Radiant
Summer 2026 Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)
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.
Senior Nuclear Engineer
Radiant is seeking a highly motivated senior nuclear engineer responsible for developing nuclear engineering solutions for our Kaleidos microreactor. This may include areas such as transportation, fuel handling, criticality safety, reactor physics modeling, and others. You will lead engineering initiatives, provide mentorship and guidance to junior engineers, and drive trade studies, strategic direction, and solutions as priorities shift in a fast-paced startup environment.
Responsibilities & Duties
- Ownership of nuclear design and analysis focus areas, for example:
- Shielding: Assessing transport, operation, self-activation, environmental activation, and waste categorization, working with both customer and regulatory requirements.
- Analysis: Run coupled core physics and thermal calculations to refine the thermal model in various scenarios.
- Mechanical: Assess damage effects and bulk material properties changes due to high flux on ceramics and metals inside the core.
- Fuel and waste: Model burnup distribution, design burnable absorber, and perform criticality assessments for transport and waste facility compatibility.
- Reactor Physics: Develop control schemes and design control systems using transient simulations to finalize source sizing and detector selection.
- Apply expertise and knowledge of nuclear industry standards and regulations.
- Develop technical requirements for hardware systems, structures, and components, leading design reviews.
- Find and develop suppliers for all components.
- Own subassembly design, manufacturing, and test schedules.
- Provide expertise and feedback on functional areas such as safety and quality via clear and constructive communication to cross functional teams.
Required Qualifications & Skills
- Bachelor’s degree in nuclear engineering or equivalent degree from accredited institution.
- 5+ years nuclear engineering industry experience.
- Experience implementing nuclear regulatory requirements.
- Proficient in at least one of the following programming languages: Python, C++, C#, or another scientific computing language.
Desired Qualifications & Skills
- Master’s or PhD in nuclear engineering or equivalent degree from accredited institution.
- Subject matter expert in one of following areas: criticality safety, fuel management, and/or radioactive material transportation.
- Self-motivated with strong organizational, written, and oral communication skills.
- Hands-on experience designing hardware and/or performing tests.
- Proficient or advanced in one of following: OpenMC, MCNP, SCALE, MOOSE, Serpent, BISON, RELAP, CFD, Pronghorn, GRIFFIN, or other nuclear software packages
- At least 1 year of software development experience:
- C, C++, or Python development experience is preferred.
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.
Top Skills
Radiant El Segundo, California, USA Office
1921 E. Maple Ave., El Segundo, CA, United States, 90245
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