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 KDU’s readiness for fueled operations, working alongside a cross-disciplinary team of engineers.
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.
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).
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 Radiant’s mission to rapidly deploy nuclear microreactors to remote locations requiring abundant, clean energy.
Knowledge of reactor physics is helpful but not required.
This role is based onsite at Radiant’s HQ in El Segundo, CA.
Extended hours or occasional weekend work may be required to support project milestones.
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: 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.
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.
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