Katherine Mcalpine reports that in findings that could change the way industries like nuclear energy and aerospace look for materials that can stand up to radiation exposure, University of Michigan researchers have discovered that metal alloys with three or more elements in equal concentrations can be remarkably resistant to radiation-induced swelling.
The big problem faced by metals bombarded with radiation at high temperatures, such as the metals that make up nuclear fuel cladding, is that they have a tendency to swell up significantly. They can even double in size.
First, it may interfere with other parts in the structure, but also when it swells, the strength of the material changes. The material density drops, said Lumin Wang, U-M professor of nuclear engineering and radiological sciences. It may become soft at high temperatures or harden at low temperatures.
This happens because when a particle flies into the metal and knocks an atom out of the crystal structure, that displaced atom can travel quickly through the metallic crystal. Meanwhile, the empty space left behind does not move very fast. If many atoms are ousted from the same area, those empty spaces can coalesce into sizable cavities.
To control the formation of these cavities, and the attendant swelling, most recent research has focused on creating micro- and nano-structures inside the metal as specially designed sinks to absorb small defects in a way that preserves the integrity of the material. But Wang and his colleagues are kicking it old school, looking at alloys that do not have breaks in the crystal structure of the atoms.
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