Director of Mechanical Engineering, Numenor (Reactor)

The Team

The Numenor team is building Valar's next reactor, the flagship program that will define how we deliver nuclear power at scale. This dedicated team owns the entire plant, from the reactor core and helium systems to cooling, plant modules, and the Citadel, uniting mechanical, systems, safety, IC&E, quality, and supply chain under one mission. The work starts with bringing the first unit to life and ends with a production line that delivers reactors faster with every build. What this team builds will power the critical infrastructure of the future.

The Role

Valar Atomics seeks a Director, Mechanical for the reactor program. This role will build and lead the mechanical engineering organization for the reactor program, including the engineering managers and responsible engineers. The scope covers the mechanically dominated system included but not limited to the reactor, control rods, helium pressure boundary, helium services, HVAC and Citadel.

The role will lead mechanical engineering from the first unit through scaled production, delivering reactor at an increasing rate. The role demands someone who can operate with hands-on technical authority and a hardware-first mentality, while maintaining the integrity, rigor and control required to ensure the design basis is met.

Key Responsibilities

Technical Leadership

• Own the mechanical design basis for the reactor, the primary helium loop, cavity cooling, helium services, plant modules, etc.
• Make the final technical call on design acceptability, margins, materials and code selection.
• Run design reviews and gate decisions from concept through design freeze.

Build, Test and Commissioning

• Take designs to hardware through procurement specifications, factory build, assembly and integrated testing.
• Set test and verification strategy with the V&V lead, and support commissioning through to first operation.
• Design for manufacture and repeatability, so each unit builds faster than the last.

Program and Team Leadership

• build, lead and mentor the mechanical organization of engineering managers and system REs.
• Manage scope, schedule and budget for mechanical within the reactor program
• Lead mechanical team structure and staffing as the program scales
• Work closely with systems engineering, safety, IC&E, quality and supply chain so the plant design stays integrated.

Basic Qualifications

• 10+ years of mechanical engineering on complex hardware, such as pressure systems, heat transfer equipment, mechanisms or large structures.
• Hands-on experience as the technical authority who signs off designs, sets margins and owns design decisions.
• Led mechanical scope on first-of-a-kind hardware from concept through build, test and commissioning.
• Strong base in stress analysis, thermal design, materials and pressure vessel and piping codes.
• Experience in managing mechanical engineering teams, including managers, and key vendor relationships across multiple project phases.

Preferred Skills and Experience

• Experience with high-temperature, high-pressure systems, such as pressure vessels, heat exchangers and piping.
• Hardware delivery: first-of-a-kind hardware taken from design through build and test, in aerospace, power generation, oil and gas, or defense.
• Helium or other gas systems, including sealing, leak tightness and rotating equipment.
• Precision mechanisms and actuators, plus the qualification testing that goes with them.
• Working knowledge of ASME pressure vessel and piping codes (Section VIII, B31.3).
• Design for manufacture and scaling from prototype to series production.
• Nuclear industry experience: commercial, defense or national laboratory. A plus, not a prerequisite.
• PE license (Mechanical): a plus.

What We Offer

• Competitive base salary
• Equity ownership in a rapidly growing advanced energy company
• Comprehensive medical benefits
• Unlimited PTO
• Free daily lunch and dinner provided onsite
• Generous PPE stipend
• High-impact startup environment with significant ownership and autonomy
• Opportunities for rapid career growth and internal advancement
• Direct collaboration with experienced operators, engineers, and industry leaders
• The opportunity to help build and scale transformative energy technology from the ground up