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Bioaccumulation and dosimetric models have been developed that allow the computation of dose rates to a wide variety of plants and animals in the context of the deep geological disposal of solid radioactive wastes. These dose rates can be compared with the threshold dose rates at which significant deleterious effects have been observed in field and laboratory observations. This provides a general indication of whether effects on ecosystems could be observable, but does not quantify the level of those effects. To address this latter issue, two indicator organisms were identified and exposure-response relationships were developed for endpoints of potential interest (mortality in conifers and the induction of skeletal malformations in rodents irradiated in utero). The bioaccumulation, dosimetry and exposure-response models were implemented and used to evaluate the potential significance of radionuclide releases from a proposed deep geological repository for radioactive wastes in France. This evaluation was undertaken in the context of a programme of assessment studies being performed by the Agence nationale pour la gestion des déchets radioactifs (ANDRA).

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Actinides /Solubility /Repository /ModellingAbstract The solubilities of plutonium, americium and neptunium measured in simulated near-field waters have been compared with those predicted using the simple thermodynamic model NearSol. The dependence of solubility on pH and redox potential is examined in an effort to understand the behaviour of actinides in disposal.The agreement was variable. Differences could be appreciable, in particular for neptunium under oxidizing conditions; conversly, the model successfully predicted the behaviour of neptunium under reducing conditions. Such comparisons pinpointed défi-ciences in the thermodynamic data base and showed the sensitivity of solubilities to certain experimental parameters such as Eh and the concentration of carbonate ions.A comparison between NearSol and the reaction pathway program PHREEQE gave generally good agreement. NearSol was quicker and easier to use, requiring only limited preselection of participating species; however it did not account for the behaviour of bulk inactive species in solution; this feature will be built into an updated version.