Information on Potential Sources and Sinks for Hydrogen in UK HLW and SF Geological Disposal Facility

Information in the technical and scientific literature has been analysed to evaluate potential sources and sinks of hydrogen in a geological disposal facility (GDF) in the UK. The likely concentration of hydrogen in the near-field is particularly important to evaluate the likely evolution of any oxide spent fuel (e.g. AGR and PWR) that may be disposed of in a GDF. Specifically, any hydrogen solubilised in the near field porewater may increase the electrochemical stability of uranium oxide, thus decreasing the rate at which radionuclides may be released from the spent fuel once groundwater comes into contact with it (after penetration of the waste container by corrosion). The review analyses processes leading to the accumulation and decrease of hydrogen in the near field, with the aim of crystallising current understanding and providing a link to the sources of information available. Sources and sinks considered include metal corrosion (especially of steels), radiolysis, geological sources, gas transport away from the facility, consumption and sorption in physico-chemical reactions and microbial metabolism.