Conservative no-effect concentrations were derived for nine radionuclides, four generic organisms (terrestrial plant and animal and aquatic plant and animal) and six environmental compartments (air, soil, fresh water, marine water, freshwater sediments and marine sediments). The concentrations were calculated using the concentration ratio (CR) approach that is used in both FASSET and RESRAD-BIOTA. In the CR approach, a single transfer factor is used to predict concentrations in plants or animals from concentrations in soil or water. Most of the CR values required for the calculations were taken from FASSET documentation. Because of the importance of tritium and C-14 in the context of CANDU reactors, CR values for these radionuclides were derived from specific activity (SA) concepts. Sediment partition coefficient (Kd) values, which were used to derive no-effect levels for sediments from the levels for water, were chosen to be the best-estimate values from the IMPACT database. Dose conversion coefficients (DCCs) were taken from FASSET and the dose rate benchmarks used were those recommended by UNSCEAR. The results provide environmental concentrations below which no detrimental effects are expected on non-human biota at CANDU sites in Canada.

The study addresses accumulation of radionuclides by mushrooms and berry shrubs from the forest soil in the 30-km area around the MCC (the Krasnoyarskii Krai, Russia). The Suillus granulatus and S. luteus mushrooms have been found to be the best bioindicators in this area. The level of 137Cs concentration in these species can reach 10 kBq/kg dry mass. The 137Cs transfer factor (TF) by the mushrooms varies 5-fold among the sites that receive radionuclides from different sources. The level of radionuclide activities accumulated by berry shrubs is 2–3 orders of magnitude lower than the activities accumulated by mushrooms. No relationship has been found between the TFs of radionuclides to the shrubs and the pathway via which the radionuclides enter the soil. The contribution of the dose due to intake of mushrooms and berries to the annual effective dose of internal exposure to residents does not exceed 150 μSv/year and 1.4 μSv/year, respectively, estimated from the registered levels of accumulated 137Cs.

Future development of nuclear energy in the frame of climate change and sustainable development needs an increased safety and consequently, robust models of environmental transfer of radionuclides. Tritium and Carbon are life elements and must be treated separately from trace elements. The IAEA promoted EMRAS (Environmental Modelling for Radiation Safety) project in order to decrease uncertainties in the predictive capability of environmental models, including the cases of aquatic and biota. To understand the processes and models reliability, nine scenarios have been developed. The Working Group contributed to the Revision of “Handbook of parameter values for the prediction of radionuclide transfer in temperate environments” TRS 364, as well. The main task of this paper is to propose ways for models' predictive power improvements, based on lessons learnt from EMRAS' exercises.

Results of radioecological investigations of rodents having different ecological specialization – wood and field mice, northern red-backed voles and mole-voles to acute (laboratory experiment) and chronic (long-term inhabiting the East Ural Radioactive Trace – EURT) irradiation are summarized. These species are greatly distinguished by a way of life, a migratory activity, an average life span etc. Numerous immunological, hematological and cytogenetical disturbances were found in more radioresistant wood and field mice and northern red-backed voles inhabiting the EURT zone (density of soil pollution by 90Sr-18.5 MBq/m2=500 Ci/km2) as compared with the reference samples. On the contrary there were no pathological shifts in more radiosensitive mole-voles from the more radioactively contaminated site (90Sr-37 MBq/m2=1000 Ci/km2. The absorbed dozes during the life for the mole-voles from the EURT zone were significantly higher (in 30 times) than these ones for mice and voles. These data testify about the possibility of radioadaptation in a series of generations in mole-voles that developed due to their ecophysiological features and isolation of settlement in the radiocontaminated zone. Mice and voles form a flowing population and slip off the prolonged influence of a damaging factor, this circumstance prevents the development of radioadaptation.

Sapropels, hydrolyzed lignin (HL), clay-salt slimes (CSS) and phosphogypsum (PG) have been used as components to develop efficacious and ecologically safe amendments. Methods and models for forecasting effectiveness of countermeasures based on application of such amendments have been proposed. It has been found that 137Cs selective sorption on organo-mineral amendments is enhanced after incubation, as compared with the calculated values on the basis of the fractions of total mass of source components and their own ability for 137Cs selective sorption. The measured RIP(K) value for the mixtures of soddy-gley soil and organo-mineral amendment at 2% was 1.2–1.6 higher than the calculated one, and at 10% 1.5–1.7 times higher than the calculated.

