How hot salt could transform nuclear power

For more than a month in total, 12 metric tons of molten salt coursed through pipes at Kairos Power in Albuquerque, New Mexico.

The company is developing a new type of nuclear reactor that will be cooled using this salt mixture, and its first large-scale test cooling system just completed 1,000 hours of operation in early January. This is the second major milestone for Kairos in recent weeks. In December, the US Nuclear Regulatory Commission granted a construction permit for the company’s first nuclear test reactor.  

Nuclear power plants can provide a steady source of carbon-free energy, a crucial component in addressing climate change. But recent major nuclear installations have been plagued by delays and skyrocketing budgets. Kairos and other companies working on advanced reactor designs hope to revive hopes for nuclear power by presenting a new version of the technology that could cut costs and construction times.

Kairos’s technology and construction approach are “just fundamentally different” from current commercial reactors, says Edward Blandford, cofounder and chief technology officer of Kairos.

Today, nearly all commercial nuclear plants use the same type of enriched uranium as fuel to generate electricity through nuclear fission reactions, and temperature is controlled with a cooling system that uses water.

But a growing number of companies are working to tweak this formula in an effort to improve on cost and safety. In the case of Kairos, the company plans to use an alternative fuel called TRISO, which is made from tiny uranium-containing kernels that can be embedded in graphite casings. TRISO fuel is robust, able to resist high temperatures, radiation, and corrosion. In addition, the reactor’s cooling system uses molten salt instead of water.

Molten salt could be a huge help in making safer nuclear plants, Blandford says. The cooling system in water-cooled reactors needs to be kept at high pressure to ensure that the water doesn’t boil off, which would leave the reactor without coolant and in danger of overheating and running out of control. It’s technically possible to boil salt, but it could only happen at very high temperatures. So those high pressures become unnecessary.

Molten-salt nuclear reactors were developed in the 1950s but were largely shelved as the industry moved toward water-cooled designs. Now, with a growing need for low-carbon power, “there’s a lot of interest in these technologies again,” says Jessica Lovering, cofounder and executive director of the Good Energy Collective, a policy research organization that advocates for the use of nuclear energy. New reactor technology options could help avoid some of the fears around the safety of water-cooled reactors, and they can also generate electricity more efficiently. 

Technology has changed a lot in the past seven decades, and molten-salt reactors never made it to large-scale commercial operation. So there’s still plenty of testing to be done before this kind of cooling system can be put to work in the highly controlled environment of a nuclear reactor. That’s where Kairos’s engineering test unit comes in. It’s the world’s largest system built to circulate Flibe, a fluoride-based salt coolant.

The system uses electric heaters to simulate the heat that would be generated by nuclear reactions in the finished reactor. Tests involve pumping a Flibe mixture through a cooling loop while engineers monitor the temperature throughout the system and the purity of the salt along the way. The company has also tested what it would be like to refuel the reactor, and how power coming out of the system can be monitored and adjusted.

Building an entire cooling system that won’t ever be used in a nuclear reactor is a considerable investment of time, money, and resources, but this approach of taking baby steps could help Kairos succeed in introducing a new nuclear technology—a historically difficult task, says Patrick White, research director at the Nuclear Innovation Alliance, a nonprofit think tank.

“One of the challenges with nuclear is that usually, the first step is to design the reactor on paper, and the next step is build the whole thing,” White says. Kairos is trying a different path, testing out components more along the way to help speed up development and avoid getting stuck in late-stage construction.

Kairos is making progress on construction, too. The company received approval in December from the NRC to build Hermes-1, its first nuclear test reactor. Hermes-1 will produce about 35 megawatts of thermal power (today’s commercial reactors typically produce around 1,000 megawatts of electricity). It’s planned for completion as soon as 2026.

Several other companies are also using molten salt or TRISO fuel in their advanced nuclear designs. X-energy, based in Maryland, is developing a gas-cooled reactor that uses TRISO fuel, and TerraPower and GE Hitachi Nuclear Energy are developing a sodium-cooled reactor that uses molten salt to store energy. 

There’s still a long road ahead before Kairos’s design and other advanced reactors can make it onto the grid. The company plans to build at least two more large-scale test cooling systems before putting the pieces together for Hermes-1, Blandford says. 

The company will also need to win an operating license for Hermes-1, the second of two major regulatory steps it’ll go through with the NRC. Next comes Hermes-2, which will include two reactors that are similar in scale and design to Hermes-1, plus a system to transform the heat generated into electricity. Finally, the company will move on to larger, commercial-scale reactors.

All of that will take some time, but Kairos and others feel the result will be worth it. “With our technology, it is unique,” Blandford says, “and it does open up unique opportunities to explore spaces that other technologies have not.”

There was some good climate news in 2023. Really.

Bad climate news was everywhere in 2023. 

It’s been the hottest year on record, with January through November clocking in at 1.46 °C (2.62 °F) warmer on average than preindustrial temperatures. Meanwhile, emissions from fossil fuels hit a new high—36.8 billion metric tons of carbon dioxide, 1.1% more than in 2022. 

Scientists are loudly warning that the world is running out of time to avoid dangerous warming levels. The picture is grim. But if you know where to look, there are a few bright spots shining through the darkness.

New technologies that can help address climate change, from heat pumps to solar panels to EVs, are coming to the market and getting cheaper. Climate policy is also developing, from incentives to support new technology to rule-making around pollution. And efforts to help the most vulnerable nations adapt to climate change are growing. 

Here are a few of those bright spots that our climate reporters saw in 2023. 

The brakes are off for electric vehicles

There’s been a spate of good news for EVs. We put the “inevitable EV” on our list of 10 Breakthrough Technologies in January, noting that strong policy support and expanding supply chains were combining to vault the technology to new relevance. 

