Summer 2026 Internship Nuclear Engineer

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 failsafe microreactor that can be transported anywhere power is needed and run for up to five years without the need to refuel. 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 utilizes modern software engineering to rapidly achieve safe factory-built microreactors that leverage existing well-qualified materials. Founded in 2020 Radiant is on track to test its first reactor next year at the Idaho National Laboratory with initial customer deliveries beginning in 2028.

Nuclear Engineering Intern
Radiant is seeking a highly motivated Nuclear Engineering Intern to support the design and analysis of nuclear systems for a 1MW HTGR nuclear microreactor. As part of the engineering team you will work alongside experienced nuclear engineers and gain hands-on experience in areas such as neutronics thermal-hydraulics shielding and fuel analysis. This internship offers direct mentorship in a fast-paced startup environment providing you with a unique opportunity to contribute to the development of the first new fueled reactor design in over 50 years.

Please note: we plan to begin interviewing for Summer 2026 internships in November/December.

Responsibilities & Duties

• Assist with nuclear design and analysis tasks including shielding neutronics thermal and fuel-related studies.
• Support coupled neutronics and thermal calculations to refine system performance models.
• Document methods results and findings in clear technical reports and presentations.
• Collaborate with cross-functional teams and provide technical input as projects evolve.
• Support the development of lower order shielding analysis models to develop rapid shielding design solutions.
• Support the development of uncertainty propagation methodology and its execution on the Kaleidos Demonstration Unit
• Perform criticality safety analysis for the Production Plant of Kaleidos reactors
• Present a final project review at the end of internship to engineers and leadership

Required Qualifications & Skills

• Currently pursuing a bachelors or masters degree in nuclear engineering or a related discipline.
• Strong academic foundation in nuclear engineering principles (e.g. reactor physics thermal-hydraulics radiation shielding).
• Proficiency in at least one programming language (Python C C# or similar).

Desired Qualifications & Skills

• Hands-on experience through coursework research projects or labs in nuclear system design or analysis.
• Familiarity with nuclear simulation codes (e.g. OpenMC Serpent MCNP MOOSE BISON RELAP CFD Pronghorn GRIFFIN).
• Prior software development experience or exposure to version control testing or documentation practices.
• Strong communication skills and ability to work in a collaborative team environment.
• Enthusiasm for Radiants mission to rapidly deploy nuclear microreactors to provide clean energy in remote locations.

Additional Requirements

• This internship is based 100% onsite at Radiants HQ in El Segundo CA.
• Extended hours or occasional weekend work may be required to support project milestones.

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: .

Benefits and Perks for Eligible Employees:

• Stock: Substantial incentive stock plan for all full-time employees.
• Medical: 100% premium coverage for base Silver level plan for employee 50% premium coverage for dependents. Platinum plans available.
• One Medical: Sponsored memberships for eligible employees and their dependents.
• Vision: 100% premium coverage for top tier plan 50% for dependents.
• Dental: 100% premium coverage for top tier plan (including orthodontia) 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.
• Burgeoning satellite offices in Oak Ridge TN and Washington D.C. near Capitol Hill.

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.