The composite rare earth chloride produced from monazite contain low levels of natural radionuclides and is being used as the input material for the production of individual rare earth compounds which have wide applications. Gross alpha, beta and 228Ra activity concentrations in composite rare earth chloride and individual rare earth compounds such as oxides of Ce, Nd, Pr, Sm, Gd etc are presented. The significant radionuclide of environmental concern is identified as 228Ra and the activity level varied between 0.1 and 7.8 Bq.g-1 in different compounds. Sporadic 228Ra levels up to 16 Bq.g-1 was observed in Lanthanum oxide. The external gamma exposure rates and airborne activity due to thorium and thoron progeny in the process locations are studied. The activity levels in liquid effluent and potential exposure scenarios are indicated.

A numerical model which simulates the dispersion of non-conservative radionuclides in the Alboran Sea has been developed. Water currents are obtained from two hydrodynamic models working on the same domain: a 2D depth-averaged model is used two calculate tides and a 2-layer has been applied to obtain the residual (mean) circulation. The output of the hydrodynamic models is first applied to calculate suspended particle concentrations and sedimentation rates over the domain, which are also required by the radionuclide transport model. This assumes that radionuclides may be present in three phases: dissolved, suspended matter and bed sediments. Exchanges between the liquid and solid phases are described through kinetic transfer coefficients. The model has been applied to simulate the dispersion of 137-Cs and 239,240-Pu introduced in the sea from atmospheric fallout. Measured and computed radionuclide concentrations in the water column and in bed sediments are, in general, in good agreement.

A numerical model that simulates the dispersion of radionuclides in the English Channel has been applied to study the dispersion of conservative and non-conservative radionuclides released from La Hague nuclear fuel reprocessing plant. The model is based upon previous work and now is able to simulate dispersion over long time scales (decades), explicitly including transport by instantaneous tidal currents and variable wind conditions. Wind conditions are obtained from meteorological statistics using a stochastic method. Outputs from the model are treated using time-series analysis techniques. These techniques allow the determination of characteristic times of the system, transport velocities and dispersion factors. This information may be very useful to support the decision-making process after an emergency situation. Thus, we are proposing that time-series analysis can be integrated with numerical modelling for helping decision-making in response to an accident. The model is first validated through its application to actual releases of 99-Tc and 125-Sb, and characteristic times for several radionuclides (a conservative one, 137-Cs and 239,240-Pu) are given next. Characteristic transport velocities and dispersion factors have been calculated as well.

Rapid response models for the assessment of the consequences of a radioactive spill in the coastal waters of Andalusia (south of Spain) have been developed. These waters comprise the Gulf of Cadiz, GoC, (Atlantic Ocean) and the Alborán Sea, AS, (Mediterranean Sea) and two models are described, covering both sectors. This subject is of high relevance since these waters are the only connection between the Atlantic and the Mediterranean. Thus, there are intense shipping activities that for instance include the transit of nuclear submarines. The models include hydrodynamic sub-models appropriate to describe the water circulation in each area. Results from the hydrodynamic models have been carefully tested through comparisons with observed tides and currents. The dispersion models are based upon a particle-tracking technique. Thus, the radioactive spill is simulated by a number of discrete particles, each one equivalent to a number of units, whose paths are computed. Turbulent diffusion and radioactive decay are calculated using a stochastic Monte Carlo method. The radionuclide concentrations may be obtained at the desired time from the density of particles per water volume. Some applications and examples of results are given.

Within the IAEA EMRAS programme, a working group was established to look at the modelling of naturally occurring radioactive material (NORM) in a variety of environments. There are many models already available. However, guidance on how and when to apply specific models is lacking in many cases. Development of models has often been carried out without a clear understanding of the possible applications of the models. Some models have been developed only for specific applications in specific industries, and are not generally useful. The work carried out during this program has resulted in the identification of several important issues that require consideration in the selection and utilization of computer models for NORM risk assessment. These issues discussed below cover suitability, selection, use and misuse of available models, as well as training and guidance for modelers, and acquisition of data for model inputs.

