In the frame of IRSN's French radioactivity observatory, aerosol samples are collected in a ten-days basis in different locations and measured by gamma spectrometry. For some studies, it is necessary to have the average of a radionuclide in aerosol samples, i.e. monthly or annually. Gamma spectrometry measurement of artificial radionuclides such as 137Cs is becoming more difficult due to decreasing radioactivity levels. Individual measurements are sometimes below the minimum detectable activity (MDA) even when low-background measurement procedures are used. In these cases, how can a MDA in an average computation be taken into account? In order to acquire this mean value, the analysis can be performed on the annual spectrum corresponding to a running sum of each individual spectrum. As for the sample, the summing is applied for the background spectrum. In this way, the 137Cs concentration in aerosols corresponding to the annual mean value is obtained. For aerosols collected in La Reunion, a mean concentration of $0.029 \pm 0.010 \mathrm{\mu}$Bq.$\textrm{m}^{-3}$ for 137Cs is obtained, when 25 measurement results on 26 samples are below the MDA. For radionuclides always detected, a good agreement between summing spectrum results and computed mean value is observed.

Uranium ore tailings and radioactive waste have been stored during four decades at the Mexican Storage Centre for Radioactive Waste (SCRW). An estimation of effective doses from sources of natural and artificial origin in the general population and workers is presented. The sampling points are located at the SCRW at a 200 m neighbouring zone of the site and at distant communities around SCRW (regional background). The effective gamma dose rates were estimated from measurements of radionuclide concentration in soil samples from 1991 to 2002. Doses from the outdoor and indoor inhalation of radon were also determined. Transfer factors for 226Ra, 210Pb, 137Cs and 40K from soil to wild edible species have been used to estimate the contribution of wild local foods to the dietary intake and to assess the supplementary doses received due to internal irradiation. The effective dose via the different exposure pathways estimated in the population that would live at the future in the immediate SCRW vicinity was two times higher than for the regional background.

Terrestrial contamination by 137Cs and 134 Cs since 1986 in France is held to originate in atmospheric nuclear weapon tests and/or the releases from the Chernobyl accident. Monthly measurements of radioactivity in terrestrial mosses are part of the monitoring protocol carried out by the Conseil Général of Tarn-et-Garonne to assess the environmental impact of the Golfech nuclear power plant radioactive releases. Since the commissioning of the NPP in 1990, these monthly measurements revealed a contamination by 137Cs and 134Cs (up to 700 and 60 BqKg-1 DW) in both sampling sites. This contamination decreased by a factor about 10 over 1990-2004 through three stages (134Cs undetectable since 1995). It is significantly correlated over large periods of time with the monthly levels of atmospheric halogens-aerosols releases by the Golfech NPP (95%, r2 = 0.35 to >0.84). These results are discussed in the light of the time since radioactive releases, of the operating and release conditions of/from the Golfech NPP and of the mosses sampled. These preliminary results bear evidence of an impact of the Golfech NPP on the terrestrial environment. They confirm that species of terrestrial mosses are particularly sensitive to low levels of atmospheric radioactive caesium contamination and are a good indicator of a radioactive fallout. They suggest that terrestrial mosses may serve to elaborate a predictive model of a caesium release, together with some relevant parameters and in the framework of a carefully defined monitoring protocol.

