Nuclear fission — the energy-producing phenomena that happens when an atom splits and produces energy — has been happening safely and efficiently inside U.S. nuclear reactors for decades. These reactors, which are all water-cooled, produce clean, green power through use of a basic approach: Initiate and control a fission chain reaction and use the resulting energy to power turbines that make electricity.
Today, 93 nuclear reactors produce about 20% of total electricity used in the U.S. Of the country’s clean electricity, nuclear energy accounts for close to 50%. According to U.S. Department of Energy’s (DOE) Office of Nuclear Energy (DOE-NE), it is a high energy density power generation source. And, while there is no energy source that produces zero carbon and zero waste over the course of its lifetime, scientists believe advanced nuclear designs could come close. Exciting new research into advanced nuclear technologies is a major reason why nuclear energy is considered a central pillar of U.S. efforts to combat climate change and meet rising demand for electricity.
“After every Fast Reactor Program review meeting, I look back and I’m shocked at how effective Argonne’s leadership is. They are excellent at seeing industry’s challenges and clearing obstacles many, many years before industry reaches them.” — Pat Everett, Oklo
“We’re always trying to think about the future,” said Bo Feng, national technical director of DOE-NE’s Fast Reactor Program and manager of DOE’s Argonne National Laboratory’s Reactor and Fuel Cycle Analysis Group. “Currently operating U.S. nuclear reactors work really well, but we want to do things even better, especially regarding resource sustainability and waste management. Fast reactors will play a crucial role in reducing our country’s carbon footprint while minimizing nuclear waste.”
Fast reactor technology uses liquid sodium, lead or other coolants in place of water to remove the heat produced by fission. (That heat is what nuclear reactors use to create the steam that turns turbines to generate electricity.) Fast reactor technology can reuse nuclear fuel which means fast reactors can produce more fuel than they consume. Ultimately, this produces less waste.
DOE-NE’s laboratory-led research and development (R&D), including the Fast Reactor Program, is essential to support industry’s demonstration of these advanced reactors.
“Thanks to investments in our national laboratories through the Department of Energy’s R&D programs, we’ve developed an extensive portfolio of design experience, software, experimental data, and test facilities for many types of advanced reactor technologies,” said Kaatrin Abbott, manager of DOE-NE’s Fast Reactor Program. “It’s a major objective to complete the design, licensing, construction and start of operations on a demonstration fast reactor by the end of this decade.”
According to Feng, the Fast Reactor Program endeavors to anticipate, confirm and develop the technical elements needed to enable and sustain successful large-scale commercialization of fast reactors. Every single R&D activity included in the increasingly important program focuses on three areas: methods, modeling, and validation; technology development; and advanced materials. These three technical areas are essential to support commercial licensing, reduce capital costs or both.
The science behind more energy, less waste
All commercial reactors in the current U.S. fleet are light water reactors (LWRs). Light water refers to ordinary H2O, which is used to remove heat from the nuclear fuel rods. Light water also slows down the neutrons born from fission. In fast reactors, water is not used. Instead, liquid metals such as sodium or lead are used to cool the nuclear fuel rods. In fast reactors, the neutrons are able to maintain very high speeds, which is how fast reactors got their name.
Thanks to fast-moving neutrons, a fast reactor can safely extract considerably more energy from the same amount of mined uranium compared to LWRs. They use much less mined uranium than LWRs and can reduce the amount of used nuclear fuel needing storage. They can enable converting unused uranium (of which there is a surprising amount left in used LWR fuels) into new fuel.
“Fast reactors offer up to 60 times the fuel efficiency of light water reactors and are designed with automatic features that safely shut the reactor down in case of accident conditions,” said Abbott.
Fast reactors can also make new use of used fuel that older reactor technologies discarded and have been storing securely since the 1940s.
A shared history of experiments
One of the reasons why Argonne leads the Fast Reactor Program is because Argonne pioneered the development of fast reactors. This started in 1951 with the design, construction and operation of the Experimental Breeder Reactor (EBR-I), a fast reactor design that produced the first electricity from a nuclear power system.
At the same time, the nuclear industry received federal support to develop and build nuclear power plants using LWR technology. Light water reactor technology wasn’t chosen for U.S. commercial power plants because it was the best option on land — it was because federal agencies and industry had data proving it was successful, safe and effective in U.S. submarines. As a result, other technologies — including sodium-cooled fast reactors — were limited to laboratory R&D programs and reserved as options for the future.
Those laboratory-led programs including EBR-I, EBR-II and the Integral Fast Reactor project, went on to quietly (and extremely successfully) demonstrate inherent safety and fuel recycling capabilities in fast reactors. Today, a reinvigorated fast reactor industry, experts at Argonne, and others in the Fast Reactor Program are working together to fill the gaps left behind when experiments halted.
Partners in pursuit of progress
Scientists and members of industry need to prove that the next generation of nuclear reactors merits robust federal and non-federal support. One way they do that is by preserving, developing and validating fast reactor experimental data and software to support licensing and deployment of new commercial fast reactors.
“We have a very strong and independent nuclear regulator in this country, the Nuclear Regulatory Commission (NRC), and it is working to modernize its regulatory framework in anticipation of non-LWR construction and operation applications from industry,” said Feng. “We all want reactors to continue to operate safely. National labs like Argonne are being asked to draw upon their fast reactor experience, legacy and new data, and experimental infrastructure to help facilitate licensing of commercial fast reactors while also reducing costs.”