In investigating the impact of discharges from the nuclear industry on non-human biota, much attention has been given to biota in marine and terrestrial environments. Relatively little attention to date has been given to the exposure of biota to groundwater containing man-made radionuclides. This area of interest is growing especially in the field of nuclear waste repositories. A scoping assessment has been performed to determine the impacts due to radiological contamination on organisms living within or coming into contact with groundwater at the Sellafield site, UK. for time periods up to 2120, modelling of contaminant release from in-ground inventories and transport in groundwater was carried out using a relatively simple assessment methodology with the MONDRIAN modelling suite. Calculated equivalent dose rates to freshwater and marine biota were significantly higher at groundwater sites within the Sellafield boundary than at locations offsite. In general, the total weighted absorbed dose rates calculated in this scoping assessment were of no radiological significance in relation to the England and Wales Environment Agency freshwater ecosystem trigger level (40 µGy h-1). The one exception to this was for bacteria, although the calculated exposure rate is believed to be inconsequential due to the very small size of bacteria.

Authorised discharges of radionuclides into sewers can result in contamination of the sludge, and so provide a pathway by which radionuclides can enter the foodchain. Specific data on the uptake of radionuclides from sludge amended land into crops is scarce. A study has been undertaken to generate data on tritium uptake by crops grown in soil amended with tritium contaminated sewage sludge using a range of soil types and crops common to the UK. The study was performed over two years. The concentration of tritium in soil fell throughout the study. It was therefore not possible to quantify individual soil to crop transfer in terms of conventional concentration ratios. Instead, an aggregated transfer quotient was estimated relating the concentration in the edible part of the crop in Bq kg-1 to the original amount of activity applied to the soil in Bq m-2. The values obtained were broadly similar at for all crop and soil types studied, being about 2 10-4 m2 kg-1. The observed values depend on factors such as temperature and rainfall, and so they should not be used in generalised radiological assessments. They are however indicative of the small amounts of tritium transferred to crops from amended soil.

Following the confirmation that Mr Litvinenko had received a large dose of 210Po, the Health Protection Agency began to prepare for public health monitoring of potentially contaminated people. Alpha counting of urine was the only practicable means of monitoring exposure. As the incident developed it became apparent that the number of samples would be likely to exceed the HPA's capacity. Therefore other UK laboratories were contacted and several agreed to assist. To validate the analyses each potential collaborator analysed a cross check sample that was the remainder from 24 hour samples that had already been measured at the HPA. The results were in good agreement. In the first four weeks of the programme, about 600 samples were collected and all were analysed using the resources in the UK. Later, the quality assurance exercise was extended to include laboratories in the UK and abroad that could potentially become involved in the analysis of samples arising from the incident. The factors underlying the success of the programme are set out. These included having a well founded Quality Assurance system in place during normal circumstances and having pre-existing links at the appropriate working level with other laboratories in the UK and abroad.

An allometric scaling approach has been used to calculate biological half-lives of elimination (TB1/2) and concentration factors (CF) for radionuclides in marine biota. Power functions of organism mass are fitted to a biokinetic database for plankton, seaweed, fish, crustaceans and molluscs, using data generated by us, in combination with reviewed data. Scaling of the CF to M-0.26 ± 0.09 is observed, compatible at ±1σ with metabolic theory predictions that metabolism scales to M0.75. We also observe scaling of TB1/2 to M+0.16 ± 0.03, within the previously reported range +0.15 to +0.30 for biota from various environments and, at < ± 3σ, slightly outside turnover rate scaling predictions to M-0.25. The elements for which the CF scales better allometrically are particle seeking, mainly lanthanides and actinides. Association of the independent term of the allometric power function a with the sediment-water partition coefficient Kd is strongest for these elements, possibly through binding to biological/organic matter. The findings from this study are relevant to extend the range of applicability of our biota dose assessment methodologies where data gaps in transfer exist.

A numerical model has been applied to simulate the fate of 226Ra radionuclides in the ocean, generated from discharges of produced water in the Norwegian Sector of the North Sea. The model simulates the transport, dilution and the (possible) deposition on the sea floor of 226Ra. Figures are presented for the concentration levels and deposition rates of 226Ra in the ambient for various assumptions for the fate of the 226Ra in the ocean (as dissolved, as adsorbed to ambient organic particles that sink down on the sea floor, and as forming Ba(Ra)SO4 particles). Concentration levels and deposition rates are compared with natural levels and fluxes of 226Ra in the ocean and to the sediment, respectively. The added concentration levels/fluxes are found to be generally relatively small, compared to natural levels/fluxes. The reason for this is attributed to the presence of fairly high natural levels/fluxes of 226Ra.