Those trends have largely continued through 2023, and that means good news for climate change, since the transportation sector accounts for nearly 20% of global emissions. 

EVs are on track to make up 15.5% of automotive sales this year, according to BNEF. Between battery electric vehicles and plug-in hybrids, this new growth means there are almost 41 million passenger EVs on the road. China has the largest share of EVs in the world, making up nearly a quarter of the global fleet. 

Batteries to power all those vehicles are becoming more widely available and cheaper. Global manufacturing for lithium-ion batteries increased by over 30% this year. And while prices ticked up slightly last year, they are down again in 2023, representing the largest annual decline since 2018. 

A wide range of policies could help continue the growth of electric vehicles. Some governments are mandating the switch away from fossil-fuel-powered cars—the European Union and United Kingdom both passed policies in 2023 mandating that all new passenger vehicles sold be zero-emissions starting in 2035. Several states in the US have adopted the same policy, with California leading the way last year and more signing on in 2023. 

Incentives are also driving consumers toward EVs. The Inflation Reduction Act in the US serves up a huge menu of tax credits for battery manufacturing, EV manufacturing, and mineral processing. 

While many signs are positive, it’s not all rosy for electric vehicles. Growth in sales slowed between 2022 and 2023, and changing demand has some automakers slowing production for models like the Ford F-150 Lightning. Charging infrastructure isn’t available or reliable enough in most markets, a problem that has become one of the biggest barriers to EV adoption. 

Cars are being sold at a record pace and road emissions are still going up, so EV sales need to accelerate to make a dent in transportation’s climate impact. But EVs’ progress so far seems to be an encouraging story of a new climate-friendly technology becoming a mainstream option. Let’s hope it keeps going in 2024—all gas, no brakes. 

—Casey Crownhart

Countries and companies are cracking down on methane 

Another encouraging development on the otherwise daunting topic of climate change is the growing recognition that cutting methane pollution is one of the most powerful levers we can pull to limit global warming over the coming years. 

Carbon dioxide has long overshadowed methane, since we emit so much more of it. But methane traps about 80 times as much heat over a 20-year period and accounts for at least a quarter of overall warming above our preindustrial past. 

On the other hand, it also breaks down far faster in the atmosphere. Together, those qualities mean that rapid cuts in methane emissions today could deliver an outsize impact on climate change, potentially shaving a quarter-degree off total warming by midcentury. That could easily make the difference between a planet that does or doesn’t tip past 2 °C.

So it was encouraging to finally hear the head of the US Environmental Protection Agency announce, at the recent UN climate conference, that it will soon require oil and gas companies to monitor methane emissions across their pipelines, wells, and facilities and sharply reduce venting, flaring, and leaks. 

As federal regulations go, preventing emissions of a combustible, planet-warming superpolllutant that isn’t even producing anything of economic value is truly about the least we can ask of an industry. But it’s a step forward that promises to eliminate the warming equivalent of about 1.5 billion metric tons of carbon dioxide by 2038.

There was other good news on methane at the UN conference as well. A group of major oil and gas companies including BP, Exxon, and Saudi Aramco pledged to cut their methane pollution by at least 80% by 2030. In addition, a handful of additional nations joined an international coalition committed to easing global emissions by 30% this decade, while others stepped up their pledges and funding.

All of this comes on top of growing global efforts to more effectively monitor and report major sources of methane pollution around the globe, and reduce emissions from agriculture and landfills. 

As with every issue when it comes to climate change, none of this is enough, too much of it is voluntary, and complications abound. But these announcements, along with other signs of progress, are slowly adding up to a less grim future, while reminding us all that we’re capable of achieving even more.

—James Temple

A crucial fund to pay for climate damages launched

While the world scrambles to slow our emissions, it’s becoming ever more clear that the damage from climate change is happening in the present tense, with wildfires, floods, and heat waves making headlines. 

So it was welcome news that this year’s UN climate conference started with a historic milestone for vulnerable countries struggling to deal with these problems. On day one of the talks, the long-anticipated loss and damage fund was officially launched.

Historically, a handful of industrialized nations like the United States, Germany, and the United Kingdom have been responsible for much of the emissions that are exacerbating extreme weather events and related disasters. Now, they are (nominally) paying for that legacy.

The purpose of this fund is to help poor and developing countries address the increasing harm from climate disasters. Many of these countries—which have contributed the least amount of emissions—are the most vulnerable to climate impacts and often lack adequate resources to manage them. The funds can help them rebuild in the aftermath of events like drought or floods, and improve a nation’s ability to withstand future catastrophes.

Advocates have been quick to point out that the total amount pledged so far is minuscule compared to the actual need on the ground. They estimate that the current pledge equates to less than 0.2% of the potential economic losses facing developing nations from climate disasters every year.

By the end of COP28 on December 12, countries had collectively committed nearly $800 million. The United Arab Emirates and Germany each pledged $100 million, the United Kingdom offered $75 million, and the United States contributed $17.5 million. 

Those numbers sound big, but a few people have made a sports analogy that puts this all in perspective. On December 9, a baseball player, Shohei Ohtani, signed a $700 million contract with the LA Dodgers. The fact that a worldwide effort to address climate change is even remotely comparable to the amount spent by a sports team on a single athlete should be a global embarrassment.

 “The rich world needs to take a good look at itself and its actions so far,” says Ritu Bharadwaj, a principal researcher at the International Institute for Environment and Development.

That being said, the fund is still a step toward equitable climate resilience. Now the focus is on continuing to scale up the commitments and making the funds more accessible to those who need them.

—June Kim