Senior Principal Mechanical Engineer

Assystem; Derby; Hybrid; GBP 60,000 - 90,000; Full time

Job summary

An established industry player in nuclear engineering is seeking a Senior Principal Mechanical Engineer to join their Fusion and Modular Nuclear Business Unit. This exciting role involves leading the design of innovative systems for net-zero power generation, conducting critical analyses to ensure safety and efficiency, and collaborating with diverse teams on cutting-edge projects. With over 55 years of experience, the company offers a dynamic environment that values creativity and technical excellence. Join a community committed to making a meaningful impact in the energy transition while enjoying attractive benefits and ongoing career development opportunities.

Benefits

Attractive social benefits

Ongoing training opportunities

Holiday bonuses

Hybrid work options

Qualifications

• Skilled in managing diverse engineering teams effectively.
• Experienced in budgeting and planning for design lifecycles.
• Strong track record in designing cooling water systems.

Responsibilities

• Lead design development for nuclear systems and components.
• Conduct DFMEA and HAZID to mitigate design risks.
• Collaborate with cross-functional teams on project specifications.

Skills

Multi-Disciplinary Team Leadership

Steam Cycle Modelling Oversight

Project Budget & Lifecycle Planning

Cooling Water Equipment Expertise

Regulatory & Compliance Knowledge

Requirements Capture Experience

Systems Engineering Awareness

Subcontractor Management

Chartered Engineer (CEng)

Security Clearance Eligibility

Education

Chartered Engineer (CEng)

Job description

2 weeks ago Be among the first 25 applicants

Assystem is a global leader committed to accelerating the energy transition. With 7,750 employees across 12 countries, we tackle the monumental task of switching to low-carbon energy. Our 55+ years of experience in highly regulated sectors ensure we deliver top-notch engineering, project management, and digital solutions.

Assystem is a global leader committed to accelerating the energy transition. With 7,750 employees across 12 countries, we tackle the monumental task of switching to low-carbon energy. Our 55+ years of experience in highly regulated sectors ensure we deliver top-notch engineering, project management, and digital solutions.

Job Description

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.

Your mission:

1. Lead and support the development of designs for systems such as Personnel Airlocks, Main Equipment Access Hatch, Fuel Transfer Channel, Piping and Electrical Penetrations, and Specialist Nuclear Doors.
2. Conduct DFMEA (Design Failure Mode and Effects Analysis) to identify and mitigate potential failure modes early in the design process.
3. Perform HAZID (Hazard Identification Study) to assess and document risks across the system.
4. Complete and maintain Human Factors Checklists to ensure ergonomics and usability are considered in design decisions.
5. Update and manage the project’s Risk Register to track, evaluate, and mitigate emerging risks.
6. Design Package Production in Line with Requirements – Oversee the creation of comprehensive design packages, ensuring alignment with project specifications, technical standards, and operational needs.
7. Management of Interfaces – Coordinate effectively between engineering teams, suppliers, and stakeholders to ensure seamless integration of cooling water systems with other reactor components.
8. Preparation of Technical Specifications – Develop clear, detailed technical specifications to guide procurement, fabrication, and installation of key cooling water system components.
9. Collaborate with cross-functional teams, including both new and existing FTEs and secondees across engineering and project functions.

Why Join the Community of Switchers?

• Over 55 years 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 our managers are promoted internally!
• Hybrid work: 1-2 days remote per week.

Qualifications

• Multi-Disciplinary Team Leadership – Skilled in managing and coordinating diverse engineering teams.
• Steam Cycle Modelling Oversight – Ability to define modelling outcomes and ensure accurate implementation.
• Project Budget & Lifecycle Planning – Experienced in budgeting and planning for full design lifecycles.
• Cooling Water Equipment Expertise – Strong track record in designing and optimizing cooling water systems.
• Regulatory & Compliance Knowledge – Well-versed in ONR, Environment Agency, and HSE regulations.
• Requirements Capture Experience – Skilled in gathering and defining technical requirements.
• Systems Engineering Awareness – Strong understanding of integrated design principles.
• Subcontractor Management – Experienced in overseeing and coordinating subcontractors.
• Chartered Engineer (CEng) – Professional accreditation in a relevant discipline.
• Security Clearance Eligibility – Capable of obtaining SC clearance for secure projects.

Additional Information

• Excellent communication skills, written and oral
• Strong leadership skills
• Focus on delivering quality output to time and budget
• Act with integrity and instil this in others
• Appreciation of wider technical issues beyond own discipline – Understands interdisciplinary challenges and their impact on projects.
• Ability to work with a high degree of independence, using own initiative and self-motivation – Proactive and capable of managing tasks autonomously.
• Confident working in a multi-party, multi-national environment – Comfortable with global teams and diverse stakeholders.
• Ability to travel within the UK to Assystem offices and customer sites.
• Contribute to high-profile nuclear projects supporting UK and international clients.

Applicants will need to meet residency criteria to attain UK security clearance if not already security cleared to SC level.

We are committed to diversity and equal opportunity, believing that diverse backgrounds foster innovative solutions. Bring your unique contributions and help us shape the future.