Senior Principal Mechanical Engineer

About the Company

Assystem stands as one of the top three independent nuclear engineering firms globally, boasting over 60 years of expertise in highly regulated sectors. The group supports complex strategic infrastructure projects for public and industrial stakeholders, with a strong focus on safety and security. Assystem operates across 13 countries with 8,000 experts, covering the entire project lifecycle through engineering, project management, and digital solutions.

About the Role

Join Assystem's expanding Fusion and Modular Nuclear (FMN) business unit as a Senior Principal Mechanical Engineer. You will be at the forefront of designing and developing new technologies for cutting-edge projects, creating technical solutions for net-zero power generation. This role requires leadership in design development, risk analysis, and stakeholder coordination.

Your Mission

• Lead and support the development of designs for critical systems including 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) and HAZID (Hazard Identification Study) to identify and mitigate potential failures and risks.
• Complete and maintain Human Factors Checklists to ensure ergonomic and usability considerations.
• Update and manage the project’s Risk Register.
• Oversee the creation of comprehensive design packages aligned with project specifications and technical standards.
• Manage interfaces between engineering teams, suppliers, and stakeholders for seamless integration.
• Prepare detailed technical specifications for procurement, fabrication, and installation.
• Collaborate with cross-functional teams, including internal FTEs and secondees.

Why Join the Community of Switchers?

• Over 55 years of experience in nuclear engineering.
• Ranked among the top 3 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 model: 1-2 days remote per week.

Qualifications

• Proven experience in Multi-Disciplinary Team Leadership.
• Oversight experience in Steam Cycle Modelling.
• Proficiency in Project Budget & Lifecycle Planning.
• Expertise in Cooling Water Equipment design and optimization.
• Strong knowledge of regulatory frameworks (ONR, Environment Agency, HSE).
• Experience in Requirements Capture.
• Solid understanding of Systems Engineering principles.
• Experience in Subcontractor Management.
• Chartered Engineer (CEng) accreditation.
• Eligibility for Security Clearance (SC).

Additional Information

• Excellent written and oral communication skills.
• Strong leadership capabilities.
• Focus on delivering quality, on time and within budget.
• Integrity and ability to instill it in others.
• Appreciation of wider technical issues beyond own discipline.
• Ability to work with a high degree of independence, initiative, and self-motivation.
• Confidence in multi-party, multi-national environments.
• Willingness to travel to Assystem offices and customer sites within the UK.
• Capability to undertake work packages supporting major UK and international Nuclear Clients.

Note: Applicants must meet certain residency criteria to attain UK security clearance. Candidates are cautioned against recruitment fraud; Assystem will never request payment or sensitive personal information during the recruitment process. Assystem is committed to equal treatment and fostering diversity.