About Radiant

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments beginning in 2028.

About the Role

Radiant is seeking a Mechanical Engineer to support the design and integration of electrical components and subsystems in a fast-paced startup environment. You’ll work alongside experienced mechanical and electrical engineers to solve challenging problems in packaging, thermal management, structural design, and system integration for advanced hardware. This role offers hands-on exposure to end-to-end hardware development from CAD and analysis through build, test, and validation.

Responsibilities & Duties:

• Support the mechanical design and ownership of electrical components and subsystems, including:

• Mechanical design of electrical assemblies such as control panels, enclosures, brackets, mounts, and supports.

• Cable and wiring harness routing, retention, strain relief, bend radius compliance, and serviceability considerations.

• Packaging of sensors, actuators, connectors, and electrical hardware within constrained assemblies.

• 3D CAD modeling and 2D drawing creation using Siemens NX, including tolerance stack-ups and GD&T basics.

• Perform first-order load calculations (static, shock, vibration) to support structural design decisions.

• Conduct thermal analysis and heat-transfer assessments for electrical components, enclosures, and assemblies.

• Support selection of materials, fasteners, and finishes appropriate for electrical, thermal, and environmental requirements.

• Participate in system integration, troubleshooting, and validation activities alongside electrical and systems engineers.

• Collect and interpret technical requirements and provide clear, constructive feedback across mechanical, electrical, software, and systems disciplines.

• Perform trade studies and first-order analyses to evaluate design options and constraints.

• Generate and maintain design documentation to support Design for Manufacturing (DFM), assembly, and serviceability.

• Support subassembly design, coordinate with manufacturing, and assist with build and test schedules.

Required Qualifications & Skills:

• Bachelor’s degree in Mechanical Engineering or a closely related field from an accredited institution.

• 3+ Years of professional hands-on mechanical design experience.

• Experience using Siemens NX or similar 3D CAD tools.

• Familiarity with mechanical design of electrical assemblies, including enclosures, brackets, and harness routing principles.

• Basic understanding of structural mechanics, load paths, and first-order stress calculations.

• Knowledge of thermal analysis, heat transfer, and thermal management concepts.

• Ability to read and create mechanical drawings, including dimensions and tolerances.

• Strong communication skills and ability to collaborate in a multidisciplinary engineering environment

Desired Qualifications & Skills:

• 5+ years of professional hands-on mechanical design experience.

• Mechanical design for high-reliability or harsh environments (nuclear, aerospace, defense, or industrial), including thermal cycling, shock, vibration, or radiation exposure.

• Experience with FEA or CFD tools for structural and thermal analysis beyond first-order hand calculations.

• Hands-on experience supporting build, integration, and test on the floor, including design iteration based on manufacturing feedback.

Additional Requirements:

• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

• Must work 100% onsite at El Segundo HQ.

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.

• Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.

• 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 full-time 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.