Self-sealing capacity of Boom Clay affected by an alkaline plume: evidences from high resolution X-ray computed tomography and hydraulic conductivity measurements

The self-sealing is an important property of clay host rocks considered for long-term geological disposal of high level radioactive waste and spent fuel. The self-sealing of Boom Clay has been demonstrated on artificially fractured fresh Boom Clay cores in the laboratory at ambient temperature and during heating and cooling cycles up to a temperature of 80 °C. As a geological disposal concept in Boom Clay includes components made of concrete, such as for instance the lining of galleries or the secondary packages for the wastes, it is important to evaluate if clay in contact with cementitious materials over a long period retains its self-sealing ability. For this purpose, we used Boom Clay samples that were percolated with young cement water (YCW, pH of 13.2, KOH dominated) and evolved cement water (ECW, pH of 12.5, Ca(OH)2 dominated) for about 5 years.