For the first time ever, Washington has signed off on a commercial nuclear microreactor running at full power. On Wall Street, nobody seems to care.
On Thursday, the Department of Energy approved the Documented Safety Analysis (DSA) for LA-based Radiant’s Kaleidos, a 1-megawatt, truck-transportable reactor that is now sitting inside the DOME test bed at Idaho National Laboratory. According to the company, it is the only microreactor design to secure DOE safety approval covering operation at power, as opposed to the zero-power criticality tests that every other entrant in the DOE pilot program has run so far.
And yet the stocks most levered to the small modular reactor story are trading like the industry is going out of business: Oklo (OKLO) closed Friday at $25.25, down 86% from its October 2025 peak and at its lowest since April 2025, while NuScale (SMR) is down 89% and sitting at a price last seen in April 2024.
Regular readers know we have been tracking the microreactor buildout since well before it was a meme (and long before it stopped being one), so let’s take a closer look at what Radiant actually got, where the rest of the pack stands, and why the market has decided none of it matters, at least for now.
What Radiant Actually Won
The DSA approval is the step that comes after DOE signed off on Radiant’s preliminary safety analysis back in February. With it in hand, Radiant moves into DOE’s Readiness Review, which will check whether the reactor and the crew operating it are ready to go nuclear. Once that is done, Radiant fuels Kaleidos and kicks off a five-phase test campaign at the National Reactor Innovation Center’s DOME facility.
The campaign goes from first criticality through progressively higher power, and ends with at least 150 hours of continuous full-power operation with no operator intervention. Radiant also plans to run the same unit for 60 effective full-power days over several months, using essentially the same design and custom fuel that customers will get. DOE’s acting Deputy Assistant Secretary for Nuclear Reactors Chimi Zacot called it “another important step forward in President Trump’s vision for an American nuclear renaissance.”
Which, to be fair, is a meaningful upgrade from what we have seen so far. As we covered in “The Rebirth Of America’s Nuclear Industry” (Jun 5) and then in “Four By The Fourth“, Antares, Valar Atomics, Deployable Energy and Aalo all hit criticality at INL ahead of Trump’s July 4 deadline, and Oklo’s Groves test reactor in Texas followed on August 5. But those were zero-power demonstrations: proof the physics works, with nothing plugged into the other end. Kaleidos is being cleared to actually make power, for weeks at a time.
