RD&D-Programme 2004 - SKB

after the end of the delay time. Sorption of radionuclides to the internal parts of the canister is
neglected.
Conclusions in RD&D 2001 and its review
SKI questions whether it is possible to obtain an improved understanding of the transport
phenomena by using a simple analytical model.
According to SKI, it is not clear whether SKB has improved the description of the transport and
reaction processes included in Comp23.
Newfound knowledge since RD&D 2001
As a complement to and for evaluation of the near-field code used in SR 97, Comp23, an alternative
code, Compulink, has been developed. This alternative code is based on the same conceptual
model as Comp23 and includes the same processes; the two codes should therefore yield
comparable results. Like the whole Proper package, Comp23 is written in Fortran 77, while
the alternative code is written as an application that is run in a Matlab and Simulink environment.
(Information on Matlab and Simulink is available on the Web at http://www.mathworks.
com/). Matlab is a well-established commercial program that is used to solve various types
of numerical problems. Matlab also contains a script language that makes it possible to write
programs and/or applications where Matlab’s own commands are used. This makes it possible
to change parameters, start simulations and save results, which in turn makes it possible to carry
out probabilistic simulations based on random number distributions generated either directly in
Matlab or by a free-standing program. Simulink is a program package that supplements Matlab
and contains routines for carrying out simulations in a graphic environment, offering the possibility
of easily combining different computation modules and thereby easily simulating complex
models. We believe that Simulink’s graphic environment, in combination with Matlab’s built-in
mathematical functions, make a model implementation in Compulink even more easily accessible
and comprehensible for developers and reviewers than the existing Fortran 77 implementation
in the Proper package. The lower learning threshold also allows access to a larger group of
developers, making the development work less sensitive to changes in the development team. At
present the Compulink application has been developed on a Windows PC, but since applications
developed in Matlab and Simulink can be run on several platforms (Windows, Unix/Linux or
Macintosh OS X), the porting work connected with platform changes is minimized. Near-field
releases calculated with Compulink show good agreement with Comp23.
Figure 18-2 shows releases from the near-field to the geosphere for a test case where an initial
canister defect occurs after 6,500 years and a larger defect after 25,000 years. The agreement
between the releases from the two codes is good for all nuclides. The computation time for
the Compulink simulation on an office computer (1,700 MHz Pentium 4 and Windows XP
operating system) is around one minute per realization, which makes the code suitable for
probabilistic simulations too.
Programme
The development of the Simulink-Matlab implementation of Compulink will continue during
the coming period; among other things, the user interface must be improved so that selection of
input data is simplified. Some of this work will be pursued in cooperation with the development
of a new Matlab-Simulink-based code for biosphere simulations. The software development
of Comp23 will, on the other hand, not continue at the same rate as before during the coming
three-year period. The reason for this is not that development resources are being shifted from
Comp23 to Compulink, but that the development need is not as great as before. There are
however areas where refinements and implementations of models are possible. An example
is models for fuel dissolution, where development of new models is taking place.
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