Juliana Duarte is an assistant professor of nuclear engineering and engineering physics. Her research focuses on thermal hydraulics, which concerns heat transfer through fluids within nuclear reactors. Duarte also studies reactor safety during transient and severe accident scenarios—or things that can go wrong while reactors are running. In this interview, she discusses the future of nuclear power, including safety, technology and policy challenges, how the field is continuing to evolve, and how it can continue to integrate into the U.S. power grid.
Q: What role do you think nuclear power plays in a more diverse energy generation portfolio?
A: Nuclear has a lot of incentives nowadays because of the need to produce more energy without the emission of carbon dioxide (CO2) and other gases that drive climate change. The United States and other countries have tax incentives for producing nuclear power. But it is important to say that nuclear power is part of the solution when it comes to clean energy. It is not the solution.
Today, the United States has 94 nuclear reactors, which provide almost 20%of our energy. We don’t want to build another 400 reactors that we’d need to get that to 100%, but we do need to make sure we’re building enough to either maintain or increase that roughly 20% to further reduce the amount of power that comes from coal and natural gas.
Q: Many of our nuclear power plants are aging. Beyond the recently completed Plant Vogtle nuclear power unit in Georgia, which ran infamously late and over budget, it seems the United States doesn’t build big commercial reactors that often. What challenges does that present for the future?
A: There are a few things at play there. Once we build something for the first time, we never really know how long it’s going to last. Usually, we’re pretty conservative and license reactors for 40 or so years initially. Most of the reactors we have today were built in the 1970s and 80s, so they have been through inspections, license extensions, equipment replacements, and so on.
But every power plant, nuclear or not, can only run for so long and will eventually have to be decommissioned. So now the challenge facing us is that in the coming decades, some of these older reactors will be facing decommission. If we don’t start building new reactors, that 20% of the energy we get from nuclear power is going to decrease.
We’ve built this one in Georgia, but before that, it had been a very long time (the last reactor to come online in the U.S. prior to Vogtle was Watts Bar Unit 2 in Tennessee, which was activated in 2016; work on the unit began in 1973, but halted from 1985 to 2007). And when you don’t build new reactors, you lose the skill in the workforce. That means when you need to start up again, it’s harder.
Q: What are small modular reactors, and how do they fit into the overall picture?
A: All of the reactors in operation today produce about a few hundred megawatts or more of electricity. In recent years, there have been major investments in developing small modular reactors that can produce up to 200 to 300 megawatts due to their economic potential benefits. Now we even have micro reactors that are being developed to generate on the scale of 10 to 15 megawatts of electricity.
And there are lots of projects like this in development. Right now, my group has funding from the Department of Energy to work on the NuScale small modular reactor, with the goal of increasing the power density in the reactor from 160 to 250 megawatts. We are also working on a project funded by the Nuclear Regulatory Commission on a boiling water reactor that is similar to General Electric’s BWRX-300. With that, we want to understand how to operate it more safely—because those reactors can be a little unstable—and to what degree safety margins can be adjusted so the reactor can be run in a way that’s economically viable, but still safe.
So, this small modular reactor technology exists and is ready but has to go through licensing and review with the NRC. These are the types of reactors that might one day supply part of a community’s power instead of being the backbone. Or they might be used for some of these energy-intensive industries because they’re simpler and more compact.
They bring lots of benefits, but cost will be an initial challenge. They’re a new type of technology, and whenever you’re building something for the first time, it’s going to be expensive.
Q: What are some advancements in the nuclear field that are exciting to you?
A: It’s not super-new, but one of the things we’ve been analyzing is the use of more passive safety systems in reactors. Nuclear reactors are very complex machines, and these passive safety technologies try to simplify them by using gravity and buoyancy, for example. Reactors need a coolant, and all reactors in the United States use water. That water needs to flow, and that’s typically done with a pump. But with passive systems, we can do that without a pump. NuScale, for example, uses gravity—the reactor heats the water, and the different densities naturally make the water flow within it. That’s a system you can use for normal operation, but you can also use passive systems in accident scenarios.
Another exciting topic has been around the recent investments in fusion technology. And at least in our department (and I believe at several other departments across the United States), we’re using the knowledge that we on the fission side have about how to build reactor systems to help with plasma physics to build fusion machines. Investments in fusion have been so much in the science of it so far, but in the last year, I’ve seen so many calls for funding to have more engineering research on how to design and build the systems that are going to work. There are a lot of things in common between fission and fusion in terms of heat removal and how to deal with radiation from the plasma. There is this growing collaboration and it’s very exciting.
Featured image caption: Assistant Professor of Nuclear Engineering and Engineering Physics Juliana Duarte discusses nuclear power, and how maturing technologies can advance the field in the United States. Credit: Joel Hallberg.