Principal Embedded Software Engineer

About Radiant

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, 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 role

Radiant is seeking a Principal Embedded Software Engineer to set the technical direction for embedded software across instrumentation and control (I&C) systems. You will define architecture, establish engineering standards, and personally drive the development of mission-critical, highly performant embedded systems that interface with sensors and actuators at the heart of a first-of-its-kind reactor design. The ideal candidate thrives in ambiguous early-stage environments, can make high-consequence technical decisions with incomplete information, and leaves a lasting organizational imprint through the systems and culture they build. You will have the opportunity to shape the embedded software foundation of the first commercialized portable nuclear microreactor, technology that will redefine how the world accesses clean, reliable power.

Responsibilities and Duties

• Define and own the embedded software architecture for I&C systems, establishing patterns and standards that scale across the full program lifecycle.
• Lead design and development of reliable, fault-tolerant embedded software for production hardware operating in demanding environments.
• Develop and bring up new drivers for I&C hardware across a range of sensing and actuation subsystems.
• Serve as the senior technical voice in design reviews, setting the bar for rigor, surfacing systemic risks, and driving decisions that span multiple subsystems and teams.
• Own the full engineering lifecycle, from architecture through test, build, and field implementation, and set expectations for how the team executes that lifecycle.
• Establish robust hardware and software testing frameworks, validation methodology, and documentation standards that meet rigorous safety requirements.
• Mentor and grow embedded engineers across the team; model technical excellence and engineering judgment.
• Partner with electrical, controls, and hardware engineering leadership to align on cross-disciplinary interfaces and constraints.

Required Qualifications and Skills

• Bachelor's degree in computer engineering, computer science, electrical engineering, or a related field.
• 8+ years of industry experience in embedded software, including significant ownership of system-level architecture decisions.
• Demonstrated experience driving architecture across complex, multi-subsystem embedded programs, not just feature ownership.
• Hands-on experience with an RTOS (Zephyr, NuttX, ThreadX, etc.), including low-level bring-up and porting.
• Deep proficiency in embedded C/C++.
• Track record of influencing technical direction beyond your immediate team, through documentation, standards, or cross-functional alignment.
• Strong communicator capable of driving consensus across engineering, program, and leadership stakeholders.

Desired Qualifications and Skills

• Experience with Zephyr RTOS at an architectural or maintainer level.
• Experience working with Simulink Autocode C++ export in a production context.
• Experience with CMake in large, multi-target embedded builds.
• Proficiency in reading and interpreting hardware schematics; ability to debug at the hardware/software boundary.
• Experience in safety-critical or high-reliability domains (aerospace, defense, medical, nuclear, or industrial).

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.

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. 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 click.appcast.io.

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.