Assessment of Marine Biota Doses Arising from the Radioactive Sea Discharges of the COGEMA La Hague Facility a Comprehensive Case Study (Consensus Appraisal)
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Assessment of Marine Biota Doses Arising from the Radioactive Sea Discharges of the COGEMA La Hague Facility A Comprehensive Case Study (Consensus Appraisal) Dr. D.B. Chambersa, Dr. E. Mullerb, S. Saint-Pierrec†, S. Le Bard aSENES Consultants Limited, Richmond Hill, Ontario, Canada bTerra Geographical Studies, Belvezet, France cCOGEMA, Vélizy, France dCOGEMA, La Hague, France Abstract. This paper reports an assessment of radiation doses to marine biota arising from the radioactive sea discharges (as liquid effluents) of the COGEMA La Hague facility. The La Hague facility is located in the north- west part of France, in the north-west tip of the Nord-Cotentin Peninsula, along the English Channel south shore. The case study was primarily based on the large amount of data from recent studies of the Nord-Cotentin Radioecology Group (GRNC) and from a recent environmental impact assessment of the La Hague facility. The primary objective of this study was to select a representative set of marine biota for the study area (i.e. the Nord-Cotentin Peninsula coast) and to assess the potential radiological impacts, in terms of biota dose-rates and their related potential health effects on marine biota, arising from the radioactive sea discharges of the COGEMA La Hague facility. For assessing potential effects to biota, the predicted biota dose rates were compared to the available guidance for the protection of populations of non-human biota. The guidance values are based on published data by international organizations (e.g. UNSCEAR and IAEA) and on a screening review of a recent database (by FASSET) on biological effects of ionizing radiation on non-human biota. The major conclusion of the case study was that the predicted dose rates to marine biota attributable to radioactive sea discharges from the La Hague facility are small, and in general, well below comparison guidance levels at which deleterious and observable health effects to populations of marine biota might, according to current knowledge, be expected. The predicted incremental dose rates arising from the La Hague facility are also, in general, well below those caused by the background radioactivity in the region. This conclusion and the dose rate predictions in this study are in close agreement with those for the marine biota of Cap La Hague reported in the MARINAII study – recently undertaken for the European Commission. This case study has been presented and discussed at a recent specific workshop of international experts held at La Hague on April 15, 2003. This paper briefly presents the case study and put a particular focus on the study consensus appraisal (which includes the major conclusion stated above) that resulted from the workshop and on an industry perspective on the emerging topic of protection of non-human biota species. The points highlighted in the consensus appraisal have been incorporated in the study final report. The reader is invited to consult the consensus appraisal, contained in the study final report, for an independent and transparent opinion on the La Hague case study that was expressed by a group of international experts. 1. Presentation of the La Hague Case Study 1.1. Background In July 2002, SENES Consultants Limited (SENES) was retained by COGEMA to conduct an assessment of radiation doses to marine biota arising from the radioactive sea discharges (as liquid effluents) of the COGEMA La Hague facility [1,2,3]. The La Hague facility is located in the north- west part of France, in the north-west tip of the Nord-Cotentin Peninsula, along the south shore of the English Channel. Fig. 1 shows the La Hague facility area within France and its regional and local settings. The assessment focused mainly on the areas along the coast of the Nord-Cotentin Peninsula. † Present address : Compagnie Générale des Matières Nucléaires – 78141 Vélizy Cedex France B.P. 4 1 It is emphasized that sea currents in the La Hague area are very strong, among the highest in Europe, especially at the north-west tip of the Nord-Cotentin Peninsula where the off-shore sea discharge pipe outfall of the La Hague facility is located. Within about 500 m from the outfall, the effluents are dispersed by about a factor of 100,000. With the strong sea currents, marine biota tend to concentrate and flourish in rocky areas along the Peninsula coast which offer protection. Away from the coast, this protection is reduced especially in sandy and muddy areas where it can be more difficult for biota to stay and survive. Sessile algae are particularly important along the coast and are a key part of the habitat structure for many organisms. A number of important food species such as lobsters, crabs, whelks, scallops, squid, and fish species are also present along the coast. 