Nuclear Notes is produced by the Breakthrough Institute, and covers the policy, regulation, technology, and business of advanced nuclear energy in the United States and beyond.
Every Thursday, we track what’s really going on in the field: the new rules moving through the Nuclear Regulatory Commission, the advanced reactors moving from design to deployment, the companies going public and the utilities merging, and the executive orders and acts of Congress reshaping how the country builds. We explain not just what happened, but why it matters and how the pieces fit together.
The Pebble-Bed Reactor Gets Its Construction Permit
X-energy’s high-temperature gas-cooled reactor has reached a major milestone, receiving a construction permit from the Nuclear Regulatory Commission, although some aspects of the project remain uncertain.
The nuclear plant is being developed by Long Mott Energy, LLC, a fully owned subsidiary of Dow, in partnership with X-energy, and will pump steam into Dow’s adjacent Seadrift chemical plant. The project comprises four of X-energy’s pebble-bed, graphite-moderated, helium-cooled reactors, though future projects could have up to 12, per X-energy.
The reactor is designed to follow load easily, whether that is electricity or industrial steam. Importantly, it will produce steam at 565 degrees C (1,049 degrees F), compared to the 270 to 285 degrees C (518 to 545 degrees F) of a typical pressurized water reactor. The higher temperature makes the steam useful in a variety of industrial processes, including at a chemical refinery. Higher-temperature steam can also generate more electricity from the same amount of thermal energy than lower-temperature steam.
The X-energy construction permit is the first permit issued for a multi-module advanced reactor, for a pebble-bed reactor, and also for a reactor that is supposed to refuel while operating. The reactor’s fuel pebbles, which are tri-structural isotropic (TRISO) fuel, are circulated through the core continuously, with old ones removed and new ones added without shutting down the reactor.
X-energy chose to pursue the Part 50 licensing process, which is the traditional two-step approach: get a permit to build, and then apply for an operating license during construction, letting those two time-consuming processes overlap. This was the first permit to be issued for a gas-cooled reactor using what the NRC calls its “risk-informed, technology-inclusive Licensing Modernization Project framework.”
The timely issuance of the permit, one month ahead of schedule, indicates progress both for the advanced reactor industry and for the NRC itself, said Adam Stein, Director of Nuclear Energy Innovation at the Breakthrough Institute. The reduced emergency planning zone (EPZ) in the approved permit is another signal of progress. Traditional large, light-water reactors were bound to a 10-mile EPZ. The approved EPZ for the Xe-100 is 400 meters, thanks to the design’s inherent safety features.
The construction permit is only the second given in the United States for a gas-graphite reactor. The first was issued in 1968 for Fort St. Vrain, in a Colorado town of the same name, 40 miles north of Denver. St. Vrain and the Xe-100 have similarities and differences. St. Vrain produced very high-temperature steam, as the X-energy plant is supposed to do, but had a different fuel cycle and design. But St. Vrain had operating problems and an impatient owner, who gave up after a few months.
The Long Mott project has heavy backing from the Department of Energy through the Advanced Reactor Demonstration Program, which is supposed to provide a total of approximately $2.15 billion in 50/50 cost-shared funding, combining an initial ~$1.23 billion award with a new award, just announced this past August, for an additional $1 billion. The total project cost is still up in the air. A few years ago, X-energy estimated the cost of completing the project would be between $4.75 billion and $5.75 billion. X-energy has not publicly announced updated cost estimates since, but the ARDP cost-sharing agreement suggests that at least $4.3 billion will be spent.
X-energy’s announcement did not say when construction would actually begin. The permit allows the company and Dow “to continue advancing the proposed project toward construction readiness, finalizing and standardizing the Xe-100 design, maturing the supply chain for long-lead components and materials, and developing an Operating License application for submission to the NRC,” X-energy said. X-energy added that taking these steps before spending money for full-scale construction is “consistent with Dow’s proven global project management practices.” Dow “is expected to consider a preliminary investment decision in 2027,” X-energy said. The company did not say when it expected to have the plant online.
While the construction permit is a sign of major progress, Wall Street seemed to have other things on its mind. As the announcement approached, with various preliminary approvals, stock in X-energy (XE) dropped by one-third in price, to a little over $10, between early October and early November. It climbed a bit after the NRC announcement and then fell back to trading between $10 and $11. Early this year it was in the mid-$30 range.
The company has some other projects further back in the pipeline. In October, it announced an agreement with American Electric Power to evaluate construction of a cluster of 12 modules in Indiana, with the electricity to be sold to Amazon. And it is developing another plant in eastern Washington State.
