RÉSUMI (MciiiLi,s(,ript rrc.rii,etl 1st S(,pt (,iiihri. 2001, o ( . (
~p t r r / I S S < , p t r i i i h c i~ 2002)Low level radioactive liquid discharges have heen carried out in the Loire rivcr since 1963. Since then, the numher of power plants located on the Loire river and ib trihutaries has heen steadily increasing to reach, in the year 2000, 14 rcactors operating on 5 different sites. The question arose to evaluate to what extent the addition of several nuclear power plants on the same river system could increase the concentrations in radionuclides in the environment and affect the dose to the puhlic. To address this issue, EDF initiated in 1998 the "Loire river and estuary radioccology" program wjiih the fucus on assessing possihle accumulation of radionuclide in river hottom sediments or on river shores. The following radionuclides were considered hecause of their importance in power plant li uid discharges: tritium, "C, j8Co. "Co, "' "' Ag, 134Cs, '37Cs, ''R.ln, "'Sh, and '311. Radionuclide concentrations in the dissolved, particulate and sedimentary forms were cvaluated using the CRESCENDO model. The development and validation of tliis model required a multi-step process. The first step was to design a 350-km long 1ü hydraulic and water transport hased on currently availahle tools and data. Next, daily tritium concentrations measured in Angers, at the downstream limit of the river, were compared with computed values. The following step was to calihrate the sediment transport model. Areas where fine particles settleà (dams and river shores) were monitored to improve our understanding of sediment dynamics. Then equations representing radionuclide exchange hetween water and particles were derived from lahoratory experiments and included in the model. After each step the coniputed values were compared to measure data sets to ensure the model adequately described the processes involved. In the final step, the CALVADOS model was used tu calculate dose to the puhlic at different locations along the Imire river. Article published by EDP Sciences and available at http://www.edpsciences.org/radiopro régulièrement depuis cette date jusqu'a atteindre, en 2000, 14 réacteurs sur 5 sites différents. 11 est donc devenu important d'évaluer si l'implantation de plusieurs centrales sur le même réseau hydrographique était de nature à augmenter les concentrations de radionucléides dans l'environnement avec répercussion s u r Ics doses reçues par le public. C'est pour répondre a cette question que EDF a entrepris en 1998 le programme << Radioécologie Loire et estuaire n avec un accent particulier sur l'examen de l'accumulation potentielle de radinnucléides dans les sédiments de fond ou sur les rives. La liste suivante de radionucléides a été considérée eu égard a leur présence dans les effluent? liquides des centrales : tritium, I4C, ''Co, '"Co, ll"n'Ag, '%, '"CS, "Mn, '"Sb et l3'1. Les concentrations de radionucléides sous forme dissoute, particulaire ou dans les sédiments ont été estimées en utilisant le modèle ...