Principal Thermal Modeling Engineer
About The Position
Radiant is seeking a Principal Thermal Modeling Engineer to set the technical direction for thermal and fluid simulation of the Kaleidos microreactor. The role leads complex and consequential modeling work for a high-temperature gas reactor, defining methods, standards, and validation strategies that inform decisions across reactor systems, cooling systems, shielding, and other areas. As a technical authority, the engineer mentors colleagues, influences program-level decisions, and supports milestones toward commercialization of the first mass-produced nuclear reactor. Radiant is an El Segundo, California-based company developing transportable nuclear microreactors. Its first reactor, Kaleidos, is a 1-megawatt unit designed for factory production and transport by land, sea, or air. The company says deployments are expected to begin in 2028. The position is 100% onsite at Radiant’s El Segundo headquarters. The successful applicant must be willing to work extended hours and weekends as necessary. Compensation includes base salary, substantial equity grants, and comprehensive health benefits; total compensation and level depend on interview performance, experience, education, and qualifications.
Requirements
- Bachelor’s degree in engineering, physics, or a similar field from an accredited institution.
- At least 10 years of relevant industry experience, with a track record of technical leadership on complex, high-consequence programs.
- Extensive experience with STAR-CCM+, Ansys Fluent, or other commercial CFD codes, including advanced turbulence and conjugate heat-transfer modeling.
- Mastery of finite element and computational fluid dynamics principles and methods, with demonstrated experience validating models against test data.
- Proficiency with CAD software, specifically Siemens NX.
- Experience building automated simulation workflows and scripting tools.
- Demonstrated ability to mentor engineers and communicate complex technical results to cross-functional teams and leadership.
- Willingness to work extended hours and weekends as necessary.
- Ability to work 100% onsite at Radiant’s El Segundo headquarters.
Nice To Haves
- Advanced degree (MS or PhD).
- Experience with radiation heat-transport modeling.
- Knowledge of nuclear reactor design, thermal-hydraulics, or safety analysis.
- Experience with multiphysics coupling, such as thermal-structural or neutronics-thermal.
- Experience with reduced-order modeling or system-level thermal-hydraulic codes.
- Experience with regulatory or safety-basis analysis.
- Driven, self-motivated approach and ownership of work end to end.
- Aerospace or automotive industry experience; prior nuclear experience is not required.
Responsibilities
- Serve as the technical authority for thermal CFD and thermal FEA modeling of Kaleidos reactor systems, owning the most complex and highest-risk analyses.
- Define modeling strategy, methodology, and best practices for turbulent flow, heat transfer, and multiphysics interactions, and drive their adoption across the team.
- Lead model verification and validation, correlate simulation results with test data, and establish confidence and uncertainty bounds for design and safety decisions.
- Architect automated simulation workflows and tooling to expand capability, accuracy, and efficiency, and set the roadmap for simulation infrastructure.
- Lead development of reduced-order analysis methods in partnership with design, systems, and test teams.
- Influence reactor, cooling, and shielding design decisions by translating analysis results into clear recommendations for engineering leadership.
- Mentor and develop engineers, set technical standards through design and analysis reviews, and contribute to hiring.
- Collaborate across disciplines to define analysis requirements, align priorities, and resolve cross-team technical tradeoffs.
Benefits
- Substantial incentive stock plan for all full-time employees.
- Medical coverage up to the base silver-level plan at 100% for employees and 50% for dependents, with plans available up to platinum level.
- Sponsored One Medical memberships for employees and their dependents.
- Top-tier vision plan coverage at 100% for employees and 50% for dependents.
- Top-tier dental plan coverage at 100% for employees, with orthodontia extra, and 50% coverage for dependents.
- Voluntary life, accident, hospital, and critical illness coverage, plus commuter benefits and FSA/HSA, offered as employee-contributed benefits.
- Eight weeks of paid parental leave for all parents and additional paid pregnancy leave for California employees.
- Nuclear Engineering Certificate Program with Penn State University, fully covered for eligible employees.
- Daily catered lunch and free snacks and drinks.
- Flexible PTO policy.
- Remote workday allocation.
- Company and team-bonding events, happy hours, and in-person camaraderie.
- Base salary, substantial equity grants, and comprehensive health benefits.
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What This Job Offers
Job Type
Full-time
Career Level
Principal
