Test engineer Jacob Wilcox displays an ingot of sodium metal after cutting into it at TerraPower, a company developing and building small nuclear reactors in Everett, Washington. Associated Press

Jennifer McDermott, Associated Press

As climate change pushes states in the US to dramatically cut their use of fossil fuels, many are coming to the conclusion that solar, wind and other renewable power sources might not be enough to keep the lights on.

Nuclear power is emerging as an answer to fill the gap as states transition away from coal, oil and natural gas to reduce greenhouse gas emissions and stave off the worst effects of a warming planet. The renewed interest in nuclear comes as companies, including one started by Microsoft founder Bill Gates, are developing smaller, cheaper reactors that could supplement the power grid in communities across the U.S.

Nuclear power comes with its own set of potential problems, especially radioactive waste that can remain dangerous for thousands of years. But supporters say the risks can be minimized and that the energy source will be essential to stabilize power supplies as the world tries to move away from carbon dioxide-emitting fossil fuels.

Tennessee Valley Authority President and CEO Jeff Lyash puts it simply: You can’t significantly reduce carbon emissions without nuclear power.

“At this point in time, I don’t see a path that gets us there without preserving the existing fleet and building new nuclear,” Lyash said. “And that’s after having maximized the amount of solar we can build in the system.”

The TVA is a federally owned utility that provides electricity to seven states as the nation’s third largest electricity generator. It’s adding about 10,000 megawatts of solar capacity by 2035 - enough to power nearly 1 million homes annually - but also operates three nuclear plants and plans to test a small reactor in Oak Ridge, Tennessee. By 2050, it hopes to hit its goal of becoming net zero, which means the amount of greenhouse gases produced is no more than the amount removed from the atmosphere.

An Associated Press survey of the energy policies in all 50 states and the District of Columbia found that a strong majority- about two-thirds-say nuclear, in one fashion or another, will help take the place of fossil fuels. The momentum building behind nuclear power could lead to the first expansion of nuclear reactor construction in the US in more than three decades.

Roughly one-third of the states and the District of Columbia responded to the AP’s survey by saying they have no plans to incorporate nuclear power in their green energy goals, instead leaning heavily on renewables. Energy officials in those states said their goals are achievable because of advances in energy storage using batteries, investments in the grid for high-voltage interstate transmission, energy efficiency efforts to reduce demand and power provided by hydroelectric dams.

The split over nuclear power in U.S. states mirrors a similar debate unfolding in Europe, where countries including Germany are phasing out their reactors while others, such as France, are sticking with the technology or planning to build more plants.

The Biden administration, which has tried to take aggressive steps to reduce greenhouse gases, views nuclear as necessary to help compensate for the decline of carbon-based fuels in the nation’s energy grid.

U.S. Energy Secretary Jennifer Granholm told the AP that the administration wants to get to zero-carbon electricity, and “that means nuclear, that means hydropower, that means geothermal, that means obviously wind on and offshore, that means solar.

“We want it all,” Granholm said during a visit in December to Providence, Rhode Island, to promote an offshore wind project.

The $1 trillion infrastructure package championed by Biden and signed into law last year will allocate about $2.5 billion for advanced reactor demonstration projects. The Energy Department said studies by Princeton University and the Decarb America Research Initiative show that nuclear is necessary for a carbon-free future.

Granholm also touted new technologies involving hydrogen and capturing and storing carbon dioxide before it is released into the atmosphere.

Nuclear reactors have operated reliably and carbon-free for many decades, and the current climate change conversation brings the benefits of nuclear to the forefront, said Maria Korsnick, president and chief executive officer of the Nuclear Energy Institute, the industry’s trade association.

“The scale of this electric grid that’s across the United States, it needs something that’s always there, something that can help really be the backbone, if you will, for this grid,” she said. “That’s why it’s a partnership with wind and solar and nuclear.”

Nuclear technology still comes with significant risks that other low-carbon energy sources don’t, said Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists. While the new, smaller reactors might cost less than traditional reactors to build, they’ll also produce more expensive electricity, he said. He’s also concerned the industry might cut corners on safety and security to save money and compete in the market. The group does not oppose the use of nuclear power, but wants to make sure it’s safe.

“I’m not optimistic we’d see the kind of safety and security requirements in place that would make me feel comfortable with the adoption or deployment of these so-called small modular reactors around the country,” Lyman said.

The U.S. also has no long-term plan for managing or disposing the hazardous waste that can persist in the environment for hundreds of thousands of years, and there’s the danger of accidents or targeted attacks for both the waste and the reactors, Lyman said. Nuclear disasters at Pennsylvania’s Three Mile Island, Chernobyl and more recently, Fukushima, Japan, in 2011 provide an enduring warning about the dangers.

Nuclear power already provides about 20% of electricity in the U.S., accounting for about half the nation’s carbon-free energy. Most of the 93 reactors operating in the country are east of the Mississippi River.

The Nuclear Regulatory Commission has approved just one of the new, small modular reactor designs - from a company called NuScale Power, in August 2020. Three other companies have told the commission they’re planning to apply for their designs. All of these use water to cool the core. The NRC is expecting about a half dozen designs to be submitted for advanced reactors, which use something other than water to cool the core, such as gas, liquid metal or molten salt. That includes a project by Gates’ company, TerraPower, in Wyoming, which has long depended on coal for power and jobs.

As utilities quit coal, Wyoming is tapping into wind and installed the third-largest amount of wind power generating capacity of any state in 2020, after Texas and Iowa. But Glen Murrell, executive director of the Wyoming Energy Authority, said it’s unrealistic to expect all the nation’s energy to be provided exclusively through wind and solar. Renewable energy should work in tandem with other technologies such as nuclear and hydrogen, he said.