Radiant is seeking a highly motivated Mechanical Engineer Fluid Systems - 2026 New Graduate to join the KDU Engineering team. You will contribute directly to the design assembly and testing of the Kaleidos Development Unit (KDU) the United States first new fueled reactor design in over 50 years. You will take ownership of projects that advance KDUs readiness for fueled operations working alongside a cross-disciplinary team of engineers.

Responsibilities and Duties

• Contribute to the design analysis and testing of KDU fluid subsystems.

• Take ownership of deliverables from concept through build and validation with guidance from senior engineers.

• Collaborate across disciplines to integrate designs and resolve technical challenges.

• Support system-level testing troubleshooting and design iteration to accelerate KDU development.

• Communicate results through design reviews technical reports and presentations to peers and leadership.

Required Skills and Qualifications

• BS in Mechanical Engineering Aerospace Engineering or a related discipline (completed or expected Spring 2026).

• Strong foundation in engineering first principles including thermodynamics fluid mechanics.

• Hands-on experience in design and build through projects research labs or internships.

• Proficiency with engineering tools (e.g. CAD analysis software lab instrumentation).

Desired Skills and Qualifications

• MS in Mechanical Engineering Aerospace Engineering or related discipline (completed or in progress).

• Prior internship co-op or project-based experience related to fluid systems.

• Ability to independently solve complex engineering tasks and seek out resources proactively.

• Comfortable working in a fast-paced startup environment with a collaborative mission-driven mindset.

• Excitement for Radiants mission to rapidly deploy nuclear microreactors to remote locations requiring abundant clean energy.

• Knowledge of reactor physics is helpful but not required.

Additional Requirements

• This role is based onsite at Radiants HQ in El Segundo CA.

• Extended hours or occasional weekend work may be required to support project milestones.

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. Radiants 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 todays advanced reactor builders dont wait for job postings. They join the winning team. If thats you contact us directly for immediate opportunities: .

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 applicants capacity to serve in compliance with U.S. export controls.

Required Experience:

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