Mechanical Engineer, Fluid Systems - 2026 New Graduate

About the role

Radiant is an El Segundo, CA-based startup developing the world’s first mass-produced, portable nuclear microreactors. The company's first reactor, Kaleidos, is a 1-megawatt, fail-safe microreactor capable of running for up to 5 years without refueling. These reactors can replace diesel generators and provide critical power for hospitals, data centers, remote sites, and military bases. Radiant uses modern software engineering to rapidly deliver safe, factory-built microreactors using existing materials. Founded in 2020, Radiant aims to test its first reactor at the Idaho National Laboratory this summer and begin delivering initial customer units in 2028.

Responsibilities

• Own end-to-end engineering of fluid systems and components, including compressors, valves, and heat exchangers.
• Perform thermal and fluids analysis to drive design decisions, verify system performance, and ensure structural integrity using first-principle hand calculations and finite element tools.
• Develop and execute manufacturing/assembly instructions and test plans.
• Create and manage a Bill-Of-Materials (BOM).
• Find and develop suppliers for all components.
• Own subassembly design, manufacturing, and test schedules.
• Own risk analysis (FMEA) for subsystems.
• Collect requirements, provide expertise and feedback to engineers in other functional areas via clear, constructive communication.

Qualifications

• Bachelor’s degree from an accredited institution in Mechanical, Materials, Aeronautical, Civil or Structural Engineering.
• Experience with fluid system architecture design.
• Experience in designing, building, and testing fluids systems.
• Proficient knowledge in fluid dynamics and thermodynamics.
• Proficient knowledge of heat exchanger design and analysis methods.
• Knowledge of thermodynamic power cycles (desired).
• Prior experience with fluid system modeling via Matlab/Python (desired).
• Experienced in design for manufacturability and ramping up hardware build in a production environment.
• Experienced in designing and operating test stands.
• Takes extreme ownership of work and a high degree of responsibility.
• Excellent communication across multidisciplinary teams.

Benefits

• 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.
• A 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. The 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: recruiting@radiantnuclear.com. 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. Compensation Range: $105K - $125K.