Southern Nuclear, Southern Company’s nuclear power plant operations business, announced in late September that it had received “first-of-a-kind approval” from the Nuclear Regulatory Commission (NRC) to use advanced fuel—accident tolerant fuel (ATF)—exceeding 5% enrichment of uranium-235 (U-235) in Plant Vogtle Unit 2. The fuel is expected to be loaded in 2025 and will have enrichments up to 6 weight % U-235. The company said this milestone “underscores the industry’s effort to optimize fuel, enabling increased fuel efficiency and long-term affordability for nuclear power plants.”
“5 weight % was deeply ingrained in all of our regulatory basis, licensing basis for shipment containers, licensing basis for the operation of the plants—it was somewhat of a line drawn in the sand,” Johnathan Chavers, Southern Nuclear’s director of Nuclear Fuels and Analysis, explained as a guest on The POWER Podcast. “Testing of the increased enrichment component has been a licensing and regulatory exercise to see how we would move forward with existing licensing infrastructure to install weight percents above that legacy 5 weight %,” Chavers told POWER.
In a press release, Southern Nuclear acknowledged this regulatory exercise and its significance to grid stability. “Nuclear power accounts for nearly half of our country’s clean energy, and Southern Nuclear is committed to pushing for innovative, game-changing technologies like the deployment of Accident Tolerant Fuel that will advance performance and further support our ability to strengthen grid reliability with 24/7 generation,” said Southern Nuclear President Pete Sena. “Realizing the significant role nuclear power plays in our country’s energy infrastructure, I especially want to recognize the NRC’s thorough yet timely review of this installation to support the future of commercial nuclear power in our country.”
Accident Tolerant Fuel Advances
Chavers said ATF became a focal point for the industry in March 2011 following the magnitude 9.0 Tohoku-Oki earthquake—the largest earthquake in Japan’s modern history. A tsunami associated with the earthquake reached heights of more than 30 meters and inundation propagated inland more than 5 kilometers from the Pacific coast, causing a crisis at the Fukushima nuclear power plant.
“In 2012, Congress used the term ‘accident tolerant fuel’ for the first time in an Appropriations Act, and that’s where it all began,” Chavers explained. “It was really for the labs and the DOE [Department of Energy] to incentivize enhanced safety for our fuel in response to the Fukushima incident.”
In 2015, the DOE issued a report to Congress outlining details of its accident tolerant fuel program. The report, titled “Development of Light Water Reactor Fuels with Enhanced Accident Tolerance,” set a target for inserting a lead fuel assembly into a commercial light water reactor by the end of fiscal year 2022. Notably, Southern Company achieved the goal four years early.
“We were the first in the world to install fueled accident tolerant fuel assemblies of different technologies that were developed by GE at our Hatch unit in 2018,” Chavers noted. The following year, Southern Nuclear installed four Framatome-developed GAIA lead fuel assemblies containing enhanced accident-tolerant features applied to full-length fuel rods in Unit 2 at Plant Vogtle. “This is the third set that we’re actually installing that is a Westinghouse-developed accident tolerant fuel, which also includes enrichments that exceed the historical limits of 5 weight %,” Chavers explained.
Going Beyond 5 Weight %
Chavers said there are essentially three “buckets” of nuclear fuel enrichments—the percent composition of the isotope of U-235. “Low-enriched uranium, or LEU, is uranium that’s from natural up to 5 weight %. High-assay low-enriched uranium—HALEU a lot of times it’s referred to—the legal definition is 5 weight % to 20%. And then above 20% is the material that’s used for national defense purposes, such as the Navy,” he said.
“We’re actually getting into that HALEU area, but we’re staying on the very low end of HALEU and referring to it as LEU+ in many terms, because we’re not going above 10% is what we expect for the existing light water reactor fleet,” said Chavers.
The benefits of going beyond traditional enrichment norms are significant, not only for the existing fleet, but also for new reactors being developed within the industry. “Many of the advanced reactors require HALEU fuel—between 5% and 20%—and we are making that first step with a legacy plant, which is helping pave the way for the advanced reactor community to install that material also,” Chavers said.
Where fuel enrichment levels ultimately end up is still a topic of discussion and may vary based on individual plant circumstances. Chavers said fuel for existing light water reactors will likely stay below 10 weight % U-235. “The most likely scenario is going to be 6, 7, maybe 8%. There are economics here, at which, the higher you go up, the more the material will cost us for enrichment services. We’ve got to balance that out with the benefits we receive from the increased enrichment in our fuel utilization or our energy performance,” he said.
The Benefits of ATF
While enhanced safety is perhaps the most significant benefit provided by ATF, advanced nuclear fuel is also important in lowering the cost of electricity. “Our ultimate goal is to enable 24-month [refueling] cycles for all U.S. nuclear power plants, to improve the quality of life for our workers, to lower the cost of electricity,” said Chavers.
“Fundamentally, [nuclear power] is a clean green power source—carbon-free. The more we can keep it running—that’s something we’re trying to go after,” noted Chavers. “We see a lot of positives in this program in that not only are we improving safety, lowering the cost, but we’re also increasing the amount of megawatts electric we can get out of the nuclear assets.”
To hear the full interview with Chavers, which contains more about ATF, the companies involved in its development, how collaboration is a key to success, the safety implications of ATF, and its importance to future nuclear power plant operations, listen to The POWER Podcast. Click on the SoundCloud player below to listen in your browser now or use the following links to reach the show page on your favorite podcast platform:
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—Aaron Larson is POWER’s executive editor (@AaronL_Power, @POWERmagazine).