Thermal-Hydraulics & Fluid Systems Engineer

El Segundo, CA

Radiant is a startup developing Kaleidos, a 1.2 MWe portable nuclear microreactor. Based in El Segundo, CA and founded by former SpaceX engineers, Radiant’s mission is to directly replace diesel generators used in remote locations and as backup power sources. Kaleidos is designed to be factory produced and operated as a fleet, enabling the lowest operating costs and deployment timelines. Our safe, economical, and reliable power sources will be demonstrated through a full-scale prototype on a 5-year development timeline – faster than any modern competing design. Radiant partners with several national laboratories and universities to perform regulatory, qualification, and research work that supports the fast-paced in-house design. Radiant is funded by awards from the Department of Energy, the Department of Defense, and by numerous venture capital firms.

Responsibilities and Duties

  • Ownership of various fluid systems for the Kaleidos reactor through preliminary designanalysis, parts selection and sourcing, critical design, system build, and system activation
  • 0-D / 1-D analysis of reactor fluid and thermal systems (Excel/Python/C#) 
  • CFD analysis of reactor fluid and thermal systems (NEK-5000) 
  • Fluid systems controls design
  • Documenting results and coordinating with engineering and licensing teams
  • Must be willing to relocate to Radiant office in Los Angeles, CA.
  • Must have ability to work or gain permission to work on export controlled technologies based in the United States.

Required Qualifications & Skills

  • Hold at least a Bachelor’s degree in mechanical/aerospace/nuclear engineering or an equivalent degree from accredited institution
  • Proficiency in the design of fluid systems: ability to size systems and select components according to engineering fundamentals (fluid dynamics, heat transfer, heat exchangers, compressible flow, strength of materials) 
  • Familiarity with PID control logic or equivalent.
  • Familiarity with working principles of heat pumps and heat engines 
  • Communicate effectively within a collaborative and interdisciplinary group  
  • Have an attitude of ownership over fluid systems design aspects.

Desired Qualifications & Skills 

  • Hands on experience designing, building and testing fluid systems.
  • Familiarity with reactor physics fundamentals: criticality, neutron transport, decay chains
  • Familiarity with MOOSE framework and applications: MOOSE, NEK-5000, RELAP-7, THM, SAM
  • Specific programming language experience: Python, C#


  • Medical: 100% up to base silver level plan for employee + 50% dependents, offers up to Platinum plans.
  • Vision: 100% coverage
  • Dental: 100% coverage, orthodontia extra
  • Voluntary Life, Accident, Hospital, Critical Illness, Commuter Benefits, and FSA are offered as employee contributed benefits.
  • Vacation/Sick time