RD&D-Programme 2004 - SKB

At present, the computational time for a single Comp23 realization with the Fortran77/UNIX
version (on the 400 MHz Sun Enterprise 450 that was used in SR 97) and the Matlab/PC version
(on an Intel 1,700 MHz Compaq Deskpro workstation) is of the same order of magnitude
(a couple of minutes) for runs with the nine nuclides used in probabilistic calculations for
SR 97. The far-field and biosphere modules give insignificant realization times in comparison
with the near-field model. Due to the high portability of the Matlab code (Matlab is available
on a large number of platforms, for example Macintosh OS X and several Unix versions), the
Matlab implementation can, with little effort, be run on another platform if the capacity of the
PC platform should for any reason be judged to be insufficient.
Figure 14-3 shows a comparison between doses calculated with the Proper modules for
radionuclide transport and with the analytical model.
The near-field model
The near-field model Comp23 will be used in SR-Can. This is the same model as was used in
SR 97 and it was originally developed from the Nuctran code /14-7, 14-9/. Comp23 is a multiple
transport pathway model that calculates transient nuclide transport in the near-field of a repository
as occurring through a network of resistances and capacitances connected together in
analogy with an electrical circuit network. Analytical solutions are included instead of fine
discretization at sensitive zones, for example at the release point from a small hole in the
canister and at the entrance to fractures, in order to speed up the calculations. While the Comp23
model used in SR 97 only was able to handle radionuclide transport by diffusion, the present
version has been modified so that advective transport can also be simulated. A further development
since SR 97 is that all nuclides of a certain element can now share the element’s solubilities
inside the canister, where solubility limitations are imposed on radionuclide concentrations.
Maximum dose peat calculated with analytical model (Sv/y)
10 —2
10 —3
10 —4
10 —5
10 —6
10 —7
10 —8
10 —1 10 —8 10 —7 10 —6 10 —5 10 —4 10 —3 10 —2 10 —1
Maximum dose peat calculated with Proper (Sv/y)
Figure 14-3. Comparison between doses calculated with the Proper modules and the analytical
module. Maximum dose up to a million years after closure of the repository with release to peat
bog in 5,000 probabilistic realizations. The deviations within the bounding lines are less than a
factor of 10.
160 RD&D-Programme 2004