A high temperature combustion method was used to analyze the 14C and 3H activities in graphite and the dose assessment was carried out to determine the clearance in the conservative way. By this method, the 3H and 14C were simultaneously trapped in the nitric acid and carbosorb, respectively. Accordingly, the sample preparation time for the measurement was reduced to the half. The combustion temperature was more than 800 degrees in centigrade for obtaining total tritium and 14C in the sample. The combustion ratio was about 99% on the graphite sample with the weight of 0.1 g. Minimum detectable activity was 0.05 Bq/g for the 14C and 0.15 Bq/g for the 3H at the same background counting time. The recoveries from the combustion furnace were around 100% and 90% in 14C and 3H, respectively. The radioactivity were 2,530 ~ 3,160 Bq/g in 14C and 1,700 ~2,040 Bq/g in 3H at this experiment. The experimental uncertainty was less than 6% in both radionuclides where the furnace recovery was dominant factor. An individual effective dose from beta and gamma radionuclides was estimated by consideration of the scenario of inhalation, ingestion and external exposure. 60Co, the radioactivity of which was measured by using HPGe detector, had a predominant effect in estimating the effective dose. The estimation showed that the graphite wastes from the dismantled research reactor should be disposed of as a low level radioactive waste rather than clearance.

Accumulation of transuranic element 241Am by photoassimilating organs and its distribution in fractions of the biomass of aquatic plant Elodea canadensis have been investigated in laboratory batch experiments. Americium was taken up by apical shoots of Elodea from water. Of the activity accumulated by the shoots, up to 80% of 241Am was detected in the leaves and 20% in the stems. Americium concentration in apical leaves was several times higher than in distal leaves. Of the 241Am activity concentrated in the shoots, 95% was bound to cell walls, membranes and organelles and 5% of the radionuclide was dissolved in cytoplasm. Less than 1% of americium accumulated in the biomass was found in the lipid extract; up to 10% of americium was bound to proteins and carbohydrates; the major part of the radionuclide (about 90%) was registered in the cell wall fraction that mainly contained cellulose-like polysaccharides. Biomass treatment with hydrochloric acid resulted in desorption of about 70% of americium, mostly from the polysaccharides.

The experiments on accumulation of 99Tc by Elodea biomass showed that 99Tc activity concentration can reach 120 ± 6 Bq/g, with the concentration factor for 99Tc 2700 ± 500 L/kg. In experiments on 99Tc release, over 504 h about 82% of the total 99Tc activity was released into the water from plant biomass; most of 99Tc was released within the first 192 h. Results of chemical fractionation of the biomass show that 99Tc contained in biomass was mainly concentrated in the exchangeable and the adsorbed fractions (83%). Thus, the data obtained using chemical fractionation of biomass confirmed the experimental data on 99Tc release, which suggested that most of the biomass-bound 99Tc was adsorbed on the biomass surface. 99Tc tightly bound to Elodea biomass (fractions of organics and mineral residue) constituted just 17% of the total 99Tc activity. Decreased illumination of Elodea shoots during the experiment did not cause any reduction in 99Tc activity concentration or concentration factor. Results of chemical fractionation of the biomass grown under lower illumination conditions show that the percentage of 99Tc tightly bound to Elodea biomass (fractions of organics and mineral residue) decreased while the 99Tc of the adsorbed fractions decreased. Our results and data reported by other authors suggest that some part of 99Tc activity can be bioavailable to living organisms and that the portion of bioavailable 99Tc can be determined by a number of factors.

Soil contamination with Co and Cd at concentration 20–25 times exceeding the Maximum Permisible Level for sod-podzolic light loam soil produced not only negative effects on the spring barley productivity formation, but also decreasing of 137Cs root uptake. Effects of Co on the barley development and 137Cs accumulation in plants was more pronounced than Cd influence. The 137Cs activity decrease in barley biomass and harvest amounted to 2.5 and 1.6 times on Cd and Co contaminated soil, respectively. The mechanisms regulating root uptake of K by barley plants in dependence of the kind of soil contamination were discussed. Seed incrustation with Zircon and Epin did not produce significant influence on Co and Cd phytotoxicity, however the use of this plant growth regulators resulted in different in direction and value effects on Co, Cd and 137Cs accumulation in barley plants at various stages of its development. The experimental data do not make it possible to link directly the effect of biologically active substances on 137Cs uptake with their influence on heavy metals toxicity, which was estimated on the base of morphological and physiological parameters of plants.

