Radiant Nuclear
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Radiant Industries Inc., commonly known as Radiant Nuclear, is an American nuclear energy company based in El Segundo, California, that designs and markets small modular reactors. The company is developing a 1MW portable microreactor called Kaleidos. It intends to replace diesel generators in hospitals, remote areas, or military bases.
The company's Kaleidos microreactor is a high-temperature, gas-cooled design using helium coolant and TRISO fuel. The reactor is designed to fit in a single shipping container and be transportable by truck. To increase flexibility, Radiant's reactors use air cooling instead of water and are designed to avoid significant on-site construction. Each reactor is designed to last 5 years without refueling, after which it is returned to the factory to be refurbished and redeployed.
Radiant was selected by the US Department of Energy in 2025 to build a demonstration reactor at Idaho National Laboratory. Its demonstration unit was shipped to the laboratory in August 2026. The company also signed an agreement with the US Air Force to build its first commercial unit at Buckley Space Force Base, and is constructing a microreactor factory in Tennessee as of 2026.
History
Doug Bernauer, an engineer at SpaceX, founded Radiant in 2020 with two other colleagues. He had investigated power generation options on Mars, and found that no companies manufactured small nuclear reactors for space use. Bernauer tried to develop a nuclear program at SpaceX before founding Radiant instead. Later that year, the company raised $1.2million from angel investors. The company was initially run out of a former dance studio, before moving into a former Hughes Aerospace warehouse in El Segundo.
In 2023, Radiant was awarded a grant by the US Department of Energy (DOE) to support a demonstration of its Kaleidos reactor at Idaho National Laboratory. The program, Demonstration of Microreactor Experiments (DOME), aims to use the former containment dome of EBR-II to test microreactors. The DOE later selected Radiant to be the first company to test at DOME. Radiant was selected by the DOE in 2025 to receive high-assay low-enriched uranium (HALEU) fuel for its first reactor demonstration, the Kaleidos Development Unit (KDU) which the company expected to begin in 2026. The DOE approved Radiant's Preliminary Documented Safety Analysis in February 2026, and the company took possession of the DOME facility soon after. Radiant received its first shipment of TRISO fuel for KDU in July 2026. On August 12, the KDU reactor was shipped to DOME from its facility in El Segundo on a specialized trailer. The company's test plan calls for at least 150 consecutive hours at full power without operator intervention.
In August 2025, the US Air Force signed an agreement with Radiant to deliver a reactor unit by 2028, as part of its Advanced Nuclear Power for Installations (ANPI) program. The following year, the Air Force announced that it had selected Buckley Space Force Base as the location for Radiant's reactor, expected to enter operation in 2028.
In August 2026, the US Army announced that it had selected Radiant to build at least one microreactor at Fort Benning, as part of its Janus Program. The company was awarded $750million, out of a total of $2.2billion, to build 15 Kaleidos reactors at Benning.
In 2024, Radiant was reported as analyzing Wyoming, Utah, Tennessee, and Idaho as locations to build a microreactor factory. The following year, Radiant selected Bar Nunn, Wyoming as their preferred site to build the facility, aiming to complete it by 2028. Radiant would have fabricated its reactors there before shipping them to a customer site. While the assembly of nuclear reactors did not attract significant opposition, residents and state legislators including Bill Allemand expressed significant concerns about the storage of spent nuclear fuel from other states. Several months later, Radiant cancelled the proposed facility in Bar Nunn in favor of one in Oak Ridge, Tennessee, on the former K-27 and K-29 site, to be called R-50. The company cited Wyoming state law, which requires spent fuel to be stored at the same site where it is produced, as the reason for the change. The proposed factory had attracted significant opposition from the Wyoming Freedom Caucus, with chair Rachel Rodriguez-Williams decrying that "California billionaires insist on saddling our landscapes with their windmills, their solar panels and now their radioactive waste". The Freedom Caucus's opposition provoked criticism from Bar Nunn mayor Peter Boyer, as well as Wyoming governor Mark Gordon and several state legislators.
Radiant applied for a permit for the R-50 factory from the Nuclear Regulatory Commission (NRC) in early 2026. The permit, under 10 CFR Part 70, allows the facility to possess and use special nuclear material. The NRC anticipated completing its review by the end of 2026. The R-50 facility is intended to produce and fuel Kaleidos reactors before shipping them to customers. The facility is intended to produce up to 50 reactors per year, and construction is underway as of 2026. R-50 is also supported by the DOE's Nuclear Energy Launch Pad initiative, which Radiant was selected for in April 2026.
Kaleidos reactor
The Kaleidos reactor is a 1MWe microreactor, designed for off-grid power generation. A high-temperature gas-cooled reactor, it uses TRISO fuel, consisting of ceramic-coated particles of uranium. Each particle is composed of a kernel of uranium oxycarbide coated with silicon carbide and carbon, and packed into a graphite compact. TRISO particles can tolerate temperatures exceeding 3,000°F (1,650°C) without damage. The reactor uses passive cooling, which dissipates heat without requiring electricity, combined with TRISO fuel to achieve a high degree of nuclear safety. Kaleidos reactors use zirconium hydride embedded within graphite blocks as their neutron moderator, allowing for highly compact design. The reactor uses inert helium gas as its coolant. It will use integrated fans to avoid using water for cooling, along with a passive air jacket driven by natural circulation to remove core heat.
Radiant has targeted minimal on-site construction, dry air cooling, and factory fabrication as key features. Each reactor is to be packaged in a single shipping container, containing the reactor, generator, and cooling system. Radiant's reactors are designed to be transportable by truck, cargo aircraft, or ship, without requiring specialized infrastructure. They are intended to be installed on prepared pads and operated for years without refueling. In many instances, the reactor's deployments will be temporary. The reactor is designed to be shipped to a customer's site and dropped into place with minimal setup. The company has stated that when deployment ends, the reactor would be picked up and shipped back to its factory. For longer deployments, the reactor will be shipped back, refueled, and returned to a customer site.
Radiant intends for their Kaleidos reactors to replace diesel generators, providing power to hospitals, military bases, data centers, or remote communities. According to the Los Angeles Times, Radiant expects that its reactors will be competitive with diesel generators in places where diesel fuel costs more than $6.50 per gallon.
Kaleidos reactors are designed to operate for five years between each refueling, with each unit expected to last 20 years. The company intends to bring spent nuclear fuel from its reactors back to its central fueling facility. Radiant has stated that the spent nuclear fuel remains entirely within the container while on a customer's site, being removed and replaced at the company's facility.
Corporate affairs
The company's chief executive officer is Doug Bernauer, who founded Radiant in 2020. Bernauer provided some of the company's initial funding.
In 2023, the company raised $40million in a funding round led by Andreessen Horowitz. By mid-2025, Radiant had raised $165million in a Series C funding round. Later that year, it hired Rita Baranwal, the former Assistant Secretary of Energy for Nuclear Energy, as its Chief Nuclear Officer. By 2026, Radiant had raised over $575million.
Equinix, a data center company, signed a commercial agreement to purchase 20 Kaleidos microreactors from Radiant.