Principal Nuclear Engineer

The role

You will lead an interdisciplinary nuclear engineering team supporting the Kaleidos microreactor. This role involves technical ownership across reactor physics, shielding, thermal-hydraulics, and regulatory evaluations.

What you will do

• Lead an interdisciplinary team working across reactor physics, core performance, shielding, dose and activation, thermal-hydraulics, safety analysis, I&C, and operations.
• Establish technical priorities, project plans, resource needs, and clear ownership.
• Serve as a technical authority for neutron and radiation transport and Monte Carlo simulation methods.
• Own nuclear engineering projects from requirements capture through final documentation.
• Guide analyses of criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding performance.
• Translate analytical results into actionable requirements and design decisions.
• Establish technically rigorous practices for model verification and validation, peer review, and configuration control.
• Collaborate with reactor systems, thermal, mechanical, electrical, test, operations, safety, and regulatory teams.
• Translate nuclear standards and regulatory requirements into analysis plans and design criteria.
• Support reactor testing and startup by defining analysis needs and instrumentation requirements.

Required qualifications

• Bachelor’s degree in nuclear engineering or a related technical discipline from an accredited institution.
• 12+ years of relevant nuclear engineering experience across 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.

Nice to have

• Master’s degree or Ph.D. in nuclear engineering or a 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 used 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.

Benefits

• 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.
• Daily catered lunch.
• Free snacks and drinks.
• Flexible PTO policy.

Before you apply

• Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls.

About the company

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force.