For example, these laboratories design, construct and operate innovative state-of-the-art sodium testing facilities such as Argonne’s Mechanisms Engineering Test Loop (METL) and several Sodium Material Test Loops. METL is a modern experimental facility capable of testing advanced components and technologies in sodium under reactor-like conditions. It was built and started up in 2018 through the Fast Reactor Program and is now operated under the National Reactor Innovation Center, a program that accelerates the testing and demonstration of advanced nuclear technologies by providing access to national laboratory assets and expertise. Although METL produces no power from nuclear fission, it simulates the hot sodium environment within an actual fast reactor. Data from its experiments can help industry anticipate and reduce capital and operational costs, and its sodium vessels can also be used to test new technologies from industry. This is an important, forward-looking step toward re-establishing fast reactor experimental infrastructure.
“If there are no operational fast reactors, how do you train people to maintain them, repair them or respond in an emergency?” said Abbott. “There are innovative solutions being developed to ensure that these technologies can be deployed on a timeline that supports our nation’s energy needs. At METL, for example, they experiment with Extended Reality (XR) equipment and software to create XR content and integrate it with the applications for testing at METL. This allows users to see what’s happening to the equipment and sensors submerged in the liquid sodium as tests are being done.”
According to Abbott, without the R&D conducted at METL and other resources developed in the Fast Reactor Program, this kind of insight and training would be impossible. Many in industry agree.
“We’ve developed an extensive portfolio of design experience, software, experimental data, and test facilities for many types of advanced reactor technologies. It’s a major objective to complete the design, licensing, construction, and start of operations on a demonstration fast reactor by the end of this decade.” — Kaatrin Abbott, DOE-NE
“After every Fast Reactor Program review meeting, I look back and I’m shocked at how effective Argonne’s leadership is,” said Pat Everett, Deputy Senior Director of Product at Oklo Inc., a private company developing next-generation fission reactors. Oklo has worked with Argonne on multiple projects and Cooperative Research and Development Agreements, frequently leveraging the R&D products and infrastructure developed through the Fast Reactor Program. “They are excellent at seeing industry’s challenges and clearing obstacles many, many years before industry reaches them.”
For example, in one DOE-NE Gateway for Accelerated Innovation in Nuclear voucher-funded project, legacy fast reactor fuel data relevant to Oklo’s design were qualified. The data, which had been collected during Argonne’s Integral Fast Reactor program in the 1980s-90s, are part of the DOE-funded Fuels Irradiation & Physics Database that was established at Argonne. The data now serve as the backbone of fuel qualification approaches for Oklo and others as it studies how its metallic fuels will perform. This provides a key piece central to the support of NRC licensing.
Oklo also works with Argonne on projects that span experiments to investigate thermal-hydraulic phenomena, prototypic fuel assembly hydraulic testing and fuel recycling, and accesses expertise and capabilities in fast reactors thanks to DOE support.
TerraPower, the company building the Natrium™ sodium-cooled fast reactor near a retiring coal plant in Kemmerer, Wyoming, has also relied on Argonne and DOE-NE’s Fast Reactor Program.
Namely, TerraPower draws on Argonne’s experience and tools for methods, modeling and validation, which are maintained and constantly improved. The work is important to validate the safety of the company’s fuel performance, core mechanics and neutronics.
“Modeling any system that uses any type of fluid is very challenging, whether you’re modeling the basic flow of fluids or the heat flow within a liquid,” explained Jocelyn Scheintaub, TerraPower’s senior manager of national lab project oversight for Natrium. “We rely on Argonne to provide us with information about thermal flow through a nuclear core. That helps us create designs that are as efficient as possible.”
Efficiency is key for the nuclear power industry, where time, cost and safety all play large-scale roles. The same themes are central to conversations about how the U.S. will reduce dependence on greenhouse gas-emitting sources of energy and decarbonize its economy.
“We would not be as advanced as we are if not for the critical work that was done in the Fast Reactor Program at Argonne and DOE’s Idaho National Laboratory,” said Bob Braun, chief operating officer at ARC Clean Technology, another Argonne industry partner working on fast reactor technologies.
ARC Clean Technology is developing the ARC-100 small modular reactor based on Argonne’s EBR-II sodium fast reactor design. “When you look at Argonne’s fuel qualifications, legacy testing data, safety analysis and all the codes that have been developed over decades, these are the fundamental underpinnings of the design and license application process,” said Braun.
“We value the ‘know how’ of the individuals working at Argonne in the fast reactor space,” said Paolo Ferroni, a consulting engineer who is technical lead of Westinghouse’s Lead Fast Reactor Project. “We value the expertise of the senior individuals who may have worked on fast reactor projects that have actually been built, and we value the modeling and simulation capabilities of the younger engineers, who are at the leading edge internationally of R&D activities in support of fast reactor analysis.”
Sharing passionate expertise
Like Ferroni, other members of industry are quick to cite the invaluable transfer of fast reactor knowledge from engineers at DOE national labs such as Argonne to engineers and thought leaders in industry.
This exchange of ideas and hands-on experience is essential to inspiring a new generation of nuclear scientists and engineers and to identifying new opportunities for development.
The XR experiments cited by Abbott are one approach to bridging the divide between historical and future innovation. Supercomputing and artificial intelligence may also contribute significantly.
According to Feng, research is already underway at Argonne to use artificial intelligence to support the Fast Reactor Program’s work, leveraging advanced modeling and simulation techniques to predict material performance years before it could be confirmed in experiments.
“A major role of national laboratories and programs like DOE-NE’s Fast Reactor Program is to conduct and support R&D needed for long-term national security and prosperity,” said Feng. “We always have to be several steps ahead to ensure that we will have the skills and infrastructure in place when the nation needs it.”
