Landscape development in the safety assessment of a potential repository in Forsmark, Sweden

One challenge in the analysis of far future radiological effects of a deep geological repository is to handle changes in time on ecosystems potentially affected. Under Swedish regulations, the time span that needs to be assessed is 100,000 yrs or more. This has historically been treated by using a reference biosphere that, in short, takes into account the total data range of the site properties that may change with different climates and sites. One problem with this strategy has always been to show that these reference biospheres have relevance for a specific site. To overcome this problem, SKB has adopted a strategy that uses site specific information together with scientific literature to build a narrative. This narrative describes the site development during a 100,000-yrs period (time frame of the present global glacial cycle). The information is used to compile a number of models that describe how the succession of abiotic and biotic features and their properties will develop at the site. The resulting Landscape Development Model is finally used in two ways: to tell the narrative of the site development based on scientific understanding and interdisciplinary consensus, and to populate the Radionuclide Model that is used to describe the effects of released radionuclides in a changing environment