For some time, the effect of radiation on concrete’s structural integrity has been recognized, particularly in the context of nuclear reactors. However, the specific mechanisms at play, and how radiation influences the material’s long-term stability, have remained largely unexplored—until now. Researchers from the University of Tokyo, among others, have unveiled new findings that help to clarify the impact of neutron radiation on concrete and how its properties can change under different radiation doses and rates.
The study, published in the Journal of Nuclear Materials, sheds light on an intriguing facet of concrete’s performance in nuclear environments: while some aspects of radiation-induced degradation are concerning, others suggest that concrete may be more resilient than previously thought. Specifically, it appears that quartz crystals, a major component of the rock aggregate used in concrete, may have the ability to heal themselves under certain conditions, potentially extending the operational lifespan of nuclear reactors.
These findings are particularly timely, as nuclear power is considered one of the cornerstones for achieving a carbon-neutral world. However, the safety and longevity of nuclear power stations—especially their structural components—remain crucial concerns. With growing calls to improve the reliability, cost-effectiveness, and overall safety of nuclear reactors, this new research provides insights that could alleviate some concerns and promote greater acceptance of nuclear energy.
Understanding Concrete’s Role in Nuclear Safety
Concrete is a composite material, made up of various compounds, including cement, aggregates, and water. Its durability and strength have made it the material of choice in the construction of nuclear reactors and other critical infrastructure. Over the years, extensive studies have been conducted to better understand the material’s characteristics, such as its compressive strength, flexural properties, and how it responds to temperature and moisture.
Until now, however, the specific ways in which concrete degrades under neutron radiation had not been thoroughly explored. Neutron radiation, which is emitted by nuclear reactors, can penetrate concrete and cause changes in its molecular structure. This degradation process could potentially compromise the structural integrity of reactor buildings and other key components over time. Thus, it is essential to understand how concrete behaves when subjected to radiation, especially in the long-term context of nuclear power plants that need to remain operational for decades.
Exploring the Role of Quartz Crystals in Concrete
The team, led by Professor Ippei Maruyama from the Department of Architecture at the University of Tokyo, has focused on one particular aspect of concrete’s composition: the quartz crystals present in the rock aggregates used in the material. Quartz, a mineral made of silicon dioxide, is a key component of many types of concrete. Since neutron radiation interacts with crystal structures, studying how quartz behaves under radiation is crucial for understanding the broader impacts on concrete.
In their research, Maruyama and his team utilized X-ray diffraction to analyze irradiated quartz crystals, which allowed them to examine how the material changes when exposed to different doses of neutron radiation. What they discovered was both surprising and enlightening: the impact of neutron radiation on quartz crystals depended not only on the total dose received but also on the rate at which the radiation was delivered.
Flux and Dose: The Key Factors in Radiation-Induced Degradation
The researchers identified two critical factors in radiation-induced degradation: the total dose of neutron radiation and the rate of exposure, known as the flux. The total dose refers to the cumulative amount of radiation a material absorbs, while the flux refers to how quickly the radiation is delivered.
At first glance, one might assume that a higher total dose of radiation would cause more damage to the material. However, the team found that the dose rate (i.e., how fast the radiation is delivered) played a significant role in how the quartz crystals expanded and degraded. Specifically, when the dose rate was higher, the amount of expansion in the quartz crystal was far greater. This phenomenon is similar to the way the sun’s radiation impacts human skin: it’s better to be exposed to sunlight over a longer period with less intensity than to be exposed to a high dose of radiation in a short burst.
In simpler terms, rapid exposure to high doses of radiation causes more immediate damage to the crystal structure of quartz, leading to amorphization—a process where the crystalline structure breaks down and becomes disordered. However, when the radiation exposure is spread out over a longer time, the crystals have more time to recover, and the amount of expansion is less pronounced.
The Healing Potential of Quartz Crystals
Perhaps the most surprising discovery was the self-healing properties of quartz crystals under neutron radiation. When quartz crystals were exposed to neutron radiation at a slower rate, the expanded crystal structure began to shrink or recover, returning closer to its original form. This phenomenon suggests that, under certain conditions, concrete could potentially “heal” some of the damage caused by neutron radiation.
This self-healing behavior could have significant implications for the longevity of nuclear reactors. If concrete’s quartz crystals can recover from radiation-induced expansion, then the degradation of concrete over time may not be as severe as previously thought. This could potentially allow reactors to operate for longer periods than initially anticipated, reducing the need for frequent repairs and replacements.
Larger Crystals and Radiation Resistance
In addition to the dose rate and the self-healing properties of quartz, Maruyama and his team also discovered that the size of the mineral crystals within the concrete plays a role in how the material reacts to neutron radiation. Specifically, larger quartz crystals exhibited less expansion under radiation than smaller ones. This suggests that the size of the mineral crystals in concrete could influence its overall resistance to radiation damage.
This finding could inform future decisions about concrete design, particularly in the context of nuclear power plants. By selecting aggregates with larger mineral crystals, engineers may be able to enhance the radiation resistance of the concrete used in reactor buildings and other critical structures.
The Road Ahead: Challenges and Opportunities
While the team’s findings are promising, there are still several challenges to overcome in fully understanding how neutron radiation impacts concrete. One of the primary goals for the future is to develop more precise models for predicting how concrete will behave under different radiation doses, rates, and environmental conditions.
Maruyama and his team also aim to expand their research to investigate how other rock-forming minerals, besides quartz, respond to neutron radiation. This broader analysis could help refine our understanding of concrete’s overall degradation process and improve predictions about its long-term durability.
Moreover, the team is working to better understand the formation of cracks within concrete as a result of mineral expansion. This knowledge could be used to improve the selection of materials and the design of concrete structures for future nuclear power plants, ensuring they can withstand the challenges posed by neutron radiation over extended periods of operation.
Implications for Future Nuclear Power and Space Exploration
In addition to its implications for nuclear energy, this research could also have applications in other fields, such as space exploration. Concrete-based materials are being considered for use in extraterrestrial construction, including structures built on the Moon or Mars. Understanding how concrete and other inorganic materials respond to radiation in space environments—where cosmic radiation and solar radiation are prevalent—could be crucial for ensuring the stability and longevity of space-based infrastructure.
By applying the insights gained from this research, engineers and scientists can design more durable materials for both nuclear power plants on Earth and potential space habitats beyond our planet.
Conclusion
The recent breakthroughs in understanding how neutron radiation affects concrete represent a significant step forward in improving the safety, durability, and longevity of nuclear power stations. While there are still many challenges to address, the discovery that quartz crystals in concrete can potentially heal themselves under certain conditions opens up exciting possibilities for the future of nuclear energy.
As the world continues to focus on carbon neutrality and the role that nuclear power can play in achieving this goal, research like this will be essential in ensuring that nuclear reactors remain safe, reliable, and efficient for decades to come. Furthermore, the insights gained from studying concrete’s response to radiation may also pave the way for innovations in materials science that extend beyond the nuclear sector, including space exploration and beyond.
Reference: Ippei Maruyama et al, Neutron flux impact on rate of expansion of quartz, Journal of Nuclear Materials (2025). DOI: 10.1016/j.jnucmat.2025.155631