Senior Nuclear Thermal-Hydraulics Engineer

Senior Nuclear Thermal-Hydraulics Engineer

Radiant is seeking a Senior Nuclear Thermal-Hydraulics Engineer to lead thermal-hydraulics and coupled physics analysis for the Kaleidos microreactor. You will own the modeling that determines how heat, coolant, and reactor core behavior interact under normal and accident conditions — work that directly informs core design, cooling systems, and safety case development for the first mass-produced nuclear reactor. This role is suited to engineers with reactor-specific thermal-hydraulics or coupled multiphysics experience who want to apply that depth to a fast-moving, factory-built reactor program.

Responsibilities & Duties

• Own and execute thermal-hydraulics analysis to evaluate design and safety performance of Kaleidos reactor systems under normal and accident conditions.
• Develop and apply coupled physics models integrating thermal-hydraulics with neutronics and/or structural response.
• Identify and implement best practices for reactor thermal-hydraulics and systems-code analysis.
• Build automated workflows to expand simulation capabilities, accuracy, and efficiency.
• Collaborate across reactor physics, mechanical, and safety teams to support licensing and design trade studies.

Required Qualifications & Skills

• Bachelor's degree in nuclear engineering, mechanical engineering, physics, or similar field from an accredited institution.
• 5+ years of relevant industry or national laboratory experience.
• Experience with thermal-hydraulics analysis and/or reactor systems codes (e.g., RELAP5, TRACE, CTF/COBRA-TF, SAM, TRANSFORM).
• Experience with high-temperature (500°F+) heat transfer analysis involving conduction, convection, and radiation.
• Experience communicating and distilling technical information with cross-functional teams.

Desired Qualifications & Skills

• Experience with coupled multiphysics modeling (e.g., MOOSE, BISON, MARMOT) or neutronics coupling.
• Experience with commercial CFD/FEA tools (STAR-CCM+, Ansys Fluent) and CAD (Siemens NX).
• Prior experience at a national laboratory, reactor vendor, or advanced reactor developer.
• Driven, self-motivated, and takes ownership of work end to end.

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.
• 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.