Idaho Microreactor Tests Begin

A Cold War Dome Gets a Second Life

The facility hosting these tests has its own dramatic history. The DOME is the 100-foot silver containment shell that once housed the Experimental Breeder Reactor-II, which ran from 1964 until it was decommissioned in 1994. Federal officials slated the structure for demolition in 2017 due to mounting maintenance costs. Then in 2019, the National Reactor Innovation Center (NRIC) stepped in and saved it, repurposing it as a test bed for new reactor designs, according to KOMO News.

The DOME officially reopened on April 8, 2026. INL Director Dr. John Wagner called it "the kind of bold and creative infrastructure investment that America's nuclear resurgence demands." The facility can host experiments up to 20 megawatts thermal. Building a comparable new structure would cost over $100 million. Reusing the dome saved that entire sum.

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Radiant's Kaleidos: A Reactor Built Like a Product

Radiant was founded by Doug Bernauer, a former SpaceX engineer. His goal is to mass-produce nuclear generators the same way Tesla mass-produces cars. "We need to replace every 1-megawatt diesel generator with an efficient, safe, and clean mass-produced small, portable nuclear reactor," Bernauer said. The company is investing $280 million in a factory in Oak Ridge, Tennessee, targeting 50 reactors per year by 2028, according to News Channel 9.

Kaleidos runs on TRISO fuel — tiny ceramic-coated pellets that can withstand temperatures up to 1,600°C without melting. Radiant says the design makes a meltdown physically impossible. On February 9, 2026, the Department of Energy approved Radiant's safety authorization request, clearing the way for full-power testing. The DOE's acting nuclear chief Mike Goff said these experiments "will test new reactor designs that will be counted on to reliably power our homes, military bases, and mission-critical infrastructure," according to Fox San Antonio.

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Military and Industry See a Clean Break from Diesel

The Pentagon has long backed this technology through Project Pele, a Department of Defense program to build mobile reactors for military bases. A single Kaleidos unit can power a forward operating base for 5 to 8 years without refueling. That eliminates the need for fuel convoys, which are among the most dangerous missions soldiers face. Energy analysts also see microreactors as the answer for AI data centers and remote mining sites that currently burn expensive diesel around the clock, according to WSET.

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Critics Warn of Safety Shortcuts and Transport Risks

Not everyone is convinced. In February 2026, the Trump administration issued a "Categorical Exclusion" for advanced nuclear reactors, exempting them from standard environmental reviews under the National Environmental Policy Act (NEPA). California Attorney General Rob Bonta led a multi-state legal challenge against the move. "The words 'exemptions, exclusions,' and 'nuclear safety regulations' should never be put together," Bonta said, according to News 3 Las Vegas.

Edwin Lyman, nuclear safety director at the Union of Concerned Scientists, pushed back on claims that the new designs are inherently safe. "To claim that you can just turn them on and they're going to be so safe that you don't have to worry — that's just fantasy," he said. The IAEA reports that 14% of all nuclear material thefts in the past decade happened during transport — the exact mode microreactors rely on. Critics at Food & Water Watch warn that "mobile" means these reactors could eventually be deployed near cities, hospitals, and schools, according to WGME.

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