Radiant's Kaleidos Microreactor Is First in Line at Earth's Only Test Bed — and Six New Roles in Seven Days Show the Clock Is Already Ticking

Radiant Just Won the World's First Microreactor Test Slot

On July 1, 2025, the Department of Energy conditionally selected Radiant, alongside Westinghouse, to run the first fueled microreactor experiments inside the Demonstration of Microreactor Experiments (DOME) facility at Idaho National Laboratory. The first experiment could begin as early as spring 2026.

DOME is the world's first microreactor test bed, a repurposed containment dome from the former Experimental Breeder Reactor II, now configured to house fueled reactor experiments producing up to 20 megawatts of thermal energy. The DOE's National Reactor Innovation Center operates it. Each test campaign runs up to six months, one at a time, and the companies pay for their own experiments. The facility is expected to operate for roughly 20 years.

For Radiant, the selection caps a competitive process that started in 2023, when the DOE funded the company's front-end engineering and experiment design work for the Kaleidos Development Unit. Radiant finished that study in November 2024. In April 2025, the DOE went further, committing high-assay low-enriched uranium to Radiant for the test (one of only five companies to receive fuel in the first HALEU distribution round). Without that fuel, the DOME slot is theoretical. With it, Radiant has a path to fueling and going critical in a government-owned facility within months.

Doug Bernauer, Radiant's founder and CEO, called the combined milestones a teaming arrangement with a single mission: "Just nine months from now we will have the opportunity to put the 53rd reactor in INL's long history into the DOME. In short order, we will fuel, go critical, and operate."

Kaleidos is designed to produce more than 1 megawatt of electricity in a transportable package, run for five years without refueling, and replace diesel generators at military installations, hospitals, and remote sites. It uses TRISO fuel particles and is meant to be built on an assembly line. Radiant's core pitch is mass production, not one-off builds.

Both the DOME selection and the HALEU allocation remain conditional. Radiant still has to clear the multi-phase DOE authorization process covering design, fabrication, construction, and testing. The company has to hit milestones to maintain its allotted time in the test bed. Sequencing depends on technology readiness, fuel availability, and a regulatory approval plan. Nothing here is guaranteed.

But the signal is clear. Radiant is first in line at the only facility on Earth built for exactly this kind of test. The company's hiring reflects it. Zero G Talent's board shows six Radiant roles added in the past week alone, spanning cost accounting, mechanical engineering, and electrical integration, all out of El Segundo.

Four Disciplines Standing Between Radiant and a Critical Reactor

Getting a 1-megawatt nuclear reactor onto a trailer, shipping it to Idaho, and running it for the first time with fuel inside spans at least four distinct disciplines, and Radiant's hiring makes that scope visible.

Nuclear engineering and core physics. Radiant's open "Nuclear Engineer, Core Physics" role requires experience with radiation transport codes (MCNP, OpenMC, or Serpent) plus reactor physics calculations covering neutronics, transient analysis, and criticality safety. The engineer will design test procedures for the 2026 DOME demonstration, verify that proposed test sequences meet safety and performance objectives, and write the documentation operators will follow inside the control room. A broader "Nuclear Engineer" listing adds shielding design, accident dose consequence analysis, and radiation detection. Both roles require a bachelor's degree in nuclear engineering and at least one to two years of industry experience; direct reactor-operator experience is desired but not mandatory.

Thermal-hydraulics. Kaleidos must transfer heat from its core reliably for up to five years without refueling, inside a package small enough to haul on a flatbed. Radiant has posted a Senior Thermal-Hydraulics Engineer role, and the broader microreactor industry confirms the demand: competing listings at companies like NuScale call for five or more years of experience in thermal-hydraulic modeling, computational fluid dynamics, and heat-pipe analysis. Purdue University's nuclear engineering program lists thermal-hydraulics and safety as a core course area specifically because of the sector's growth.

Controls and systems integration. A portable reactor that deploys to a military forward operating base or a remote data center cannot rely on a full plant staff. The control architecture has to run with minimal on-site intervention. Radiant's Core Physics role explicitly mentions supporting "control room GUI development" and operator training, tasks at the intersection of nuclear engineering and human-factors design. The company's broader job board shows parallel demand for electrical and mechanical integration engineers, suggesting the test campaign's instrumentation and data-acquisition systems are a significant hiring category on their own.

Fuel engineering. Less visible in the public postings but structurally essential. Kaleidos is designed to use existing, well-qualified fuel materials. Radiant emphasizes that the company is not waiting on new fuel qualification campaigns. But preparing a fueled test at DOME still demands engineers who understand fuel behavior under irradiation, waste categorization, and the interface between fuel design and the shielding and neutronics analyses the nuclear team runs.

