Full time • On-site • El Segundo, CA
Annual Salary Range $140,500 – $202,475 • Offers Equity
Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.
About the Role
Radiant is seeking a Lead, Test Engineering to own the strategy, execution, and team leadership for testing Kaleidos hardware and systems. This is a hands-on technical leadership role: you will directly manage a team of test engineers and serve as the technical owner for multi-discipline testing across the program. This is not limited to thermal, materials, structural, mechanical, and special-process testing.
You will lead test development across our product and build our test site from the ground up. This infrastructure will support rapid design iteration in development, evaluating thermal performance, material behavior, structural and mechanical response, leak integrity, and system reliability, and then transition into architecting acceptance testing for production units. You will work closely with design, analysis, materials, manufacturing, quality, supply chain, and operations teams to ensure designs are validated, robust, and production-ready.
Responsibilities & Duties
Test Hardware & Infrastructure Development
Lead requirements definition, design, and implementation of Radiant’s test hardware, including test rigs, fixtures, instrumentation, data acquisition, controls, and support systems for components, subsystems, and integrated systems.
Build, commission, calibrate, and maintain test capabilities across thermal, materials, mechanical, structural, and leak/flow disciplines.
Establish operating procedures, safety controls, and facility readiness for high-energy, high-temperature, vacuum, pressurized, and hazardous-materials environments.
Define equipment specifications, manage vendor selection and procurement, and plan test space layout.
Work with quality to manage calibration programs, measurement traceability, and uncertainty analysis for all test equipment.
Test Strategy, Planning & Technical Ownership
Own and lead the test strategy across development, qualification, and production acceptance phases.
Define test objectives, plans, success criteria, instrumentation strategies, and data requirements for hardware and systems.
Serve as the technical authority for test methods, measurement quality, and data integrity.
Translate analytical predictions and design requirements into targeted test campaigns that validate 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 functional, performance, environmental, transient, off-nominal, and endurance testing.
Operate test hardware hands-on with a strong emphasis on repeatability, data quality, and safety.
Analyze test data to assess system performance, thermal and mechanical behavior, and reliability.
Compare test results against analytical predictions and work with design teams to resolve discrepancies.
Collaborate with engineers to conduct root cause investigations, identify anomalies or failures, and implement corrective actions supported by test evidence.
Balance test coverage, technical risk, schedule, cost, and hardware availability to enable rapid iteration while maintaining safety and rigor.
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 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 test processes, labs, and safety culture over time including standards for test documentation, data management, configuration control, and knowledge capture.
Cross-Functional Collaboration
Partner closely with design and analysis 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 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 complex mechanical, thermal, or electromechanical systems.
Hands-on experience building and operating test setups for high-energy or high-temperature hardware.
Experience designing test instrumentation and data acquisition systems, and analyzing test data.
Experience with leak testing methods (helium leak detection, pressure decay) and flow/thermal test setups.
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 managing a team of test engineers or technicians.
Experience with test facility or test stand development from the ground up, including safety reviews and hazard analysis (e.g., JHA, HAZOP, FMEA).
Experience with hazardous-gas handling.
Experience testing rotating turbomachinery, heat exchangers, fluid systems, mechanisms, or controls.
Experience with structural test methods, including strain gauges, load cells, and test-to-FEA correlation.
Experience with data acquisition and analysis tools (e.g., LabVIEW, Python, MATLAB, Beckhoff hardware, PLCs).
Familiarity with relevant industry standards (API, ASME, ISO, ASTM) and measurement uncertainty practices (e.g., ISO 17025).
Experience with pressure vessel and pressure system testing and safety (e.g., ASME BPVC).
Experience in nuclear, aerospace, defense, or other regulated, high-reliability environments.
Startup or fast-paced hardware development experience.
Prior nuclear experience is not required.
Additional Requirements
Must be willing to work extended hours and weekends as necessary to accomplish our mission.
Must work 100% onsite at El Segundo HQ.
Stock: Substantial incentive stock plan for all full-time employees.
Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.
One Medical: Sponsored memberships for employees and their dependents.
Vision: 100% top tier plan coverage + 50% for dependents.
Dental: 100% top tier plan coverage, orthodontia extra, 50% for dependents.
Voluntary life, accident, hospital, critical illness, commuter and FSA/HSA are offered as employee contributed benefits.
8-weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA employees.
Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.
Daily catered lunch. Free snacks and drinks.
Flexible PTO policy. Remote workday allocation.
Company and team-bonding events, happy hours and in-person camaraderie.
Beautiful El Segundo headquarters close to the Pacific Ocean.
Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s full-time new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.
The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.
We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law.
This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.