Senior Nuclear Engineer

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El Segundo, CA
In-Office
134K-208K Annually
Greentech • Hardware • Energy
Radiant's goal is to bring one of the world's first factory-constructed microreactors to market.
The Role

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 driven Senior Nuclear Engineer to join our team! You will own modeling methods and reactor physics calculations of neutronics parameters such as reactivity, kinetics parameters, and energy deposition distributions used within our cutting-edge custom-made Digital Twin simulation software. You’ll be responsible for assessing conservatism and verifying assumptions within the modeling methods and documenting all results. Because these methods are pivotal in the safety analysis, you will play a key role in the commercialization of the first mass-produced nuclear reactor. 

Responsibilities and Duties:   

  • Own modeling methods of core neutronics and reactor physics calculations supporting Radiant’s transient safety analyses. 
  • Perform calculations of energy deposition distributions, reactivity coefficients, kinetics parameters, and control blade worths to input into Digital Twin models. 
  • Verify assumptions and assess conservatism of neutronics models. 
  • Document methods for both technical and non-technical audiences. 
  • Assist in Verification & Validation (V&V) efforts for the Digital Twin. 
  • Review and support other nuclear analyses across the company in reactor physics, shielding, and radiation detection. 

Required Skills and Qualifications: 

  • Bachelor’s degree in nuclear engineering or a similar field from an accredited institution. 
  • 4+ years of experience with Monte Carlo nuclear engineering software such as OpenMC, MCNP, Serpent, SCALE, etc. 
  • Experience documenting analysis methods and assumptions. 
  • Strong programming skills in any language, preferably Python.

Desired Skills and Qualifications: 

  • Knowledge and experience in reactor kinetics. 
  • Basic knowledge of thermal hydraulic principles. 
  • Experience communicating and distilling information with cross-functional teams.  
  • 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. 

This is an exempt salaried role.


Annual Salary Range
$133,500$207,900 USD

Total Compensation and Benefits
Radiant compensates people for impact and invests in those who continue to raise the bar. Radiant’s new hire compensation package includes base salary, substantial equity grants, and comprehensive health benefits. Total compensation and level are determined through a rigorous evaluation of interview performance, experience, education, and qualifications, and are designed to support continued growth as scope, responsibility, and impact expand at Radiant.
The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team. If that’s you, contact us directly for immediate opportunities: [email protected].

Benefits and Perks for Eligible Employees:

  • Stock: Substantial incentive stock plan for all full-time employees.
  • Medical: 100% premium coverage for base Silver level plan for employee + 50% premium coverage for dependents. Platinum plans available.
  • One Medical: Sponsored memberships for eligible employees and their dependents.
  • Vision: 100% premium coverage for top tier plan + 50% for dependents.
  • Dental: 100% premium coverage for top tier plan (including orthodontia) + 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.
  • Burgeoning satellite offices in Oak Ridge, TN and Washington, D.C., near Capitol Hill.

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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The Company
HQ: El Segundo, CA
130 Employees
Year Founded: 2019

What We Do

Radiant is a clean energy startup building a nuclear microreactor. A climate-friendly alternative to diesel generators, Radiant's Kaleidos 1MW microreactor will be the world's first portable, zero-emissions power source that works anywhere. We plan to test our development reactor by 2026 and if successful, it will be the first new commercial reactor design to achieve a fueled test in over 50 years. Our microreactor can bring power to remote parts of the world and provide backup power for life-saving applications in hospitals or disaster-relief scenarios.

Why Work With Us

Our world-class team has prior experience in complex hardware development from SpaceX, McMaster, The Boring Company, and renowned national laboratories that define our mentality to radically improve our microreactors. We care deeply about our mission to reduce carbon emissions, and have fun while doing so from trivia nights to ski retreats.

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