DeWitte says the Aurora demonstration reactor will require several thousand pounds of Haleu fuel. It’s a tall order considering that until a few months ago, the fuel was effectively nonexistent in the US. INL estimates that it has enough spent nuclear fuel on site to produce up to 10 metric tons of Haleu. After a year of recycling the spent fuel, the lab has produced over 1,000 pounds of near-fuel-grade material, but Jess Gehin, chief scientist at INL’s nuclear science and technology directorate, expects to increase this production rate as the lab refines its processes.

INL is using spent fuel from the Experimental Breeder Reactor-II, a nuclear power station that provided electricity for much of the lab for nearly 30 years and also used recycled fuel. To turn the reactor’s spent fuel into Haleu, INL scientists first separate the uranium-235 from unwanted elements, such as plutonium, produced during the reactor’s operation. This involves soaking the spent fuel in a bath of molten salt and then zapping the concoction with a big dose of electricity to heat it to nearly 1,000 degrees Fahrenheit.

Since the uranium-235 used in the Experimental Breeder Reactor was enriched to 67 percent, it must also be blended to bring it to enrichment levels below 20 percent by mixing the uranium-235 with other isotopes that can’t be used as fuel. Finally, the downblended uranium-235 is converted into small pucks just a few centimeters across that can be used as feedstock for the fuel fabrication process.

“This technology has been around for decades, so there’s really limited technology challenges in processing the fuel,” says Gehin. “It’s just a matter of the rate at which we can process it, and we’re working to accelerate that.”

The National Energy Institute predicts that by 2030 America’s annual demand for Haleu fuel will be 100 times larger than it is today, driven largely by the expansion of advanced commercial reactors like Oklo’s Aurora. INL won’t be able to supply all this fuel on its own, nor was it meant to. Its job is to produce enough of the stuff to allow Oklo and other companies working on advanced nuclear energy to demonstrate their reactors. To truly meet the surge in demand, the US will need a robust commercial supply chain.

Last year, Department of Energy officials announced they had awarded the nuclear energy company Centrus a $115 million contract to kickstart the commercial production of Haleu fuel at the Centrus uranium enrichment plant in Ohio. Earlier this month, the department gave another nuclear energy company, BWX Technologies, a $3.6 million contract to produce the fuel, which BWX plans to deliver by 2024.

Unlike Idaho National Laboratory, these companies will be enriching uranium to produce Haleu rather than downblending highly enriched uranium from spent nuclear fuel. Even though Oklo’s reactors can run on recycled nuclear fuel, the first units to hit the grid will almost certainly be powered by fresh uranium fuel. According to Rex Geveden, CEO of BWX Technologies, enriching uranium to produce Haleu fuel is the only sustainable way forward. “Using spent fuel is really only good for a limited number of reactors,” says Geveden. “The nation’s going to need enrichment capability again.”

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