RD&D-Programme 2004 - SKB

14.2.2 Radionuclide transport and dose
Radionuclide transport calculations are performed in order to estimate the risk of environmental
and health effects from a repository. Since many of the parameters in this type of calculation
either have a natural variability or are incompletely known, probabilistic calculations are
performed where the model parameters are permitted to vary in accordance with some kind of
prescribed probability distribution. In SKB’s previous safety assessments, transport calculations
have been carried out with a probabilistic computational chain that includes transport through
the near-field and far-field and dose calculations in the biosphere. These probabilistic calculations
utilize the results of other simulations for parts of the input database. Figure 14-2 shows
the interaction between the different models intended to be used in the SR-Can calculations,
along with calculation modules for transport calculation (for near-field, far-field and biosphere).
The figure also shows how these modules are linked to other calculation tools and what data
the different models require. These data can be given as probability distributions for most input
parameters. These probability distributions may be based on e.g. experimental data or on the
result of a previously performed calculation which, for different reasons, may not be suitable to
incorporate in the probabilistic transport calculation chain.
Time-consuming groundwater flow calculations based on interpretations and modellings of
site-specific borehole data will be carried out in a separate code (Connectflow or DarcyTools)
and used in different ways in the transport models. Correlated probability distributions from
flow calculations are used as input data for the radionuclide transport models for the near-field,
the far-field and the biosphere.
Borehole data
3D rock
properties
Site specific
transport data
Inventory
and chain
decay
Groundwater
flow calculations
Near field flow
F factors
Travel times
Release points
Near field
transport model
Far field
Biosphere
Release Release Dose
transport model
transport model
Experimental near
field data, geometry,
defect growth, fuel
dissolution, etc
Site characterisation,
surface hydrology
models and human
consumption data
Figure 14-2. Schematic illustration of different sub-models in the radionuclide transport
calculation.
158 RD&D-Programme 2004