farming area near the villages of Taromskoe and Sukachevka. Further work is needed to assess the significance of this contamination.
The project team, having regard for the IAEA guidelines and, in particular, Principles 4 and 5 of Ref. [9.2], concludes that the Dniprodzerzhinsk site and the waste storage areas at Zhovti Vody are hot spots.
Safety assessments need to be undertaken at these facilities and submitted to the national regulatory authority. In considering appropriate countermeasures, the following guidance from the IAEA should be considered [9.2]:
(a)When existing waste management facilities cannot meet the post-closure risk constraints or dose constraints, efforts should be made to minimize risk and dose to what is reasonably achievable. In judging what is reasonably achievable in such cases, the dose at which
intervention would be considered today is an appropriate benchmark. This is around
10 mSv/a.
(b)The option of relocating tailings to a more favourable site for closure would not normally provide the optimum strategy because of the large volumes of waste to be moved.
(c)If the cost associated with different options is the main factor for consideration, then a quantitative cost–benefit analysis may be
used. Such an analysis should consider the time period over which radiation doses and other impacts are to be integrated, spatial cutoff points and the monetary value of averting a unit of collective dose.
9.5.WASTE STORAGE/DISPOSAL FACILITIES
The following waste storage facilities were considered as potential local hot spots:
(a)The Ecores facility near Minsk;
(b)RADON type radioactive waste storage sites at Kiev and Dnipropetrovsk;
(c)Waste storage facilities at nuclear power plants.
Technical information on these facilities is presented in Section 7.
9.5.1.Ecores facility
The Ecores facility comprises two closed trenches and two repositories that are being progressively filled. It accepts radioactive waste from the nearby Sosny Institute and from more than 100 organizations from the industrial, research and medical sectors. The facility is 2 km from the Slouch River and within the Dnieper River basin, but remote from the Dnieper River. This facility is below the current international standards for the engineered disposal of low and intermediate level waste. The project team considers Ecores to be a potential hot spot with a possible medium impact at the local level. Reconstruction of Ecores is in progress and this will reduce the potential for human exposure and environmental impact.
9.5.2.RADON radioactive waste storage sites in Ukraine
Information on the RADON radioactive waste storage sites in Kiev and Dnipropetrovsk is provided in Section 7. These facilities contain large quantities of radioactive waste, including spent radiation sources and tritium bearing liquids and gases. Tritium has leaked from the Kiev radioactive waste storage site towards the Vita River, but concentrations in surface waters are below the maximum permissible levels for drinking water.
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