Senior Mechanisms Engineer

Location: El Segundo, CA Employment Type: Full time Location Type: On-site Department: Engineering / Mechanical Engineering Compensation Range: $133.5K – $184.8K Equity: Offers equity grants as part of the compensation package. Overview Radiant is an El Segundo, CA-based start‑up building the world’s first mass‑produced, portable nuclear microreactors. The first reactor, Kaleidos, is a 1 megawatt, fail‑safe microreactor that can be transported anywhere power is needed and run for up to five years without refueling. Portable nuclear power can replace diesel generators and provide critical power for hospitals, data centers, remote sites, and military bases. 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 The role is for a Senior Mechanisms Engineer who will design and develop critical mechanisms within Kaleidos. The engineer will solve unique challenges creating efficient and reliable mechanisms that control reactivity or actuate critical safety features. Impact includes fueling the first commercial reactor design in over 50 years by 2026. Responsibilities & Duties Ownership of critical mechanisms such as the control blade actuator or air jacket valves. Conduct trade studies and develop designs to meet program requirements. Perform detailed thermomechanical analysis (static strength, durability/fatigue) and kinematic analysis to determine structural integrity and performance margins using hand calculations and finite element tools. Develop and execute manufacturing/assembly instructions and test plans. Create and manage a Bill‑of‑Materials (BOM). Find and develop suppliers for components. Own subassembly design, manufacturing, and test schedules. Own risk analysis (FMEA) for subsystems. Collect requirements and provide expertise and feedback to engineers in other functional areas via clear, constructive communication. Required Qualifications & Skills Bachelor’s degree from an accredited institution in Mechanical or Aeronautical Engineering. 4+ years of experience designing mechanisms. 4+ years of experience performing stress analysis using hand calculations and finite element tools (e.g., Abaqus, Ansys, FEMAP). Desired Qualifications & Skills Experience designing multi‑component assemblies in CAD (NX or similar). Experience designing hardware that was manufactured, deployed, and iteratively improved. Experience designing pneumatic systems. Experience integrating electromechanical components such as motors or encoders. Experience working with interdisciplinary teams. Solid understanding and application of GD&T. Proficiency with both hand‑calc analytical methods and higher‑fidelity finite element analysis. Ability to derive free‑body diagrams for unfamiliar systems. Self‑motivated with strong organizational, written, and oral communication skills. Experience with text‑based software development tools. Additional Requirements Willingness to work extended hours and weekends as needed. Must work 100% onsite at El Segundo HQ. Benefits & Perks Equity: Substantial incentive stock plan for all full‑time employees. Medical: 100% coverage up to base silver level for employees plus 50% for dependents; offers up to platinum plans. One Medical: Sponsored memberships for employees and dependents. Vision: 100% top‑tier plan coverage plus 50% for dependents. Dental: 100% top‑tier plan coverage; orthodontia extra and 50% for dependents. Voluntary life, accident, hospital, critical illness, commuter, and FSA/HSA benefits as employee‑contributed. 8‑weeks paid parental leave for all parents; additional paid pregnancy leave for CA employees. Daily catered lunch with free snacks and drinks. Flexible PTO policy and mandatory 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. The new‑hire 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 growth as scope, responsibility, and impact expand at Radiant. If you are a motivated engineer eager to join a pioneering team, contact us directly for immediate opportunities: View email address on click.appcast.io . 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. #J-18808-Ljbffr