[Prospects of systemic radioecology in solving innovative tasks of nuclear power engineering].

A need of systemic radioecological studies in the strategy developed by the atomic industry in Russia in the XXI century has been justified. The priorities in the radioecology of nuclear power engineering of natural safety associated with the development of the radiation-migration equivalence concept, comparative evaluation of innovative nuclear technologies and forecasting methods of various emergencies have been identified. Also described is an algorithm for the integrated solution of these tasks that includes elaboration of methodological approaches, methods and software allowing dose burdens to humans and biota to be estimated. The rationale of using radioecological risks for the analysis of uncertainties in the environmental contamination impacts,at different stages of the existing and innovative nuclear fuel cycles is shown.

[Statistical prediction of radioactive contamination impacts on agricultural pasture lands].

Based on the literature data analysis, the rationale is given for the use of probabilistic approaches to solve the problems of estimation of a long-lived radionuclide uptake in animal products. Methods for statistical prediction of radioactive contamination consequences for agricultural pasture lands have been devised and implemented in the form of models and program modules. These offer the estimation of radionuclide transfer between the links of an agricultural chain, taking into account variability in the migration parameters, estimation of soil contamination limits based on the preset risk levels for the stuffs produced and statistical coordination of standards. An illustration is given of the application of the above methods using statistical characteristics of 137Cs migration parameters in the soil-plant-animal produce chain. Further trends have been formulated in the development of the risk concept as applied to the assessment of radioecological situations of radioactive contamination of the agricultural land.

[Probabilistic assessment of radionuclide accumulation in agricultural products and permissible levels of soil radioactive contamination].

A number of models have been developed to assess the risks of radionuclide accumulation in agricultural products and to determine the permissible levels of soil radioactive contamination. The proposed approach takes into account uncertainties of some parameters that describe the radionuclide content in different links of food chains. The models are implemented in the form of software for on-line computations. The validity of applying the probabilistic methods for assessing the impacts of radioactive fallout as compared with the deterministic ones is demonstrated on some specific examples. A universal nature of the dependence between the risks of radionuclide content in products and the density of soil contamination is shown. Contamination limits of the agricultural land are found to vary significantly as a function of the risk size. Directions for further research are defined within the framework of this research.

[Ranking of radionuclides and pathways according to their contribution to the dose burden to the population resulting from NPP releases].

Approaches are described towards estimating the consequences of radioactive contamination of ecosystems by nuclear fuel cycle enterprises with the rationale for the optimal specification level for nuclear power plants (NPP) operating in the normal mode. Calculations are made based on the initial data of the IAEA project, INPRO ENV, dealing with the ranking of radionuclides escaping to the environment from the operating NPPs. Influence of various factors on rankings of radionuclides and pathways of public exposure is demon- strated. An important factor is the controlled radionuclide composition of atmospheric NPP releases. It has been found that variation in the dose coefficients for some radionuclides leads to significant changes not only in the ranking results but also in the estimates of total dose burdens. Invariability is shown of the estimation concerning the greatest contribution of the peroral route to the population dose of irradiation in the situation considered. A conclusion was drawn on the need of taking into consideration uncertainties of different factors when comparing effects on the environment from enterprises of conventional and innovative nuclear fuel cycles.

Effects of chronic exposure in populations of Koeleria gracilis Pers. from the Semipalatinsk nuclear test site, Kazakhstan.

Morphological and cytogenetic abnormalities were examined in crested hairgrass (Koeleria gracilis Pers.) populations inhabiting the Semipalatinsk nuclear test site (STS), Kazakhstan. Sampling of biological material and soil was carried out during 3 years (2005-2007) at 4 sites within the STS. Activity concentrations of 10 radionuclides and 8 heavy metals content in soils were measured. Doses absorbed by plants were estimated and varied, depending on the plot, from 4 up to 265 mGy/y. The frequency of cytogenetic alterations in apical meristem of germinated seeds from the highly contaminated plot significantly exceeded the level observed at other plots with lower levels of radioactive contamination during all three years of the study. A significant excess of chromosome aberrations, typical for radiation exposure, as well as a dependence of the frequency of these types of mutations on dose absorbed by plants were revealed. The results indicate the role radioactive contamination plays in the occurrence of cytogenetic effects. However, no radiation-dependent morphological alterations were detected in the progeny of the exposed populations. Given that the crested hairgrass populations have occupied the radioactively contaminated plots for some 50 years, adaptation to the radiation stress was not evident. The findings obtained were in agreement with the benchmark values proposed in the FASSET and ERICA projects to restrict radiation impacts on biota.

[System radioecology: modeling of ecological processes and radiation risk assessment].

