Investigation of the importance of site-specific fauna in environmental risk assessment for routine atmospheric radionuclides releases
Résumé
Although there is still some development of radiological assessment models for non-human biota and their usage, the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA) have already established an internationally recognized system to be used on such assessments. They are often used to evaluate whether or not regulatory decisions are protective of the environment. Non-human biota is typically evaluated using Reference Organisms (ROs) or Reference Animals and Plants (RAPs), the latter defined by the ICRP for a default set general to all exposure situations and the former more dependent on the specifics of the assessment. However, it still remains open whether the use of an increased number of ROs or RAPs would improve the ability to demonstrate protectiveness of the environment or not. In this paper, the representativeness of a hypothetical broader list of fauna is tested in terms of the geometrical characteristics and habits for radiological risk assessments in the case of routine discharges from a nuclear installation. A list of terrestrial representative animal species, compiled from ecological surveys carried out around the Cadarache centre located in the South-East of France, was evaluated. In this compilation, the characteristics (dimensions, habits, etc.) differ from default ROs used in the Environmental Risks from Ionising Contaminants Assessment and management (ERICA) and from the ICRP RAPs. Despite the differences between geometries for those site-specific species and the ROs (including RAPs), the absorbed dose rates calculated for the ROs were very close to those calculated for the site-specific species. Regardless of the organism represented, the absorbed dose rates from calculated for discharge scenarios for the Cadarache centre releases is mainly related to internal exposure, particularly for tritium (3H) and carbon 14 (14C). Dose coefficients (DCs) are shown to be size independent for 3H and 14C, which are the dominant radionuclides for the source term. This shows that there would be an acceptable difference between species from the same organism group. Additional, sensitivity analyses were conducted to determine if the use of generic, predefined ROs is enough to assure an adequate protection of endangered species. The result of this evaluation indicates that, at least technically, the use of generic ROs for non-human biota radiological risk assessment covers sufficiently other species, including endangered ones.