The project aimed at the improvement of the scientific basis for the application of biosphere models in the framework of long-term safety studies of nuclear waste disposals.
Site-specific biosphere models were derived following the Reference Biosphere Methodology that was developed within the international project BIOMASS in order to ensure the development of consistent and scientifically justified biosphere models for application in long-term performance assessments for nuclear waste disposals. For these purposes, five European locations, covering a wide range of environmental and agricultural conditions were described and characterised.
In the BioMoSA study the radionuclides 36Cl, 79Se, 99Tc, 129I, 135Cs, 226Ra, 231Pa, 230Th, 237Np, 239Pu, and 238U were considered which are usually most relevant in performance assessment studies of nuclear waste disposals.
For each of the sites, a biosphere model has been developed specifically. As far as possible, site-specific parameters have been selected for element-independent parameters (e.g. irrigation rates, agricultural practices, human consumption rates, potential critical groups) and element-dependent parameters (e.g. transfer factors soil-plant, distribution coefficients, migration of radionuclides in soil). Site-specific calculations have been performed for each of the sites considered. Annual individual doses were calculated, important processes and parameters were identified and the uncertainties of the results were estimated by means of stochastic calculations. To enable a comparison, all results were normalized to an activity concentration in groundwater of 1Bq/m³ for each of the radionuclides considered.