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nanotimes News in Brief

11-06/07 :: June/July 2011

Materials for Nuclear Applications // Berkeley Scientists Pioneer Nanoscale Nuclear Materials Testing Capability

© Text: Aditi Risbud, LBL S

cientists at Berkeley Lab, the University of California at Berkeley, and Los Alamos Nati-

onal Laboratory have devised a nanoscale testing technique for irradiated materials that provides macroscale materials-strength properties. This tech- nique could help accelerate the development of new materials for nuclear applications and reduce the amount of material required for testing of facilities already in service.

“Nanoscale mechanical tests always give you hig- her strengths than the macroscale, bulk values for a material. This is a problem if you actually want to use a nanoscale test to tell you something about the bulk-material properties,” said Andrew Minor, a faculty scientist in the National Center for Electron Microscopy (NCEM) and an associate professor in the materials science and engineering department at UC Berkeley. “We have shown you can actually get real properties from irradiated specimens as small as 400 nanometers in diameter, which really opens up the field of nuclear materials to take advantage of na- noscale testing.”

In this study, Minor and his colleagues conducted compression tests of copper specimens irradiated with high-energy protons, designed to model how

damage from radiation affects the mechanical pro- perties of copper. By using a specialized in situ me- chanical testing device in a transmission electron mi- croscope at NCEM, the team could examine – with nanoscale resolution – the nature of the deformation and how it was localized to just a few atomic planes.

Three-dimensional defects within the copper created by radiation can block the motion of one-dimen- sional defects in the crystal structure, called dislo- cations. This interaction causes irradiated materials to become brittle, and alters the amount of force a material can withstand before it eventually breaks. By translating nanoscale strength values into bulk pro- perties, this technique could help reactor designers find suitable materials for engineering components in nuclear plants.

“This small-scale testing technique could help extend the lifetime of a nuclear reactor,” said co-author Peter Hosemann, an assistant professor in the nu- clear engineering department at UC Berkeley. “By using a smaller specimen, we limit any safety issues related to the handling of the test material and could potentially measure the exact properties of a material already being used in a 40-year-old nuclear facility to make sure this structure lasts well into the future.”