Radiant is developing a transportable 1-MW helium-cooled micro-nuclear reactor designed to replace diesel generators for commercial, military and data-center customers.
ABOUT RADIANT Radiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. The company’s first reactor, Kaleidos, is a 1-megawatt, fail-safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. Portable nuclear power with rapid-deploy capability can replace similar-sized diesel generators and provide critical asset support for hospitals, data centers, remote sites, and military bases. Radiant’s unique, practical approach to nuclear development leverages modern software engineering to rapidly deliver safe, factory-built microreactors that use existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028. ABOUT THE ROLE Radiant is seeking a Lead Test Engineer, Power Generation to own the strategy, execution, and team leadership for testing the power generation system including turbomachinery, heat exchangers, controls, and primary cooling systems. This role is ideal for a hands-on technical leader who enjoys building test infrastructure, running complex hardware, and mentoring engineers and technicians while remaining deeply involved in day-to-day testing. You will lead testing development for our high-speed machinery and own creating our test site from the ground up. This test infrastructure will be used to iterate quickly on our designs evaluating vibration, performance, thermal behavior, and system reliability in development and transition into acceptance testing for production units. This role works closely with mechanical design, analysis, manufacturing, and operations teams to ensure turbomachinery designs are validated, robust, and production-ready. Responsibilities & Duties: Test Site & Infrastructure Development - Lead requirements definition, design, and implementation of Radiant’s test site. - Design, build, commission, and maintain test rigs, fixtures, instrumentation, and support systems for turbomachinery, heat exchangers, controls, and primary cooling systems. - Establish operating procedures, safety controls, and facility readiness for high-speed, high-energy, and high-temperature test environments. Test Strategy, Planning & Technical Ownership - Own and lead the turbomachinery test strategy across development, qualification, and production acceptance phases. - Define test objectives, plans, success criteria, instrumentation strategies, and data requirements for high-speed rotating machinery and supporting thermal-fluid systems. - Serve as the technical authority for vibration, rotordynamic, and bearing-related testing. - Translate analytical predictions (critical speeds, stability margins, transient response) into targeted test campaigns that validate design assumptions and retire risk. - Balance test coverage, technical risk, schedule, and hardware availability to enable rapid iteration while maintaining safety and rigor. Test Execution & Data Analysis - Plan and execute development, qualification, and acceptance tests including startup/shutdown, transient, off-design, and endurance testing. - Operate test hardware hands-on with a strong emphasis on repeatability, data quality, and safety. - Analyze test data to assess vibration behavior, rotordynamic stability, bearing performance, thermal response, and overall system performance. - Compare test results against analytical predictions and work with design teams to resolve discrepancies. - Collaborate with mechanical engineers to conduct root cause investigations, identify anomalies or failures, and implement corrective actions supported by test evidence. Technical Leadership & Team Development - Provide technical leadership and mentorship to test engineers and technicians. - Act as a player-coach: remain hands-on while scaling testing capability, throughput, and organizational maturity. - Support hiring, onboarding, and technical development of turbomachinery test personnel. - Develop work estimates, test schedules, and status updates for program leadership. - Review and approve test procedures, reports, and data packages. - Establish standards for test documentation, data management, and knowledge capture. - Help mature Radiant’s turbomachinery test processes, labs, and safety culture over time. Cross-Functional Collaboration - Partner closely with turbomachinery mechanical engineers to ensure designs are testable and adequately validated. - Review component and system-level design documentation with an eye toward test coverage, instrumentation, and risk. - Collaborate with thermal, manufacturing, quality, and operations teams to support prototype, first-article, and production hardware testing. - Represent testing in design reviews, test readiness reviews, and technical leadership discussions. Required Qualifications & Skills: - Bachelor’s or Master’s degree in Mechanical Engineering or a related field, or equivalent experience. - 8+ years of experience in testing, development, or validation of turbomachinery, rotating equipment, or complex mechanical systems. - Hands-on experience testing high-speed rotating machinery and high-temperature hardware. - Experience correlating test results with analytical predictions and design intent. - Demonstrated technical leadership and ability to drive complex test efforts to completion. - Strong written, verbal, and organizational skills. Desired Qualifications & Skills: - Prior experience leading or mentoring test engineers or technicians. - Experience with power generation or other high-reliability power generation systems. - Strong understanding of rotordynamics, vibration, and bearing behavior as applied to real hardware testing. - Familiarity with rotordynamic analysis tools (e.g., XLrotor, Dyrobes, or equivalent) from a t