Technical Report NTB 86-23

BIOMOVS Test Scenario Model Comparison Using BIOPATH

This report presents the results of the irrigation test scenario, presented in the BIOMOVS intercomparison study, calculated by the computer code BIOPATH. This scenario defines a constant release of Tc-99 and Np-237 into groundwater that is used for irrigation.

The system of compartments used to model the biosphere is based upon an area in northern Switzerland and is essentially the same as that used in 'Projekt Gewähr' to assess the radiological impact of a high-level waste repository.

Two separate irrigation methods are considered, namely ditch and overhead irrigation. Their influence on the resultant activities calculated in the groundwater, soil and different food products, as a function of time, is evaluated.

The sensitivity of the model to parameter variations is analysed which allows a deeper understanding of the model chain. These results are assessed subjectively in a first effort to realistically quantify the uncertainty associated with each calculated activity.