This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. This is a busy time of year for all of us, and that’s certainly true in the advanced nuclear industry. MIT Technology Review released our list of 15 Climate Tech Companies to Watch less than two months ago. Since then, awardee Kairos Power has had three big announcements about its progress toward building next-generation nuclear reactors.  Each of these bits of news represents an interesting aspect of the process. So let’s dig into the announcements and what they mean for where nuclear technology is going. First, a quick refresher on Kairos Power: While nuclear plants today overwhelmingly use pressurized water to keep reactors cool, Kairos is using molten salt. The idea is that these reactors (which are also smaller than those typically built today) will help generate electricity in a way that’s safer and more efficient than conventional nuclear power. When it comes to strategy, Kairos is taking small steps toward the ultimate goal of full-size power plants. Construction began earlier this year on Hermes, the company’s first nuclear test reactor. That facility will generate a small amount of heat—about 35 megawatts’ worth—to demonstrate the technology. Last week, the company announced it received a construction permit for the next iteration of its system, Hermes 2. This plant will share a location with Hermes, and it will include the infrastructure to transform heat to electricity. That makes it the first electricity-producing next-generation nuclear plant to get this approval in the US. While this news wasn’t a huge surprise (the company has been working with the Nuclear Regulatory Commission for years), “any day that you’re getting a permit or a license from the NRC is an unusual and special day,” Kairos CEO Mike Laufer told me in an interview.   The company is developing a plan to work on construction for both Hermes and Hermes 2 at the same time, he added. When I asked if Hermes is still on track to start up in 2027 (as we reported in our profile of the company in October), Laufer said that’s an “aggressive timeline.” While construction on test reactors is rolling, Kairos is forging ahead with commercial deals—in October, it announced an agreement with Google to build up to 500 megawatts’ worth of power plants by 2035. Under this agreement, Kairos will develop, construct, and operate plants and sell electricity to the tech giant. Kairos will need to build multiple reactors to deliver 500 MW. The first deployment should happen by 2030, with additional units to follow. One of the benefits of building smaller reactors is learning as you go along and making improvements that can lower costs and make construction more efficient, Laufer says.  While the construction permit and Google deal are arguably the biggest recent announcements from Kairos, I’m also fascinated by a more niche milestone: In early October, the company broke ground on a salt production facility in Albuquerque, New Mexico, that will make the molten salt used to cool its reactors. “Salt is one of the key areas where we do have some unique and specialized needs,” Laufer says. And having control over the areas of the supply chain that are specialized will be key to helping the company deliver electricity reliably and at lower cost, he adds.  The company’s molten salt is called Flibe, and it’s a specific mix of lithium fluoride and beryllium fluoride. One fun detail I learned from Laufer is that the mixture needs to be enriched in lithium-7 because that isotope absorbs fewer neutrons than lithium-6, allowing the reactor to run more efficiently. The new facility in Albuquerque will produce large quantities of high-purity Flibe enriched in lithium-7. Progress in the nuclear industry can sometimes feel slow, with milestones few and far between, so it’s really interesting to see Kairos taking so many small steps in quick succession toward delivering on its promise of safe, cheap nuclear power.  “We’ve had a lot of huge accomplishments. We have a long way to go,” Laufer says. “This is not an easy thing to pull off. We believe we have the right approach and we’re doing it the right way, but it requires a lot of hard work and diligence.” Now read the rest of The Spark Related reading For more details on Kairos and its technology, check out our profile of the company in the 15 Climate Tech Companies to Watch package from October.  If you’re dying for more details on molten salt, check out this story I wrote in January about a test system Kairos built to demonstrate the technology.  STEPHANIE ARNETT/MIT TECHNOLOGY REVIEW | GETTY, ADOBE STOCK Another thing Donald Trump pledged to enact tariffs on a wide range of products imported into the US. The plans could drive up the cost of batteries, EVs, and more, threatening to slow progress on climate and potentially stall the economy. Read more about the potential impacts for technology in the latest story from my colleague James Temple.  Keeping up with climate   The UN climate talks wrapped up over the weekend. In the resulting agreement, rich nations will provide at least $300 billion in climate finance per year by 2035 to developing nations to help them deal with climate change. (Carbon Brief)→ This falls well short of the $1 trillion mark that many had hoped to reach. (MIT Technology Review) Utilities might be spending a lot of money on the wrong transmission equipment on the grid. Dollars are flowing to smaller, local projects, not the interstate projects that are crucial for getting more clean energy online. (Inside Climate News) Sustainable aviation fuel is one of the only viable options to help clean up the aviation industry in the near term. But what are these fuels, exactly? And how do they help with climate change? It’s surprisingly complicated, and the details matter. (Canary Media) Automakers want Trump to keep rules in place that will push the US toward adoption of electric vehicles. Companies have already invested billions of dollars into an EV transition. (New York Times) There’s a growing chasm in American meat consumption: The number of households that avoid meat has increased slightly, but all other households have increased their meat purchases. (Vox) Trump has vowed to halt offshore wind energy, but for some projects, things take so long that a four-year term may not even touch them. (Grist)