Thermal Modeling Engineer

About Radiant Radiant is an El Segundo, CA-based startup building the world’s first mass‑produced, portable nuclear microreactors. The company’s first reactor, Kaleidos, is a 1‑megawatt, fail‑safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. Portable nuclear power with rapid‑deploy capability can replace similar‑sized diesel generators and provide critical asset support for hospitals, data centers, remote sites, and military bases. Radiant’s unique, practical approach to nuclear development leverages modern software engineering to rapidly deliver safe, factory‑built microreactors that use existing, well‑qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028. Thermal Modeling Engineer (CFD) Radiant is seeking a driven Thermal Modeling Engineer with expertise in CFD and thermal FEA modeling. You will design, develop and implement simulations for the Kaleidos microreactor to ensure high fidelity, reliability, and safety of our systems. You’ll work on cutting‑edge technical problems for a high temperature gas reactor that inform decisions across reactor systems, cooling systems, shielding, and more. You will have an opportunity to work in an interdisciplinary environment and drive milestones forward to unlock commercialization of the first mass‑produced nuclear reactor. Responsibilities and Duties Develop and execute thermal analysis and CFD to evaluate design and performance of Kaleidos systems. Document analysis results to communicate clear and actionable outputs. Expand CFD capabilities, accuracy, and efficiencies via methods and workflow development projects. Own pipeline for producing analysis geometry from mechanical design CAD. Develop methods and calculations to support and build confidence in lower‑fidelity thermal analysis methods. Required Qualifications and Skills Bachelor’s degree in engineering, physics, or similar field from an accredited institution. 3+ years experience with Star CCM+ or Ansys Fluent. Proficiency with CAD software (Siemens NX). Strong understanding of finite element and computational fluid dynamics modeling principles and methods. Experience communicating and distilling information with cross‑functional teams. Desired Qualifications and Skills Experience with radiation heat transport modeling. Knowledge of nuclear reactor design. Driven, self‑motivated, and takes ownership of work end to end. Additional Requirements Must be willing to work extended hours and weekends as necessary to accomplish our mission. Must work 100% onsite at El Segundo HQ. Benefits and Perks Stock: 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 offered as employee contributed benefits. 8‑weeks of paid parental leave for all parents. Additional paid pregnancy leave for CA 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. Beautiful El Segundo headquarters close to the Pacific ocean. Total Compensation and Benefits Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant. If that’s you, contact us directly for immediate opportunities: View email address on click.appcast.io. We are an equal opportunity employer and all qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity or expression, pregnancy, age, national origin, disability status, genetic information, protected veteran status, or any other characteristic protected by law. Unfortunately, we are unable to provide visa sponsorship at this time. This position involves access to technology that is subject to U.S. export controls. Any job offer made will be contingent upon the applicant’s capacity to serve in compliance with U.S. export controls. Compensation Range: $107.5K - $150K #J-18808-Ljbffr