Gas-induced Radionuclide Transport in Disturbed and Undisturbed Boom Clay and Boom Clay–Bentonite Interfaces

In deep geological repositories, gas can be generated by different mechanisms like anaerobic corrosion, radiolysis and microbial degradation. If the gas generation rate is larger than the capacity for diffusive transport of dissolved gas, a free gas phase will be formed, eventually leading to gas breakthrough events. Depending on the timing of gas breakthrough, dissolved radionuclides (RN) and contaminants could be driven out of the clay faster than the normally expected diffusive transport. A column experiment was designed in which a water saturated clay core is put directly on top of a thin BC core which has been previously saturated with a tracer solution (0.01 mol/l NaI). A He gas pressure is applied and stepwise increased. Upon gas breakthrough, the water on top of the column is expelled and analysed for its iodide content. The measured concentration io-dide is linked to the amount of NaI saturated pore water that was displaced. Based on the obtained results, it can be concluded that the transport of radionuclides and con-taminants due to a gas breakthrough is indeed possible but seems very limited.