Clay minerals are one of the most important components in soil for radiocesium sorption. There are many types of clay minerals in soil, and their capacities for cesium (Cs) sorption differ. However, the effects of differing clay mineral amounts and compositions on Cs sorption behavior have not been clarified yet. In this study, therefore, we studied Cs sorption on illite, kaolinite, and illite–kaolinite mixtures, carrying out batch sorption test and sequential extractions to investigate Cs sorption mechanisms. The amount of sorbed Cs in the mixtures did not depend on the illite content, but the amount of exchangeable Cs decreased as the illite content increased. Conversely, the amount of fixed Cs in the mixtures increased with increasing illite content. These results suggest that the distribution of Cs sorption between ion exchange sites and fixed sites may be dependent on the illite/kaolinite ratio. In addition, we can estimate the amount of sorbed Cs in an illite-kaolinite mixture from the amounts of sorbed Cs in illite and in kaolinite, and the abundance ratio of each clay mineral in the clay mixture. This is basic knowledge needed for long-term assessment of Cs mobility in soil.

The results of numerical experiments by definition of propagation zones Cs137 in the Kara Sea in case of a radiological contamination offset from the estuary Ob are tendered. The stationary source of a radioactivity dumping was set in surface layer of river and seawaters mixing zone in the Ob Bay. The modeling was carried out on the basis of a numerical solution of the three-dimensional equation of passive impurity transport with turbulent diffusion and with allowance for of processes of a half-decay and sedimentation on suspension. The equation was considered concerning total concentration of a radioactive impurity in seawater (in dissolved state and suspended matter). The assumptions of a stationarity of concentrations Cs137 ratio in different states and constant suspended matter distribution in water column were done. The part of radionuclides content in suspension from total radionuclide content was set in particular coefficient p on the basis of nature measurements. As a result simulation we obtained the predominant transfer Cs137 in northern and north-east direction from an estuary Ob and the sufficiently strong dependence of the scales of propagation on the coefficient p.

Siberian Chemical Enterprises (SCE), located 15 km from the city of Tomsk downstream the Tom river, has been put into operation in 1953 and has become one of the main uranium and plutonium production facilities in the world. In this paper the results are repoted on the concentrations of uranium-234, uranium-235 and uranium-238 in soil near the SCE. Experimental results on uranium isotopes determination in soil around the SCE on-site and off-site are discussed.

Reload of spent nuclear fuel of nuclear submarines and its subsequent transportation for reprocessing may be carried out by the vessel – floating technical base (FTB). Up to 4–5 reactor cores (∼ 1016 Bq) can be taken aboard, transportation can occur for long distance. In case of the accidents with infringement of protective barriers, FTB may be a significant source of radiation hazard. Two hypothetical accidents associated with explosion and fire aboard and sinking the FTB are analyzed. In the first case a source term for the release and aerial radionuclide spreading out have been estimated, in second case radiation consequences have been estimated for water way taking into account remaining protective barriers. Main task of the assessments was radiation impact on population and environment at long distances from the source.

Measurements of indoor radon concentrations were performed in 44 workplaces and 87 dwellings in the region of Epirus, north-western Greece, using electret and alpha-track detectors. Radon concentrations followed a log-normal distribution with an arithmetic mean of (92 ± 54) Bq m-3 in workplaces and (86 ± 52) Bq m-3 in dwellings. In all cases, radon levels were below 400 Bq m-3, which is the action level proposed by the European Commission. Comparing summer and winter measurements, no statistically significant seasonal variation was established. However, radon concentrations measured in basement and ground floor levels were significantly higher (p < 0.001) than those measured in the first and upper floors. A mean annual effective dose of 0.64 and 1.63 mSv y-1 was estimated for occupational and residential exposure, respectively. The reported data contribute to the assessment of radon distribution and dose estimate at the national level.

