Radiant
Builds Kaleidos, a 1 MWe transportable microreactor for bases and data centers.
On the record
Checkpoint: Summer 2026 fueled, full-power Kaleidos test at INL DOME facility
The call
Radiant has government contracts and cash, but its whole story rests on one unproven reactor test at Idaho National Lab.
Radiant is a startup building small modular nuclear reactors designed to work with special fuel. The company has $1.8 billion in the bank and government approval to proceed, which makes it harder for competitors to copy right away. However, at least four other well-funded startups like Oklo and X-Energy are building almost identical reactors in the same space, and older nuclear companies like Westinghouse and General Atomics have way more money and experience. The summer of 2026 full-power test at Idaho National Lab will be the make-or-break moment: if Radiant's reactor works as promised, the company becomes much less risky, but if the test fails or gets delayed, that story falls apart entirely.
Why
01
AI pressure: None apparent. AI data center power demand is a customer tailwind here, not a predator; no AI product replaces a physical reactor. Could AI do the core job? Unlikely.
02
Bigger players: Westinghouse, BWXT, General Atomics, TerraPower. Deeper-pocketed nuclear players compete for the same DOE microreactor slots and Army/Air Force contracts Radiant is chasing. Could a giant copy it? Probably.
03
What protects it. DOE safety approvals, HALEU fuel allocations, and signed Buckley AFB and Equinix contracts give it a regulatory and customer head start.
What would change this call
Outcome of the summer 2026 fueled, full-power Kaleidos test at INL's DOME facility. Success or failure directly determines whether Radiant's reactor design is technically viable.
Announcement of the winner of the U.S. Army's 2026 microreactor program. Shows whether Radiant or a rival like Oklo or BWXT secures a key government deployment.
Whether Radiant is added to or remains excluded from DOE's Project Prometheus initiative by end of 2026. Indicates if Radiant is being sidelined from top-tier federal AI-nuclear partnerships versus peers.
Announcement of the winner of the U.S. Army's 2026 microreactor program. Shows whether Radiant or a rival like Oklo or BWXT secures a key government deployment.
Whether Radiant is added to or remains excluded from DOE's Project Prometheus initiative by end of 2026. Indicates if Radiant is being sidelined from top-tier federal AI-nuclear partnerships versus peers.
Key numbers
- $300M+ Series D at $1.8B valuation
- Equinix pre-ordered 20 Kaleidos units
- DOE second HALEU allocation for Buckley AFB
Named risks
- Summer 2026 fueled full-power Kaleidos test at INL could fail or slip, delaying 2028 delivery.
- Excluded from DOE's $60M Project Prometheus AI-nuclear initiative naming 32 partners including Oklo and X-Energy.
- HALEU fuel supply depends on Centrus Energy, the only domestic commercial producer.
- Pre-revenue status with capital-intensive product and years to first commercial delivery in 2028.
- Nuclear sector stock weakness at public peers Oklo and X-Energy in July 2026 could pressure future funding sentiment.
Rivals, as read in July 2026
| Rival | Direction | Evidence |
|---|---|---|
| Oklo | gaining on | Public at ~$7.7B market cap and named Project Prometheus partner as of Jul 24, 2026 |
| X-Energy | gaining on | Public since Apr 2026, ~$6.5B market cap, 11 GW pipeline with Amazon/Dow deals |
| Aalo Atomics | gaining on | Achieved zero-power criticality on Aalo-X test reactor in 2026 ahead of Radiant's INL test |
| Antares Nuclear | gaining on | Raised $470M Series C in Jul 2026 after hitting criticality in same DOE program |
| TerraPower, Westinghouse, BWXT, General Atomics | contesting | Deeper nuclear expertise and capital, part of same ANPI cohort as Radiant |
Questions people ask
- Is Radiant profitable in 2026?
- No. Radiant is pre-revenue as of mid 2026, with first commercial reactor deliveries targeted for 2028 under contracts like the Air Force's Buckley Space Force Base deal announced April 22, 2026. Revenue depends on a successful summer 2026 fueled reactor test at Idaho National Laboratory.
- Could AI replace Radiant's nuclear reactor business?
- No. Radiant's core product requires physical reactor manufacturing, TRISO fuel handling, and DOE/NRC regulatory approval, none of which AI can substitute. Radiant uses an internal digital-twin tool called SimEngine for design and monitoring, but this supports rather than replaces its regulated hardware business.
- Who owns Radiant, the nuclear microreactor company?
- Radiant is privately held and venture-backed, founded in 2020 by former SpaceX engineers Doug Bernauer and Bob Urberger. Its Series D closed December 17, 2025 for over $300 million led by Draper Associates and Boost VC, valuing the company at over $1.8 billion.
- Who is Radiant's biggest competitor?
- Radiant competes most directly with Oklo (public, ~$7.7B market cap as of July 24, 2026) and X-Energy (public since April 2026, ~$6.5B market cap, 11 GW pipeline). Both are named partners in DOE's Project Prometheus AI-nuclear initiative announced July 22-24, 2026, while Radiant is not listed.
- Has Radiant had layoffs?
- No layoffs are reported. Headcount data from Crustdata shows growth from about 11 employees in June 2021 to 531-538 by June 2026, a 114% year-over-year increase, consistent with active hiring for its Oak Ridge, Tennessee manufacturing facility.
- What is the most important upcoming event for Radiant?
- The pivotal event is Radiant's first fueled, full-power test of its Kaleidos reactor at Idaho National Laboratory's DOME facility, scheduled for summer 2026 after DOE approved its safety documentation on February 9, 2026. Success or failure here will shape its 2028 delivery timeline.
Timeline
- 2026-07-23DOE selects Radiant for second HALEU fuel allocation to support Buckley deployment
- 2026-07-21NRC presentation says Army 2026 microreactor program winner announcement is imminent
- 2026-04-22Air Force/DIU selects Radiant to build microreactor at Buckley Space Force Base
- 2026-02-09DOE approves Radiant's DARK safety documentation, confirms summer 2026 INL test
- 2025-12-17Radiant closes Series D, over $300M, at $1.8B valuation led by Draper Associates, Boost VC
- 2025-05-27Radiant closes $165M Series C led by DCVC
- 2023-04Radiant closes $40M Series B led by Andreessen Horowitz
- 2022-03Radiant closes $12.6M Series A led by Union Square Ventures
- 2020Radiant Industries founded by Doug Bernauer and Bob Urberger
Revision history
29 July 2026
First assessed. Losing its protection. The text above is fixed as of this date and is not edited afterwards.
In the same band
Sources
- Radiant bags $300M-plus to commercialize its microreactors (2025-12-17)
- Radiant closes $165 Million Series C (2025-05-27)
- Nuclear startup Radiant raises $300M at $1.8B valuation (2025-12-17)
- Radiant raises over $300 million (2025-12-17)
- Equinix-backed microreactor firm Radiant raises $300m (2025-12-19)
- Air Force selects Radiant to deliver microreactors to Buckley Space Force Base (2026-04-22)
- DOE Selects Radiant for Second HALEU Allocation (2026-07-23)
- Radiant Nuclear
- Radiant receives DOE approval of PDSA (2026-02-09)
- Advanced Reactor Landscape: Current Status and Moving Forward (2026-07-21)
- Radiant, Headcount, Funding & Open Jobs (2026-07-07)
- El Segundo's Radiant Hits $1.8B Valuation (2025-12-19)