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Working to prevent nuclear proliferation

Kyler Turner is a graduate student working with Gary Solbrekken, a mechanical and aerospace engineering assistant professor, to test fuel plates that would allow research reactors to operate on low-enriched uranium. Turner poses with flow test equipment the research group constructed in their lab to run experiments that evaluate plate deformation due to coolant flow. Graduate student Jesse VanEnglenhoven and undergraduate honors researcher Aaron Siddons are also working on the project.

A Mizzou Engineering researcher has joined a national effort to prevent nuclear proliferation by helping tackle the tricky technical problem of finding a way to fuel high-performance research reactors with low-grade uranium.

Many research and test reactors throughout the world were designed to use highly enriched uranium to produce radiation for experiments in virtually every scientific field. Because that high-enriched uranium can be a component in nuclear bombs, the U.S. Department of Energy (DOE) has been working for decades to convert nuclear reactor sites around the world to low-enriched uranium fuel that cannot be used to build an atomic weapon.

Gary Solbrekken, a mechanical and aerospace engineering assistant professor, has received $78,137 from the DOE’s Argonne National Laboratory to test new fuel plates designed to allow domestic high-powered research reactors to operate effectively on low-enriched uranium. The new fuel plates must be thinner than existing plates so that enough water can flow between those plates to allow the reactor to run at full power, but still stiff enough to withstand the water’s pressure, Solbrekken said.

“There’s a safety issue and a quality issue that we’re trying to balance,” Solbrekken said.

Solbrekken’s research, part of a larger project coordinated by the Argonne National Laboratory, is slated to be complete by the end of next September. Additional phases would examine how fuel plates react to water pressure when they are stacked as they would need to be under the low-enriched uranium fuel plan.

The new, thinner fuel plates Solbrekken is examining would include a low-enriched uranium foil that Argonne lab researchers have developed to replace the high-enriched uranium that now fuels research reactors.

The foil contains less than 20 percent of a form of uranium useable for nuclear weapons—called U235—compared to highly enriched uranium fuel, in which about 90 percent of the uranium is U235. The remaining uranium is U238, an inert form found naturally in rocks.

While the uranium foil would reduce the U235 concentration to levels well below what is needed to build a nuclear bomb, it also would remove the binding mechanism that strengthens existing fuel plates, Solbrekken said. The U235 in highly enriched uranium—which already contains aluminum atoms—is mixed with more aluminum powder to create a strong, rigid plate, he said. Some preliminary analysis suggests the thinner fuel plates could be less rigid and potentially buckle under reactor coolant system pressure, he said.

“It’s an unknown phenomenon right now, but it is of concern,” Solbrekken said. “The potential for buckling needs to be investigated.”

If successful, the new low-enriched uranium fuel system could be broadly applied to high-performance research reactors scheduled for conversion around the world. The National Nuclear Security Agency Global Threat Reduction Initiative, which leads the U.S. program to minimize the use of highly enriched uranium, aims to complete the conversion of all civilian domestic research reactors by 2014, according to a DOE report on the process.