The Tejo River flows between Spain and Portugal discharging in the Atlantic Ocean. In its Spanish section receives discharges from three nuclear power plants (NPP) being the Almaraz NPP located nearby the Portuguese border. This paper summarizes and analyses the radionuclide concentrations in surface water, sediments and fish in Tejo River from the years 2001 to 2005. The surface waters, following radiochemical procedures, were analysed for total and residual beta, 137Cs and 90Sr by beta measurements using proportional counters and for 3H by liquid scintillation counting, after isotopic enrichment. Radionuclide concentrations were determined in sediments and fish by gamma spectrometry. The results obtained for 137Cs and 90Sr in surface waters are low and of the order of magnitude of the background. Regarding the 3H, the activities are higher than those obtained for other rivers. The levels of artificial and natural radionuclides in fish are below the minimum detectable activity with the exception to 40K. For sediments, the 228Ra, 226Ra and 137Cs concentrations increase with the decreasing of the sediment size. An opposite behaviour was observed for 40K. The data show that the radioactivity levels in Tejo River are low and within the values measured in other Portuguese rivers except for 3H in water which values are higher due to the influence of the Almaraz NPP.

The need of less conservative but reliable risk assessment for accidental tritium release was recognized in the frame of present debate on nuclear energy future. While the fusion reactor is only in research phase and risk assessment are not extremely stringent, Romania faces a debate on near future of nuclear energy with heavy water reactors, known to have a large load and release of tritium. Both tritium and 14C are key radionuclide for CANDU and are also directly involved in the life cycle of plants and animals. An interdisciplinary approach is proposed in order to better handle the environmental transfer of tritium under accidental conditions and preparatory steps are presented.

Continental aquifers flow along topographic gradients toward coastlines in many geologic environments. Wherever aquifers intersect coastlines, ground water mixes with seawater infiltrated in marine sediments. In this mixing zone, sediment-pore fluid interactions create geochemical gradients that migrate back and forth on short (e.g., tides, waves) and long time scales (e.g. seasonal and eustatic sea level fluctuations). We focus on sorption and ion exchange characteristics of radium in these mixing zone sediments using laboratory column experiments. Previous studies have shown salinity affects radium sorption, but this process has not been investigated in porous sediments where solution ionic strength may fluctuate over a range of time scales. Additionally, different sediment types present within this subsurface zone may act as temporally and spatially variable source/sink sites for Ra. These sediments may have been underestimated in Ra mass balances for estimating coastal ground water fluxes. We performed microcosm sediment column experiments to examine Ra behavior and quantify the source/sink capacity of sediments. Longitudinal dispersivity results indicate local flow field variability was minimal during experiments. Radium desorption from sediments occurs rapidly (within 60 to 120 minutes) with exposure to solution and is generally high in the shallow portion of the subterranean mixing zone.

The reactive oxygen species (ROS)-signaling pathway is very important in heavy metal toxicity. Induction of the antioxidative defense mechanism, comprising ROS-scavenging enzymes and metabolites, in plants after environmental uranium contamination has been insufficiently studied in the past. This study aimed to analyze oxidative stress related responses in Arabidopsis thaliana after uranium exposure. Seventeen-day-old seedlings were exposed to 0, 0.1, 1, 10 and 100 μM uranium for 3 days. After exposure to 100 μM uranium, a decrease in fresh weight for leaves and roots was observed, leaves colored anthocyanous and roots were stunted and yellow. To reveal the importance of oxidative stress in uranium toxicity, alterations in ROS-scavenging enzymes were studied at protein and transcriptional level. Superoxide dismutase (SOD) capacities increased in leaves and roots after exposure to 100 μM uranium but no differences were observed for catalase (CAT) capacities. Transcript levels of different SODs located at various cellular compartments were affected depending on the place of action. Gene expression of CAT in leaves and roots was also affected after uranium exposure. Results indicate that oxidative stress plays an important role in uranium toxicity but suggest that plant responses differ for leaves and roots.