The through-line across all four disciplines is the 2026 test deadline. Radiant has said it is on track to test Kaleidos at Idaho National Laboratory this summer, with customer deliveries targeted for 2028. That schedule compresses what would normally be a multi-year qualification process into roughly two years of active engineering work.

Westinghouse Is Racing Radiant Into the Same Test Bed

Westinghouse Electric Company is running a parallel track with its eVinci microreactor, and the two programs are competing for the same thin pool of engineers who can actually build these things.

Westinghouse will test a scaled-down 3-megawatt-thermal version of eVinci, a heat-pipe-cooled design targeting 5 megawatts of electricity for commercial deployment. The company submitted its Preliminary Safety Design Report to the National Reactor Innovation Center in September 2024 (the first developer to reach that milestone), and Jon Ball, president of eVinci Technologies at Westinghouse, said the company is targeting deployment of multiple commercial units by the end of the decade. Westinghouse's eVinci team draws on more than 300 engineers.

That head start on safety documentation matters. Westinghouse completed its front-end engineering and experiment design phase before Radiant and has already moved into the DOE authorization pipeline's later stages. But the DOME sequencing criteria (technology readiness, fuel availability, and regulatory approval plan) mean that being first in line doesn't guarantee being first to test. Both companies are self-funding their campaigns, and both must hit milestones to hold their slots.

Ultra Safe Nuclear Corporation was also part of the original October 2023 DOE funding round. The three companies split $3.9 million for front-end design work, but didn't make the final cut for the first DOME experiments. That leaves Westinghouse and Radiant as the two companies whose hiring timelines most directly signal where portable nuclear is heading.

Westinghouse has an advantage in scale. The company operates the largest installed base of commercial reactors in the world and can pull from decades of institutional knowledge. Radiant, a startup headquartered in El Segundo, is building its team from scratch. The salary bands on Radiant's open roles reflect what it takes to lure experienced hardware engineers away from aerospace, defense, or established nuclear firms.

Both companies are now in that same multi-phase DOE authorization process. The engineers they hire in the next six months will determine whether those timelines hold — or slip.

Defense Forward Operating Bases and AI Data Centers Are Both Calling

The Department of Defense has been trying to shrink its diesel supply chain since at least 2016, when a Defense Science Board task force concluded that battlefield energy demand would "increase significantly over the next few decades" and that nuclear power was "uniquely suited" to meet it. The energy density advantage is roughly two million to one over diesel. That finding launched Project Pele, the Strategic Capabilities Office's effort to design, build, and demonstrate a transportable microreactor, a program that broke ground at Idaho National Laboratory in September 2024.

Project Pele is the most visible defense microreactor program, but it is not the only one pulling on the same engineering talent. The Air Force and the Defense Innovation Unit selected Antares to develop a microreactor option for Joint Base San Antonio. The Army's Janus Program is evaluating nuclear power for installations where grids are fragile and resupply is expensive. In February 2026, Valar Atomics flew an unfueled microreactor on a C-17 from Southern California to Hill Air Force Base in Utah, a logistics proof-of-concept that treated energy hardware as mission-essential equipment.

Radiant's Kaleidos is threading through this same defense pipeline. The company has named both organizations as partners, and its reactor is designed to provide sustained power for Department of the Air Force critical infrastructure. Kaleidos uses TRISO fuel, the same particle-based fuel form at the heart of Project Pele, and passive helium cooling with zero on-site water requirements, a constraint that matters when the deployment site is a forward operating base or a remote Arctic outpost.

But defense is only half the demand picture. The AI data center buildout is creating a parallel pull on microreactor developers. Tech giants have committed more than $10 billion to small modular reactor procurement, with the first SMR facilities expected online by 2030. Microreactor builders are positioning for a share of that market by offering faster deployment timelines and siting flexibility that conventional nuclear cannot match.

Radiant has explicitly targeted this overlap. Equinix, a major data center operator, signed a purchase agreement for 20 Kaleidos units. The company lists data center operators alongside military installations, remote mining operations, disaster relief agencies, and remote communities as target customers. Kaleidos is designed to deliver baseload power for up to 20 years on a single fuel load, a value proposition that reads the same whether the customer is running GPU clusters or a tactical operations center.

This dual-use demand is what makes Radiant's DOME timeline a hiring catalyst rather than just a technical milestone. Every open position exists because the end markets are real enough to fund them and close enough to deployment to need them now. The bottleneck is not demand. It is the number of engineers who can build a reactor that fits on a truck, survives transport on a C-17, and runs unattended for two decades on a schedule that matches both a Pentagon deployment plan and a data center construction timeline.

