Nuclear Engineer

Radiant; El Segundo (CA); On-site; USD 107,000 - 146,000; Full time

Benefits offered by this job

Equity stock plan

Medical coverage

One Medical membership

Vision coverage

Dental coverage

Life and accident & FSA/HSA

Job summary

Radiant is seeking a highly motivated Nuclear Engineer to develop nuclear engineering solutions for the Kaleidos microreactor. You will lead initiatives in shielding, criticality safety, and reactor physics modeling, collaborating with a fast-paced startup team.

The role requires a Bachelor’s in nuclear engineering, 1–2 years of experience, and programming skills (Python, C++, or FORTRAN). Onsite work at El Segundo HQ is required with cross-functional collaboration.

Qualifications

• Bachelor’s degree in nuclear engineering or an equivalent degree.
• 1–2+ years of nuclear engineering industry experience.
• Experience with radiation transport methods (MCNP/OpenMC/Serpent).
• Proficient in Python, C++, C#, FORTRAN.
• Basic knowledge of thermal hydraulic principles.
• Strong organizational, written and oral communication skills.

Responsibilities

• Own nuclear design and analysis tasks (shielding, neutronics, dose, transient analysis).
• Collaborate with engineers across functions and communicate findings clearly.
• Perform other nuclear design and analysis duties as assigned.

Skills

Python

C++

C#

FORTRAN

Neutronics

Radiation shielding

Dose assessment

Analytical skills

Education

Bachelor's in nuclear engineering

Tools

MCNP

OpenMC

Serpent

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 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 highly motivated Nuclear Engineer responsible for developing nuclear engineering solutions for our Kaleidos microreactor. This may include nuclear engineering areas such as radiation shielding, criticality safety, accident dose consequence, reactor physics modeling and design, transient analysis, and radiation detection. You will lead and own nuclear engineering initiatives and studies, strategic direction, and work closely with a collaborative nuclear and engineering team in a fast‑paced startup environment. The ideal candidate is passionate about advanced reactor design, detail‑oriented, effectively communicates, and a tenacity to solve interesting technical challenges.

Responsibilities & Duties

• Ownership of Nuclear design and analysis, examples include:
  • Shielding: Operational dose and shutdown activation analysis, waste categorization, and alignment of shielding design to customer and regulatory requirements.
  • Neutronics: Analysis of ex‑vessel reactor fluxes and energy deposition, criticality safety, and verification and validation (V&V) of the nuclear toolbox and reactor models.
  • Accident and Dose Consequence: Radiological dose consequence from different accident scenarios for the Kaleidos demonstration and production units.
  • Transient Analysis: Run coupled neutronics and thermal calculations to further understanding of the reactor dynamics of the Kaleidos reactor design.
• Collect requirements, provide expertise and feedback to engineers in other functional areas via clear, constructive communication.
• Other nuclear design and analysis duties as assigned.

Required Qualifications & Skills

• Bachelor’s degree in nuclear engineering or equivalent degree from an accredited institution.
• 1‑2+ years of nuclear engineering industry experience (MS equivalent to 2 yrs).
• Experience with radiation transport methods, including with codes such as MCNP/OpenMC/Serpent.
• Proficient in at least one of the following programming languages: Python, C++, C#, FORTRAN, or another scientific computing language.
• Basic knowledge of thermal hydraulic principles.
• Self‑motivated with strong organizational, written, and oral communication skills.
• Experience working in an engineering organization and developing high‑quality work.

Desired Qualifications & Skills

• Experience with variance reduction techniques and associated software (Attila4MC and/or ADVANTG), is a plus.
• Strong experience with OpenMC, Serpent, MCNP, Attila4MC, MOOSE, RELAP, Pronghorn, GRIFFIN, or other similar nuclear software packages.
• Competency in distributed software development processes and high‑performance computing environments.
• Familiarity with CAD design software (NX, SolidWorks, and/or SpaceClaim), is a plus.
• Familiarity with dose consequence methods and software such as MAACS or NRC‑RADTRAN.
• At least 1 year of software development or scripting experience.
• Hands‑on experience designing hardware and/or performing tests.

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.

The best of today’s advanced reactor builders don’t wait for job postings. They join the winning team.

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: $106,500 - $146,475