RD&D-Programme 2004 - SKB

20.3 Understanding and conceptual models
The authorities’ regulations require that future safety assessments provide a more realistic
description of the biosphere and an estimation of the consequences of a release for surrounding
fauna and flora /20-3/. The site investigations make the biosphere concrete, which entails that
simplifications in how the biosphere is conceptualized must be valid for the site in question.
The development of process-based models is deemed to be an appropriate way to demonstrate
understanding at the same time as a numerical result is obtained for the safety assessment, see
section 20.4. A systems ecology approach is taken, where both biotic and abiotic processes in
the ecosystems are taken into account. Knowledge of the processes is found within many areas,
for example in conceptual and numerical models for forestry, and in studies of the cycling of
nutrients in lakes and seas or of the cycling of toxic pollutants. On the other hand, this information
has seldom been used for studies of radionuclide cycling. Generalizations are also required
for the long time horizons and varying environments that are considered in a safety assessment
for a deep repository.
In order to get a credible description of the evolution of the biosphere, the conceptual models
that are used must be in harmony with scientific opinion within the fields of not only radioecology,
but also ecology, ecotoxicology and environmental protection.
Conclusions in RD&D 2001 and its review
See section 20.2.
Newfound knowledge since RD&D 2001
SKB has begun the work of compiling process descriptions in a similar manner as for other
repository parts /20-4/. It is a large task due to the multitude of processes in the biosphere.
Interaction matrices have been a useful tool for identifying important processes and for defining
the parameters and variables that need to be determined in the site investigations /20-5/, see
further section 20.11.
SKB has continued to adapt the systems ecology approach to describe the cycling of radionuclides
in the biosphere. Long-term work with doctoral candidates is being pursued at the
Department of Systems Ecology at Stockholm University, the Department of Limnology at
Uppsala University and at the University of Kalmar. The results of this work are presented
below within the relevant programme area.
Several general studies have been published which compile current radioecological knowledge.
A review of bioaccumulation factors in aquatic environments and a statistical analysis of
relationships between various environmental factors have been done /20-6/. A knowledge
compilation has been made of biosphere parameters for the radionuclides in the most recent
safety assessments /20-7/ and comprises the basis for a radionuclide catalogue. Knowledge
regarding radioecology and environmental effects is being compiled in the international
programmes Bioprota, Embras, the IUR’s waste task group and the EU projects Fasset and
Erica, see section 20.9.
Several international symposiums have been followed up: Ecorad 2001, IUR-Setac in Antwerp
and IUR-Andra in Nancy have provided valuable information and good contacts for this work.
Programme
The long-term support for competence development continues as described above.
Documentation for the biosphere matrix will be supplemented during the upcoming period.
Submatrices will be created for the subprogrammes described below. The process compilation
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