Scales and sludge are commonly formed during oil and gas extracting and processing operations. They usually appear when injection and formation water with different chemical characteristics come into contact. When the produced water is brought to the surface alongside with the oil, a precipitate can be deposited on the walls of pipes and equipment, forming the so-called scales. Otherwise they can accumulate in the form of sludge on the bottom of storage tanks, separators, and other equipment. Radium is the main radionuclide brought to the surface with oil and produced water and it co-precipitates with barium forming complex compounds of sulfates, carbonates and silicates. These compounds are the main constituents of scale and sludge. The objective of this work was to relate the radium content of scales and sludge to their chemical and mineralogical composition. Samples were taken from a PETROBRAS Unit in the State of Sergipe, in Northeast Brazil. They were collected either from the inner surface of water pipes or from containers in the waste storage area of the Unit. Oil was separated from the solid material in a Soxhlet extractor equipment by using aguarras as solvent. The concentrations of 226Ra and 228Ra were determined by gamma spectrometry. Both the mineralogical and chemical composition of samples were determined by X-ray diffraction and X-ray fluorescence, respectively, and used to characterize samples as scales or sludge. The results showed that scales are mainly formed by BaSO4 and CaCO3 while sludge composition is quite variable, having higher contents of SiO2 and FeO3 than those observed on scale samples. The measured activity concentrations of 226Ra and 228Ra are strongly correlated for both kinds of samples.

The pilot operation of the nuclear power plant (NPP) Temelín first block was started up in 2001 and of the second block in 2002. Since 1990, the systematic attention has been paid to the monitoring of the hydrosphere reference level in the NPP Temelín vicinity. The Temelín NPP waste water influence has been monitored and assessed since 2001. The monitoring has been focused especially on the tritium, strontium-90 and caesium-137 concentration changes in water, river bottom sediments, fish, and in the water plants biomass. The observed half-lives indicate that the strontium-90 and caesium-137 releases fully interfere with the residual contamination after the nuclear weapons tests and the Chernobyl accident in the last century. Only the tritium concentrations in water samples, taken in the Vltava River downstream from the NPP Temelín waste water outflow, show a measurable influence.

The results of an environmental survey of tritium in the vicinity of Creys-Malville nuclear plant are presented. The plant, which was shut down in 1998, is currently in its initial stage of dismantling. Measurements in the terrestrial environment do not provide any indication that tritium levels are significantly above the regional background. Tritium concentrations in groundwaters and in the river Rhône waters are at their background level too, with values in the range 0.94-1.64 Bq/l. In contrast, the various aquatic compartments of the river (fishes, plants, sediments) show enriched non-exchangeable bound tritium concentrations both upstream and downstream of the power plant, with values up to 14.7, 49 and 1495 Bq/kg (dry weight) respectively. Although fine particles of tritiated compounds entering in the composition of luminous paints have been suspected on several occasions, the nature and the origin of this tritium source, which is not related to the nuclear plant, remain unknown and will require further investigations.

The TOCATTA model simulates 14C transfer within terrestrial and/or continental water ecosystems, in response to chronic and accidental hypothetical emissions of 14C, in a liquid and/or gaseous form. This model has been developed from bibliographical knowledge on C cycling and common hypothesis to existing 14C transfer models, in order to come within the conceptual and mathematical frameworks of the SYMBIOSE project. In this context, the conceptual modelling deals with discretizing the continental biosphere into elementary components likely to be contaminated and identifying interactions or transfer processes of 14C between two components. The mathematical modelling for calculating stocks and fluxes under accidental conditions is based on a system of differential equations expressing conservation of pollutant activity for each component of the conceptual model. It is shown that the analytical solutions obtained when temporal derivatives of the differential equation system are equal to zero correspond to the activities at “steady-state" simulated for chronic contaminations.

Tritium concentrations of groundwater samples from the Environmental Monitoring Program at IPEN (Institute of Nuclear and Energetic Researches), São Paulo, Brazil, covering the years 2000 to 2003, were determined by liquid scintillation counting and the results laid in the range of 20 Bq$\cdot$L-1 to 91 Bq$\cdot$L-1. The effective committed dose for general public considering the highest concentration value is 1.3 μSv$\cdot$y-1, which is below the ICRP dose limit of 1mSv$\cdot$y-1. Tritium concentration of radioactive liquid effluents samples from the IEA-R1 research reactor storage tank showed values from 3.6×103 Bq$\cdot$L-1 to 6.2×103 Bq$\cdot$L-1, approximately 1000 times below the Brazilian daily discharge limit of 3.7×106 Bq$\cdot$L-1.

