Current Concerns on Durability of Concrete Used in Nuclear Power Plants and Radioactive Waste Repositories

Nuclear power, while viewed with mystique and apprehension, continues to play a significant role in global energy supply despite its limitations. Concrete, the most prevalent construction material, serves as a critical element in nuclear facilities, including radioactive waste repositories and nuclear power plants. It is favored due to its capability to provide adequate shielding against radiation, economical viability, ease of construction, and effective retention of radionuclides. However, assessing the long-term durability of concrete structures in these settings is crucial, as existing knowledge on concrete durability beyond several decades of expected service life is scant. These structures are subjected to slow chemical degradation processes over time that progressively alter their physical and chemical integrity. Current challenges in concrete durability highlight issues such as alkali-silica reaction, delayed ettringite formation, leaching, and carbonation, all of which may worsen under extreme conditions like high temperatures, radiation exposure, moisture, cyclic loading, and acidity. These degradation mechanisms lead to microstructural evolution, cracking, and changes in transport properties that remain inadequately understood due to limited experimental timeframes. This paper offers an overview of these durability concerns, focusing on long-term chemical degradation, including a case study on calcium leaching.