2012:48 Technical Note, Use of Solubility Limits in the SR-Site Safety Assessment

In a radioactive waste disposal environment, in some potential situations (scenarios) a disposed canister containing spent fuel may be breached and the fuel may come into contact with groundwater. The concentration of a radioactive element such as uranium may rise to a level where the solution is saturated. No more of the radioactive element may dissolve and a precipitated solid may be formed. In this situation the radioelement is solubility limited, affecting the groundwater flux of the radioelement leaving the near field.

As part of the SSM’s Initial Review phase, the treatment of solubility limits in SKB’s SR-Site safety assessment has been reviewed to understand: if the treatment is scientifically sound, has a sufficiently wide coverage of key aspects of the assessment, uses adequate models and data and is of appropriate quality.

At the heart of the SKB approach is a spreadsheet tool called Simple Functions that calculates the solubility limit of radioactive elements given the groundwater chemistry. The SKB tool COMP23 takes the supplied solubility limits as one of many parameter values and calculates the resultant risks over time for alternative disposal scenarios.