Staff Nuclear Engineer

Radiant Industries•El Segundo, CA

23h•Onsite

About The Position

Radiant is seeking a Staff Nuclear Engineer to provide technical expertise across the nuclear design and analysis of its Kaleidos reactor. The role spans core physics, neutron and radiation transport, shielding, activation and dose, thermal-hydraulics, safety analysis, instrumentation and controls, reactor operations, and regulatory evaluations. It combines hands-on analysis with technical ownership across major nuclear engineering workstreams. The engineer will lead complex projects from requirements definition and early design trades through model development, analysis, verification and validation, testing, and regulatory documentation. The role also helps establish analytical methods and technical standards, mentors engineers, and serves as a technical interface between nuclear analysis and the broader reactor engineering organization. The successful candidate will bring strong technical judgment and engineering fundamentals, translate complex analysis into practical design decisions, work with significant autonomy across disciplines, and drive difficult engineering problems through closure. Radiant is an El Segundo, California-based company developing transportable, mass-produced nuclear microreactors. Its first reactor, Kaleidos, is a 1-megawatt unit designed for factory production and transport by land, sea, or air. Radiant says it is under contract to deliver power to the U.S. Army, Navy, and Air Force, has signed pre-order agreements with Equinix, and anticipates deployments beginning in 2028. This position is 100% onsite at Radiant’s El Segundo headquarters and may require extended hours when needed.

Requirements

Bachelor’s degree in nuclear engineering or a related technical discipline from an accredited institution.
At least 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, 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.
Ability to work independently on technically complex problems and drive work from definition through technical closure.
Strong written and verbal communication skills, including explaining 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 Radiant’s El Segundo headquarters.

Nice To Haves

Master’s degree or Ph.D. in nuclear engineering or a 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 used 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 a growing engineering organization.
Demonstrated experience mentoring engineers and providing technical review across complex engineering programs.

Responsibilities

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 and design iteration through model development, analysis, technical review, and final documentation.
Perform and guide analyses of criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding performance.
Develop, review, and improve high-fidelity neutron and radiation transport models for reactor design, safety, testing, and regulatory evaluations.
Translate analytical results into actionable requirements and design decisions affecting the core, shielding, control systems, instrumentation, fluid systems, structures, and surrounding hardware.
Lead multidisciplinary technical trades and evaluate interactions among nuclear performance, thermal behavior, mechanical design, controls, operations, manufacturability, and safety.
Establish and improve practices for model verification and validation, peer review, configuration control, uncertainty evaluation, and technical documentation.
Document analytical assumptions, limitations, uncertainties, margins, and conclusions clearly and defensibly.
Develop analytical methods, workflows, and tools to improve the accuracy, efficiency, and scalability of Radiant’s nuclear engineering capability.
Collaborate with reactor systems, thermal, mechanical, electrical, test, operations, safety, and regulatory teams to resolve multidisciplinary design challenges.
Work with the regulatory organization to translate applicable nuclear standards and requirements into analysis plans, design criteria, calculation packages, and verification activities.
Support reactor testing and startup by defining analysis needs, instrumentation requirements, acceptance criteria, and methods for comparing predicted and measured performance.
Provide technical mentorship and review for engineers across nuclear design and analysis activities.
Identify technical risks, develop practical mitigation strategies, and drive complex nuclear engineering problems through closure.
Communicate technical status, risks, decisions, and recommendations clearly to engineering teams and company leadership.

Benefits

Substantial incentive stock plan for all full-time employees.
Medical coverage: 100% up to the base silver-level plan for employees and 50% for dependents, with plans up to Platinum available.
Sponsored One Medical memberships for employees and dependents.
Vision coverage: 100% top-tier plan for employees and 50% for dependents.
Dental coverage: 100% top-tier plan for employees, with orthodontia extra, and 50% for dependents.
Voluntary life, accident, hospital, and critical illness coverage, plus commuter and FSA/HSA options, offered as employee-contributed benefits.
Eight weeks of paid parental leave for all parents.
Additional paid pregnancy leave for California employees.
Nuclear Engineering Certificate Program with Penn State University, fully covered for eligible employees.
Daily catered lunch.
Free snacks and drinks.
Flexible PTO policy.
Remote workday allocation.
Company and team-bonding events, happy hours, and in-person camaraderie.
Full-time new-hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits; compensation and level are determined based on interview performance, experience, education, and qualifications.