Evidence check: Radiant

As of October 13, 2026 · Prepared by Alphaneo

Summary

Radiant has strong public validation on capital and customers, but its central technical milestone is late and unconfirmed. Radiant (El Segundo, CA, founded 2020) builds Kaleidos, a 1 MWe portable microreactor meant to replace diesel generators at bases, data centers and remote sites (Wikipedia opens in a new tab).

It has raised more than $500M (Wikipedia opens in a new tab), most recently a Series D of over $300M (December 2025) reported at a valuation above $1.8B. It holds an Army award of up to $750M for up to 15 reactors (World Nuclear News opens in a new tab) and plans an Air Force unit at Buckley Space Force Base by 2028 (NEI Magazine opens in a new tab).

The open question is the reactor itself. Radiant targeted completing its first fueled test at Idaho National Laboratory by September 30, 2026. As of this check, we found no public announcement that the reactor has reached criticality.

What's verifiable

Each item below links to the public source it comes from.

Area	Fact	Source
Funding	Series D of over $300M, closed December 17, 2025, led by Draper Associates and Boost VC	Orrick opens in a new tab
Funding	Lockheed Martin Ventures joined as a strategic investor, February 17, 2026; amount not disclosed	Radiant opens in a new tab
Product	Kaleidos: 1 MWe, helium-cooled, TRISO fuel, fits one shipping container, about 5 years between refuelings	Wikipedia opens in a new tab
Test	First TRISO fuel delivered to INL's DOME facility, July 1, 2026	Radiant opens in a new tab
Test	Five-phase plan ending in 150 hours at full power without operator intervention; target was Q3 2026	NEI Magazine opens in a new tab
Customer	Army Janus program: up to $750M for up to 15 reactors, funding tied to technical milestones, 2027–2031	World Nuclear News opens in a new tab
Factory	R-50 factory in Oak Ridge, TN, up to 50 reactors a year; NRC license review targeted for Q4 2026	NEI Magazine opens in a new tab

What's missing

The most important claims rest on targets and reports that public sources can't confirm.

Test status. The Q3 2026 target for completing the DOME test has passed. We found no public announcement of installation, fueling or criticality as of early October (Venture Atlas audit opens in a new tab).
Valuation. The $1.8B+ figure is reported, not confirmed by the company, and it isn't stated whether it is pre- or post-money (Silicon Valley Investclub opens in a new tab).
Army contract terms. "Up to $750M" is a ceiling tied to milestones. The site, schedule and what triggers each payment aren't public (Radiant opens in a new tab).
Commercial orders. A reported agreement with Equinix for 20 reactors appears in secondary sources (Wikipedia opens in a new tab); we did not find binding terms.
Unit economics. Price per reactor, cost of power and margins aren't disclosed.
Reactor license. The NRC lists Kaleidos as pre-application. The factory license and a commercial reactor license are separate approvals.

How the round compares

Radiant's last reported valuation sits below its closest peer's newer marks, so the next round will turn on the DOME result.

Company	Round	Amount	Valuation	Source
Valar Atomics	Reported talks, July 2026 (not closed)	About $1B	About $6B, reported, not closed	AI Weekly opens in a new tab
Antares Nuclear	Series C, July 2026	$470M	Not disclosed	Axios opens in a new tab
Valar Atomics	March 2026	$450M ($340M equity, $110M debt)	$2B	Dealroom opens in a new tab
Radiant	Series D, December 2025	Over $300M	Over $1.8B, reported	Orrick opens in a new tab

Antares also won a Janus award (World Nuclear News opens in a new tab), so Radiant competes with funded peers for the same Army program.

Key risks

Test slip. Every downstream date (factory output, the 2028 Air Force unit, Army deployments) assumes the DOME test succeeds soon. A long delay moves all of them.
Licensing. A commercial reactor still needs regulatory approval for each deployment path. The factory license doesn't cover operating reactors.
Fuel supply. Kaleidos runs on HALEU, which is scarce. Supply depends on DOE allocations and a Centrus agreement signed in September 2026 (Wikipedia opens in a new tab).
Milestone-based revenue. The Army money is paid only as technical goals are met, between 2027 and 2031.
Factory history. Radiant canceled its planned Wyoming factory in October 2025 over spent-fuel storage law before choosing Oak Ridge (Wikipedia opens in a new tab). Siting and local approval remain real risks for later sites.

Five questions to ask the founder

Where is Kaleidos in the five-phase DOME test today, what caused the slip from Q3, and what is the new date for each phase?
Of the Army's "up to $750M," how much is committed now, and which milestone releases the first payment?
Which customer agreements are binding purchase orders with deposits, and which are letters of intent?
What is the target price per reactor and cost per megawatt-hour at 50 units a year, and what does the first unit actually cost?
How many reactors' worth of HALEU fuel is contracted for 2027–2030, and what happens to deliveries if supply falls short?

Sources

Public sources only, as of October 13, 2026. This is an evidence check, not investment advice or a recommendation to buy or sell. Alphaneo has no position in or relationship with Radiant. Prepared by Alphaneo, alphaneo.ai.

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