Nuclear Engineer, Sensors

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…