Detailed description of experimental set-up and procedures for gas-driven RN-transport

The gas generated in the near field of a geological repository in clay will first dissolve in the ground water and be transported away from the repository by diffusion as dissolved species. However if the gas generation rate is larger than the diffusive flux, the porewater will get oversaturated and a free gas phase will be formed. This will lead to a gas pressure build-up and finally to an advective gas flux. With this gas flux, contaminated water could be expelled. Work package 5 of the EC FORGE research programma should help us to answer the question: “to what extent can a gas pressure build-up enhance the radionuclide transport in clay?” To answer this question, we will perform experiments with permeameter cells using undisturbed Boom Clay. After infiltration of a clay core with porewater that contains an anionic tracer, a gas breakthrough test will be performed to measure gasinduced transport of this tracer. A preliminary test was executed with an existing cell. The results of this preliminary test are presented in this report, and based on this results the design of the experimental cells was improved.