1.6.RADIOACTIVE WASTE STORAGE AND DISPOSAL SITES

Radioactive waste disposal sites in the Dnieper River basin include:

(a)The Ecores State facility near Minsk, which comprises two closed trenches and two repositories that are being progressively filled. This facility accepts radioactive waste from the nearby Institute of Radiation Physics and Chemistry Problems, National Academy of Sciences of Belarus (Sosny), and from more than 100 organizations from the industrial, research and medical sectors. The facility is 2 km from the Slouch River; the nearest pond is 1.6 km away. This facility is below current international standards for engineered disposal of low and intermediate level waste. However, the repository is remote from the Dnieper River and any environmental impact in the future will be localized.

(b)Two disposal sites operated by the RADON State enterprise at Kiev and Dnipropetrovsk. These sites handle both radioactive waste and spent radiation sources from the non-nuclear power plant sector, including the industrial, medical and agricultural sectors.

(c)Many disposal or ‘temporary’ storage sites in Belarus and Ukraine for waste from the Chernobyl nuclear power plant. The largest of these is the Buriakovka repository, which consists of 30 trenches with a 1 m thick bottom isolation clay.

These facilities have the potential for moderate impact within the local area. There are no significant radioactive waste disposal sites in the Russian section of the Dnieper River basin.

Waste storage sites are not considered to have a major impact because of the high degree of engineered containment. However, most radioactive waste storage sites at nuclear power plants are close to capacity.

1.7. NON-POWER SOURCES

Non-power sources include research reactors and those arising from the application of radioisotopes and radiation in medicine, industry and research.

The research reactors at the Sosny Institute near Minsk and the Institute for Nuclear Research at Kiev are shut down. The decommissioning of these reactors will be a significant source of radioactive waste. However, in their current state they do not directly impact on the environment.

Disused radiation sources are a potential source of exposure if not properly managed. They are often very intense sources of radiation, and in the past poor management has resulted in high exposures of individuals in several countries. Regulatory authorities need to maintain a register of sources and ensure that they are properly licensed and managed.

Overall, non-power sources have a limited and localized impact on the environment and public health.

1.8.HUMAN RADIATION EXPOSURE FROM ENVIRONMENTAL SOURCES

Exposure to radiation at low doses, which is typical for public exposure from environmental sources, can cause stochastic detrimental health effects (i.e. malignancies and hereditary effects). The fundamental quantity used in radiation protection to characterize the level of human exposure associated with stochastic health effects is the ‘effective dose’. The unit of effective dose is the sievert (Sv), but the smaller unit of millisievert (mSv) is more appropriate for normal exposures.

The worldwide level of annual natural background exposure, including external exposure, consumption of food and water containing natural radionuclides, and inhalation of radon with its daughter products, amounts on average to 2.4 mSv, with a range from 1 to 10 mSv. In Ukraine the mean background exposure is about 2.5 mSv, which is in line with worldwide levels.

The internationally recommended annual dose limit for controlled exposures of the general public is equal to 1 mSv. For prolonged exposure situations from all environmental radioactive sources, including natural and human-made sources, the International Commission on Radiological Protection (ICRP) recently recommended a generic intervention level of existing annual dose equal to 10 mSv as the level below which intervention is unjustified, taking into account radiological, economic and social factors.

Radiation exposure of the population of the Dnieper River basin is caused by both naturally

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occurring radionuclides and human-made radionuclides, mainly nuclear fission products (137Cs, 90Sr and some others). The pathways of long term environmental human exposure include external exposure with gamma radiation and internal exposure via ingestion of contaminated food and drinking water as well as inhalation of airborne radionuclides.

Whereas natural radiation accompanies the whole human history, significant environmental contamination with human-made radionuclides occurred during two time periods: first in the 1950s and 1960s as a result of global stratospheric fallout from worldwide nuclear weapons tests and later in 1986 when a large radioactive release occurred directly into the Dnieper River basin due to the Chernobyl accident. Local contamination of the Dnieper River basin in 1986 led to the highest population doses caused by the Chernobyl accident in Europe.

In the long term after the Chernobyl accident, the inhabitants of areas contaminated with radionuclides in 1986 are still subjected both to external exposure from 137Cs gamma radiation and to internal exposure due to consumption of local foodstuffs containing 137Cs and, to a lesser extent, 90Sr. Inhalation of plutonium radionuclides and 241Am does not significantly contribute to human doses. In accordance with the environmental behaviour of 137Cs and 90Sr, external exposure prevails in areas with dominantly black soils, and the contribution of internal exposure to the total (external and internal) dose does not exceed 10%. In contrast, in areas with light sandy soils, the contributions due to internal and external exposure are comparable, and, in areas with peaty soils, the internal exposure dominates. At present, along with consumption of local agricultural vegetable and animal (milk and meat) foods, consumption of natural foods (lake fish, forest mushrooms and berries, game), which is typical for the Dnieper River basin population, significantly contributes (up to 50–70%) to 137Cs intake in the human body and the associated internal dose.

