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Summer 2026 Internship - Nuclear Engineer

El Segundo, California, United States

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 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. Radiant’s 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.

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 bachelor’s or master’s 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 Radiant’s mission to rapidly deploy nuclear microreactors to provide clean energy in remote locations.

Additional Requirements

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

Total Compensation and Benefits

Radiant's new hire compensation package includes base salary, substantial equity grants, and comprehensive benefits. Total compensation and level are determined through a holistic evaluation of your interview performance, experience, education, and qualifications. 

Benefits and Perks for Eligible Employees:

  • 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.

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.

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