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 a seeking a Nuclear Engineer Core Physics responsible for designing and implementing nuclear-specific testing operations at our 2026 demonstration. You will be responsible for the design of a large portion of the test campaign which includes providing analysis to verify that the proposed testing is both safe and meets the tests objectives. This position will work closely with nuclear engineers to establish test success criteria and systems / operations engineers to implement written procedures.

Responsibilities & Duties:

• Collect testing requirements objectives and success criteria from nuclear engineers.

• Develop procedures that satisfy test requirements within the operational bounds of Kaleidos.

• Perform various reactor physics calculations (neutronic and transient analyses) to verify proposed testing sequence addresses all requirements.

• Document testing procedures and support operator training and control room GUI development.

Required Qualifications & Skills:

• Bachelors degree in nuclear engineering or equivalent degree from an accredited institution.

• 2 years of experience with reactor operations.

• Experience with radiation transport methods including with codes such as MCNP/OpenMC/Serpent.

• Knowledge of thermal hydraulic fundamentals.

Desired Qualifications & Skills:

• 4 years of experience with reactor operations.

• Direct experience as a reactor operator of an existing nuclear reactor.

• Hands-on experience in developing technical procedures human factors engineering or operational interface design.

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. 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:

IC