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Radiant is building the world's first mass-produced, portable nuclear microreactors. The company's flagship product, Kaleidos, is a 1-megawatt, fail-safe microreactor designed to be transported and deployed anywhere power is needed, running for up to 5 years without refueling. The reactor can replace diesel generators and support hospitals, data centers, remote sites, and military bases. Founded in 2020, Radiant is preparing to test its first reactor at Idaho National Laboratory with initial customer deliveries expected in 2028.
As a Reactor Systems Engineer, you will support the technical integration of this first-of-a-kind reactor. With no operating predecessor and an immature supply chain, you'll help ensure that design decisions across nuclear physics, thermal-hydraulics, controls, structures, materials, fuel, and licensing integrate into a safe, on-time delivery. The role is hands-on and technical—you'll work with thermal models, component specifications, and subsystem designs—while developing cross-disciplinary collaboration skills.
Key responsibilities include:
- Translate between reactor physics, thermal-hydraulics, materials, controls, mechanical design, manufacturing, and regulatory teams, surfacing assumptions and tensions at team boundaries
- Maintain libraries of P&IDs, sensors, and subsystem specifications to support alignment from design through operations
- Identify cross-cutting risks early and drive resolution
- Collaborate with safety analysis and licensing teams to keep design decisions, safety cases, and regulatory submissions consistent
- Support development of design basis, safety classification, and technical specification documentation
- Assist in component and subsystem testing, including test plans, data collection, and design feedback
- Maintain the technical baseline (requirements, configuration, change control, risk registers, documentation) using lightweight startup processes
- Communicate clearly with engineers and leadership; contribute to technical documentation for regulators and customers
Writing is a core part of the job—specifications, decision memos, and system descriptions keep the team aligned.
REQUIREMENTS:
- Bachelor's degree in nuclear, mechanical, aerospace, systems, or related engineering discipline
- 3–5 years of full-time professional engineering experience with exposure to systems engineering, integration, or cross-disciplinary technical work on complex hardware
- Ability to work effectively across multiple engineering disciplines
- Developing experience collaborating on cross-functional technical efforts
- Strong written and verbal communication skills, including ability to produce clear technical documents
- Good organizational skills; able to track open items and follow through on assigned work
- Ability to apply first-principles thinking and contribute sound judgment amid ambiguity and incomplete data
- Exposure to highly regulated or high-consequence industries (nuclear, aerospace, defense, advanced energy, medical devices, semiconductor equipment) preferred
- Experience in first-of-a-kind or early-stage hardware programs a plus
- Familiarity with nuclear reactor design, safety, or regulatory frameworks (10 CFR 50/52/53, NQA-1, GDCs, defense in depth) a plus but not required
- Startup or small-team experience, or strong interest in that environment, preferred
- Must be willing to work extended hours and weekends as necessary
- Must work 100% onsite at El Segundo HQ
- Eligibility to work in the U.S. and ability to meet export control requirements
