Researchers from the University of Tokyo have conducted a groundbreaking study on the long-term effects of nuclear radiation on concrete with info on the material’s structural resilience.
While the findings raise some concerns, they also offer surprising reassurance—most notably, the ability of quartz crystals within concrete to repair themselves over time. This suggests that nuclear reactors housed in concrete structures may have a significantly longer operational lifespan than previously estimated. Given that nuclear energy is widely regarded as one of the most viable alternatives to fossil fuels, these findings play a crucial role in ensuring the safety, reliability, and economic feasibility of nuclear power.
Beyond the reactors themselves, nuclear power plant safety also depends on the durability of construction materials. Concrete, one of the most widely used building materials in the world, is essential to these facilities. However, the precise effects of neutron radiation on concrete have remained largely unexplored until now.
“Concrete is a composite material made up of multiple compounds. These can vary depending on various factors, including local geography, especially rock aggregate, a major concrete component. But rock will often contain quartz. So, understanding how quartz changes under different radiation loads can help us predict how concrete should behave in general,” explained Professor Ippei Maruyama from the university’s Department of Architecture.
Maruyama and his research team have been tackling this complex issue since 2008. Given the high cost of studying neutron radiation-induced degradation, they developed a strategic approach, combining an extensive review of scientific literature with expert interviews. Their latest breakthrough comes from experiments using X-ray diffraction to analyze irradiated quartz crystals.
The study focused on two key variables: radiation dosage and exposure rate (flux). The researchers discovered that when a quartz crystal is subjected to a specific radiation dose, the extent of its expansion is significantly greater at a high dose rate than at a lower one. This suggests that slower exposure allows more time for the damaged crystal structure to recover.
Maruyama emphasized this point, stating, “The discovery of the flux effect indicates not only that neutron radiation distorts the crystal structure, causing amorphization and expansion, but that there is also a phenomenon where the distorted crystals recover, and the expansion diminishes. Hence, a lower rate affords more time to heal.”
Additionally, the study found that the size of mineral crystals within concrete plays a role in its durability. Larger quartz crystals exhibited less expansion, suggesting that grain size influences how concrete responds to radiation.
“Considering these findings, the degradation of concrete due to neutrons, which is currently a concern, may involve less expansion than previously thought,” Maruyama noted. “Consequently, degradation may be less severe than anticipated, potentially allowing nuclear power plants to operate more safely over longer periods.”
Moving forward, the research team aims to examine how radiation affects other rock-forming minerals to understand the mechanics of material expansion better. They also hope to predict crack formation based on mineral behavior, which could inform the selection and design of concrete materials for future nuclear power plants.
The study is published in the Journal of Nuclear Materials.