About Radiant

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.

About the Role

Radiant is seeking a Principal Thermal Modeling Engineer with deep expertise in CFD and thermal FEA to set the technical direction for thermal and fluid simulation of the Kaleidos microreactor. You will lead the most complex and consequential modeling problems for a high-temperature gas reactor, defining the methods, standards, and validation strategy that inform decisions across reactor systems, cooling systems, shielding, and more. As a recognized technical authority, you will mentor engineers, influence program-level decisions, and help drive the milestones that unlock commercialization of the first mass-produced nuclear reactor.

Responsibilities & Duties

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 multi-physics interactions, and drive their adoption across the team.

Lead model verification and validation, correlating simulation results with test data and establishing confidence and uncertainty bounds for design and safety decisions.

Architect automated simulation workflows and tooling that expand capability, accuracy, and efficiency, and set the roadmap for simulation infrastructure.

Lead the 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 the technical bar through design and analysis reviews, and contribute to hiring.

Collaborate across disciplines to define analysis requirements, align priorities, and resolve cross-team technical tradeoffs.

Required Qualifications & Skills

Bachelor’s degree in engineering, physics, or a similar field from an accredited institution; advanced degree (MS or PhD) preferred.

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 (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.

Desired Qualifications & Skills

Experience with radiation heat transport modeling.

Knowledge of nuclear reactor design, thermal-hydraulics, or safety analysis.

Experience with multi-physics 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, and takes ownership of work end to end.