Is nuclear power going to help the United States decarbonize its energy supply and fight climate change?

Probably not.

That is the conclusion of a remarkable new study published in the Proceedings of the National Academy of Sciences in early July — remarkable because it is not written by opponents of nuclear power, as one might expect given the conclusion. The authors are in fact extremely supportive of nuclear and view its loss as a matter of “profound concern”:

Achieving deep decarbonization of the energy system will require a portfolio of every available technology and strategy we can muster. It should be a source of profound concern for all who care about climate change that, for entirely predictable and resolvable reasons, the United States appears set to virtually lose nuclear power, and thus a wedge of reliable and low-carbon energy, over the next few decades.

Still, despite their evident belief in the need for nuclear power, the researchers are unable to construct a plausible scenario in which it thrives. And it’s not for lack of looking — the paper is a methodical walk through the possibilities for both existing and new nuclear technology. The researchers really want it to work. They just can’t see it happening.

It’s a relatively short paper; let’s quickly hit the important takeaways.

The existing nuclear fleet is shrinking

Existing nuclear plants in the US are having a rough time, getting undercut on energy markets by cheaper natural gas and renewables. A wave of retirements is underway that is probably going to take around 10 GW of nuclear capacity offline.

A handful of states have taken measures to keep nuclear plants open (see this post), but doing so requires “expensive refurbishment and careful regulatory consideration,” the authors write, and will only “slow, not reverse, the losses.”

So then what about new plants?

Existing nuclear plant technology is a dead end

Existing nuclear plants are light-water reactors (LWRs), which were always intended to be the first generation of nuclear plants. But subsequent generations have not materialized, and we’re still mostly dealing with LWRs.

Attempts to build new LWRs in the US have been a fiasco, ending up canceled (as in the beleaguered Summer plant in South Carolina, which was 40 percent complete) or endlessly delayed and over-budget (as in the new Vogtle reactors in Georgia).

The researchers are blunt about the prospects for new plants based on existing technology:

There is no reason to believe that any utility in the United States will build a new large reactor in the foreseeable future. These reactors have proven unaffordable and economically uncompetitive. In the few markets with the will to build them, they have proven to be unconstructible. The combination of political instruments and market developments that would render them attractive, such as investment and production credits, robust carbon pricing, and high natural gas costs, is unlikely to materialize soon.

And it’s worth noting that those political instruments and market developments, if they did manifest, would also benefit nuclear’s low-carbon competitors, which are already kicking its ass.

What about advanced, non-LWR designs?

Advanced nuclear plant designs are not happening

The agency responsible for shepherding advanced nuclear designs to commercial viability is the Department of Energy’s (DOE) Office of Nuclear Energy (NE).

The researchers did a close analysis of NE’s efforts, “using budget data acquired through the Freedom of Information Act and semistructured interviews with 30 senior nuclear energy experts.”

What they found is that NE has spent about $2 billion pursuing advanced designs since the late 1990s, with “very little to show for it.” Funding is inadequate, half of it goes to maintain existing testing infrastructure, it varies from year to year, and it’s spread shallowly across several technologies and research labs.

“In interviews with leaders across the enterprise,” they write, “those associated with the DOE and the national laboratories expressed either alarm or despair at the trajectory of advanced fission innovation in the United States.”

Theoretically, this decade-plus record of dysfunction could be turned around with “more competent stewardship of nuclear innovation, substantially greater appropriations, and a change in energy markets,” but all those, they note, are “very heavy lifts.”

The one bright spot in the advanced-nuclear area is TerraPower (Bill Gates’s nuclear startup), which has had some limited success getting licenses and testing from the feds, but in general “has found it remarkably challenging to build or secure access to the range of equipment, materials, and technology required to successfully commercialize its innovative design” — so challenging, in fact, that it’s now partnering with China.

The authors conclude that advanced fission designs have no hope at all of commercializing in the US by mid-century, which is when the US economy needs to be decarbonized.

Small modular reactors to the rescue? Maybe not.

The other great hope of the industry is factory-built small modular reactors (SMRs), which are — or will be, it is hoped — faster and cheaper to build than giant plants because they are smaller and built from standardized parts. They can be deployed incrementally, matched to energy demand in particular times and places, and are meltdown-proof without human intervention.

Several companies, most notably NuScale (which has already submitted its design to the feds), are trying to develop light-water SMRs. NuScale wants to build a test reactor on the grounds of the Idaho National Laboratories and more than a dozen companies have inquired about doing the same.

So, with already-proven technology and lower construction costs, are SMRs the key to saving nuclear in the US?

Using “a combination of engineering economic analysis and the use of structured procedures to elicit expert judgments,” the researchers took a close look at SMRs. Indeed, they “expended much effort in developing plausible scenarios of how an SMR domestic market might develop.”

The results? Grim. Under every plausible scenario, power from SMRs is (and remains, even with subsequent generations of the tech) substantially more expensive than power from competitors. So they probably can’t compete directly in power markets.

The researchers also examine four indirect ways that SMRs could build a market:

Industrial process heat: One alternative is to use SMRs to generate heat rather than power, for use in industrial applications that require high temperatures. The researchers find a substantial market exists for such heat, but when the costs of SMRs are compared to the cost of alternative heat sources (like natural gas), “the number of potential customers falls precipitously.”

