Non-intrusive geo-electrical ERT monitoring of high-level radioactive waste experiments in Tournemire URL

Geophysical electrical resistivity tomography (ERT) is a promising measurement technique for nonintrusive monitoring of an engineered barrier system (EBS) of geological disposal of high-level radioactive waste. Electrical resistivity is sensitive to water content and temperature, which are the key variables characterizing the response of the EBS. In order to assess the technology readiness level of the ERT technique for EBS operational monitoring, ERT survey campaigns have been carried out in two field demonstrator developed at the underground research laboratory (URL) in Tournemire (France) within the project 'Modern 2020', called ERT experiment and LTRBM. Preliminary ERT surveys were carried out to establish the background resistivity of the experimental areas and assess the quality of electrode installation and survey protocols. Monitoring ERT surveys are underway after the installation of both experiments in July 2018 (LTRBM) and September 2018 (ERT experiment). Results of firsts blank test surveys carried out on both experiments confirmed that the resistivity of the host rock around both experiments area is quite homogenous and lower than 100Ωm. Preliminary results of the monitoring period for both experiments are also promising, different materials within the installation are identifiable and changes in resistivity due to water injection and temperature increase are also expected to be noticeable.