Senior Principal Mechanical Engineer

Join the Fusion and Modular Nuclear Business Unit. Assystem has an exciting opportunity for a Senior Principal Mechanical Engineer to join our expanding Fusion and Modular Nuclear (FMN) business unit. As leaders in the design and development of new technologies, you will have the opportunity to work across multiple cutting‑edge projects developing technical solutions making net‑zero power generation a reality.

Responsibilities

• Lead and support the development of designs for Personnel Airlocks, Main Equipment Access Hatch, Fuel Transfer Channel, Piping Penetrations, Electrical Penetrations and Specialist Nuclear Doors.
• Conduct DFMEA (Design Failure Mode and Effects Analysis) to identify and mitigate potential failure modes early in the design process.
• Perform HAZID (Hazard Identification Study) to assess and document risks across the system.
• Complete and maintain Human Factors Checklists to ensure ergonomics and usability are considered in design decisions.
• Update and manage the project’s Risk Register to track, evaluate, and mitigate emerging risks.
• Oversee Design Package Production in line with project requirements, ensuring alignment with specifications, technical standards and operational needs.
• Manage interfaces by coordinating between engineering teams, suppliers, and stakeholders to ensure seamless integration of cooling water systems with other reactor components.
• Prepare clear and detailed Technical Specifications to guide procurement, fabrication and installation of key cooling water system components.
• Collaborate with cross‑functional teams, including both new and existing FTEs and secondees across engineering and project functions.

Benefits

• Over 55 years in nuclear engineering.
• Ranked among the top three largest nuclear engineering companies.
• Attractive social benefits, including an engaging Employee Committee and holiday bonuses.
• Ongoing training with numerous career opportunities.
• 70% of managers are promoted internally.
• Hybrid work: one to two days remote per week.

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