From relative gas permeability to in situ saturation measurements

Water saturation is a key factor to assess the safety of concrete storage structures of radioactive waste. Our laboratory has developed a nondestructive method of measuring the in situ water saturation. A pulse sensor, designed to measure effective gas permeability, is firstly casted in the concrete structure. The in situ gas permeability is then periodically measured by analyzing the gas flow rate through the pulse sensor. The relationship between relative gas permeability and liquid saturation of the same material is simultaneously determined by laboratory tests. A numerical simulation of in situ gas flow is then performed, based on the above-mentioned relationship. The in situ saturation is finally deduced by comparing with numerical simulation results. This method has been validated by a laboratory study carried out on a mortar and in situ feasibility of this method has been also proven in an industrial context.