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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 Principal Nuclear Engineer, you will lead the interdisciplinary nuclear engineering organization supporting Kaleidos development. This role combines hands-on technical authority with people leadership across reactor physics, neutron and radiation transport, shielding, activation and dose, thermal-hydraulics, safety analysis, instrumentation and controls, operations, and regulatory evaluations.
Key responsibilities include:
- Leading an interdisciplinary nuclear engineering team across multiple technical domains
- Establishing technical priorities, project plans, and resource allocation for the nuclear engineering organization
- Serving as technical authority for neutron transport and Monte Carlo simulation methods
- Owning nuclear engineering projects from requirements through design, analysis, verification, validation, testing, and regulatory documentation
- Guiding analyses of criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding
- Translating analytical results into actionable design requirements and decisions affecting core, shielding, control systems, instrumentation, and structures
- Establishing rigorous practices for model verification and validation, peer review, configuration control, and uncertainty evaluation
- Collaborating across reactor systems, thermal, mechanical, electrical, test, operations, safety, and regulatory teams
- Translating nuclear standards and regulatory requirements into analysis plans, design criteria, and verification activities
- Supporting reactor testing and startup by defining analysis needs, instrumentation requirements, and acceptance criteria
- Identifying technical risks and driving complex problems to closure
- Mentoring nuclear engineers through technical guidance and coaching
The role requires 100% onsite work at Radiant's El Segundo headquarters.
REQUIREMENTS:
- Bachelor's degree in nuclear engineering or related technical discipline from accredited institution
- 9+ years of relevant nuclear engineering experience in reactor design, analysis, testing, licensing, safety, or operations
- Demonstrated experience leading complex nuclear engineering projects and multidisciplinary technical teams
- Experience hiring, managing, mentoring, or technically leading nuclear engineers
- 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 criticality, reactivity coefficients, depletion, power distribution, shutdown margin, radiation transport, and uncertainty analysis
- Experience translating analysis into reactor design decisions, technical requirements, safety conclusions, or regulatory documentation
- Familiarity with model verification and validation, configuration control, peer review, and nuclear software quality practices
- Strong written and verbal communication skills for explaining complex analyses, assumptions, uncertainties, and technical conclusions
- Willing to support extended hours when needed to meet critical program milestones
PREFERRED QUALIFICATIONS:
- Master's degree or Ph.D. in nuclear engineering or related discipline
- 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 analysis tools
- Proficiency with Python or another language for simulation automation and data post-processing
- Experience with coupled neutronics and thermal-hydraulics or other multiphysics analyses
- Familiarity with DOE authorization, NRC licensing, nuclear codes and standards, or regulatory safety analysis
- Experience supporting reactor testing, commissioning, startup, or operational readiness
