What’s nuclear’s role in a net-zero future?

For many Americans, our vision of nuclear energy was shaped by The Simpsons. Neon green waste pouring out of pipes, mutated three-eyed fish, and narrowly avoided meltdowns serve as the main visual touchpoints millions have to the places that can harness the power of atomic energy, a process that today generates about 19% of the U.S. mix.

Most energy forecasts factor nuclear power into a carbon-neutral future. According to the Department of Energy, the U.S. needs to triple its nuclear capacity in order to meet its net-zero goal by 2050 while keeping up with increasing demand for electricity. More than 20 countries also pledged to do the same at COP28 last year.

“Nuclear power is absolutely essential to meeting our climate goals,” says Kathryn Huff, assistant secretary of the Office of Nuclear Energy at the DOE. Where renewable sources can be constrained by location or variability, nuclear power can run 24/7, requires less land, and can even sit in the footprints of outdated coal mines. (It also is a rare energy source that enjoys bipartisan support, as illustrated by the favorable House vote on the Atomic Energy Advancement Act in late February.)

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For some, though, going full-bore into nuclear development raises environmental red flags. Instead of emitting planet-warming greenhouse gases, the technology creates toxic waste and heightens the risk of nuclear weapons development. That’s before you consider the risk of catastrophic events like the Fukushima Daiichi accident in 2011. “Do we compound the problems of climate change with the proliferation of nuclear energy?” says Matthew McKinzie, a senior director at the Natural Resources Defense Council (NRDC). 

A new wave of “advanced nuclear” technologies like small-scale reactors promises to help bridge this divide, and navigate some of nuclear’s other big stumbling blocks in the process. Yet many of these proposals involve emerging ideas—including fusion, a white whale of nuclear physics—that are largely unproven and untested. Is investing billions in nuclear energy truly essential to reaching a net-zero future?

Small footprint, big money 

Before we dig in, a quick refresher for the English majors: The reactors at a nuclear plant use uranium as fuel to split atoms (that’s fission). The heat created by this process turns water into steam, which in turn spins a turbine that creates electricity. It’s a remarkably efficient process. One recent paper found that, by 2050, the lifetime emissions of a nuclear plant are the same as those of a comparable footprint of wind energy—4 grams of CO2 equivalent per kilowatt-hour. Fossil fuel sources, for comparison, would emit 78-109 grams of CO2 equivalent per kilowatt-hour.

Although nuclear is a clean source of energy in terms of greenhouse gases, it’s also complex and expensive, and it requires many more safety considerations than, say, solar panels. Projects in the U.S., including recently completed reactors in Georgia, and abroad have seen significant delays and cost-overruns in the billions of dollars.

Robert Brecha, who directs the Sustainability Program at the University of Dayton in Ohio, is one of many experts who’s assessed the economics of nuclear power and climate change mitigation. A study he co-authored just 10 years ago projected that nuclear could, in some cases, be more viable for moving away from fossil fuels than just relying on renewables. But since then, sources like solar have decreased in price by up to 90% and increased in their share of the world’s electric generation. “That, I think, changes the dynamics of some of this,” Brecha says. 

Looking purely at the price of electricity, renewables have already won the race, Brecha says. An analysis published in 2023 found that nuclear power can be the most expensive conventional energy option, with a cost of $141 to $221 per megawatt-hour. (Nuclear isn’t a renewable source because of its reliance on uranium mining.) Compared with renewables, its costs were surpassed only by the most-expensive scenarios for residential rooftop solar.

Despite the price tag, proponents like Huff say nuclear is essential for keeping emissions in check. Pointing to billions of dollars of private investment and taxpayer funding, she says there’s no other choice but to strive to build nuclear at the same rate seen from 1970 to 1990, when many of America’s 54 plants were originally built. “It’s going to be basically maxing out what we have ever done and ideally doing slightly more than that,” she says. 

The promise of “advanced nuclear”

Worldwide, nuclear power accounts for some 10% of global energy generation, and even the newer technologies rely on the same basic concept of fission, using uranium as fuel. “Advanced nuclear,” according to the DOE, includes technologies that have yet to be licensed by the U.S. Nuclear Regulatory Commission because of their new designs, fuels, and cooling systems. All of these advances would require a different type of licensing, explains Bemnet Alemayehu, a senior staff scientist at the NRDC. 

Yet, these fresh ideas have many of the same issues as their predecessors. Poor cost competitiveness is preventing new nuclear designs from taking off, says the NRDC’s McKinzie. “It doesn’t look that great for nuclear energy’s potential between now and 2050,” he says. “We don’t see nuclear energy as a near- or midterm solution.” One prototype that was slated to be built in Idaho ended up being canceled because of cost overruns and scheduling delays. The Bill Gates–backed TerraPower project, meanwhile, has struggled to get started.

While both NRDC scientists criticized February’s Atomic Energy Advancement Act largely due to safety concerns, Huff says the bill is intended to make “regulatory improvements” that would reduce the timeline on some permits and make nuclear projects more feasible to build. Huff says it’s interesting to explore how the Nuclear Regulatory Commission “can change its processes without changing its standards.” “We need to start moving on technologies that we currently have available, and nuclear is really one of them,” she says. Both NRDC scientists, however, warn that any reduction of oversight or regulations is troublesome.

Nuclear’s place in the energy mix

When it comes to filling the grid’s gaps in a net-zero future, nuclear is a reliable choice, says Huff. What’s important to understand, however, is that nuclear is not a replacement for renewables like wind and solar, but a supplement. Economically, the University of Dayton’s Brecha says, it doesn’t seem like nuclear is the core of a clean energy future. Rather, according to analyses from the International Energy Agency and others, it plays a complementary role as what’s termed “baseload” power: managing fluctuations in energy generation and covering for a lack of adequate storage.

Accompanied by a massive renewables buildout, nuclear power could also reduce transmission needs as a “centralized, dense” energy option, Huff says. “You can really reduce the total system cost by including nuclear in that system because it backs up some of that renewable capability.” It also produces heat, which could be used in other industrial applications like smelting.

The eternal question

Even if costs and timelines shrink, one issue remains for all nuclear projects: where to put the waste. “We care about things other than just the access to energy and the availability of energy,” Huff says. “We also care about the environmental impacts, and the land use for nuclear power is quite a bit smaller than things like solar and wind.” 

She says the DOE is actively looking for equitable solutions to the nuclear waste issue, which includes finding ways to consolidate and federally manage spent nuclear fuel in ways that reduce the burden “on communities that didn’t commit to maintaining storage.”

That nuclear waste issue is a problem for Brecha as well. “For me, part of what sustainability means in the big picture is that we don’t do things that leave a mess for future generations to clean up,” he says. “For me, the nuclear waste issue is still one that we haven’t solved.”

Correction 3/21/24 11:15 am: An earlier version of this story mis-stated Robert Brecha’s title at the University of Dayton. He’s the director of the university’s Sustainability Program.