Determination of background radiation dose-rates is important in the process of assessing risks to the environment from exposure to human activities both in terms of deriving the incremental dose-rate and as a point of reference for evaluating the significance of the exposure level. A consideration of the available literature on naturally occurring radionuclides in wild plants and animals quickly illustrates a paucity of data coverage in numerous cases. Most notable is the lack of comprehensive information for the important dose-forming radionuclides such as 210Po and 210Pb. In order to collate data concerning these radioisotopes for components of the ecosystem, field work was conducted in a semi-natural, mountainous location in central Norway. Preliminary (since no correction was made for ingrowth from 210Pb) whole-body activity concentrations of 210Po in 2 species of small mammal were commensurate with activity concentrations reported for reindeer muscle sampled at proximate locations, falling at a level of some 10s of Bq kg-1 by fresh weight. Statistical analyses of the data showed that bank vole and shrew 210Po data constitute different populations with different mean ranks. Unweighted dose-rates attributable to the presence of internally distributed 210Po were calculated to be 0.07 μGy h-1 for Bank vole.

In order to test the suitability of using Brassica juncea for the remediation by phytoextraction of soils contaminated with 238U and 226Ra, the transfer process to the plant was studied. A soil with high natural uranium mineralization was used for the study. When the soil was not manipulated, the transfer factor (TF) was 0.24 ± 0.02 and 1.5 ± 0.3 for 238U and 226Ra, respectively. These low values, especially for 238U, are due to the radionuclides being associated in the soils with fractions unavailable to the plant. For the possible use of phytoextraction for remediation of contaminated soils it is therefore necessary to enhance the availability of the radionuclides in the soil. In this sense, soil pH is a major factor influencing the availability of these elements in the soil for plant uptake through their speciation. In this work, the effect of pH on the TF of 238U and 226Ra was studied. Also, citrate was used to attempt to enhance the bioavailability of the two radionuclides in the soils, and therefore their uptake by Brassica juncea and translocation to the shoots.

The physicochemical state of radionuclides of Sr, U, REE and Th(IV) and their natural analogs in the river Techya (Chelyabinsk reg., RF) is analyzed in connection with seasonal variations of the chemical composition of water. It is shown that the chemical state of Sr(II) and U(VI) strongly depends on the level of CO2 in the river water. A high level of soluble carbonate leads to co-precipitation of to 10–15% Sr(II) and to 20% U(VI) on the surface of mineral (Ca - Si - Al - O + Fe - O phase mixture) and biological suspensions with the size of >3 micron. The rest of Sr(II) exists in the river water in the form of aqua-cations. Uranium (VI) is present in the water as a set of hydroxo- and carbonate complexes which do not interact with the cation-exchanger and in the form of Ca2UO2(CO3)3 which may be involved in the ion-exchange interaction. Th(IV) and La (III) are found to exist in the water as hydroxo-complexes (<80%) and in the form of suspension (<20%). When the concentration of CO2 in the river water decreases to the level typical of the autumn period, the suspended CaCO3 vanishes and the fraction of Ca2UO2(CO3)3 in the water changes.

The objective of this study is the implementation of a method combining extraction chromatography and liquid scintillation counting (LSC) technique to the determination of 90Sr in milk samples. The strontium separation is performed using the commercially available Sr-resin (Eichrom) and the beta counting is carried out using a liquid scintillation detector system (Tri-Carb 3170 TR/SL, Packard). Firstly, the trials are performed with 300 mL of milk and 0.7 g of resin. Validation trials are carried out using spiked milk samples with different 90Sr activities and the accuracy of the methodology is also been tested with an IAEA 152 reference milk sample. The results obtained had shown good accuracy of expected value. The minimum detectable activity (MDA) obtained for a confidence level of 95% and 60 minutes of sample counting time was 0.20 Bq L-1. In order to improve the detection limits for 90Sr, 1 liter of milk and 3 g of resin were used and the MDA value in these conditions was improved to 0.012 Bq L-1. The method was applied to the determination of the 90Sr concentrations in milk samples from different regions of Portugal.

Inhalation of suspended particulates originating from contaminated soil is an important exposure pathway that may result from disposal of long-lived solid radioactive waste. A hypothetical scenario was evaluated involving long-term irrigation of agricultural land with contaminated water and ensuing accumulation of radionuclides in surface soil. One of the factors affecting the dose from inhalation of suspended soil particulates is the radionuclide enhancement (enrichment) in airborne soil particles relative to that of the underlying soil. The enhancement factor (enrichment factor) is defined as a ratio of airborne particle activity concentration (Bq kg-1) to surface soil activity concentration (Bq kg-1). The values of this parameter and its effect on inhalation dose were evaluated for different soil types and inhalation exposure conditions.