The effects of decay chain-ingrowth on nuclide migration in the engineered barrier system

The migration of radionuclide through the buffer material was analyzed by considering the precipitation caused by decay-chain ingrowth. In the analysis, the temporal and spacial isotopic ratio in the buffer material was taken into account for determining the shared solubility for each radionuclide. The release rate of radionuclide from the outer surface of buffer material to surrounding rock is generally lower in such realistic analysis considering precipitation in the buffer material than calculated by the model neglecting precipitation. This result shows the model not considering such effects is more conservative for the safety assessment. It is also shown that the realistic analysis considering precipitation defined by the shared solubility can provide a large margin in the safety assessment. (author)