A Q&A with ORNL’s Denise Adorno Lopes explores next-generation fuel research
Nuclear fuel is a modern marvel, reliably providing nearly 20 percent of the nation’s electricity, 24 hours a day, 7 days a week. Formed from uranium dioxide pellets and stacked into rods, this fuel sustains a controlled chain reaction that releases heat and produces steam to turn turbines and produce one of the largest sources of reliable, affordable, and secure electricity available.
As energy demands grow, next-generation fuels must deliver more power, last longer, and perform safely under extreme conditions. As a senior R&D staff member in the Advanced Fuel Fabrication Group at the Department of Energy’s Oak Ridge National Laboratory, Denise Adorno Lopes is at the forefront of this new generation of fuel development.
She has a background in physics, advanced degrees in metallurgical and materials engineering and global experience spanning industry and research. Lopes brings a deep understanding of how to advance the science of uranium alloys and accelerated fuel qualification. Her work is shaping how next-generation fuels are designed, tested and deployed to ensure energy security and U.S. competitiveness.
Q: What makes nuclear fuel the most efficient form of creating energy?
A: Nuclear fuel stores an enormous amount of energy in a very compact amount of space. The uranium dioxide pellets used in nuclear reactors are extremely energy dense, with a single pellet offering more energy per mass unit than most other energy forms.
Paired with the fact that modern nuclear reactors operate with very high-capacity factors, meaning they can run between 330 to 350 days per year with only short outages for maintenance, nuclear is among the most reliable sources of baseload electricity. This reliability is very helpful for supporting the grid’s high-demand applications such as data centers and other critical infrastructure.
Q: How can improved fuel design make reactors safer and even more efficient?
A: Commercial nuclear fuel is meticulously designed to only use a small fraction of uranium’s potential energy — typically between 3 and 5 percent in conventional fuel. Better fuel designs and alternative fuel chemistries can increase energy extraction, improve how heat is transferred through the reactor, and broaden operating margins.
At ORNL, we’re supporting advanced fuels research including doped ceramics, composite fuels like TRISO, metallic and ceramic-metal composite fuels, and higher-conductivity compounds. All of these efforts aim to improve the microstructure of fuel and improve how heat is conducted, which can peak temperatures and lower the risk of adverse events.
As we research fuels, we’re also looking at advanced cladding materials and enhanced manufacturing methods to improve accident tolerance. We’re also investigating how modern instrumentation — in-core sensors, improved monitoring and digital twin models — can enable responsive operation and predictive maintenance.
Q: What new concepts are being explored to create better nuclear fuels?
A: Researchers are developing new nuclear fuel forms to support advanced reactor designs that demand higher efficiency, even greater safety margins, and better utilization of waste. Although traditional nuclear fuel is proven and stable, new designs move heat through the reactor with greater efficiency. Next-generation reactors require also fuels that are more uranium dense and transfer heat better than traditional fuel and can operate for longer under the highly corrosive, extreme temperature environments of a nuclear reactor.
The key scientific challenges in developing these advanced fuel forms center on fabrication and how the fuel performs during irradiation, or when fuel is being hit with neutrons. Fabricating advanced fuels using uranium nitride and uranium carbide is challenging because they react easily with oxygen and moisture. Their production requires precise control of how the fuel is composed — especially the amounts of carbon and nitrogen — and careful regulation of the atmosphere during manufacturing.
During irradiation, these fuels can swell, release gases, and their microstructures can change. We don’t have a lot of experimental data exist to validate the long-term behavior of these fuels, so addressing fabrication complexities and irradiation uncertainties is essential to ensure reliable, safe and reproducible fuel performance in advanced reactors.
Q: How does your research aim to improve nuclear fuel design?
A: My work focuses on accelerating qualification of new fuels through an integrated approach that takes much less time compared with traditional methods. Our group at ORNL accomplishes this by incorporating tightly controlled fuel fabrication and characterization, targeted irradiation experiments like our MiniFuel campaigns using ORNL’s High Flux Isotope Reactor, and advanced computational modeling and data analytics. By combining modern materials characterization, irradiation testing, and multiscale modeling, we create an accelerated framework to evaluate performance, shorten qualification timelines and reduce risk during deployment.
Q: How could advances in fuel design change the way we power the world with nuclear energy?
A: Advances in nuclear fuel designs allows for advanced reactor designs. With more options available, there are more possibilities for faster deployment of smaller reactors tailored to diverse needs, like remote sites, industrial loads, data centers, microgrids and space applications, instead of only very large, centralized plants. Faster qualification and modular manufacturing could lower costs and expand the range of locations and use-cases where nuclear energy can provide much needed power.
UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
