Lead Nuclear Engineer

About the role

Radiant, an El Segundo‑based startup developing portable nuclear microreactors, is looking for a Lead Nuclear Engineer to head the nuclear design and analysis team for its Kaleidos reactor. You will provide both technical direction and people leadership across a broad range of nuclear disciplines.

Key responsibilities

• Lead an interdisciplinary team covering reactor physics, core performance, shielding, thermal‑hydraulics, safety analysis, instrumentation & controls, and reactor operations.
• Hire, manage, and develop a high‑performing group of nuclear engineers, setting priorities, schedules, budgets, and ownership for deliverables.
• Own the full engineering lifecycle from requirements capture through model development, analysis, verification, validation, testing, and regulatory documentation.
• Guide critical analyses such as criticality, reactivity control, shutdown margin, power distribution, depletion, temperature feedback, radiation transport, dose, activation, and shielding performance.
• Collaborate with systems, mechanical, electrical, test, safety, and regulatory teams to resolve multidisciplinary design challenges and support reactor testing and startup.

Required profile

• Bachelor’s degree in nuclear engineering or a related field.
• 5+ years of nuclear engineering experience in reactor design, analysis, testing, licensing, safety, or operations.
• At least 1 year of experience managing direct reports.
• Strong communication skills to convey complex analyses to multidisciplinary audiences.

Required skills

• Deep knowledge of neutron transport theory and Monte Carlo simulation (MCNP, OpenMC or similar).
• Experience with reactor physics concepts: criticality, reactivity coefficients, depletion, power distribution, shutdown margin.
• Proficiency in shielding, radiation dose, activation analysis, and safety analysis.
• Familiarity with model verification & validation, configuration control, and peer‑review processes.
• Programming/scripting ability in Python for simulation automation and post‑processing.

What we offer

• Substantial equity incentive plan for all full‑time employees.
• Comprehensive medical, vision, dental, and life insurance coverage.
• Paid parental leave, flexible PTO, daily catered lunch, and on‑site snacks.
• Beautiful headquarters near the Pacific Ocean with in‑person team events.