Principal Nuclear Engineer

About the role

Radiant is seeking a Principal Nuclear Engineer to lead interdisciplinary nuclear engineering work for its portable micro‑reactor, Kaleidos. The role blends people leadership with hands‑on technical ownership across core physics, neutron and radiation transport, shielding, thermal‑hydraulics, safety analysis, instrumentation, controls, operations, and regulatory evaluations.

Key responsibilities

• Lead a cross‑functional team covering reactor physics, core performance, shielding, dose, activation, thermal‑hydraulics, safety, I&C, and operations.
• Own nuclear engineering projects from requirements capture through model development, analysis, technical review, and final documentation.
• Serve as the technical authority for neutron and radiation transport and Monte Carlo simulation methods.
• Translate analytical results into actionable design decisions for core, shielding, control systems, instrumentation, fluid systems, and structures.
• Establish rigorous practices for model verification, validation, peer review, configuration control, and uncertainty evaluation.

Required profile

• Bachelor’s degree in nuclear engineering or a related discipline.
• 12+ years of nuclear engineering experience in reactor design, analysis, testing, licensing, safety, or operations.
• Proven experience leading complex nuclear projects and multidisciplinary teams.
• Deep knowledge of neutron transport theory, Monte Carlo methods, and nuclear data.

Required skills

• Monte Carlo simulation tools such as MCNP, OpenMC, SCALE, Serpent, Shift, Griffin, or MOOSE‑based applications.
• Expertise in neutron and radiation transport, shielding, activation, dose, criticality, reactivity coefficients, depletion, power distribution, and shutdown margin.
• Strong understanding of thermal‑hydraulics, safety analysis, instrumentation & controls, and regulatory documentation.
• Proficiency in Python or similar scripting languages for simulation automation and data post‑processing.

What we offer

• Substantial equity incentive plan for all full‑time employees.
• Comprehensive medical, vision, dental, and life insurance coverage.
• 8 weeks paid parental leave, additional pregnancy leave for CA employees.
• Daily catered lunch, free snacks, flexible PTO and remote‑work day allocation.
• Beautiful El Segundo headquarters near the Pacific Ocean.