A technique that makes it possible for irradiated materials to be tested at a nanoscale level was developed by researchers from UC Berkeley, the Lawrence Berkeley National Laboratory and the Los Alamos National Laboratory.
The study, published online in Nature Materials on June 26, looked at copper that had been irradiated by ion beams in order to more closely examine the effects of the radiation on the material.
According to Andrew Minor, an author of the study and associate professor in material sciences at UC Berkeley, though nanoscale testing has been performed before, when materials are studied at very small scales, the bulk value — the strength of the material — normally changes, and the materials cannot be used for comparison.
“You’d assume (the materials) would all have the same strength, until you go to the really small scales and the number you get for strength changes,” Minor said. “It’s a problem if you want to get a bulk value for a small-scale test.”
Peter Hosemann, a co-author of the study and assistant professor of nuclear engineering at UC Berkeley, said the difference was due to the size effect, which means materials at a smaller dimension do not have the same properties as when they are tested in larger amounts because of deformation in the materials.
However, Hosemann said when the material is irradiated, it becomes damaged and brittle and therefore less likely to deform. As a result, the bulk strength of the nanoscale-tested copper remained the same as the values on a larger scale, even after being exposed to radiation.
According to Hosemann, following this study, his next step is to study actual components from reactors that had been exposed to radiation. Since irradiated materials can be studied at a nanoscale level, Hosemann said smaller samples are now needed.
“Smaller radioactive amounts of materials are much safer to handle for students and researchers who might be exposed to radiation,” he said.
In addition, he said the testing would allow scientists to look more closely at the reactors, accelerators and other materials exposed to radiation and to evaluate the amount of damage done.
“We’re getting a better understanding of what radiation does to structure materials,” Hosemann said. “It also will help for lifetime extension programs, when they want to run reactors longer than they were originally designed for.”
Minor added that nanoscale testing allows researchers to examine the effects of the radiation on the material on a microscopic scale in order to test its properties.
“The basic advantages of small-scale testing are that you can do it inside the electron microscope,” Minor said. “You can see what’s going on inside the material while you’re deforming it and get feedback in terms of evaluating the material.”
Stuart Maloy, program manager for advanced nuclear energy programs at Los Alamos National Laboratory and a co-author of the study, said the discovery is a promising development in allowing researchers to study how nanoscale testing applies to materials besides copper, both existing and undiscovered.
“If we develop some new material and looked at making it at the atomistic scale, now we can actually test it with just a small amount of the material,” Maloy said. “We can predict what will happen in the future at the larger scale.”