New collaboration with University of Utah tackles nuclear waste

Newswise – It’s one of the most pressing questions in nuclear power: What about waste? A new collaboration between Idaho National Laboratory and the University of Utah hopes to answer that question by making fuel recycling a reality for advanced reactors.

The region’s innovative refining technology, based on early nuclear research, won funding from the prestigious Advanced Research Projects Agency – Energy in March.

Contrary to the way nuclear waste is portrayed in popular culture, the radioactive material that comes out of nuclear power plants uses fuel rods – piles of hard, metal-coated ceramic pellets removed from a commercial nuclear reactor. And while it is safely and securely stored, much of this spent fuel still contains useful uranium-235 that can be used to make new fuels. In fact, more than 90% of the potential energy remains in the fuel rods when removed from the reactor.

Old technologies for new reactors

Reducing waste is also on the minds of today’s advanced reactor companies. Many reactor designs under development use mineral fuels similar to those used in older nuclear reactors. When INL researcher Tae-Sic Yoo examined historical data from early fuel testing, he noticed that heating the mineral fuel after it left the reactor caused a natural separation between useful materials and unwanted waste products. “It’s hard to mix, like oil and water,” Yu said.

Yu realized that this could be an excellent recycling method for advanced reactors, especially with advances in instrumentation and testing in the decades that followed early research. Yu and fellow INL researcher Mason Childs have conducted preliminary tests on the concept as part of an INL-directed research and development project, which has shown promising results in separating fission products from useful fuel materials. Now Yu and Childs will work with the University of Utah to further investigate the process in the hopes that it will be commercially viable for mineral fuels.

make change

The key to this reprocessing method is the method of heating the fuel.

If you’ve ever used an induction hob, you know that it’s a quick and efficient way to heat cookware by generating a magnetic field at a specific frequency, rather than conducting heat through a heating element.

Using a specialized “zone refining” furnace that works in the same way, Yoo and Childs can precisely control the heating to partially melt the fuel and allow unwanted elements to separate naturally from the useful uranium. The lab-scale mini-furnace has already helped create an important proof of concept using uranium slugs as an alternative to radioactive fuel.

“We added impurities to the uranium to make it more like used fuel, which is quite a challenge,” Childs said.

One of the most exciting advantages of this zone refining technology is its ability to separate useful uranium without the need for a large-scale chemical process. Other reprocessing methods use materials such as molten salts that require additional disposal and safeguards, resulting in more waste in the process. This zone refining process could one day allow advanced reactors to reprocess fuel in buildings, which could save time and money, and keep the fuel in a safe place to reduce security risks.

As part of an expanded three-year project awarded by the US Department of Energy’s Advanced Research Projects Agency for Energy (ARPA-E), INL will partner with Michael Simpson of the University of Utah Department of Materials Science and Engineering to purchase a second furnace that will allow the university to conduct its own testing and develop Computer models to better understand and predict fuel behavior. It will also help researchers develop advanced devices to more accurately measure conditions inside the furnace, and to test additional metallic fuels.

Define the future of fuel

The team hopes the technology will continue to yield positive results as testing expands over the project’s three-year lifespan. If the project continues beyond this time frame, long-term goals include testing the radioactive fuel, which requires additional safeguards to handle, and investigating whether a modified technology can be applied to ceramic fuels used in commercial reactors today.

“This is an exciting opportunity to see if an old idea can help influence future reactors,” Yu said.

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