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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 for rapid deployment to hospitals, data centers, remote sites, and military bases. Founded in 2020 and headquartered in El Segundo, CA, Radiant is preparing to test its first reactor at Idaho National Laboratory this summer, with initial customer deliveries expected in 2028.
As Senior Nuclear Thermal-Hydraulics Engineer, you will own thermal-hydraulics and coupled physics analysis for the Kaleidos microreactor. This role directly shapes how heat, coolant, and reactor core behavior interact under normal and accident conditions—work that informs core design, cooling systems, and the safety case for the first mass-produced nuclear reactor.
Key responsibilities include:
- Execute thermal-hydraulics analysis to evaluate design and safety performance under normal and accident conditions
- Develop and apply coupled physics models integrating thermal-hydraulics with neutronics and/or structural response
- Identify and implement best practices for reactor thermal-hydraulics and systems-code analysis
- Build automated workflows to expand simulation capabilities, accuracy, and efficiency
- Collaborate across reactor physics, mechanical, and safety teams to support licensing and design trade studies
You will need a Bachelor's degree in nuclear engineering, mechanical engineering, physics, or similar field, plus 5+ years of relevant industry or national laboratory experience. Required expertise includes thermal-hydraulics analysis and reactor systems codes (RELAP5, TRACE, CTF/COBRA-TF, SAM, TRANSFORM), high-temperature heat transfer analysis (500°F+), and ability to communicate technical information across functional teams.
Desired qualifications include coupled multiphysics modeling experience (MOOSE, BISON, MARMOT), commercial CFD/FEA tools (STAR-CCM+, Ansys Fluent), CAD (Siemens NX), and prior experience at national laboratories, reactor vendors, or advanced reactor developers. The role requires 100% onsite presence at El Segundo HQ and willingness to work extended hours as needed.
Radiant offers substantial equity grants, comprehensive health benefits (medical, dental, vision), 8 weeks paid parental leave, daily catered lunch, flexible PTO, and a collaborative team environment near the Pacific Ocean.
