Senior Nuclear Engineer

Radiant; El Segundo (CA); On-site; USD 134,000 - 185,000; Full time

Benefits offered by this job

Stock options

Medical plan

One Medical

Vision plan

Dental plan

Life insurance

Paid parental leave

Lunch & snacks

Flexible PTO

Team events

Job summary

Radiant, an El Segundo, CA-based startup, seeks a Senior Nuclear Engineer to own modeling methods and reactor physics calculations for neutronics parameters used in our Digital Twin software. You will assess conservatism, verify assumptions, and document results, playing a key role in safety analysis and commercialization of the first mass-produced reactor.

The role requires a Bachelor's in nuclear engineering, 4+ years with Monte Carlo tools (OpenMC, MCNP, Serpent, SCALE), and strong Python

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.

Responsibilities

• 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.

Skills

Monte Carlo sims

Nuclear reactor physics

Python programming

Education

Bachelors in Nuclear Eng

Tools

OpenMC

MCNP

Serpent

SCALE

Job description

About Radiant

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, fail‑safe microreactor that can be transported anywhere power is needed and run for up to 5 years without refueling. 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 leverages modern software engineering to rapidly deliver safe, factory‑built microreactors that use existing, well‑qualified materials. Founded in 2020, Radiant is on track to test its first reactor at the Idaho National Laboratory this summer, with initial customer deliveries beginning in 2028.

About The Role

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 & 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 Qualifications & Skills

• 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 Qualifications & Skills

• 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.

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.

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.

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.

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.

Compensation Range: $133.5K - $184.8K