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. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.

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.

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 a seeking a Nuclear Engineer, Core Physics responsible for designing and implementing nuclear-specific testing operations at our 2026 demonstration. You will be responsible for the design of a large portion of the test campaign, which includes providing analysis to verify that the proposed testing is both safe and meets the test’s objectives. This position will work closely with nuclear engineers to establish test success criteria and systems / operations engineers to implement written procedures.

Responsibilities & Duties:

• Collect testing requirements, objectives, and success criteria from nuclear engineers.

• Develop procedures that satisfy test requirements within the operational bounds of Kaleidos.

• Perform various reactor physics calculations (neutronic and transient analyses) to verify proposed testing sequence addresses all requirements.

• Document testing procedures and support operator training and control room GUI development.

Required Qualifications & Skills:

• Bachelor’s degree in nuclear engineering or equivalent degree from an accredited institution.

• 2+ years of experience with reactor operations.

• Experience with radiation transport methods, including with codes such as MCNP/OpenMC/Serpent.

• Knowledge of thermal hydraulic fundamentals.

Desired Qualifications & Skills:

• 4+ years of experience with reactor operations.

• Direct experience as a reactor operator of an existing nuclear reactor.

• Hands-on experience in developing technical procedures, human factors engineering, or operational interface design.

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. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.

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.

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 Loads & Dynamics Engineer to own and execute structural loads, vibration, and dynamic analyses for complex mechanical systems associated for Kaleidos, the world's first portable microreactor and supporting hardware. You will play a critical role in ensuring structural integrity and survivability across all phases of the product lifecycle, including manufacturing, transportation, handling, deployment, and operational environments.

This role requires a hands-on engineer who is comfortable working in ambiguous, fast-paced environments and collaborating closely with structures, mechanical design, thermal, nuclear, and test teams.

Responsibilities & Duties:

• Develop and own static, dynamic, and transient loads for reactor systems, support structures, and transport configurations.

• Perform structural dynamics analyses, including modal, random vibration, shock, sine vibration, and fatigue assessments.

• Implement explicit dynamics simulations to model nonlinear reactor response under transient seismic and transportation event cases.

• Define and analyze transportation and handling environments, including shock and vibration from road, rail, air, or sea transport.

• Generate load cases and environments to support structural sizing, design margins, and verification plans.

• Conduct finite element analyses (FEA) using tools such as ANSYS, Abaqus, or similar tools.

• Collaborate with design engineers to influence hardware architecture, material selection, and joint design.

• Support test planning and correlation, including shaker tests, modal surveys, and structural verification testing.

• Develop and maintain analysis documentation, reports, and requirements for internal reviews and regulatory interfaces.

• Contribute to failure investigations, root cause analyses, and design improvements

• Help establish best practices for loads, dynamics, and structural verification within a growing engineering organization.

Required Qualifications & Skills:

• Bachelor’s degree in Mechanical Engineering, Aerospace Engineering, Structural Engineering, or a related field.

• 2+ years of experience in loads, dynamics, or structural analysis for complex mechanical systems.

• Strong fundamentals in structural mechanics, dynamics, and vibration.

• Experience with finite element modeling and analysis of metallic and composite structures.

• Proficiency with industry-standard FEA tools (e.g., ANSYS, Abaqus, Nastran).

• Familiarity with design allowables, safety factors, and margin-of-safety methodologies.

• Ability to work cross-functionally and communicate analysis results clearly to both technical and non-technical stakeholders.

Desired Qualifications & Skills:

• Experience in aerospace, launch, defense, nuclear, or heavy industrial hardware environments.

• Dynamics modeling software experience (LD-Dyna, Abaqus explicit, or other).

• Background in shock and vibration testing and test-article correlation.

• Knowledge of fatigue, fracture mechanics, and bolted joint analysis.

• Experience defining or interpreting environmental specifications and requirements.

• Master’s degree or PhD in a relevant engineering discipline.

• Familiarity with nuclear, spaceflight, or safety-critical system requirements.

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. If that’s you, contact us directly for immediate opportunities: recruiting@radiantnuclear.com.

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.