The consequences for the man and the environment of the discharges of nuclear facilities depend on the importance and the nature of the discharges, but also on the environment which receives them. Thus, the impact of a pollution, which is expressed in term of toxicity, risk or economic consequences, varies according to the characteristics of the environment and the use of this environment by the man. The radioecological sensitivity can be defined as the response of the environment to a radioactive pollution. For a determined discharge, the higher is the response, the more sensitive is the environment. If all the ecosystems appear sensitive, their sensitivity does not concern the same criteria and it is currently difficult to compare these criteria between them. The idea of the SENSIB project is to create a standardized tool which makes it possible to represent and to compare with the same scale the sensitivity of various ecosystems. The SENSIB project aims to develop both a methodology to calculate sensitivity indexes and a radioecological sensitivity scale usable for risk management.

The aim of the study was to measure the carbon 14 activity at natural level in air samples using classical methods of radiochemistry and beta counting. Three different methods have been tested in order to minimise the detection limit. In the three methods, the first step consists in trapping the atmospheric carbon 14 into NaOH (1N) using a bubbling chamber. The atmospheric carbon dioxide reacts with NaOH to form Na2CO3. In the first method the Na2CO3 solution is mixed with a liquid scintillate and is directly analysed by liquid scintillation counting (LSC). The detection limit is approximately 0.3 Bq.m-3 of air samples. The second method consists in evaporating the carbonate solution and then counting the solid residue with a proportional gas circulation counter. The detection limit obtained is equivalent to the first method (0.36 Bq.m-3 of air samples). In the third method, Na2CO3 is precipitated into CaCO3 in presence of CaCl2. CaCO3 is then analysed by LSC. This method appears to be the most appropriate, the detection limit is 0.04 Bq.m-3 of air samples.

The present study is the second part of a program of characterization of the site surrounding the SoGIN Garigliano Nuclear Power Plant (Southern Italy), which is currently involved in decommissioning activities. In the first phase of the project the reference groups of the population were established on the basis of a socio-economical study of the site; the radiological doses due to the assumed radioactive releases during the decommissioning phase were calculated by using climatological, hydrological, geomorphological parameters of the studied area; transport and diffusion specific models of some radionuclides in the environment were implemented to calculate the dose using specific evaluation software. The second part of the study focuses on the project of an environmental network designed in order to ensure the continuous monitoring of the radioactive release concentrations. All the criteria for the choice of grid points, by considering specific paths of transfer in the environment, were established for all the environmental compartments. A field campaign was carried out aiming to assess the “zero level" due to the natural radioactivity and past anthropogenic activities.

In France, the mining and milling of uranium ore and the disposal of uranium mill tailings involved nearly 200 sites of very different nature. Being in charge of both the review of some remediation reports and the routine monitoring of the environment provides IRSN with selective data on most sites. The data collected by IRSN as well as those available from other data sources often remain incomplete therefore preventing IRSN from presenting a global view or answering some specific questions. In order to overcome this difficulty, it was decided, under the aegis of the Ministry of Ecology and Sustainable Development, that IRSN should develop a program of investigations organized in two parts: Part 1, called “State of knowledge" is aimed at assessing the amount of information available and at consolidating it into a user-friendly computerized database. The main goal is to identify the occurrence of significant enhanced radiological levels in the environment and to detect any lack of information concerning the various sites. This paper gives an overview of the information already collected. Part 2, called “specific studies" is aimed at fixing the gaps in the database by implementing new investigations on specific sites. It could lead to improvements in networks for the monitoring of radioactivity in the environment.

