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Senior Fluid Systems Engineer

Radiant - El Segundo, CA, USA - In-office - posted 2026-10-12

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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, Radiant is preparing to test its first reactor at Idaho National Laboratory with initial customer deliveries expected in 2028. As Senior Fluid Systems Engineer, you will own the complete engineering lifecycle of Kaleidos fluid systems—from preliminary design through build and production. This includes the primary loop subsystems and power conversion loop responsible for converting reactor core heat into electrical power. Key responsibilities: - Own end-to-end engineering of fluid systems and components (compressors, valves, heat exchangers) - Perform complex thermal and fluids analysis using first-principle calculations and finite element tools to drive design decisions and verify system performance - Conduct trade studies to optimize systems and meet program requirements - Develop and execute manufacturing/assembly instructions and test plans - Create and manage Bills-of-Materials (BOM) - Source and develop suppliers for all components - Own subassembly design, manufacturing, and test schedules - Perform risk analysis (FMEA) for subsystems - Collect requirements and provide expertise to cross-functional teams You will have instrumental impact on fueling the first new commercial reactor design in over 50 years. The role requires 100% onsite work at El Segundo headquarters and willingness to work extended hours and weekends as needed. REQUIREMENTS: - Bachelor's degree in Mechanical, Materials, Aeronautical, Civil, or Structural Engineering from an accredited institution - 5+ years of experience designing, building, and testing fluid systems - Experience with fluid system architecture design - Proficient knowledge of fluid dynamics and thermodynamics - Proficient knowledge of heat exchanger design and analysis methods DESIRED QUALIFICATIONS: - Knowledge of thermodynamic power cycles - Prior experience designing piping systems for thermal growth using hand calculations and FEA tools - Experience with process piping design and testing codes (ASME B31.3, ASME PCC-2) - Fluid system modeling via Matlab/Python - Design for manufacturability and hardware production ramp-up experience - Experience designing and operating test stands - Extreme ownership and high responsibility orientation - Excellent multidisciplinary team communication - Prior nuclear experience not required

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