Senior Software Engineer - Simulation

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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe, factory-built microreactors that leverage existing, well-qualified materials. Founded in 2020, Radiant is on track to test its first reactor next year at the Idaho National Laboratory, with initial customer deliveries beginning in 2028.

About the Role - Senior Software Engineer, Simulation

Radiant is seeking a highly driven Senior Software Engineer with a strong background in physics or mechanical engineering. You will collaborate with mechanical, electrical, and nuclear teams to simulate physical systems with an appropriate degree of fidelity, write software for deployment to production hardware, and improve our simulation and test software stack, including our cutting-edge, custom-built Digital Twin system. You will have an opportunity to work in an interdisciplinary environment with a high degree of ownership and drive to move milestones forward to unlock the commercialization of the first mass-produced nuclear reactor.

Responsibilities and Duties

• Develop thermal, hydraulic, and nuclear models for reactor and reactor subsystem physics.
• Design and implement technical architecture for simulation systems.
• Build software infrastructure to support Digital Twin simulation, visualization, and data processing capabilities.
• Contribute to the technical roadmap for thermal and safety analysis simulation. Implement model tuning strategies as models and frameworks evolve.
• Establish and champion best practices for simulation software development, code quality, and testing.
• Collaborate with Hardware, Nuclear, and Electrical engineering teams to develop software-in-the-loop and hardware-in-the-loop testing capabilities.
• Deliver mission-critical internal simulation products while maintaining code quality and managing technical debt.
• Mentor junior engineers and contribute to building a high-performance team culture.

Required Qualifications

• 5+ years of professional software engineering experience with significant depth in simulation, scientific computing, or physics-based modeling.
• Strong proficiency in programming languages such as Python, Rust, C#, or C/C++.
• Experience with simulation tools, physics-based modeling, numerical methods, or computational science.
• Hands-on experience with numerical solvers, visualization frameworks, and automated testing approaches for scientific software.
• Strong foundation in software engineering best practices, including version control, code review, and CI/CD pipelines.
• Demonstrated ability to drive technical projects independently with minimal oversight.
• Bachelor's degree in physics, mechanical engineering, computer science, or a similar field, or equivalent experience.

Preferred Qualifications

• Advanced degree (Master's or Ph.D.) in physics, mechanical engineering, computer science, or a similar field.
• Experience with simulation or computational modeling, parallel computing, or high-performance computing.
• Background with modern simulation frameworks, finite element analysis, or computational fluid dynamics tools.
• Track record of successful cross-functional collaboration with Hardware, Nuclear, and Electrical engineering teams.
• Strong communication skills with the ability to explain technical concepts to diverse audiences.
• Experience with Machine Learning, Deep Learning, AI, or other probabilistic modeling techniques.

Work Environment

• Must work 100% onsite at El Segundo HQ.
• Must be willing to work extended hours and weekends as necessary to accomplish our mission.

Total Compensation and Benefits

Radiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications. 

Benefits and Perks for Eligible Employees:

• Stock: Substantial incentive stock plan for all full-time employees.
• Medical: 100% premium coverage for base Silver level plan for employee + 50% premium coverage for dependents. Platinum plans available.
• One Medical: Sponsored memberships for eligible employees and their dependents.
• Vision: 100% premium coverage for top tier plan + 50% for dependents.
• Dental: 100% premium coverage for top tier plan (including orthodontia) + 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.

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.