Key points
- Oklo (OKLO) closed up about 6% Tuesday, then jumped again after hours to near $48 a share.
- X-Energy (XE) closed up about 7% and extended to $18.50 after hours on the same report.
- Bloomberg says both are joining a near-$200 million Trump administration push to speed AI power plants, alongside Microsoft and Nvidia.
- The wider nuclear group rallied too: Centrus Energy (LEU) near 10%, NuScale Power (SMR) over 9%, Cameco (CCJ) about 4.5%.
Oklo (OKLO) and X-Energy (XE) didn't need much help Tuesday. The two nuclear reactor developers closed the regular session up about 6 percent and 7 percent, part of a broad rally across the nuclear sector. Then, after the closing bell, they jumped again, this time on a specific report: Bloomberg said Oklo and X-Energy are joining Microsoft and Nvidia in a Trump administration-led effort to speed up power plant construction for AI data centers.
What Bloomberg reported
Bloomberg's report leans on an internal document, not an official statement, and puts the program's budget near $200 million. The reasoning behind it is straightforward: the AI data center boom has pushed up electricity prices for ordinary ratepayers in parts of the country, and this is the government's attempt to answer for it. An official announcement was expected as soon as Wednesday, July 22.
The market didn't wait for those details. Oklo closed the regular session at $44.13 and kept climbing once the bell rang, reaching $47.85 after hours. X-Energy did the same, closing at $16.79 before pushing to $18.50 in after-hours trading. Both of those after-hours moves track back to tonight's report specifically; the daytime gains belonged to the whole nuclear sector, which is worth unpacking next.
The rest of the nuclear group moved too
Tuesday's rally wasn't limited to the two companies Bloomberg named. Centrus Energy (LEU) closed up close to 9.5 percent and NuScale Power (SMR) gained about 9.4 percent, the day's two biggest movers outside Oklo and X-Energy. NANO Nuclear (NNE) and Cameco (CCJ) also finished higher, up about 5.4 percent and 4.5 percent. Established power producers with existing nuclear fleets joined in too, with Constellation Energy (CEG) up about 3.4 percent and Vistra (VST) around 2.7 percent.
| Stock | Tuesday's close | After hours |
|---|---|---|
| X-Energy (XE) | +7.2% | +10.2% more |
| Oklo (OKLO) | +6.3% | +8.4% more |
| Centrus Energy (LEU) | +9.5% | flat |
| NuScale Power (SMR) | +9.4% | +1.6% more |
| NANO Nuclear (NNE) | +5.4% | +1.3% more |
| Cameco (CCJ) | +4.5% | +0.8% more |
| Constellation Energy (CEG) | +3.4% | -0.2% |
| Vistra (VST) | +2.7% | flat |
That second column is the tell. Every name in the group had a strong regular session, but once the closing bell rang, only Oklo and X-Energy kept climbing. The rest of the sector went mostly flat after hours. Whatever pushed the broader group higher during the day, the Bloomberg report is what's moving these two stocks tonight.
Where this fits with what's already in motion
This isn't the government's first nuclear-for-AI push this year, and it's worth separating tonight's report from what's already underway. The Department of Energy's Reactor Pilot Program set a goal for at least three advanced reactor designs to reach criticality, meaning a sustained, controlled fission reaction, by July 4, 2026. Three companies in the program hit that mark: Antares Nuclear, Valar Atomics, and Aalo Atomics. A fourth, Deployable Energy, got there too, outside the program. Oklo itself was selected for three separate projects under that same pilot program, though its own reactor, the Groves Isotope Test Reactor in Texas, is still working toward criticality after the DOE approved its safety analysis on July 1. That's a distinct effort from the one Bloomberg described Tuesday, which centers on data center power supply rather than reactor testing milestones. Read more in our explainer on AI's power problem and the stocks feeding the nuclear buildout.
Regulation has been moving in the same direction. The Nuclear Regulatory Commission proposed a rule in April that would let commercial reactor applicants lean on safety work the government already completed through the DOE or the Department of War, instead of repeating it from scratch. The rule traces back to an executive order that directed the NRC to build an expedited licensing path for reactor designs already proven safe under DOE or military oversight, including designs being tested at military bases under a Pentagon microreactor pilot. None of that changes what Oklo or X-Energy need for their own commercial licenses, but it lowers the odds that a design proven safe once has to prove it all over again for a different customer.
Microsoft and Nvidia's involvement fits a pattern that's been building all year. Both companies have been funding pieces of the AI buildout well beyond their core products, something we cover in more detail in our look at the circular deals tying Nvidia, Microsoft, and OpenAI together. Electricity, not chips, has increasingly been the bottleneck behind big tech's close to $725 billion in AI data center spending plans this year, and nuclear power's ability to run around the clock without direct carbon emissions is the main reason it keeps showing up in these plans.
What's still unconfirmed
What's missing is everything past the headline. Nobody has said which federal agencies would run the program, and nobody has spelled out how the near-$200 million would split across four companies or what Oklo and X-Energy would be on the hook to deliver in return. That's the gap between a leaked document and an actual government announcement. Until Wednesday's confirmation lands, Tuesday's after-hours prices for both stocks are indicative trading on a report, not settled fact.
