Is Nuclear Energy Having a Renaissance?

For a while there, nuclear energy looked like it was on its way out. After taking off post-World War II, it lost momentum toward the dawn of the 21st century, when sagging public support and mounting costs led to dozens of cancellations in the U.S. and drove the rate of new proposals off a cliff. Only a few reactors have been built in the U.S. this century; the most recent, Georgia Power’s Plant Vogtle units 3 and 4, were years behind schedule and billions of dollars over budget. Vogtle-3 came online last summer, with Vogtle-4 — which was delayed even further by an equipment malfunction — expected to follow early this year.

It’s funny how time works, though. With demand for reliable zero-carbon energy rising, a new wave of nuclear developers is trying to recapture some of the industry’s long-lost momentum. They’re entering the race to net-zero with big ambitions — and much smaller reactor designs. Whether you’re wondering about the state of the U.S. nuclear power sector, what’s new about new nuclear, where the nuclear waste is going, and of course, whether it’s safe, read on.

Let’s start with the basics.

How do nuclear plants work?

Nuclear reactors generate electricity using a process called fission. Inside the reactor’s core, a controlled chain reaction splits unstable uranium-235 into smaller elements; that process releases heat — a lot of heat.

The reactors in today’s U.S. nuclear fleet fall into two categories: boiling water reactors and pressurized water reactors. Each circulates water through the reactor core to manage the temperature and prevent meltdowns, and both use the heat produced by fission to create steam that powers turbines and thereby generates electricity. The main difference is in the details: Boiling water reactors use their coolant water to produce electricity directly, by capturing the steam, whereas pressurized water reactors keep their coolant water in a separate system that’s under enough pressure to prevent the water from turning to steam.

Some experimental reactors and newer commercial designs use different cooling systems, but we’ll get into those later. Lastly, while nuclear energy is not considered renewable, in the sense that it relies on a finite resource (enriched uranium) for fuel, it is a zero-emission energy source.

How did U.S. nuclear energy become what it is today?

The sector emerged in the late 1950s and expanded rapidly over the next several decades. At its peak, the country’s nuclear fleet included 112 reactors — a number that has declined to about 90 today. Most of the surviving plants were built between 1970 and 1990.

The shrinkage has partly to do with the nuclear disarmament movement, which arose during the Cold War and grew to encompass nuclear power development, as well. (As it happens, much of the present day environmental movement has its roots in anti-nuclear activism.) Then there was the partial nuclear meltdown at Three Mile Island in 1979, which intensified existing public opposition to nuclear energy projects. That growing pushback, combined with reduced growth in electricity demand and the significant up-front investments nuclear plants required, caused some projects to be scrapped and fewer to be proposed. The Chernobyl nuclear disaster in 1986 seemed to confirm everyone’s worst fears.

Interest began to reemerge in the U.S. in the early 2000s as the budding public awareness of climate change cast doubt on the future viability of fossil fuels, but the 2011 Fukushima nuclear accident quashed many of those plans. The last U.S. nuclear plant to start up before Vogtle-3 entered construction in 1973 but was suspended for two decades before its completion in 2016.

What’s nuclear power’s role in the current energy system?

As of 2022, 18.2% of U.S. electricity came from the country’s remaining nuclear reactors, according to federal data. That’s less than we’ve seen in decades.

The share of nuclear power on the grid has been slowly dwindling as aging reactors are shut down and other resources — mainly natural gas and renewables — have taken on a greater proportion of the country’s electricity-generating burden. The share of electricity from renewables surpassed energy from nuclear for the first time in 2021; in 2022, renewables contributed 21.3% of U.S. electricity.

Like coal and gas plants (and renewables when paired with sufficient storage), nuclear provides baseload power — meaning it sends electricity onto the grid at a consistent, predictable rate — as opposed to sources like wind and solar on their own, which provide intermittent supply. Electric utilities depend heavily on nuclear plants and other baseload resources to match supply with continuously fluctuating demand, accommodating the variability of wind and solar without sending too much or too little power onto the grid, which would cause power surges or blackouts.

Is nuclear power safe?

Generating electricity using nuclear fission remains a divisive issue that cuts across partisan lines. In the inaugural Heatmap Climate Poll, nuclear came in a distant last among clean energy sources people feel comfortable having in their communities.

Some major environmental groups like the Sierra Club and Greenpeace maintain that the risk of serious disasters at nuclear power plants poses an unacceptable risk to communities and ecosystems. Others, including the Nature Conservancy, view it as a reliable low-carbon energy resource that’s — crucially — available to us today, while promising but immature options such as long-duration energy storage are still catching up.

Historically, nuclear has caused far fewer fatalities than fossil fuels, which generate all kinds of toxic, potentially deadly pollution — and that’s without factoring in their contribution to climate change and its associated disasters.

The companies now hoping to pioneer a new generation of nuclear reactors in the U.S. say their designs incorporate the lessons learned from the accidents in Chernobyl and Fukushima, putting even more safeguards in place than the fleet of reactors operating across the country today. (There’s still a debate over whether the proposed reactors will actually be safer, though.)

