Senior Mechanical Engineer, 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 Senior Mechanical Engineer for the reactor program. This role will own the design, build, and test of mechanical subsystems within the reactor plant, including the reactor, control rods, helium pressure boundary, helium services, HVAC, and Citadel. You will take hardware from concept through build, test, and commissioning on the first unit, then help drive it into repeatable, scaled production.

The role demands someone who is hands-on and hardware-first, while bringing the rigor and discipline required to ensure the design basis is met.

Key Responsibilities

Design and Analysis

• Own the mechanical design of assigned subsystems, from requirements and concept through detailed design and design freeze.
• Perform and review stress, thermal, and fluid analyses (FEA and CFD) to validate margins, materials, and code compliance.
• Develop 3D CAD models, assemblies, and drawings, applying GD&T and tolerance analysis.
• Present designs at design reviews and drive actions to closure.

Build, Test and Commissioning

• Take designs to hardware through procurement specifications, vendor management, factory build, and assembly.
• Plan and execute component and integrated testing with the V&V team, and support commissioning through first operation.
• Design for manufacture and repeatability, so each unit builds faster than the last.

Collaboration and Leadership

• Work closely with systems engineering, safety, IC&E, quality, and supply chain so the plant design stays integrated.
• Mentor junior engineers and contribute to design standards, documentation, and configuration management.
• Lead root cause investigations and drive corrective actions on hardware issues.

Basic Qualifications

• Bachelor’s degree in Mechanical Engineering or a related field.
• 5+ years of mechanical engineering on complex hardware, such as pressure systems, heat transfer equipment, mechanisms, or large structures.
• Proven track record taking hardware from design through build and test.
• Strong base in stress analysis, thermal design, materials, and pressure vessel and piping codes.
• Proficiency in CAD (SolidWorks, Creo, NX, or similar) and engineering drawing standards.

Preferred Skills and Experience

• Master’s degree in Mechanical Engineering or a related field.
• Experience with high-temperature, high-pressure systems, such as pressure vessels, heat exchangers, and piping.
• First-of-a-kind hardware experience 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.