Principal Software Engineer Simulation

Radiant is an El Segundo CA-based startup building the worlds first mass-produced portable nuclear microreactors. The companys 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. Radiants 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

Radiant is seeking an experienced Lead Software Engineer for Simulation to mentor and lead the engineering team responsible for reactor physics modeling thermal-hydraulics simulations and Digital Twin this role you will serve as the technical lead for a high-performing team while maintaining technical depth ensuring our simulation infrastructure enables Radiant to design test and validate reactor systemsaccelerating our path to commercialization.

Responsibilities and Duties

• Lead technical architecture and implementation for simulation systems across thermal hydraulic and nuclear reactor physics models.
• Mentor and provide technical guidance to simulation engineers developing reactor and subsystem physics models.
• Design and scale software infrastructure to support Digital Twin simulation visualization and data processing capabilities.
• Define and own the technical roadmap for thermal and safety analysis simulation. Develop and execute strategies for model tuning as models and frameworks evolve.
• Drive technical excellence by establishing best practices for simulation software development code quality and testing standards.
• Collaborate cross-functionally with Hardware Nuclear and Electrical engineering teams to accelerate software-in-the-loop and hardware-in-the-loop testing capabilities.
• Own delivery of mission-critical internal simulation products while ensuring sustainable development practices and technical debt management.
• Contribute to team growth through technical mentorship and promoting a high-performance engineering culture.

Required Qualifications

• 8 years of professional software engineering experience with significant depth in simulation scientific computing or physics-based modeling.
• Deep technical expertise in programming languages such as Python Rust C# or C/C with demonstrated ability to drive architectural decisions.
• Experience providing technical leadership and mentorship to engineering teams.
• Strong background in simulation tools physics-based modeling numerical methods or computational science with proven ability to guide technical strategy.
• Expertise 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.
• Proven ability to balance hands-on technical contributions with technical leadership and mentorship.
• Bachelors degree in physics mechanical engineering computer science or a similar field or equivalent experience

Preferred Qualifications

• Advanced degree (Masters or Ph.D.) in physics mechanical engineering computer science or a similar field.
• Experience as a technical lead on simulation or computational modeling parallel computing or high-performance computing projects.
• 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 translate technical complexity for 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 compensates people for impact and invests in those who continue to raise the bar. Radiants 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 todays advanced reactor builders dont wait for job postings. They join the winning team. If thats you contact us directly for immediate opportunities: .

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 applicants capacity to serve in compliance with U.S. export controls.