Analysis of radionuclide migration from SFL 3-5

A preliminary safety assessment has been performed of a deep repository for long-lived low- and intermediate-level. waste, SFL 3-5. The main objectives of the assessment is to evaluate the capacity of the facility to act as a barrier to the release of radionuclides and toxic pollutants, and to illustrate the importance of different site characteristics for the safety of the repository. The three hypothetical sites investigated are the same as those used for the safety assessment of a deep repository for spent fuel carried out in parallel to this work. This report concerns the modelling of the migration of radionuclides and toxic metals from SFL 3-5. The migration in the near field and the geosphere is modelled, and the resulting dose to man is estimated. The main part of this work is based on a reference scenario defined within the safety assessment. In addition, the effect of human activities has been investigated by analysing the consequences of a release of radionuclides and toxic metals to wells. From the completed study it can be concluded that the radionuclides of importance for the safety are those that are highly mobile and long-lived, e.g. 36Cl and 93Mo. In addition, the site where the repository is built has a significant influence on the safety. Two factors are particularly important: the water flow rate at the depth where the repository is located, and the ecosystem in the areas on the ground surface where releases may take place in the future. High water flow rate in the rock around the repository can be compensated for by better barriers in the near field. However, they must perform satisfactorily over a very long period of time