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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries beginning in 2028.
Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)
Radiant is seeking a highly motivated New Graduate Mechanical Engineer 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. Depending on your background and interests (fluid systems, mechanisms, or structures), you will take ownership of projects that advance KDU’s readiness for fueled operations, working alongside a cross-disciplinary team of engineers.
Responsibilities and Duties- Contribute to the design, analysis, and testing of KDU subsystems (fluid systems, mechanisms, or structural components).
- 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, statics, dynamics, and strength of materials.
- 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, mechanisms, or structures.
- 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.
Total Compensation and Benefits
Radiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications.
Benefits and Perks for Eligible Employees:
- 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.
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.
Top Skills
What We Do
Radiant is a clean energy startup building a nuclear microreactor. A climate-friendly alternative to diesel generators, Radiant's Kaleidos 1MW microreactor will be the world's first portable, zero-emissions power source that works anywhere. We plan to test our development reactor by 2026 and if successful, it will be the first new commercial reactor design to achieve a fueled test in over 50 years. Our microreactor can bring power to remote parts of the world and provide backup power for life-saving applications in hospitals or disaster-relief scenarios.
Why Work With Us
Our world-class team has prior experience in complex hardware development from SpaceX, McMaster, The Boring Company, and renowned national laboratories that define our mentality to radically improve our microreactors. We care deeply about our mission to reduce carbon emissions, and have fun while doing so from trivia nights to ski retreats.
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