The US Navy has picked Radiant's 1MW Kaleidos microreactor for a prototype plant at Naval Weapons Station Crane in IndianaThe Pentagon wants it running by September 2028 to keep critical systems powered through potential grid outagesKaleidos has not publicly gone critical yet, and one unit will back critical loads, not the whole baseThe US Navy wants one of its most important weapons installations to keep running if the commercial grid goes down, so it chose a nuclear reactor that can be trucked in to do the job.The Navy said it had selected Radiant Industries to design, build, and deliver a prototype microreactor power plant for Naval Weapons Station Crane in southern Indiana, a day after the California startup announced the win.Brendan Rogers, Assistant Secretary of the Navy for Energy, Installations and Environment, said dedicated reactor power means "our critical naval support systems will never go dark."A 'portable' nuclear reactor for critical infrastructureRadiant's reaction to being picked has been jubilant: President and COO Tori Shivanandan said there is "no organization in the world with more experience in nuclear power" than the Navy, and the company now bills itself as the only nuclear firm selected by the Army, Navy, and Air Force.It has multiple reasons to be proud; Kaleidos is a factory-built, helium-cooled, TRISO-fueled reactor rated at 1MW of electricity. Radiant says it can travel by road, sea, or air; needs no cooling water, major excavation, or extensive on-site construction; and runs for up to five years per fuel load over a 20-year life.It will not roam around Crane; the whole unit travels in tandem. Radiant handles its own fueling, refueling, and spent-fuel storage, so host sites never keep spent fuel and can be returned to greenfield within two years of removing a unit, per the company.The US Army's Janus program (which procured this) requires all radiological material to leave a host site within two years of shutdown, meaning either enlisting the US Department of Energy to help with any potential disposals or shuttling it elsewhere, often on public roads. Critics see the flip side: anti-nuclear group Beyond Nuclear argues the model puts reactors loaded with irradiated fuel on public highways on their way back to the factory. The Navy's announcement gives no output, cost, or schedule; the 1MW figure is Radiant's. That is modest for a sprawling installation, and Army officials have been clear that Janus reactors are not meant to run whole bases. They will stay tied to the grid, and Jeff Waksman, the Army's principal deputy assistant secretary for installations, said they are "not going to provide 100% of the power on any of these installations."The chosen deployment location is no ordinary one; Crane hosts the Naval Surface Warfare Center Crane Division and the Crane Army Ammunition Activity, which, together, handle weapons development, electromagnetic warfare, strategic missions, advanced manufacturing, and conventional munitions production, according to the Navy.This isn't the Navy's first onshore reactor play; in March 1962, a portable 1.75MW pressurized water reactor known as PM-3A went critical at McMurdo Station in Antarctica, and a Navy team ran it for a decade. It suffered a hydrogen fire in its first year, shut down for good in 1972 amid cost and corrosion concerns, and removing it meant shipping thousands of tons of contaminated gravel and soil back to the US, according to the Naval Historical Society of Australia. Waksman has cited Janus' two-year cleanup rule as a key break from how the military ran reactors in the 1950s and 1960s.None of this means Crane won't get its reactor, but it does create red tape and a cautious environment. On the other side of the equation, the Pentagon has a hard deadline and an eager host state; the Navy's reactor program is lending its expertise; and Radiant has a $750 million Army contract in tow.However, for now, the Navy has picked a reactor that has never publicly run at power to keep a weapons base lit when the grid fails, and testing at Idaho National Laboratory will decide whether "never go dark" is a plan or a hope once it happens.