Mechanical Engineer, Electrical Systems

About the role

About Radiant 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, fail-safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. 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 leverages modern software engineering to rapidly deliver safe, factory-built microreactors that use existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028. About the role Radiant is seeking a highly motivated early-career 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—while contributing directly to Radiant’s mission to deploy the first successfully fueled commercial reactor in over 50 years by 2026. 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 Assist in the design and setup of test fixtures and test stands for acceptance and qualification testing 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 Develop, document, and execute basic test plans and procedures to verify mechanical and thermal performance 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 Hands-on experience with mechanical design through coursework, labs, internships, senior design projects, or engineering clubs Proficiency or coursework 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 Introductory 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 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. 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: [email protected] . 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.