It is well known that radiation is harmful to living tissues and materials. But now, MIT engineers are surprised to find that radiation can actually help some alloys repair themselves and extend their service life. This can obviously help inform future power plant designs. In nuclear reactors, radiation accelerates corrosion of most materials, leading to eventual failure and potentially catastrophic consequences. So in this new study, researchers at the Massachusetts Institute of Technology and Lawrence Berkeley National Laboratory began quantifying corrosion at different radiation levels.
But they were taken aback by their discovery. When studying specific nickel and chromium alloys, the team found that radiation actually made the material more resistant to corrosion.
The experiments centered on a nuclear reactor that uses melting salts of sodium, lithium and potassium as coolants. This high-temperature, salty mixture can damage surrounding alloys and corrode the metal over time. But the team found that when the alloy was bombarded with radiation from proton accelerators, corrosion took twice as long.
“We’ve repeated it dozens of times, with different conditions,” said Michael Short, lead researcher on the study. “And every time we get the same result.” The team continued to study the mechanisms behind this surprising result. Using a transmission electron microscope, the researchers imaged the alloy surface and came into contact with the molten salt at a temperature of 650 degrees C.
They found that radiation created tiny defects in the metal, making it easier for its atoms to move. This means they can quickly fill holes in corrosive salts. To some extent, radiation helps the alloy become “self-healing”.
The team said the findings should help inform future nuclear reactor designs and provide a more accurate estimate of the life of materials in existing facilities.
The study was published in the journal Nature-Communications.