Senior Thermal Modeling & Analysis Engineer

About the Role

Radiant is seeking a driven Senior Thermal Modeling & Analysis Engineer to own high-fidelity CFD and thermal modeling for the Kaleidos microreactor. You will analyze heat generation and transport, high-temperature gas flow, and thermal interactions across reactor systems, cooling systems, shielding, and surrounding hardware under steady-state, transient, and off-normal conditions.

Your work will directly influence system architecture, component design, material selection, operating limits, test planning, and safety margins. You will work across mechanical, fluid systems, nuclear, structures, controls, and test engineering to develop validated analytical tools that support the commercialization of the first mass-produced nuclear reactor.

Responsibilities & Duties:

• Own thermal and CFD analyses from problem definition through model development, execution, validation, documentation, and design recommendation.

• Model turbulent gas flow, conduction, convection, radiation, conjugate heat transfer, and coupled multiphysics behavior across Kaleidos systems.

• Evaluate steady-state, transient, and off-normal operating conditions to identify hotspots, thermal gradients, heat loads, flow distribution, pressure losses, and system margins.

• Define modeling assumptions, boundary conditions, material properties, and appropriate fidelity based on the engineering decision being supported.

• Translate analytical results into actionable design recommendations and collaborate with engineering teams through design iteration.

• Establish and implement simulation best practices, including convergence assessment, mesh and time-step independence, sensitivity studies, uncertainty evaluation, and model verification.

• Correlate analytical models with test data and update modeling assumptions based on measured system behavior.

• Build automated, reproducible workflows for parametric studies, design exploration, post-processing, and simulation efficiency.

• Develop and validate reduced-order models that support system-level analysis and rapid design iteration.

• Clearly communicate assumptions, limitations, risks, margins, and recommendations to cross-functional teams.

Required Qualifications & Skills:

• Bachelor’s degree in mechanical, aerospace, nuclear engineering, physics, or a related field.

• 5+ years of relevant thermal, CFD, or thermal-fluid analysis experience.

• Extensive experience with STAR-CCM+, Ansys Fluent, or comparable CFD software.

• Strong foundation in heat transfer, fluid mechanics, turbulence modeling, and numerical methods.

• Experience performing steady-state and transient thermal-fluid analyses.

• Experience with model verification, sensitivity studies, and validation or test correlation.

• Ability to prepare and simplify CAD geometry for analysis using Siemens NX or comparable software.

• Experience using Python or another scripting language to automate simulation and post-processing workflows.

• Demonstrated ability to translate analytical results into engineering decisions and communicate effectively across disciplines.

Desired Qualifications & Skills:

• Experience modeling high-temperature gas systems, nuclear reactors, propulsion systems, turbomachinery, or other complex energy systems.

• Experience with thermal FEA and coupled fluid-thermal-structural analysis.

• Experience modeling radiative heat transfer, including surface-to-surface or participating-media radiation.

• Familiarity with nuclear heat generation, decay heat, neutronics coupling, or radiation transport.

• Experience developing reduced-order or system-level thermal-fluid models.

• Experience with high-performance computing, optimization, or large parametric simulation campaigns.

• Driven, self-motivated, and capable of owning technically ambiguous problems end to end.

Additional Requirements

• Willing to support extended hours when needed to meet critical program milestones.

Benefits and Perks

• Stock: Substantial incentive stock plan for all full-time employees.

• Daily catered lunch. Free snacks and drinks.

• Flexible PTO policy. Remote workday allocation.