After 1995, average total annual doses of inhabitants of settlements located in the Chernobyl accident areas, caused by environmental 137Cs and 90Sr, ranged from 0.1 to about 5 mSv; the contribution of 90Sr being usually below 5%. The inhabitants of the settlements of the Gomel and Mogilev regions of Belarus and the Bryansk region of the Russian Federation, where 137Cs soil

contamination exceeds 1 MBq/m2, are subjected to the highest exposure levels. In many tens of settlements, the average annual exposure level still exceeds the national action level of 1 mSv.

The contribution of freshwater pathways to public exposure is dependent on the direct consumption of water and fish containing radionuclides as well as on the flooding of land used for livestock grazing/haymaking and utilization of river water for irrigation of agricultural land, which leads to subsequent human exposure via terrestrial pathways. In the lower Dnieper River reaches, which were not subjected to direct radionuclide contamination in 1986, almost all the Chernobyl exposures are attributed to water pathways; however, the dose itself is very low. In most of the directly Chernobyl contaminated areas the human dose is much higher (see previous paragraph), but it is mostly attributable to terrestrial pathways.

The exception is a number of ‘closed’ lakes (without a regular outflow) located in peaty areas, in which the concentration of 137Cs (and to a lesser extent of 90Sr) in water and fish is much higher than in the nearest rivers. These concentrations do not significantly decrease with time, and in many lakes still exceed the permissible levels for drinking water and especially for fish. The consumption of contaminated fish prevails as the pathway of internal exposure of the inhabitants of the nearest settlements. In some of these settlements the average annual human dose exceeds 1 mSv, and therefore closed lakes and their inhabited surroundings are considered in this report as actual local hot spots.

Another source of internal exposure of the inhabitants of some Ukrainian riparian settlements via consumption of river water and fish is the release of uranium radionuclides and their daughter products from mining and milling facilities located in the Dnipropetrovsk region. Significantly elevated levels of 234U, 238U and 210Po in water have recently been detected in rivers downstream of Zhovti Vody and of the uranium tailings dumps of the Prydniprovsky chemical plant. For people drinking water from contaminated rivers, an associated annual internal dose of the order of 0.1 mSv has been estimated. However, there are insufficient data from other pathways (contaminated food, radon, etc.) to determine the total exposure of individuals living in these areas. As the uranium concentration in river water approaches or could approach the national action level, both sites are identified as local hot spots.

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1.9.ANALYSIS OF HOT SPOTS AND POSSIBLE ACCIDENTS

Following the UNDP Hot Spots Workshop in Kiev, the following definitions, which take account of radiation protection methodology, were proposed.

Hot spot. A technical facility, object or local natural site that is contaminated with radionuclides or, in the future, could become a source of environmental radioactive contamination above reference levels or could result in human or biota exposure above radiological criteria.

Transboundary hot spot. A hot spot that is, or in the future could become, a source of environmental radioactive contamination above reference levels or could result in human or biota exposure above radiological criteria on the territory of another country.

National hot spot. A hot spot that occupies, or in the future could occupy, a substantial national territory and that has no significant transboundary impacts.

Local hot spot. A hot spot that occupies a local area.

Initially, the group made a list of candidate hot spots. A screening process was then applied, based on the above criteria, to determine the final list as follows.

Actual hot spots:

(a)The Pripyat floodplain area within the CEZ. This is assessed to be a transboundary hot spot with a current impact and a greater impact during times of high flooding.

(b)The radioactive waste dumps on the former Prydniprovsky chemical plant site in Dniprodzerzhinsk and of the uranium processing operation in Zhovti Vody. These are actual national hot spots with a potential for a major impact over a very long period if impoundment structures erode or fail catastrophically.

(c)Inhabited areas in the three countries with high levels of Chernobyl caused radioactive contamination, including closed lakes in which concentrations of 137Cs in fish or drinking water exceed the permissible levels. These are local hot spots but occur in all three countries.

Potential hot spots:

(i)The Chernobyl shelter in the event of its collapse (transboundary hot spot);

(ii)The Chernobyl cooling pond in the event of dam failure (national hot spot).

(iii)The Ecores and RADON facilities at Kiev and Dnipropetrovsk, until reconstruction is complete (local hot spots).

