Thermal‐induced fracture evolution and acoustic signature of Beishan granite: Insights into tensile strength of barrier system for high‐level radioactive waste disposal

Abstract Granite is commonly used as an engineered construction material and a natural geological barrier to prevent radionuclide migration in deep geological disposal of high‐level radioactive waste (HLW). However, the exothermic decay of radionuclides during disposal may threaten the stability and integrity of natural geological barriers. In this study, the tensile strength and acoustic emission (AE) signal of Beishan granite were investigated through Brazilian splitting tests (BST) at various treatment temperatures. The results revealed a significant deterioration in Brazilian tensile strength (BTS) with increasing temperature, with an 88% reduction in BTS at 1000°C. The most pronounced degradation occurred between 400 and 600°C, where the damage variable ( D t ) increased by 0.3. As the treatment temperature increased, there was a general rise in the AE peak events, the cumulative number of AE events, and the AE b ‐value of Beishan granite during the BST, with tensile events being predominant through the rise time/amplitude ratio (RA)‐average frequency (AF) distribution. Additionally, it was found that the orderliness of the scatter distribution of the AE energy during the loading process increased as the treatment temperature rose. These findings underscore the critical influence of thermally induced microcracking on the long‐term performance and safety of granite as a geological barrier for HLW disposal.