Lead Nuclear Engineer

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 technical and people‑oriented Lead Nuclear Engineer for our nuclear design and analysis group focused in areas such as core physics, shielding, instrumentation & controls, and reactor operations. You will lead a high‑performing team through the design, development, and test stages of the Kaleidos microreactor. You will own the schedule, budget, hiring, and execution of nuclear‑related milestones with a key focus on safety, reliability, portability, and performance. The ideal candidate is comfortable in interdisciplinary environments working cross‑functionally with engineers and leadership, is fluent in engineering first principles, has tenacious creative problem‑solving abilities and keen to get to the solution of a problem, and loves to mentor and motivate engineers to deliver their best work. You will play a critical role in driving the first portable nuclear microreactor to market. Responsibilities & Duties: Manage an interdisciplinary team of nuclear engineers focused in areas such as safety analyses, core performance, shielding – including operational dose, activation, shutdown dose – I&C, operations, thermal‑hydraulics and more. Hire, lead, and grow a high performing team of nuclear engineers. Own nuclear engineering projects end to end including requirement capture, multi‑disciplinary design iteration, simulation pipeline development, analysis post‑processing, and summarization for regulatory deliverables. Collaborate with regulatory team on nuclear industry standards and requirements. Mentor engineers through actionable feedback and coaching. Required Qualifications & Skills: Bachelor’s degree in nuclear engineering or equivalent degree from accredited institution. 5+ years nuclear engineering industry experience with relevant software use, including MCNP and/or OpenMC. Deep knowledge of neutron transport and Monte Carlo simulation theory. 1+ year managing direct reports. Desired Qualifications & Skills: Master’s or PhD in nuclear engineering or equivalent degree from accredited institution. Subject matter expert in one of following areas: safety analysis, shielding, instrumentation and controls, reactor operations, and/or radioactive material transportation. 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: 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 Radiant