Geophysical Methods To Exclude Undeclared Activities At A Geological Repository

Disposal of spent nuclear fuel is expected to be carried out according the IAEA safety standards. The site investigations are needed to demonstrate the suitability of the site to be selected for the geological repository. The hydraulic impermeability of the hosting geological formation surrounding the repository is essential for the safety case. Therefore, performance of rock mass and engineered systems as containment and isolation barriers are considered during planning, design, construction, operating and closing of the repository. At a geological repository the new challenge is to verify the accountancy using indirect methods by excluding undeclared activities.The designers and rock engineering of a repository need site characterization data from different geophysical surveys, pilot drillholes ahead of tunnel front with related geophysical, geological, and hydrogeological investigations, and monitoring. Geophysical methods have developed and focused on the site-specific scientific and technical needs. Their role in safeguards have been under discussion during the development of IAEA safeguards approaches for geological disposal to detect undeclared activities. Geophysical methods have been proposed Design Information Verification as the rock engineering needs the understanding of the host geology. The exploratory works provide sets of safeguards-relevant information, but in practice only the engineered underground constructions can be accessed to be verified. The other application is related to Containment and Surveillance, i.e. detection of human intrusion. In particular, the monitoring of the site conditions gives assurance about the natural responses of the formation and should detect unknown and unwanted phenomena. The Additional Protocol was introduced for this purpose to exclude undeclared activities, but it does not include the application of geophysical techniques. However, the public research for rock engineering and safety case supports the same safeguards mission at a geological repository. In this paper, the current understanding the applicability of geophysical techniques for safeguards purposes is analyzed. The focus is in the resolution and detection capabilities of the active electromagnetic, electric, and seismic sounding and corresponding passive monitoring.