In this contribution, the results of the radioactivity bio-monitoring of the Vltava River before (1996-2000) and after (2000-2003) the start-up of the PWR-type South Bohemian nuclear power plant are presented. The liquid radioactive effluents are discharged into the Vltava River, which also serves as a source of drinking water intended for Prague. The bio-monitoring was made by means of water plants and freshwater bivalve that are found along the watercourse. Biological samples were processed and then the activity of natural and man-made radionuclides was assessed by gamma-spectrometry. The analysed statistical data did not prove any impact of the three years NPP operation on the Vltava River radioactivity.

There is much current interest in managing and manipulating radionuclide transfer from soils to plants, either for `safe' crops or for phytoextraction of radionuclide contaminated soils. Potentially there is biodiversity in plant uptake that might aid these efforts. We have established the effects of phylogeny (evolutionary history) on the uptake of numerous heavy metal and nutrient elements. Here, using the same Residual Maximum Likelihood techniques, we report phylogenetic effects on radionuclide uptake by plants derived from databases of several hundred species of plants we have collated over recent years. There are differences of at least two orders of magnitude in the concentration to which plants take up isotopes of Cs, Sr, Cl, Ru, S, and I. When analysed using hierarchical Analysis of Variance coded using a recent molecular phylogeny of flowering plants it is clear that for no radionuclide is all the variation inter-specific. Rather, for all radionuclides some of the inter-taxa variation is associated with higher taxonomic levels. In general, therefore, groups of plants with high and low uptake of radionuclides, and that might be useful for managing or manipulating radionuclide uptake, can be delineated. Here we discuss some of these groups and how they might be useful.

In many regions subjected to the contamination after the ChNPP accident forest products play an important role in radiation impact on the population. The decision making framework to optimise implementation of forest countermeasures in the long term after the ChNPP accident is described. The approach is based on the analysis of the main exposure pathways related to contaminated forest and application of different criteria (reduction of individual dose, cost for implementation; cost of averted dose of 1 man-Sv; secondary ecological effect and psycho-social impact) for the selection of optimal countermeasures strategies. Results of the application of the approach proposed for the study area (Novozybkov district, Russian Federation) are presented. The results emphasize the effectiveness of the application of a flexible decision support technologies for the optimization of countermeasures taking into account radioecological and economic features of contaminated forests.

Among the naturally occurring isotopes the determination of radium is the most difficult ones. In this work some alpha-spectrometric source preparation methods to determine radium were measured. The aim of our work was to investigate the feasibility of MnO2-coated discs for radium detection with a semi-conductor PIPS detector. This method based on the sorption of radium onto MnO2-coated surfaces. Parameters of this method were measured, and efforts were made to solve the incidental problems. In the case of using polyamide discs for base material, the executed experiments were showed that it might be applied to detection of 226Ra, however the resolution was weak. It can be caused by the surface roughness and by the width of the MnO2 coat. In the consecutive investigates we have these parameters changed. Whereas the surface roughness of MnO2 cannot be changed more, smooth surfaces could produce in another way, so there were took several surfaces into account, like stainless-steel, nickel, copper and chrome plate. Regarding our results - in the case of optimal width of MnO2 coat - using MnO2-coated discs is a simple and effective source preparation method in radium measurement.

Should an important release of radionuclides occur in the environment, one would quickly have to assess radionuclide concentration in media and foodstuff, deduce the potential exposition of concerned populations to the radiations, predict the evolution of the situation and propose different scenarios of managing the contaminated zones. To achieve this, the ASTRAL code was created, which can be used by a relatively large group of people composing crisis centres or making predictive impact studies. The starting point of the assessments is the ground deposit of radionuclides: the atmospheric dispersion phase and the cloud exposure are not taken into account here. The calculations achieved concern time evolution of radionuclide concentration in compartments of the agricultural and forest food chain as well as assessment of doses due to external and internal exposure. These values are compared to regulation limits and/or intervention levels. Different simulations of contaminated zones management can be led by applying counter-measures, dispositions meant to reduce the accident's impact on environment and populations. The seventy radionuclides taken into account in the present version are some of those met in case of accidents or during the exploitation of a Pressurized Water Reactor (PWR). They relate to 37 elements: Ag, Am, Ba, Br, Cd, Ce, Cl, Cm, Co, Cr, Cs, Eu, Fe, I, Ir, La, Mn, Mo, Nb, Nd, Ni, Np, Pm, Pr, Pu, Rb, Rh, Ru, Sb, Sm, Sn, Sr, Tc, Te, Y, Zn, Zr. On a temporal point of view, the predictions extend to 3 years after the deposition. The internet technology chosen for this version offers important advantages: the spreading and maintenance of the tool are very easy, the code may be installed on a portable computer, the access to results is much quicker, the interface is very user friendly, so that no training is needed to perform calculations. As for any radioecological tool, a large number of parameters intervene in the calculations. All parameters can be modified, even though different user profiles grant different rights in handling them.

