About Radiant

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 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. Radiants 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 an experienced Senior Software Engineer to design and implement robust software systems that power our reactor simulation and Digital Twin this role you will serve as a key technical contributor on a high-performing team owning the architecture tooling and infrastructureincluding evaluation and integration of frameworks third-party software and simulation toolsthat enables our simulation engineers to model test and validate reactor systemsaccelerating our path to commercialization.

Responsibilities and Duties

• Implement and contribute to software architecture for simulation systems across thermal hydraulic and nuclear reactor multi-physics models.

• Collaborate with and support simulation engineers developing reactor and subsystem physics models.

• Build and maintain software infrastructure to support Digital Twin simulation visualization and data processing capabilities.

• Contribute to 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 following and reinforcing best practices for simulation software development code quality and testing standards.

• Evaluate and recommend third-party software tools open source libraries and simulation frameworks for adoption by the team.

• Collaborate cross-functionally with Hardware Nuclear and Electrical engineering teams to accelerate software-in-the-loop and hardware-in-the-loop testing capabilities.

• Contribute to the delivery of mission-critical internal simulation products while ensuring sustainable development practices and technical debt management.

• Support team growth through knowledge sharing and contributing to a high-performance engineering culture.

Required Qualifications

• Bachelors degree in physics mechanical engineering computer science or a similar field.

• 5 years of professional software engineering experience with significant depth in high performance computing (HPC) computational science Machine Learning or a related advanced computing field.

• Expert-level proficiency in programming languages such as Python Rust or C/C.

• Strong background in 3rd party simulation tools physics-based modeling numerical methods or computational science with proven ability to execute technical strategy.

• Proficiency with visualization frameworks open source platforms 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 deliver high-quality hands-on technical contributions within a collaborative team environment.

Preferred Qualifications

• Advanced degree (Masters or Ph.D.) in physics computer science mechanical engineering or a similar field.

• Experience contributing to simulation or computational modeling parallel computing or high-performance computing projects.

• Background with modern simulation frameworks finite element analysis or computational fluid dynamics tools.

• Experience with Machine Learning Deep Learning or other probabilistic modeling techniques.

• Experience in highly regulated industries (aerospace defense automotive nuclear or medical devices).

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.

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. 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: .

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.

Required Experience:

Senior IC