Long-term acoustic emission monitoring of a new alkali-activated material for sealing structures in nuclear waste repositories

The crucial part of nuclear waste storage is the construction of sealing structures made of reliable, well-understood, and safe materials. Within the SealWasteSafe project, we compared the performance of an innovative alkali-activated material (AAM) and standard salt concrete (SC), as potential materials for sealing structures for nuclear waste repositories. Two 340-liter-cubic specimens were studied for up to ∼250 days by a multisensory monitoring setup. Specifically, the long-term acoustic emission monitoring aimed to analyze the development of microstructural changes within materials. The monitoring analysis showed fewer acoustic emission events in AAM compared to SC in the first 61 days. After approximately two months of monitoring, the number of AE events in AAM significantly exceeded the number of events in SC. The analysis showed, however, that the increased AE activity was mainly caused by the surface effects of the AAM material and not by the formation of cracks within the material. This contribution presents the use of acoustic emission analysis, both in the time and frequency domains, for monitoring and characterization of materials with potential use as engineering barriers for nuclear waste repositories.