Mechanical Engineer - 2026 New Grad (Fluid Systems, Mechanisms, or Structures)

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.

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, 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).

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, 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.

Additional Requirements

- 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% premium coverage for base Silver level plan for employee + 50% premium coverage for dependents. Platinum plans available.

- One Medical: Sponsored memberships for eligible employees and their dependents.

- Vision: 100% premium coverage for top tier plan + 50% for dependents. - Dental: 100% premium coverage for top tier plan (including orthodontia) + 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.