Five Nuclear Bills Are Folded Into the Permitting Debate
With a dwindling number of working days left for Congress before Thanksgiving and then the Christmas/New Year’s legislative break, some nuclear energy issues have gained new life in the past week by being folded into the Bipartisan American Affordability and Jobs Act, also known as BAAJA. BAAJA is a major federal permitting reform package trying to make its way through the Senate. And if these nuclear bills can tag along for the ride, well, that would be great.
The bills include the Efficient Nuclear Licensing Hearings Act, which would dispense with the longstanding statutory requirement that the NRC must hold a hearing before it grants a construction permit or operating license for a reactor, even if no hearing has been requested by anybody whose interest would be affected by the plant. It would also eliminate the need for an “uncontested hearing” on a uranium enrichment plant if none was requested by such a person. The hearing process is expensive and cumbersome, and sometimes superfluous. “Contested” hearings—the hearing process where affected individuals, groups, or organizations may contest an application, amendment, or agency action—would remain intact.
The American Enrichment Deployment Act would let companies build an enrichment plant “at risk” before they have a license in hand to operate it. That is already the rule for other plants in the fuel supply chain, like the ones that convert powdered uranium into uranium hexafluoride, the form that goes into centrifuges. The version of the bill added to BAAJA requires local reporting requirements and also removes the longstanding statutory rule that enrichment facilities must have an environmental impact statement; instead, they would be subject to the National Environmental Policy Act, like any other nuclear project.
The NRC Staff Pay Alignment Act is intended to stop the brain drain from the agency, whose personnel have often found higher-paid jobs in the private nuclear sector. The NRC could pay career employees up to 10 percent over the current maximum. The bill, if enacted, could also induce some NRC staff to delay retirement, since their pensions are based on their last few years of pay. The NRC, like many federal agencies, has a large number of senior staff who are eligible to retire but could keep working for several more years.
The Department of Energy Nuclear Transparency Act would require the department to publicly disclose extensive information about any authorizations it gives for nuclear work at its facilities. The Department has recently authorized several companies to test their cores with chain reactions.
All of the bills have strong bipartisan support, but are only a small piece of the BAAJA puzzle. Capitol Hill is hashing out provisions on NEPA, the National Historic Preservation Act, the Clean Air Act, transmission policy, and more. And the short session has a lot of other business to handle. It has not passed a budget for the current fiscal year, and the stopgap measure in place expires on December 11. It has also not passed the Pentagon’s budget, the National Defense Authorization Act, or the Farm Bill.
A Microreactor Takes a Step Forward
Radiant’s Kaleidos reactor, which can fit in a shipping container and can produce one megawatt of electricity, has received approval for its safety analysis from the Department of Energy and will proceed to full power testing for an extended period, the company said, making it the first microreactor to do so.
The testing will culminate in “at least 150 hours of continuous operation at full power without operator intervention,” the company said. The test will be run at the Idaho National Laboratory. Radiant is supposed to deliver commercial models to the Buckley Space Force Base in Colorado and Fort Benning in Georgia in 2028.
Replacing Concrete with a Steel Composite
Purdue will fabricate steel parts, connect them, assemble them into larger structures, and fill them with concrete to test a system that would replace conventional steel-reinforced concrete for small modular reactors.
One composite structure will mimic a section of a reactor containment building, while the other will replicate a section of a surrounding building. The Department of Energy’s National Reactor Innovation Center, the Electric Power Research Institute, and the Nuclear Energy Institute will participate. The work expands on preliminary experiments from last year.
The cost of nuclear-grade steel-reinforced concrete is a major driver of reactor construction costs.
Another “Catastrophe” Disappears Without a Trace
A fire broke out in a room at the Savannah River National Laboratory, a weapons plant, on October 28. The Energy Department, which owns Savannah River, declared a Site Area Emergency and closed off the site, and the Federal Aviation Administration closed the airspace above. The Energy Department later concluded that there was no detectable radioactive contamination and only one minor injury. The kerfuffle has been resolved.
This was followed by breathless reports that one of the reactors at Arkansas Nuclear One was hit by lightning at 100 percent power (but 100 percent is the normal mode of operation). The reactor shut down as designed, without incident.
Savannah River was also in the news in 2025, when a worker there found a wasp nest that had radioactivity. News reporting failed to note that the hazard wasn’t the radiation; it was the wasps themselves.
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