The study was done to determine concentrations of radionuclides and heavy metals and to evaluate the frequency of chromosomal aberrations in samples of Elodea canadensis, a submerged plant, collected in different parts of the Yenisei River. Samples were collected in the area subjected to radioactive impact of the Mining-and-Chemical Combine (MCC) at Zheleznogorsk and in the control areas, upstream of the MCC. The investigations showed that Elodea biomass in the area affected by MCC operation contained a long inventory of artificial radionuclides typical of the MCC discharges. Upstream of the MCC, in the control sampling areas, the sediments and the Elodea biomass contained only one artificial radionuclide – 137Cs. Thus, the exposure doses to Elodea shoots and roots upstream of the MCC are small (not more than 8 μGy/d) and the main contribution to them is made by natural radionuclides. At the MCC discharge site (the village of Atamanovo) and downstream of it, the total dose rate increases almost an order of magnitude, reaching its maximal values – 72 μGy/d for Elodea shoots and 58 μGy/d for roots. Cytogenetic investigations of Elodea roots showed that at the MCC discharge site (the village of Atamanovo) and downstream of it the occurrence of chromosomal aberrations in ana-telophase and metaphase cells of Elodea was considerably higher than in the control area. It is highly probable that this simultaneous dramatic increase in the total exposure rate and the occurrence of chromosomal aberrations in Elodea is associated with the radiation factor. It is suggested that Elodea is affected not only by the radiation factor but also by the chemical factor – toxicity of heavy metals.

Natural radioactivity is associated with the vast mineral resources in South Africa in such concentrations that the radionuclides from the natural uranium and thorium decay series are found to pose concern for public exposure to communities living around these areas. The radiological impact of all operations is monitored as part of the license obligations, imposed by the South African National Nuclear Regulator Act [1]. Two main pathways giving rise to significant exposures are of interest: (a) direct ingestion resulting from regular and continuous use of contaminated water for drinking purposes, and (b) regular consumption of fish and other food products harvested from and/or grown in contaminated areas. To measure the individual nuclides in foodstuffs at the required sensitivity level in order to evaluate the yearly dose due to an individual source at a screening level of 25 μSv/a, one is faced with a required lower limit of determination (LLD) of 0.1 to 0.5 Bq/kg for certain foodstuffs. For some of the nuclides this LLD can only be obtained with radiochemical separation through acid destruction of dried foodstuffs followed by individual element separations. In this study the digestion of foodstuffs in an open-vessel microwave system followed by the determination of 210Po through radiochemical separation by spontaneous deposition onto silver discs and subsequent measurement by α-spectrometry, has been evaluated. The levels of 210Po in a variety of foodstuffs were determined and the estimated dose for the adult age group, resulting from consumption was evaluated. The dose from 210Po varied from 4 to 250 μSv/a for the various foodstuffs, with the largest intake from fish (about 0.5 Bq/day). The assessment of natural radionuclides in foods allowed us to evaluate the items that present the highest risk to the population, and compare this to the limits established by the National Nuclear Regulator (NNR). Not much data of this kind is available in South Africa. However, one would need more accurate consumption/intake values to calculate the actual yearly dose and the potential radiological impact on the public.

The paper reports on the experience and specific findings of a research team involved in emergency preparedness and response management activities using the decision support systems (DSS) RODOS and MOIRA in conjuction with domestic radiological assessment tools. Two cases are discussed – the ConvEX 3, 2005, international alert exercise targeting a CANDU reactor at Cernavoda nuclear power plant in Romania, and Oltenia 07 – a nation-wide drill around a scenario involving transborder effects from a VVER reactor at Kozloduy, Bulgaria.

The scope of the paper is the current radioecological situation on the Kola Peninsula. Activity of existing enterprises in the region increases the potential danger of radioactive contamination. One of such enterprises is the ship reparation yard Nerpa specializing in the disposal of decommissioned nuclear submarines of the Russian Federation Navy since 1992. The aim of the study is to determine the degree of Nerpa influence on the environment by investigation of spatial distribution of 137Cs in the upper soil horizons and lichens as the most reliable indicator of radioactive contamination.