Monitoring the rock barrier around a deep repository using scaled seismic studies

Many countries are now investigating the engineering solutions required to safely dispose of high-level radioactive waste in a deep repository. In the multi-barrier concept the final barrier between the waste in a repository and the outside environment is tin rock mass around the repository. It is therefore important that the stability of this rod mass be monitored to validate predictions and to provide confidence that the effectiveness of this barrier is maintained. Microseismic, acoustic emission (AE) and ultrasonic methods are scaled seismic investigations that provide remote methods of examining the disturbance and damage induced in the rock mass, caused by the operating conditions of a repository (mechanical, thermal and hydraulic stresses, ant chemical and biological processes), which could lead to pathways for radio nuclides to escape to the outside environment. In this paper we show results from AE and ultrasonic monitoring of the Prototype Repository Test, operated by the Swedish nuclear waste agency, SKB, in order to simulate a disposal tunnel in a real deep repository for high level radioactive waste.