Technischer Bericht NTB 85-32

Radioökologische Modellierung der Biosphäre am Beispiel des Modellgebietes Oberbauenstock

The biosphere model is the final link in the chain of radionuclide transport models used for radiation dose calculations for nuclear waste repositories.

The dispersion of radionuclides from a low and intermediate level waste repository in the biosphere and their uptake by man through food pathways is investigated with a compartment model. The relevant biosphere parameters were based on the model site at Oberbauenstock and compiled as a model data set for further use in the biosphere modelling. Nuclide concentrations in the biosphere compartments and foodstuffs as well as annual individual radiation doses are calculated with the computer program BIOSPH.

The present report contains a description of the model area and of its subdivision into 4 compartments, a compilation of the relevant parameters and the simplifying assumptions that have been made, discussion of mathematical modelling of nuclide transport in the biosphere and of the calculation of the individual radiation doses, a technical description of the computer program BIOSPH and a detailed presentation of the results from the model calculations.

The safety calculations show that the radiation doses calculated for the base case scenario with realistic/conservative parameter values are negligible. Even for an accumulation of several conservative assumptions, one calculates doses that are clearly under the protection standard of 10 mrem per year.