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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 for first reactor testing at Idaho National Laboratory with initial customer deliveries beginning in 2028.
As Staff Nuclear Engineer, you will provide technical leadership across all aspects of nuclear design and analysis for Kaleidos. This is a hands-on technical role combining deep analysis with ownership of major nuclear engineering workstreams. You will lead complex projects from requirements definition through design trades, model development, analysis, verification and validation, testing, and regulatory documentation.
Key responsibilities include:
- Provide technical leadership across reactor physics, core performance, shielding, dose and activation, thermal-hydraulics, safety analysis, instrumentation and controls, and reactor operations
- Own complex nuclear engineering projects from requirements capture through final documentation
- Perform and guide analyses of criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding
- Develop, review, and improve high-fidelity neutron and radiation transport models for design, safety, testing, and regulatory support
- Translate analytical results into actionable requirements and design decisions affecting core, shielding, controls, instrumentation, fluid systems, and structures
- Lead multidisciplinary technical trades evaluating interactions between nuclear performance, thermal behavior, mechanical design, controls, operations, manufacturability, and safety
- Establish rigorous practices for model verification and validation, peer review, configuration control, uncertainty evaluation, and technical documentation
- Develop analytical methods, workflows, and tools to improve accuracy, efficiency, and scalability of nuclear engineering capability
- Collaborate across reactor systems, thermal, mechanical, electrical, test, operations, safety, and regulatory teams
- Work with regulatory organization to translate nuclear standards into analysis plans, design criteria, and verification activities
- Support reactor testing and startup by defining analysis needs, instrumentation requirements, and acceptance criteria
- Mentor engineers across nuclear design and analysis activities
- Identify technical risks, develop mitigation strategies, and drive complex problems to closure
- Communicate technical status, risks, and recommendations to engineering teams and leadership
The ideal candidate brings deep technical judgment, strong engineering fundamentals, and the ability to translate complex nuclear analysis into practical reactor design decisions. You should be comfortable operating with significant technical autonomy, working across disciplines, and driving difficult engineering problems through closure.
REQUIREMENTS:
- Bachelor's degree in nuclear engineering or related technical discipline from accredited institution
- 8+ years of relevant nuclear engineering experience across reactor design, analysis, testing, licensing, safety, or operations
- Demonstrated experience owning complex nuclear engineering projects involving multiple technical disciplines and stakeholders
- Deep knowledge of neutron transport theory, Monte Carlo simulation methods, nuclear data, and statistical convergence
- Professional experience developing and applying MCNP, OpenMC, or comparable neutron and radiation transport models
- Strong understanding of reactor physics concepts including criticality, reactivity coefficients, depletion, power distribution, shutdown margin, neutron and gamma transport, and uncertainty analysis
- Experience translating analytical results into reactor design decisions, technical requirements, safety conclusions, or regulatory documentation
- Experience developing or reviewing technically rigorous analysis methodologies, models, calculation packages, or engineering standards
- Familiarity with model verification and validation, configuration control, peer review, and nuclear software quality practices
- Demonstrated ability to operate independently on technically complex problems and drive work from definition through closure
- Strong written and verbal communication skills to explain complex analyses, assumptions, uncertainties, and technical conclusions to multidisciplinary teams
- Must be mission driven and willing to support extended hours when needed
- Must work 100% onsite at El Segundo headquarters
PREFERRED QUALIFICATIONS:
- Master's degree or Ph.D. in nuclear engineering or related technical discipline
- Subject-matter expertise in safety analysis, shielding, radiation dose and activation, instrumentation and controls, reactor operations, thermal-hydraulics, or radioactive-material transportation
- Experience with high-temperature gas-cooled reactors, microreactors, advanced reactors, or first-of-a-kind nuclear systems
- Experience with SCALE, Serpent, Shift, Griffin, MOOSE-based applications, or similar nuclear analysis tools
- Proficiency with Python or another language for simulation automation, model generation, and analysis post-processing
- Experience with coupled neutronics and thermal-hydraulics or other multiphysics analyses
- Familiarity with DOE authorization processes, NRC licensing, nuclear industry codes and standards, or regulatory safety analysis
- Experience supporting reactor testing, commissioning, startup, or operational readiness
- Experience developing analytical methods, technical standards, or nuclear engineering capabilities within growing engineering organization
- Demonstrated experience mentoring engineers and providing technical review across complex engineering programs
