Principal Software Engineer - Simulation

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 development. In 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 systems\u2014accelerating 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.
• 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 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.