Work package 2: Gas generation

For more information, please contact Delphine Pellegrini, (WP2) leader.

This work package will examine the rate of hydrogen production in order to provide information in support of repository performance assessment. The key processes to be better understood are the impact of radiation on near field materials and the role of chemical processes, in particular the corrosion of metals. Experiments will measure hydrogen production rates from the corrosion of steel in contact with bentonite under different test conditions, improving our understanding of these issues. Understanding the effectiveness of processes which may mitigate the volume of hydrogen close to the point of origin, are an important input for assessing the influence of the global evolution of hydrogen generation within the repository. Short and longer term irradiation experiments will be undertaken in parallel to understand the influence of the boundary conditions of the tests and the temporal evolution of parameters.

In a geological repository, containers will be exposed simultaneously to water and radiation. Hydrogen production and migration will be affected by a number of factors including the solid and liquid phases of the engineered barrier and irradiation. The effect of radiation on the production of hydrogen and on the chemical conditions in the near field that may affect gas evolution will be studied using irradiation facilities. The expected outcome of these studies is to provide a more accurate assessment of the kinetics of hydrogen production and its migration than is available at present. This knowledge is an important factor in the understanding of the likelihood of the development of discrete gas phase within a repository. These processes will be addressed by experimental and numerical modelling and specific issues that will be studied include:

• Consumption of hydrogen by reaction with radiolytic products such as hydroxide ions
• Inhibition of corrosion by the products of radiolysis
• Effect of water chemistry e.g. the influence of carbonate reactions with hydroxide ions
• Effect of clay/cement barriers on hydrogen production and its migration through samples under irradiation

The sensitivity of these processes on hydrogen production will be investigated.