1.2. The Objectives of This Study The first objective of this study is to select a representative set of marine biota for the study area (i.e. the Nord-Cotentin Peninsula coastal area) and to assess the potential impacts on the marine biota arising from the radioactive sea discharges of the La Hague facility. The impacts on the marine biota are estimated in terms of potential radiation dose rates and their associated potential health effects. Radiation dose rates in the study area are modelled. For assessing the potential effects to the biota, predicted biota dose rates are compared to guidance values for the protection of populations of marine biota. The guidance values are based on published data by international organizations [4,5] and on a screening review by SENES of a recent database (by FASSET1) on biological effects of ionizing radiation on non-human biota [6]. The generic guidance values derived by SENES are similar to those published in MARINA II2 [7]. Ref. [6,7,8] are two recent key European studies of particular relevance for this case study of the La Hague facility. Beyond the comparison to the guidance values, a second objective is to compare the results of this assessment to the related FASSET guidance [8]; to the marine biota dose rate results in Ref.[7]; and to identify considerations for potential study follow-up. 1.3. Method of Assessment The assessment carried out by SENES was largely based on the results of environmental studies conducted by the Nord-Cotentin Radioecology Group (GRNC3 in French) which provides the most comprehensive knowledge-base on environmental measurements (sea water, sediment, marine biota) and environmental transfer models of radionuclides for the La Hague coastal area [9,10]. It also accounts for the most recent (1996) environmental impact assessment of the La Hague facility [11] which comprises a baseline description of the Nord-Cotentin marine environment. 1 Framework for ASSessment of Environmental impacT (FASSET) is a major European research project, funded by the European Commission, which has carried out, a set of specific studies on the assessment fundamentals for marine biota exposed to radiation; including the identification of candidate representative (called “reference”) biota for European marine ecosystems and an extensive database on doses and effects. 2 MARINA II is a set of studies undertaken for the European Commission to provide the Oslo Paris Convention with information on radioactive discharges, concentrations and an assessment of their impact. It gives dose rate results for a number of marine biota categories of the COGEMA La Hague facility and of the BNFL Sellafield facility coastal areas. MARINA II also includes generic guidance values for the protection of marine biota. 3 In 1997, the GRNC was set following a French government initiative. It includes experts from various stakeholders: governmental agencies, operators, NGO laboratories and foreign organizations. Its main mandate was to conduct: an in-depth review and analysis (data validation included) of the historical radioecological data (both routine emissions and accidental releases) obtained from various organizations; and a retrospective dose assessment (model development & validation included) of the Nord-Cotentin. 2 Base Case (Goury) - In this study, the dose rate to marine biota attributed to La Hague sea discharges is the key parameter for assessing the potential health effects of ionizing radiation on the populations of marine biota. The most recent full review by the GRNC of all available data has addressed historical data up to year 1996 which is taken as the reference year. Goury was chosen as the reference location for estimating doses to marine biota because this coastal region was reported to have, in general, the highest coastal radionuclide concentrations in environmental media as a result of the radioactive sea discharges of the La Hague facility. The dose-rate assessment results for each location along the coast are simply proportional to the ratio of the dispersion factors relative to Goury. The base case dose rate calculations were made in units of absorbed dose and do not account for the differences in the relative biological effectiveness (RBE) of alpha, beta and gamma radiation. The base case dose rates do not account for background (man-made or natural) radioactivity as this was addressed separately in this study. In order to assess dose rates to marine biota in the coastal area of La Hague, SENES carried out the following activities. The dose assessment methodology is further detailed in Ref. [1,2,3,13]. 1.4. Results of Dose Assessment 1.4.1.Base case coastal zone – Goury The marine biota dose rates estimated for selected species in coastal areas are small (by at least 2 to 3 orders of magnitude) compared to the lowest generic guidance values for the protection of populations of marine biota (Fig. 2). Since the radionuclide concentrations in biota, water and sediments from Goury are higher than for other coastal locations, the dose rates to biota in other coastal regions are expected to be lower.