What about nuclear waste?

Spent uranium fuel is radioactive, and will remain radioactive for a very long time. As a result, there’s still a lot of disagreement about where that waste should go.

The federal government tried in the early 2000s to create a national repository in Nevada’s Yucca Mountain, but the project was stopped by intense local and regional opposition. The Western Shoshone, a tribe whose members have long faced exposure to radioactive fallout from nearby nuclear tests, sued the federal government in 2005. Harry Reid, a former U.S. Senator from Nevada who served as Majority Leader from 2007 to 2015, also fought against the repository.

In the absence of a central repository, the waste produced by nuclear plants is usually stored in deep water pools, which keep the spent fuel cool, or in steel casks onsite to keep the radiation from escaping into the surrounding environment.

If a repository eventually opens, some existing waste will likely be moved out of temporary storage and relocated there.

Why aren’t more traditional nuclear plants being built nowadays?

In short, the concrete behemoths that have long been the norm in the U.S. are really, really expensive to build. They also — like the two new Vogtle reactors — have a tendency to go way over their deadlines and budgets. That makes the electricity nuclear plants generate particularly expensive.

The vast majority of U.S. coal plants were built during the same few decades as most of the country’s nuclear reactors. But when utilities started to face more pressure to reduce their carbon emissions, toppling coal’s reign over the power sector, utilities wound up preferring to build cheaper — and, at least at the time, less controversial — natural gas power plants over nuclear power plants.

But public opinion is beginning to shift. About 57% of American adults favor building new nuclear power, a Pew Research Center survey found last year, compared with 43% in 2016. Though support is higher among Republicans than Democrats, it’s on the rise within both parties.

What are advanced nuclear reactors, and how are they different?

Today’s electric grid is a far cry from the 20th-century grid that traditional nuclear reactors were built for, and the new reactor models that are making the most headway reflect those changes. In general, these designs are smaller, cheaper (at least on paper), and more flexible than those already in operation.

Unlike traditional reactors, which generally require a lot of custom fabrication to be completed at the project site, small modular reactors — such as the ones being developed by NuScale Power — have components that are meant to be made in a factory, assembled quickly wherever they’ll operate, and combined with other modules as needed to increase power output. Fast reactors (so-named for their highly energized neutrons), like Bill-Gates-fronted TerraPower’s Natrium design, circulate coolants other than water through the core. (Natrium uses liquid sodium.)

Advocates of next-generation nuclear power are optimistic that the first such reactors will come online before the end of the decade. Several of the leading proposals have run into financial and logistical troubles over the last couple of years, however. In November, NuScale canceled its flagship project at the Idaho National Laboratory. It had been on track to be the first commercial small modular reactor built in the U.S. but was thwarted by rising costs, which caused too many expected buyers of its electricity to pull their support.

What’s going on with nuclear power outside the U.S.?

Nuclear’s image is recovering globally, too. Some of the companies working on demonstration reactors in the U.S. have been outspoken about wanting to see their designs supplant fossil fuels and provide abundant energy all over the world. Meanwhile, many countries are devoting plenty of their own resources to nuclear power.

Japan, which shuttered its sizable nuclear fleet in the aftermath of the Fukushima accident, is slowly bringing some of its nuclear capacity back online. In December, Japanese regulators lifted an operational ban on the Kashiwazaki-Kariwa Nuclear Power Plant, the largest nuclear plant in the world.

Nuclear power is also enjoying renewed popularity in parts of Europe, including France and the U.K. In France, where the long-dominant technology has faltered in recent years, a half-dozen new nuclear power plants are in the works, and even more small modular reactors could follow. The U.K. is also planning a new wave of nuclear development.

Elsewhere, including in Germany, nuclear hasn’t found the same traction. After delaying the closure of its last three nuclear reactors amid natural gas shortages caused by the war in Ukraine, Germany closed the reactors last spring, eliciting a mixed reaction from environmental groups.

Meanwhile, China has close to 23 gigawatts of nuclear capacity under construction — the “largest nuclear expansion in history,” Jacopo Buongiorno, a professor of nuclear science and engineering at MIT, told CNBC last year.

What role will nuclear play in the energy mix of the future?

It’s still early days for most of the world’s next-generation nuclear reactors. With even the most promising designs largely unproven, there’s plenty of uncertainty about where today’s projects will ultimately lead. That makes it tricky to predict what role nuclear power will play in the energy transition over the coming decades.

There’s plenty of interest in building more capacity, however. In December, at COP28, the U.S. and 24 other countries — including Japan, Korea, France and the UK — signed on to a goal of tripling global nuclear energy capacity by 2050 in order to stay on track to reach net-zero emissions by then. Nuclear plants could also be an important source of carbon-free energy for producing green hydrogen, a nascent industry that got a major boost from tax credits under the Inflation Reduction Act.

But the U.S. Energy Information Administration’s most recent capacity forecast projects that the total amount of electricity from the country’s nuclear plants will decline in the coming decades — representing just 13% of net power generation by 2050.