Also, private companies (unlike utilities) can’t pass costs on to customers, so they’re less likely to take a chance constructing unfamiliar tech that still faces unresolved siting and regulatory issues. “When it comes time to sign contracts and pour concrete,” they conclude, “it is highly unlikely that any industrial customer would opt for a light water SMR.”

Power + desalination: Another frequently discussed alternative is to use SMRs as a kind of hybrid. The thing about nuclear plants is that they need to run more-or-less constantly; it’s expensive and inefficient to turn them on and off. But on-and-off power is what’s needed to flexibly complement variable renewable energy.

So the idea is to run SMRs constantly; when power is needed, they would provide power, and when it’s not, they would desalinate water. But after a close examination of the water situation in the US, the researchers found that there are only a few niche markets where desalination might be needed in the next few decades. And where they exist, desalinating with natural gas is much, much cheaper. This is likely another dead end, at least in the relevant time frame.

Military bases: Another thought is that SMRs might be used to power military bases — that the US military might serve as a kind first customer, helping SMRs scale up. The authors deem this “both unwise and unlikely to succeed.”

It is unlikely to succeed because the unique design requirements for the military are likely to yield an SMR too expensive for commercial viability. It is unwise because using the military as a tool to revive a particular industry is a Pandora’s box of political and ethical issues.

Plus, as they note, defaulting to the military to save nuclear is tantamount to admitting commercial defeat — not something likely to inspire market confidence.

SMRs for export: The final idea tossed around to jumpstart SMRs is building them for export. The idea is that other countries will have political and energy systems more amenable to nuclear. And the authors’ analysis supports the notion that there’s a global market for “many hundreds of light water SMRs.”

But there are substantial barriers. For one thing, many of the potential customers face “economic, political, and institutional realities” that render them unprepared to handle nuclear power at scale, and likely unwilling to accept close oversight by the US.

Aside from that, most decarbonization in the world will need to come from a select few big countries, and most of those countries are already nuclear-capable and unlikely to import hundreds of power plants from a geopolitical rival. “We remain skeptical that a US industry of factory-manufactured SMRs could be built primarily on the basis of exports,” they conclude.

In short, there don’t seem to be any viable markets to scale SMRs up. Consequently, “several hundred billion dollars of direct and indirect subsidies would be needed to support their development and deployment over the next several decades.”

On top of that, the US Nuclear Regulatory Commission would need to radically update and revise its regulatory review process. On top of that, the US would need to commit to total decarbonization, clearly and unequivocally enough to give markets confidence that carbon prices will reach and exceed $100/ton. And this would all have to happen soon, in the next few years.

“All these developments are possible,” they note, “but we believe they are most unlikely.”

There’s probably not going to be a nuclear wedge

So let’s review. Current, giant LMR reactors aren’t going to get built in the US — they have proven economic and political suicide. Even keeping current plants open will require extraordinary interventions. Advanced fission is unlikely to commercialize in the next few decades. And SMRs currently face grim market prospects. They are unlikely to mature and scale up without hundreds of billions in subsidies, substantial reform at NE and NRC, and a high, secure national carbon price.

It’s not impossible to imagine a high carbon price in coming decades, or natural gas prices rising, and SMRs finding success in niche markets. And it’s certainly possible to imagine failing to fully decarbonize by mid-century and needing nuclear to finish the job. The researchers are blunt about what would be needed for nuclear to be ready by then.

To assure that we have safe and affordable advanced reactor designs that can be deployed at scale by midcentury, the United States will need to dramatically increase and refocus the budget of the DOE’s NE toward advanced reactor development. Perceptive and ruthlessly pragmatic program officers will need to be recruited: ones with a sense of the mission’s urgency. The government would have to sustain that higher level of support in the face of constant short-term political pressures and, undoubtedly, organized opposition from advocates of other generating sources. Part of that increased budget would have to be dedicated to building new infrastructure, such as fast-flux test facilities and other system test beds. Even with a higher budget, surge funding may be needed in some years to support demonstration reactor development and program leadership would eventually have to focus on moving two or three systematically chosen designs to the point of commercialization.

“Perhaps these things can happen; the United States is no stranger to ambitious undertakings,” they conclude, “but it will take both vision and a level of commitment that are sorely lacking today.”

Nuclear proponents might reasonably respond that, yes, nuclear cannot contribute to decarbonization without substantial policy help. But decarbonization by mid-century will be impossible without substantial policy, period. No combination of technologies can scale up fast enough without help.

But renewable energy technologies seem to be on a trajectory toward subsidy independence (though plenty of policy and regulatory barriers to advanced energy tech remain). They are falling in cost at ridiculous rates — not just wind and solar, but storage, EVs, and other grid-edge technologies as well. Policy can accelerate their progress, or impede it, but at this point it cannot stop them. They have a momentum of their own, purely on economics.

Nuclear is in a different situation. Its current trajectory is decline; it needs lots and lots of new policy and public money to reverse that trajectory. That is a much more difficult political lift. And like the authors of the PNAS paper, I don’t have much faith that it will get done. For better or worse, renewable energy is the name of the game for the next few decades.