Factors underlying nuclear fuel swelling seen at nanoscale for first time

Most types of fuel shrink as they chemically burn (in air), but nuclear fuel initially swells as it is consumed (burned) in a nuclear reactor. Understanding the factors that drive this swelling will help engineers develop higher performance fuels, which could be even safer and more efficient than those used in current nuclear energy plants.

As uranium atoms split to produce energy, fission products build up within fuel rods. Those products can be liquid, solid or gaseous, and the development of solid fission products impacts nuclear fuel performance inside a reactor. But, a clear picture of the size and location of these solid fission products has been elusive until now.

Scientists at the U.S. Department of Energy's Idaho National Laboratory are among the pioneers performing microscopic studies of irradiated nuclear fuel. By using a focused ion beam to prepare fuel samples for examination with a scanning electron microscope, the scientists were able to see nanoscale microstructural features. The team captured some of the clearest pictures ever obtained of solid fission products within used nuclear fuel. They found gas bubbles with an interior coating of solid fission products that came in a variety of shapes and sizes. By analyzing these first-of-a-kind images, scientists can glean information about the size, shape and distribution of fission products, which in turn can provide insight into the factors that underlie nuclear fuel swelling and performance.

More information: http://www.microscopy-today.com/jsp/print_archive/print_archive.jsf#