The background and tasks have been formulated of system radioecology as an separate branch of radiation ecology based on the use of a system analysis and mathematical modeling. The need is justified for developing methods of this scientific discipline to assess radiation resistance of natural systems and radioecological risks. Some specific examples are demonstrated of the application of different approaches when analyzing functioning of forest biogeocenoses after acute irradiation and studying impacts of radioactive contamination of meadow ecosystems on humans and biota. Trends of further studies are outlined and focused on the improvement of system radioecology methods combined within the integrated methodology framework.

[Genetic variability in Scots pine populations from the Bryansk region contaminated by radioactive pollutants as a result of the Chernobyl NPP accident].

The method of isozymic analysis of megagametophytes is used for an estimation of genetic variability in populations of Scots pine (Pinus sylvestris L.), inhabiting contrast on the level of radioactive contamination (60-17800 Bq/kg on 137Cs) sites in the Bryansk region, undergone to radioactive pollution as a result of the Chernobyl accident. Values of all investigated parameters of genetic variability (heterozygosity, frequency of polymorphic loci, Jivotovski index) and frequencies of the mutations for loss of enzymatic activity increase with a doze absorbed by critical organs of pine trees. Presented data show that a high level of mutation occurrence is intrinsic for descendants (seeds) of pine trees in the investigated populations, and genetic diversity in the populations is essentially conditioned by radiation exposure.

[Cytogenetic effects in Koeleria gracilis Pers. populations from the Semipalatinsk proving ground].

The proliferative activity and the frequency of cytogenetic disturbances in apical meristem of coleoptile sprouts at germination of seeds collected from crested hairgrass populations inhabiting contrast in level of radioactive contamination sites of the Semipalatinsk test site (Kazakhstan) are studied. Sampling of biological material and soil was carrying out during three years (2005-2007). The absorbed dose to critical organs of crested hairgrass vary depending on a site from 2.8 up to 262.2 mGy/year. A sognificant correlation between the frequency of cytogenetic disturbances in apical meristem and dose absorbed in crested hairgrass critical organs is found. Devere aberrations such as single and double bridges make the main contribution to spectrum of structural mutations as well as lagging chromosomes. In spite of the fact that the crested hairgrass populations have occupied the sites with a high level of radioactive contamination for a long time, the data analysis fails to reveal radio-adaptation effect.

[Cytogenetic effects in Scots pine populations from the Briansk region contaminated by radioactive pollutants as a result of the Chernobyl NPP accident].

Aberrant cell frequency in root meristem of germinated seeds collected from four populations of Scots pine in the Bryansk Region that was radioactively contaminated as a result of the accident at the Chernobyl NPP in 1986 significantly exceeded the control level durring all three years of study (2003-2005). An analysis of cytogenetic disturbances occurrence in dependence on radiation situation characteristics such as 137Cs and 90Sr content in pine cones, 137Cs specific activity in soil, and calculated doses absorbed by pine tree generative organs shows an increase in biological effect with dose burden increasing. Findings obtained are in agreement with the results of our previous studies on cytogenetic effects induction in Scots pine populations experiencing chronic radiation (the 30-km zone of the ChNPP) and technogenic (a radioactive waste reprocessing facility) impact.

[The dose estimation of woody plants in the long-term after the Chernobyl NPP accident].

Dosimetric models have been developed to estimate the exposure doses of woody plants growing in the area contaminated by long-lived radionuclides. The models are parameterized based on the data obtained from the experimental plots in the south-west districts of the Bryansk region affected by radioactive fallout of the Chernobyl NPP accident. Doses are estimated to generative organs of pine trees from these plots. The contribution from various sources and types of ionizing radiation to the absorbed dose formation for these objects is determined.

[Regulatory radiation risks' for the population and natural objects within the Semipalatinsk Test Site].

Advisability of using risks as indicators for estimating radiation impacts on environmental objects and humans has been jusified. Results are presented from identification of dose burdens distribution to various cohorts of the population living within the Semipalatinsk Test Site (STS) and consuming contaminated farm products. Parameters of dose burden distributions are estimated for areas of livestock grazing and the most contaminated sectors within these areas. Dose distributions to meadow plants for the above areas have been found. Regulatory radiation risks for the STS population and meadow ecosystem components have been calculated. Based on the parameters estimated, levels of radiation exposure of the population and herbaceous plants have been compared.

Chernobyl radionuclide distribution, migration, and environmental and agricultural impacts.

The distribution and migration of radionuclides released into the environment following the Chernobyl accident in 1986 are described. The Chernobyl disaster resulted in the consumption of farm products containing radionuclides as a source of irradiation of the population due to the prevalence of a rural type of human nutrition in the affected region. Economic and radiologic importance of countermeasures for reducing the impacts of the accident are described. The basic radioecological problem is described in which the area where direct radiation contamination of biota was observed is considerably smaller than the zone where concentrations of radionuclides through the food chain exceeded the permissible standards. The radiation-induced effects in biota in the affected area are described. In the long-term post-accident period, the radionuclide distribution between components of ecosystems (including humans) and doses are considered in comparison to a technologically normal situation of nuclear power plant operation. This analysis demonstrates that if radiation standards protect humans, then biota are also adequately protected against ionizing radiation.

