About Radiant

Radiant is an El Segundo, CA-based startup building the world’s first mass-produced, portable nuclear microreactors. Rising energy demand is straining the U.S. grid and driving up utility costs, emissions, and interconnection backlogs. Radiant decentralizes energy, producing power close to where it’s used. Its first reactor, Kaleidos, is a factory-built, 1-megawatt, fail-safe microreactor that can be transported by land, sea, or air and runs up to 5 years without refueling. Deployed locally without a decade-long build or permitting fight, Kaleidos provides independent power for critical infrastructure like military bases, data centers, hospitals, and remote sites. Founded in 2020, Radiant is under contract to deliver power to the U.S. Army, Air Force, Navy, and has pre-order agreements with Equinix, with deployments beginning in 2028.

About the Role

Radiant is seeking a highly motivated Nuclear Engineer to own sensor and instrumentation solutions for our Kaleidos microreactor. This includes radiation detection, neutron flux monitoring, and instrumentation design and qualification for reactor physics, shielding, and safety analysis applications. You will lead and own instrumentation 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 has a tenacity to solve interesting technical challenges.

Responsibilities & Duties

Ownership of sensor and instrumentation design and analysis, examples include:

• Radiation Detection: Design, specify, and qualify in-core and ex-core detector systems (fission chambers, ion chambers, and other detector technologies) for neutron flux and radiation monitoring.

• Detector Modeling: Support detector response modeling and verification using radiation transport codes to ensure sensor design meets performance requirements.

• Environmental Qualification: Evaluate and validate sensor survivability and performance under high-temperature, high-radiation, and accident-condition environments.

• Systems Integration: Partner with reactor control and data acquisition (DAQ) engineers to integrate sensor outputs into reactor monitoring, protection, and control systems.

• Verification & Validation: Support V&V of instrumentation against customer and regulatory requirements.

• Collect requirements, provide expertise and feedback to engineers in other functional areas via clear, constructive communication.

• Other nuclear instrumentation and sensor design/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), with exposure to radiation detection or instrumentation.

• 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

• Hands-on experience designing, testing, or qualifying sensors/instrumentation in harsh environments (high temperature, high radiation).

• Experience with data acquisition (DAQ) systems and integration with reactor control systems.

• Experience with variance reduction techniques and associated software (Attila4MC and/or ADVANTG), is a plus.

• 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: [email protected].

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.