Senior Reactor Systems Engineer

About RadiantRadiant 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 RoleWe are seeking a Senior Reactor Systems Engineer to design and implement mission-critical procedures for reactor operators managing our groundbreaking nuclear microreactor technology. This role offers a rare opportunity to bridge engineering, operations, and human factors in a highly technical and fast-paced environment. You will collaborate with a multidisciplinary team to translate complex hardware and software designs into clear, executable, and DOE or NRC compliant procedures. Your work will ensure that Reactor Operators (ROs) and Senior Reactor Operators (SROs) can efficiently and safely execute test, commissioning, and operational activities.This position goes beyond traditional systems engineering - you will also gain hands-on experience as a Reactor Operator (RO), directly influencing the development of operational software, procedures, and future reactor designs.Responsibilities & Duties:Qualify as an operator to gain firsthand experience, ensuring procedures align with real-world execution.Collaborate closely with engineers to improve operator interfaces, procedural workflows, and software tools.Support testing and iterative improvements of digital twin scenarios, operator systems, and human-machine interfaces.Ensure compliance with DOE and NRC standards, maintaining strict formatting, clarity, and usability in procedural documentation.Develop and refine operational procedures that integrate both software and hardware-in-the-loop testing.Required Qualifications & Skills:6-7+ years of full-time professional experience in engineering problem-solving, including system design, analysis, or testing.Proficiency in managing or optimizing complex hardware and software processes for testing and operations.Ability to apply first principles thinking to solve problems and make decisions in uncertain or ambiguous situations.Background in highly regulated industries (e.g., nuclear, aerospace, aviation, maritime).Desired Qualifications & Skills:Prior experience working as an operator in nuclear environments (e.g., nuclear energy, naval reactors, or radiation-controlled facilities), with familiarity in safety protocols, regulatory compliance, and high-reliability operations2+ years of full-time nuclear operations experience.Licensed as Senior Reactor Operator or Naval equivalent.Hands-on experience in developing technical procedures, human factors engineering, or operational interface design.Prior operations background such as mission control room operator.Proficiency in Python, UNIX, for procedure testing within the simulator environments.Experience with human factors and user-centered instructions for operational workflows.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.Willingness to travel 50% - 60% of the time as needed for projects.Benefits and PerksStock: 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 BenefitsRadiant 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 us.fitly.work 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.Compensation Range: $133.5K - $184.8KLocationEl Segundo, CAEmployment TypeFull timeLocation TypeOn-siteDepartmentEngineeringMechanical EngineeringCompensation$133.5K – $184.8K • Offers Equity