Possible accidents: in addition to these actual and potential hot spots, an accident at a nuclear power plant was considered. A major accident at a nuclear power plant is considered to be of very low probability, having regard for major and ongoing improvements at nuclear power plants in the Russian Federation and Ukraine. However, a large release would have considerable transboundary impacts, especially in the Black Sea if the source were in the south of Ukraine.

1.10. CONCLUSIONS

1.10.1. Chernobyl affected areas

(1)High levels of radioactivity remain within the CEZ. Important hot spots within this zone are the floodplain along the Pripyat River, the Chernobyl nuclear power plant cooling pond and the Chernobyl shelter.

(2)There is still transboundary transfer of radionuclides (mainly 90Sr) by rivers within the Dnieper River basin. The most important source is the floodplain of the Pripyat River within the CEZ.

(3)The concentrations of 137Cs and 90Sr in river waters of the Dnieper River basin have decreased significantly and are now below the maximum permissible levels set by the national authorities and recommended by expert international organizations. Almost all the 137Cs washed out of contaminated areas is immobilized in bottom sediments within the reservoirs of the Dnieper River. The impact of these sediments is low and will decline further with decay and further deposition of sediments on top of the contaminated sediments.

(4)Lakes with no regular outflows still present a radiological problem arising from higher levels of 137Cs in water and fish.

(5)The levels of radioactivity in forest foods (wild game, mushrooms, berries) in some Chernobyl affected areas are above permissible levels, as are those in milk and beef produced by cattle grazing on contaminated floodplains.

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1.10.2. Nuclear power plants

(6)Routine discharges from nuclear power plants in the Russian Federation and Ukraine are generally well below authorized limits and do not contribute to significant contamination of the environment.

(7)A legislative and regulatory basis established in both the Russian Federation and Ukraine ensures that all nuclear power plants operate with a valid licence. A legal mechanism exists for regulatory body review and assessment of plant safety and renewal of plant licences on a regular basis.

(8)In recent years the safety of RBMK and WWER reactors has been subject to considerable regulatory and international scrutiny. Major engineering upgrades have been undertaken to improve safety. An international in-depth safety assessment process is under way to optimize the improvement programmes. There is room for improvement in emergency preparedness and response.

1.10.3. Uranium mining and milling

(9)Uranium mining and milling in Ukraine has had a negative impact on the environment. The most serious problem is caused by about 100 × 106 t of tailings and other radioactive waste from past and current operations. Most of the tailings dumps have not been properly rehabilitated and will pose a long term problem unless they are properly stabilized. Tailings D at Dniprodzerzhinsk is considered to have the greatest potential for pollution of the environment because of its proximity to the Dnieper River, the evidence of current seepage and the possibility of catastrophic failure of the impoundment. The situation in the region of tailings C and adjacent to it needs regular control, and decisions on further use should be taken with regard to IAEA recommendations and on the basis of a cost– benefit analysis.

(10)There is a paucity of data on the levels of radionuclides in the vicinity of uranium mines and mills and radioactive waste impoundments. Consequently, it is not possible to estimate the current or future dose rates from these sources with any degree of accuracy.

(11)There is a need to urgently start the development of modern standards on the

protection of the environment, radiation safety and monitoring in the zone of influence of the uranium sites, consistent with the requirements of Ukrainian law and the recommendations of international organizations such as the IAEA.

1.10.4. Other radiological sources

(12)Medical and industrial uses of radioisotopes do not pose significant risks to the population of the Dnieper River basin. Radioactive sources with a high radioactivity could be a source of local exposure. Regulatory authorities should ensure that they are properly licensed and managed.

(13)There are many disposal or temporary storage sites for Chernobyl waste in Belarus, the Russian Federation and Ukraine. There is a need to continue to monitor and characterize the most hazardous of these sites; however, their impact appears to be quite localized and does not represent a major source of contamination of surface waters.

(14)There are two RADON type waste storage facilities at Kiev and Dnipropetrovsk in the Ukrainian section of the Dnieper River basin. Further safety assessments need to be undertaken to assess their environmental impact.

(15)The Ecores State facility near Minsk does not comply with international standards for the storage or disposal of radioactive waste. This facility is a potential source of radioactive contamination of the local population, but not of the Dnieper River basin as a whole.

1.10.5. Human exposure to radiation

(16) The average dose rate to Ukrainian citizens from natural radiation sources is about 2.5 mSv/a, which is close to the global average. This value is also considered to be a reasonable estimate of the average dose rate to the population of the Dnieper River basin as a whole.

(17)The inhabitants of areas contaminated with radionuclides from the Chernobyl accident in 1986 are still being subjected both to external exposure from 137Cs gamma radiation and to internal exposure due to consumption of local foodstuffs containing 137Cs and, to a lesser extent, 90Sr. The most important factors

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