The Regulatory Calendar That Actually Drives Hiring

Most hiring analysts read a DOE press release about a microreactor test bed and think the talent demand starts now. It doesn't. It started months ago, and it will spike again at specific, predictable milestones tied to a regulatory calendar most job boards ignore.

Radiant's Kaleidos is moving through two parallel authorization tracks, and each one dictates a different hiring rhythm. The first runs through DOE's Reactor Pilot Program, created in June 2025 to fast-track advanced reactor demonstration outside the national labs. Under that pathway, Radiant filed its authorization request in November 2025 under a 45-day approval framework and has already cleared the second of three required nuclear safety document submissions. That second submission, the Preliminary Documented Safety Analysis, is the one that actually drives headcount. Preparing a PDSA for a transportable reactor means Radiant's nuclear engineers, thermal-hydraulic analysts, and safety-case writers have been working at full tilt for the better part of a year. The third and final submission will demand another concentrated push, likely pulling in additional shielding and neutronics specialists on contract.

The second track runs through the Nuclear Regulatory Commission, and it operates on a longer clock. Radiant has been in pre-application engagement with the NRC since October 2022. The Kaleidos design is transportable, helium-cooled, and designed so that refueling and major maintenance happen at a central manufacturing facility rather than on site, which Radiant's own regulatory engagement plan says simplifies the approval problem. But "simpler" is relative. The NRC is still building out a risk-informed, performance-based framework for microreactors, with inspection procedures targeted for early 2026. Until that framework solidifies, every microreactor developer faces a licensing timeline that could stretch years beyond the DOE authorization.

This is where the hiring pattern gets counterintuitive. The DOE pathway lets Radiant move fast on the test bed, and that's where the near-term demand sits: integration engineers, test engineers, and the people who will actually operate Kaleidos at the DOME facility. But the NRC licensing track is what determines whether Kaleidos ever ships commercially, and that's where the sustained, multi-year hiring need lives. Radiant's current job listings reflect both timelines at once, with roles like Senior Equipment Engineer and Principal Electrical Engineer, Integration & Test pointing toward the test-bed phase, while the company's ongoing regulatory engagement quietly builds the team it will need for a full NRC license application.

Oklo's Aurora powerhouse offers a useful comparison. The DOE approved Aurora's PDSA in June 2026, and Oklo broke ground on the Aurora-INL facility in September 2025. Oklo CEO Jacob DeWitte said the approval helps establish a foundation for future Aurora deployments and commercial licensing. Oklo is already building before it has final safety approval, which means its hiring preceded the regulatory green light. Radiant is following a similar logic: staff up for the test, staff up for the license, and accept that the two timelines will overlap in ways that don't show up on a quarterly earnings call.

Don't watch the DOE press releases. Watch the PDSA submissions, the NRC pre-application meeting schedules, and the gap between a company's test-bed authorization and its commercial license application. That gap is where the hiring actually happens, and right now, Radiant is standing in it.

El Segundo and Idaho Falls: The Two Zip Codes That Matter

Radiant's entire nuclear engineering team sits in a single El Segundo, CA headquarters, and every open role lists the same hard requirement: 100% onsite. The company's reactor physics, shielding, criticality safety, and accident-dose-consequence work happens in one building near the Pacific Ocean, and the roles are filling up fast. The Lead Nuclear Engineer posting drew 73 applicants in two weeks.

El Segundo is already dense with advanced-reactor and aerospace firms. Valar Atomics, Arbor Energy, and Antares all list nuclear and thermal roles across the Los Angeles metro, and Boeing, Northrop Grumman, and The Aerospace Corporation run radiation-effects and survivability groups out of the same South Bay corridor. Radiant's job postings ask for MCNP, OpenMC, and Serpent experience, the same tools used in weapons-effects and naval-reactor work. The company is hiring directly out of a talent pool that defense aerospace built.

The other cluster is Idaho Falls. Idaho National Laboratory is hiring an Engineering Program Lead for Transportable Microreactor Operations and Construction, a role tied directly to the DOME test bed where Radiant plans to run Kaleidos. INL's broader careers page is pushing nuclear-reactor-technology staff as part of its energy-future pitch, and the DOME test bed is the anchor pulling those hires inland.

The geography tracks the work. Design, analysis, and regulatory prep stay in El Segundo. Fueled demonstration, licensing validation, and operations testing move to Idaho. Radiant's $300 million raise, announced in December 2025 just six months after its Series C, funds both sides of that split. If you're a nuclear engineer deciding where to be useful in 2025, the answer is one of two zip codes.

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