It’s been acknowledged for a while that radiation affects how concrete holds up structurally. Nevertheless, the specifics were previously unclear. Researchers, including a team from the University of Tokyo, have now identified which concrete properties influence its structural performance under various neutron radiation levels. Their discoveries present some alarming aspects while alleviating others; for instance, quartz crystals within the concrete have the capability to self-repair, which might mean some nuclear reactors can operate longer than earlier anticipated.
It’s been acknowledged for a while that radiation affects how concrete holds up structurally. Nevertheless, the specifics were previously unclear. Researchers, including a team from the University of Tokyo, have now identified which concrete properties influence its structural performance under various neutron radiation levels. Their discoveries present some alarming aspects while alleviating others; for instance, quartz crystals within the concrete have the capability to self-repair, which might mean some nuclear reactors can operate longer than earlier anticipated.
Significant incidents related to nuclear power plants understandably create anxiety among people. However, many view nuclear energy as essential in achieving a carbon-neutral future. This highlights the necessity to enhance safety, reliability, cost-effectiveness, and other factors to mitigate fears and increase acceptance of this energy source. One crucial element that relates to safety and durability in nuclear power facilities is the materials utilized in their construction, particularly the concrete used across various structures. Known for its strength, concrete has been the subject of extensive research to better comprehensively understand its material traits. Yet, only recently have scientists begun to investigate in detail how neutron radiation from nuclear reactors can affect the lifespan of concrete.
“Concrete is a composite material, composed of various substances. These components can differ based on multiple elements, including local geology, particularly the rock aggregate that comprises a significant part of concrete. Rock frequently contains quartz, so evaluating how quartz reacts to different radiation levels can provide insights into how concrete itself is likely to perform,” explained Professor Ippei Maruyama from the Department of Architecture. “Investigating the degradation caused by neutron radiation is notably costly, which has made in-depth research challenging. Our team has been tackling this issue since 2008, developing strategies by reviewing extensive literature and interviewing experts. This led to our recent experiments using X-ray diffraction to study irradiated quartz crystals.”
The team analyzed two factors regarding neutron radiation: the total dose of radiation the samples exposed to and the rates at which they received this radiation, known as flux. The findings were somewhat unexpected; for a specific total neutron radiation dose, quartz crystals exhibited significantly more expansion when the dose rate was higher and vice versa. An analogy could be drawn with sun exposure on skin — while it’s commonly recommended to avoid prolonged direct sunlight without protection, the same amount of exposure can be less concerning if spread out over time.
“The identification of the flux effect signifies that not only does neutron radiation cause distortions in the crystal structure leading to amorphization and expansion, but that there’s also a tendency for the distorted crystals to heal, resulting in a decrease in expansion — hence, a slower rate provides more opportunity for recovery,” Maruyama noted. “Additionally, we observed that the extent of this healing phenomenon varies depending on the size of mineral crystals in the concrete. Larger grains exhibited less expansion, indicating a size-dependent influence. Considering these findings, the concerns surrounding concrete degradation due to neutron radiation may entail less expansion than previously assumed. Thus, the degradation might be less severe than feared, which could allow nuclear energy facilities to function more safely for extended periods.”
The team now plans to address various obstacles in comprehending how different rock-forming minerals expand, further elucidating the mechanisms of expansion and cultivating the ability to forecast the expansion of aggregates based on their material traits and external conditions. They also aim to predict crack formation as a result of mineral expansion. This research could enhance the choice of materials and design for future nuclear power facilities. Moreover, it might offer critical insights into the stability and durability of inorganic materials intended for use in extraterrestrial structures and construction efforts in Earth’s orbit and beyond.
