A $1.3 million award from the U.S. Department of Energy will help U-M examine one of the major challenges facing nuclear reactors today, and help train the next generation of nuclear engineers.
U-M will receive $465,000 to support three graduate students in nuclear engineering over the course of three years, including a summer working at a national laboratory. Another $20,000 in undergraduate scholarships will be awarded to students going into a nuclear field.
In addition to the grants supporting students, $831,876 will fund research into how high doses of radiation, combined with high temperatures, affect materials inside advanced fast nuclear reactors.
Fast reactors for nuclear power differ from the reactors currently in operation in the United States because they don’t slow down the neutrons that are released in each fission reaction. The high-speed neutrons allow these reactors to re-use spent fuel from current reactors.
“Fast reactors also can destroy some very long-lived radioactive products of fission,” says Gary Was, Walter J. Weber Jr. Professor of Sustainable Energy, Environmental and Earth Systems Engineering. So recycling fuel can “reduce the amount of time radioactive waste needs to be stored,” he adds.
However, faster neutrons are more damaging to the structural components inside the reactor, such as the metal tubes around the uranium fuel, so these parts will need to be tougher against radiation damage. In order to make sure advanced reactors will be reliable for their lifetime, engineers need to understand exactly how radiation affects the metal alloys used to build them.
“In the U.S., we don’t have test reactors that can cause that level of radiation damage in a reasonable time frame,” Was says. “Instead, researchers have been looking for ways to imitate the degradation caused by a fast reactor environment more quickly. The team will expose strips or plates of metal alloys to a barrage of iron ions, or iron atoms with an electric charge, to simulate many years” worth of neutron damage in a matter of days.
By mounting the alloy samples on a heated surface, the team will mimic the temperatures inside a reactor, which range from 660 degrees to 930 degrees Fahrenheit, depending on how close the material is to the heart of the fission reactions.
Zhijie Jiao, research scientist in the Department of Nuclear Engineering and Radiological Sciences, is leading the experiments to be carried out in the Michigan Ion Beam Laboratory using the Tandetron accelerator. Was and Emmanuelle Marquis, assistant professor of materials science and engineering, are co-investigators.
In order to find out whether their ion-beam-induced radiation damage truly looks the same as real reactor damage, colleagues at Los Alamos National Laboratory in California will examine components from a decommissioned U.S. fast reactor. Using high-resolution imaging technologies such as electron microscopes, the teams will compare the degradation sustained in reactors and from ion beams down to the microscale. U-M also is providing funds to Oak Ridge National Laboratory in Tennessee, so that collaborators there can create computer models to describe how materials change in nuclear reactors.
“It’s become very important to find other ways besides reactor irradiations to learn how materials respond to radiation,” Was says. “It’s not simple, it’s not straightforward, but we’re getting close.”
