2011:11 Handling Interfaces and Time-varying Properties in Radionuclide Transport Models

Quintessa’s QPAC code has been used to investigate the Qeq approach. The conclusions from this simulation study are the following. The basic approach to calculating Qeq values is sound, however, narrow channels could lead to the same release as larger fractures with the same pore velocity, so a channel enhancement factor of √10 should be considered. A spalling zone that increases the area of contact between flowing water and the buffer has the potential to increase the release significantly.

Quintessa’s AMBER software has been used to explore the effects of glacial episodes on radionuclide transport with time-varying properties. The simulation results show that for both single and multiple glacial episodes the time-dependency of model parameters did not result in much change to the calculated peak fluxes to the biosphere. These conclusions are preliminary and could be changed if different radionuclides are important in the SR-Site assessment.

A detailed review of MARFA code and the associated documentation has been undertaken. New semi-analytic methods have been developed in order to provide a means of checking the accuracy of MARFA calculations. The strengths and weaknesses of MARFA code have been explored in detail.