RD&D-Programme 2004 - SKB

Newfound knowledge since RD&D 2001
In SR 97, the biosphere was divided into squares sized 250 x 250 metres that were associated
with the typical ecosystems lake, running water, sea (archipelago and coast), mire (bog),
agricultural land and well. Biopath models that described the different typical ecosystems were
developed /20-9, 20-18/. The advantage of this approach is that the causes of the variation in
estimated dose can be separated. Uncertainty analyses and sensitivity analyses showed that the
biological processes need to be described better and that the physical parameters need to be
measured better /20-9, 20-11/. The site-specific information was limited in SR 97, however,
since few biosphere investigations have been conducted on the old study sites.
In the Safe project, the safety assessment for SFR, a time-dependent evolution was introduced
for different types of ecosystems /20-10/ and site-specific biosphere data. Investigations were
conducted to obtain a better body of data /20-19/.
New models for the coastal area were developed for Safe based on the principles of systems
ecology /20-20, 20-21/. They describe the flow of carbon-14 through the food web and the
concentration of carbon-14 is calculated in different compartments without using concentration
factors. The transfer of radionuclides is based solely on mechanisms such as food ingestion,
photosynthesis and degradation. This model was tested for other radionuclides, such as cesium.
The results are promising and are described in internationally published articles /20-22 to 20-24/
and are included in Linda Kumblad’s doctoral thesis /20-17/.
Similar development of systems ecology models is under way for lakes and is being tested for
Eckarfjärden, which is included in the Forsmark area. The models are based on previous studies
/20-25 to 20-27/.
A general systems ecology modelling tool, Ecopath, was evaluated in 2004 as an independent
general modelling tool for radionuclide transport in the food web /20-28/.
A review of modelling tools has been initiated to evaluate the potential of the Biopath and
Prism tools vis-à-vis other modern modelling tools, both general graphic modelling software
(e.g. Simulink/Matlab, Stella/Ithink, Powersim, Modelmaker, Madonna) and specific codes for
safety assessments (Amber, Goldsim, Ecolego and Ecopath). After a cursory review, Simulink/
Matlab were selected as having the greatest potential and flexibility for future biosphere
analyses. The probabilistic simulations are handled in the code @Risk coupled to Matlab.
The biggest advantages are high computing power and an open, well-used and transparent code,
which means there are many users and therefore a good base for updating and maintenance
of the tool. Another advantage is that systems ecology models can easily be implemented in
Simulink/Matlab /20-29/. The disadvantage is that a tool library must be built up to provide a
rational working environment for safety assessment. A basic tool library, Biomat and Tensit,
was developed during 2003 and 2004 to enable compartment models and radionuclide chains
to be handled and improve data management. Development of Biomat was done in cooperation
with Posiva. The tool has been tested with the biosphere models from SR 97 and in international
comparisons (PSACoin) against Biopath/Prism and Amber /20-30/, see Figure 20-1. The tool is
promising, and it will be used for the biosphere calculations in SR-Can. The tool will be tested
for other parts of the computational chain as well, see further section 18.3 and Chapter 14.
Programme
The systems ecology models will be further developed for lake and land. The Tensit toolbox
in Simulink/Matlab will be further developed to provide a good environment for safety assessments
and ready-to-use models for wells, dose to man, irrigation and templates for the lake,
sea and land ecosystems. Methods for how site-specific data is to be used will in particular be
studied. This presumes an integration with Gis databases and other numerical tools such as
Femlab. The goal for SR-Can is to have a fully functional simulation environment with Tensit.
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