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.

Radiant is seeking a Senior Thermofluids Systems Engineer, Power Conversion to own system-level thermodynamic modeling of our power conversion architecture. This architecture converts heat from nuclear fission into electricity for the customer .You will define operating points that balance system performance and constraints, deliver clear boundary conditions for the teams building fluid systems and turbomachinery, and serve as the primary technical bridge into control systems engineering & reactor modelling teams. This role is critical to delivering the first new commercial reactor design in over 50 years.

Responsibilities

• Own system-level thermodynamic performance modeling of the power conversion architecture, including design and off-design operating points across startup, shutdown, transients, and off-nominal conditions.

• Develop and maintain interface requirements and boundary conditions (pressures, temperatures, flow rates, control signals) for fluid system components, pressure equipment, turbomachinery, and power electronics.

• Work with engineers owning hardware and subsystems to develop architectural changes accommodating nominal and off-nominal operation, driving trades across performance, cost, weight, schedule, and safety.

• Serve as the primary interface to control systems engineering, providing plant-level dynamic behavior models, operating envelopes, and control-relevant boundary conditions for reactor control scheme development.

• Build and maintain performance models (e.g., MATLAB, Python, Simulink) characterizing fluid system behavior across all operating states.

• Lead root-cause analysis for cycle performance anomalies, correlating test data with system models to inform engineers owning hardware components.

• Perform or review trade studies to optimize cycle and fluid system architecture against program requirements.

• Own system-level risk analysis (FMEA) for fluid subsystems and cycle performance.

• Communicate clearly with both technical and non-technical audiences across multidisciplinary teams.

Required Qualifications

• Bachelor's degree in Mechanical, Aerospace, Chemical, or Systems Engineering from an accredited institution.

• 5+ years of experience in thermodynamic/power cycle modeling, systems engineering, or performance engineering, including requirements development and system-level verification.

• Strong working knowledge of thermodynamics and fluid dynamics as applied to power generation cycle design.

• Proficiency in system modeling tools such as MATLAB, Simulink, or Python for performance and simulation analysis.

• Strong first-principles analytical skills, with the ability to manage competing priorities and communicate program status clearly.

Desired Qualifications

• Experience with fluid system architecture, including piping, compressors, valves, and heat exchangers.

• Experience supporting control scheme development for thermal or power generation plants.

• Familiarity with process piping and pressure vessel codes such as ASME B31.3, BPVC Section VIII, and BPVC Section III.

• Experience with turbomachinery performance modeling or heat rejection system design (e.g., cooling towers, air-cooled condensers).

• Experience supporting hardware build, assembly, and test in a production or development environment.

• Prior experience with FMEA and formal risk management processes.

• Nuclear industry experience is a plus but not required.

Additional Requirements

• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

• Must work 100% on-site 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 are 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.

The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: [email protected].

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.

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.