The French-German Initiative for Chernobyl (FGI), implemented by IRSN and GRS from 1997 until the end of 2003, included the “Project on the Radioecological Consequences of the Accident". The most relevant fields of radioecology and post-accidental aspects have been studied. The main goal was to collect and harmonise in NIS countries, the data and results on these topics. These data have been verified, validated and organized in a common georeferenced database REDAC (RadioEcological Database After Chernobyl). For linking the data, topographic maps and maps of contamination by 137Cs have been used and relevant environmental non-radioactive data have been included. The operational database built will also allow the management of the wastes disposal sites. Countermeasures used after the accident have been described and classified. An evaluation of their effectiveness has been done. The database constitutes a tool for the development and validation of operational, assessment and explicative models. This allows the quantification and assessment of radionuclide transfer in the ecosystems. The main parameters influencing the transfers can be identified. REDAC should be completed by further investigations, for example on transuranic elements, and extended to larger geographical zones and combined with others provided by different organisations.

This paper is intended to present the experience feedback of the IRSN's involvement in the reflection on the management of a nuclear crisis. It sums up some results of the French FARMING working group, corresponding to the mobilization of a wide range of Agricultural Technical Institutes and to the appraisal of a compendium of agricultural countermeasures for the rehabilitation of rural contaminated territories in post accidental situations. Indeed, in France, since a few years, this problem has been almost exclusively considered by radiation protection experts, with no involvement of the other concerned actors. But according to the weight of the agro industrial sector in this country and to the problems related to the management of contaminated food in post accidental situations, the cooperation between radiation protection experts and agro industrial stakeholders appeared more and more necessary. Indeed, above all, farmers and other local actors would take a significant part to the rehabilitation actions from the short term to long term of a nuclear crisis period and then share the responsibilities of the crisis management. The working group has therefore opened new debates at the national level and valuable results have been obtained from the meetings at technical and strategic levels.

The Chernobyl reactor accident in April 1986 released some 3-6.105 TBq 137Cs and 2-4.105 TBq 90Sr to atmosphere. About half of this was deposited within 20 km of the site, leading to extensive death of trees and other biota, and the establishment of a human exclusion zone. High levels of contamination remain in this zone. Nonetheless, birch (Betula spp.) and willow (Salix spp.) have recolonised the forest areas, while abandoned agricultural land has succeeded to tall grassland and scrub. This study summarises observations on invertebrate populations in sites with gamma dose rates varying from 0.1 to 140 μSv h-1. Corresponding activity concentrations were 3.103 to 3.106 Bq kg-1 dw 137Cs and 103 to 2.106 Bq kg-1 dw 90Sr in the top 5 cm of soil. Sub-surface bait lamina penetration decreases with increasing concentrations of 137Cs and 90Sr in soil. At the highest levels of contamination there is also some loss of above-ground invertebrate diversity; although little change in total biomass. Trials on earthworms in soils from the region and matched soils spiked in the laboratory have proved variable. However, there is a non-significant indication of depressed growth rates in all contaminated regimes compared to control populations.