Nuclear Engineer - Core Physics

About Radiant

Radiant is an El Segundo, CA-based company building the world's only mass-produced, transportable nuclear microreactors. The U.S. grid is under growing strain, with power demand accelerating, driving higher utility costs, rising carbon emissions, and interconnection backlogs. Radiant has a solution, transportable, on-site power. Our first reactor, Kaleidos, is 1 megawatt: small enough to be factory-built, transported by land, sea, or air, and deployed wherever power is needed. 1 MW can power 1000 homes for five years. Ship it back and we refuel for a 20 year operating life. We made energy a product that can be used for critical infrastructure like military bases, data centers, hospitals, and remote sites, as well as the commercial main street businesses that keep America running. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Navy and Air Force and has signed pre-order agreements with Equinix, with deployments 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 test’s 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:

• Bachelor’s 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.

• Nuclear Engineering Certificate Program: 100% covered educational program with Penn State University, for eligible employees, to rapidly upscale into nuclear.

• 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 full-time 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: [email protected].

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.

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.