Epidemiological studies have shown a trend towards an excess number of leukaemia cases in the region of Nord-Cotentin (France) where, in particular, the La Hague nuclear reprocessing plant is located. In 1997, it was suggested that the risk of leukaemia was associated with some aspects of lifestyle, in particular, the consumption of local seafood and use of local beaches. To respond to public concern, the French Ministries of the Environment and Health decided to commission complementary epidemiological studies and a detailed radioecological analysis. The radioecological study was entrusted to a group of experts with various backgrounds (inspectors, governmental experts, operators, experts from non-governmental laboratories and foreign experts)--the Nord-Cotentin Radioecology Group. Its principal objective was to assess realistically the exposure to ionising radiation of young people from 0 to 24 years of age who had lived near the La Hague nuclear reprocessing plant and to estimate their risk of radiation-induced leukaemia from 1978 through 1996, the period covered by the epidemiological studies. The Group chose to use a three-stage approach: reconstruction of the population of young people from 0 to 24 years who resided in the region between 1978 and 1996, assessment of their exposure to all sources of ionising radiation, and estimation of the risk of radiation-induced leukaemia attributable to this exposure. The collective red bone marrow dose due to the discharges from the local nuclear facilities from Nord-Cotentin has thus been estimated at approximately 0.5 man-Sv, which is less than 0.2% of the total exposure to ionising radiation, including natural and medical sources and fallout from atmospheric testing and the accident at Chernobyl. The number of cases of radiation-induced leukaemia attributable to discharges from the local nuclear facilities based on the estimated level of exposure was around 0.002 over this period. This is the best estimate, in the current state of knowledge, of the incidence of radiation-induced leukaemia attributable to environmental exposure to ionising radiation among the young people living in the vicinity of the La Hague reprocessing plant based on mean habits for the population. This estimate must be interpreted in the light of the limitations inherent in the risk assessment process, and some participants in the Nord-Cotentin Radioecology Group have expressed reservations about it. Nonetheless, the number of cases estimated here is low in comparison to the four cases of leukaemia observed during the same period. It is thus very improbable that exposure attributable to local nuclear facilities is implicated to any salient degree in the elevated incidence of leukaemia observed in this region among young people.

This paper presents a review of available data on the average level of equivalent dose to the red bone marrow in France, due to natural and some medical exposures. The sources of exposure to ionising radiation which were studied are medical examinations involving x-rays (diagnostic radiology), inhalation of radon and thoron, cosmic irradiation, terrestrial irradiation and intakes of natural radionuclides. This review is based, where possible, on specific data for France. The influence of age on exposure levels is studied when data are available. The total equivalent dose to the red bone marrow is estimated at 2.4 mSv year(-1), 2.7 mSv year(-1) and 5.4 mSv year(-1) respectively for adults (> or =18 years old), children (3-17 years old) and infants (0-1 year old). The high level of exposure for infants is explained by the important contribution of 210Po. The average equivalent dose to the red bone marrow for adults is also compared with the average committed effective dose due to the same exposure sources. The importance of medical exposure and natural exposure due to intake of natural radionuclides emphasises the importance of obtaining more information about these sources of exposure.

Article published by EDP Sciences and available at http://www.edpsciences.org/radiopro C. ROMMENS et al dispersion of gases and aerosois into the environment (ahnosphere contamination and ground deposition), their transfer in the biosphere (soils, plants and animals) and their impact to a memher of the public (individual effective and equivalent doses, external exposure to the plume and to the deposits, interna1 exposure hy inhalation and ingestion). FOCON96 uses ergonomic windows and proposes many capahilities (modnlar architecture, default values, choice of libraries, acces to al1 the parameters of the models, listing of resniîs, management of resnlt iïies, calculations made directly, etc.). In the European context, an intercomparison with the PC-CREAM code, developped hy the National Radiologid Protection Board, has shown the coherence of the results of the two codes. A comparison of the windows and capabilities has shown that FOCON96 was easier to use. FOCON96 is not adapted to calculate the doses received dnring one particnlar year that are due to the discharges of a facility in operation for a long period of t h e . An evolution of the software will he considered if this kind of assessment is generalized.

Abstract. The Nord-Cotentin radioecological study was conducted in different stages. First, an assessment tool was developed and implemented to estimate the number of leukaemia radio-induced by the operation of nuclear facilities of the La Hague site (Nord-Cotentin region, France). Then, an uncertainty analysis was initiated to verify if the confidence intervals around the best estimate previously calculated allows to confirm the low impact of the nuclear facilities. The modelling of the terrestrial ecosystems was especially studied because of the paucity of results of measurements. That is also why the methodology built to reconstruct the statistical laws for each parameter of the model mixes the bibliographic knowledge and exploitation of a national database of environmental measurements. The application of this methodology for up to forty parameters shows that the possibility of fitting an accurate distribution such as a normal or a lognormal law is strongly linked with the availability and the number of measured data.

Abstract. As part of the work of the Groupe Radioecologie Nord Cotentin (the Nord Cotentin Radioecology Group or GRNC), a study has been carried out of potential routes of exposure associated with the industrial extraction of gelling agent from seaweed harvested on the coastline of the English Channel. The main question was whether the seaweed transformation operations tend to eliminate or concentrate the radioactivity in the consumed products. Work carried out in 1989 showed that the extraction of gelling agents from seaweed results in a significant reduction in the artificial radioactivity present in the raw product for radionuclides such as 137 Cs, 125 Sb, 1(K Ru-Rh, Co, 99 Tc, n0m Ag, but with the exception of 90 Sr. However, it seemed important to complete this work by studying transfers of 1 2 9 I, plutonium isotopes ( 238, 239 ' 240 Pu), 241 Am and 244 Cm. The seaweed species studied (Laminaria digitata and Chondrus crispus) were collected during February 1999 in the port of Goury, 5 km from the outlet pipe of the La Hague COGEMA nuclear reprocessing plant. This new study confirms that a significant proportion of the artificial radioactivity present in the initial product is eliminated in the end products, including Iodine, Plutonium, Americium and Curium.