[Chernobyl and the environment].

Analyzed information which describes a wide spectrum of the consequences of radioactive contamination of natural ecosystems by the Chernobyl accident. The main regularities of radionuclide migration in the environment was been considered and scales of radiation damage to biota assessed. The area where signs of direct damage to biota are visible is shown to be noticeably smaller in size that the area where radionuclide concentration in environmental objects is above the permissible levels. The importance of the impact of radioactive contamination of natural ecosystems is assessed in terms of formation of exposure doses to the population. The conclusion was made that the detriment from all the factors is larger for humans (direct irradiation, limitation of the economic activity, etc.) than for biota.

[Prediction of 137Cs behaviour in the soil-plant system in the territory of Semipalatinsk test site].

A mathematical model of 137Cs behaviour in the soil-plant system is presented. The model has been parameterized for the area adjacent to the testing area Ground Zero of the Semipalatinsk Test Site. The model describes the main processes responsible for the changes in 137Cs content in the soil solution and, thereby, dynamics of the radionuclide uptake by vegetation. The results are taken from predictive and retrospective calculations that reflect the dynamics of 137Cs distribution by species in soil after nuclear explosions. The importance of factors governing 137Cs accumulation in plants within the STS area is assessed. The analysis of sensitivity of the output model variable to changes in its parameters revealed that the key soil properties significantly influence the results of prediction of 137Cs content in plants.

[Prediction of 137Cs accumulation in animal products in the territory of Semipalatinsk test site].

The paper describes mathematical models for 137Cs behavior in the organism of horses and sheep pasturing on the bording area to the testing area "Ground Zero" of the Semipalatinsk Test Site. The models are parameterized on the base of the data from an experiment with the breeds of animals now commonly encountered within the Semipalatinsk Test Site. The predictive calculations with the models devised have shown that 137Cs concentrations in milk of horses and sheep pasturingon the testing area to "Ground Zero" can exceed the adopted standards during a long period of time.

Decision making framework for application of forest countermeasures in the long term after the Chernobyl accident.

After the ChNPP accident a very large part of the territories covered by natural and artificial forests are contaminated with long-lived radionuclides, especially 137Cs. To protect people against exposure associated with forest contamination in the most affected regions of the NIS countries, countermeasures have been developed and recommended for the forest management. The paper presents a decision making framework to optimise forest countermeasures in the long term after the ChNPP accident. The approach presented is based on the analysis of the main exposure pathways and application of radiological, socio-economical and ecological criteria for the selection of optimal countermeasures strategies. Because of the diversity of these criteria modern decision support technologies based on multi-attributive analysis were applied. The results of the application of this approach are presented in a selected study area (Novozybkov district, Bryansk region, Russian Federation). The results prove and emphasize the need for a flexible technique to provide the optimised forest countermeasures taking into account radioecological, social and economic features of contaminated forests.

Comparative radiation impact on biota and man in the area affected by the accident at the Chernobyl nuclear power plant.

A methodological approach for a comparative assessment of ionising radiation effects on man and non-human species, based on the use of Radiation Impact Factor (RIF) - ratios of actual exposure doses to biota species and man to critical dose is described. As such doses, radiation safety standards limiting radiation exposure of man and doses at which radiobiological effects in non-human species were not observed after the Chernobyl accident, were employed. For the study area within the 30km ChNPP zone dose burdens to 10 reference biota groups and the population (with and without evacuation) and the corresponding RIFs were calculated. It has been found that in 1986 (early period after the accident) the emergency radiation standards for man do not guarantee adequate protection of the environment, some species of which could be affected more than man. In 1991 RIFs for man were considerably (by factor of 20.0-1.1 x 10(5)) higher compared with those for selected non-human species. Thus, for the long term after the accident radiation safety standards for man are shown to ensure radiation safety for biota as well.

[137Cs vertical migration in boggy soils in the long term after the Chernobyl accident]. / Vertikal'naia migratsiia 137Cs v volotnykh pochvakh v otdalenny period posle avarii na ChAES.

137Cs vertical migration in boggy soils has been studied 15 years after the Chernobyl accident. The rate of vertical migration of the radionuclide is shown to be dependent on the peculiarities of formation of peatbogs, their moistening regime and soil properties. 137Cs migration in a high-land peatbog is characterized by higher intensity then in lowland or transitional peatbogs. Differences in 137Cs vertical migration are to a large extent caused by the contents in soil of exhangeable and mobile radionuclide forms. The derived experimental data that describe 137Cs distribution over the profiles of peaty soils of different type are used for parameterization of two-component convective-diffusion model. Ecological and effective half-life periods of 137Cs content reduction in the soil root layer have been calculated. A long-term prediction is given of the dynamics of the radionuclide content in the root layer of peaty soils.