SlipstreamJobs tracks this role from the company's public career site. Apply directly on the employer's site.
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 for first reactor testing at Idaho National Laboratory and initial customer deliveries in 2028.
As Senior Reactor Engineer, you will lead testing and verification of critical components, mechanisms, and subsystems within the Kaleidos microreactor. You will own the complete testing lifecycle—from requirements definition and test planning through execution, data analysis, and technical review. Your focus will be on core-related hardware, reactivity control mechanisms, instrumentation, and other reactor subsystems. You will work closely with nuclear, mechanical, thermal, controls, and test engineering teams to ensure hardware meets functional, performance, and safety requirements.
Key responsibilities include:
- Leading testing and verification of reactor components, core assemblies, reactivity control mechanisms, and instrumentation
- Owning test activities from requirements definition through execution, data analysis, and documentation
- Developing test plans, procedures, instrumentation requirements, and acceptance criteria
- Collaborating with multidisciplinary engineering teams to develop test strategies and resolve technical challenges
- Performing engineering analyses and comparing experimental results against analytical predictions
- Reviewing and technically approving test procedures, verification reports, and engineering documentation
- Supporting reactor operations, commissioning, and integrated testing through procedure reviews and readiness assessments
- Investigating hardware failures and test anomalies to identify root causes and implement corrective actions
- Translating test findings into design improvements while maintaining rigorous requirements traceability and configuration control
This role combines hands-on test engineering with direct involvement in reactor design and development. You will need strong engineering fundamentals, practical testing experience, and sound technical judgment to develop and review test procedures, evaluate hardware performance, and drive complex engineering problems to resolution.
The position is 100% onsite at Radiant's El Segundo headquarters and may require extended hours when needed.
REQUIREMENTS:
- Bachelor's degree in nuclear engineering, mechanical engineering, or related technical discipline from an accredited institution
- 5+ years of relevant experience in reactor engineering, hardware testing, design verification, or complex hardware development
- Demonstrated experience developing and executing component or subsystem tests, including planning, instrumentation, data analysis, and performance evaluation
- Strong engineering fundamentals in mechanical systems, heat transfer, materials, instrumentation, and component performance
- Understanding of reactor operating principles, safety functions, and component-level performance requirements
- Experience developing technical procedures, establishing acceptance criteria, and evaluating results against engineering requirements
- Experience troubleshooting hardware failures, conducting root cause investigations, and implementing design improvements
- Ability to interpret engineering drawings, specifications, and technical requirements while independently owning multidisciplinary engineering projects
PREFERRED QUALIFICATIONS:
- Master's degree or Ph.D. in nuclear engineering, mechanical engineering, or related technical discipline
- Experience with reactor components, core assemblies, reactivity control mechanisms, instrumentation, or safety-critical hardware
- Experience with high-temperature gas-cooled reactors, microreactors, advanced reactors, or first-of-a-kind nuclear systems
- Familiarity with reactor physics, thermal-hydraulics, nuclear safety, and reactor operations
- Experience supporting reactor testing, commissioning, startup, or operational readiness
- Experience with test instrumentation, data acquisition systems, and testing under demanding thermal, mechanical, or environmental conditions
- Proficiency with Python, MATLAB, or similar engineering tools for test automation and analysis
- Familiarity with DOE authorization processes, NRC licensing, nuclear industry standards, or nuclear quality assurance requirements
