Spring 2026 Internship - Mechanical Engineer (Fluid Systems, Mechanisms, or Structures)

Radiant Nuclear•El Segundo, CA

41d

About The Position

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.

Requirements

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.

Nice To Haves

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.

Responsibilities

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.