Five US microreactor designs went critical in the summer of 2026
Five US microreactor designs completed first zero-power criticality tests between June and August 2026, all under DOE authorization rather than NRC licenses: Antares Nuclear's Mark-0, Valar Atomics' Ward 250, Deployable Energy's Unity, Aalo Atomics' Critical Test Reactor, and Westinghouse's eVinci. Four went critical at DOE-complex sites and Valar's at the Utah San Rafael Energy Lab, with the Valar details per POWER magazine's account. Radiant shipped its 1 MWe Kaleidos to Idaho National Laboratory's DOME test bed in August 2026 for the field's first full-power test campaign, targeted for completion in the third quarter of 2026, per Radiant's announcement, and BWXT plans formal testing of the Army's Project Pele prototype as early as 2027. Deployment money so far is federal: the Army's Janus program totals up to $2.2 billion across five vendors, with a first reactor targeted to operate by September 30, 2028; no nuclear microreactor supplies power to a US commercial grid today, per AP.
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