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Our Vacancy

Principal Mechanical Engineer

  • Defence
  • Contracting /
  • Helensburgh
  • 10/06/24
  • On site

Assystem is an international company with one mission: accelerate the energy transition around the world.

Every day, our 7,500 switchers located in 12 countries (Europe, Middle East, Pacific Asia & Africa) connect their six thousand billion neurons to tackle the task of the century: switching to low-carbon energy.

We are a collective committed to the actors who are making the energy switch. Sharing our knowledge, expertise and values allows us to innovate and think differently about the energy transition.

Drawing on more than 55 years’ experience in highly regulated sectors subject to strict security and safety requirements, we provide our customers with engineering and project management services, as well as digital services and solutions to optimize the performance of complex infrastructure projects throughout their life cycle. The Group is currently ranked second in the world for nuclear engineering.

To ensure a viable, efficient, and reliable energy future for all.

Job Description

Join us a Principal Mechanical Engineer
📍 Location: Helensburgh
📝 Contract/Staff Position

Your Future Team 

The role involves working as part of a multi-disciplinary engineering team within the Approving Authority. The primary purpose of the role is to directly support current operations and future programmes.

The team consists of Mechanical, Civil, Building Services and Electrical Engineers and are responsible for the authorship, development, assessment, and maintenance of engineering design substantiation for Client Facilities.

Your Missions

  • 📑 Manage Infrastructure Design Substantiation documents.
  • 🔄 Handle design changes/concessions.
  • 📊 Present Design substantiations to Client safety committees.
  • 📅 Develop EIMT Schedule, procedures, and results.
  • 📝 Produce Periodic Review of Safety reports.
  • 🗣️ Advise internal and external stakeholders.
  • 🕵️‍♂️ Conduct Independent Technical Review.
  • 🛠️ Apply engineering knowledge to nuclear/high-risk environments.
  • 🏗️ Justify mechanical/structural design modifications.

Why join the community of Switchers?:

🔹 The Group is currently ranked Third in the world for nuclear engineering.

🔹A dynamic career management policy to enable our employees to progress through our five business lines: operations, project, technical, sales and support functions

🔹Provide opportunities to work on exciting, global projects

🔹Access to an employee assistance programme with free mindfulness, health, wellbeing resources and a confidential support line available 24/7 via phone or text

🔹Discount vouchers for days out and restaurants, eye test and glasses vouchers, cycle to work scheme, free flu jabs

At Assystem, we celebrate diversity and creativity. We believe in harnessing unique perspectives to shape innovative solutions. Your skills and daring spirit are what truly matter. Join us and help shape the future! 🌟

My profile


  • ✅ Produce robust technical justifications for mechanical/structural design modifications in high hazard industries.
  • ✅ Apply theoretical and practical methods across the engineering lifecycle in nuclear/high-risk environments.
  • ✅ Utilize a blend of general and specialist engineering knowledge to incorporate existing and emerging technologies.
  • 🌡️ Experienced in high-risk environments.
  • 🔍 Familiarity with safety case development techniques such as HAZID/HAZOP studies.
  • 🏢 Hybrid role with occasional visits to Client site near Helensburgh and Glasgow offices.
  • 🔒 Security Clearance: SC, sole UK National.
  • 🎓 BEng in Mechanical or Structural engineering (or equivalent).
  • 👷 Chartered Engineer status (or equivalent).
  • ⚠️ Safety case related training.


We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter !. Bring your unique contributions and help us shape the future.

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