Principal Mechanical Engineer

Company Description

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

Are you a Principal Mechanical Engineer with a passion for leading technical teams and delivering high-impact engineering solutions in a highly regulated environment? Do you thrive in a collaborative, dynamic setting where your leadership, technical insight, and ability to inspire others make a real difference? If so, we want to hear from you!

Your future team:

As a Principal Mechanical Engineer, you will lead multi-disciplinary teams in the development of innovative technical solutions that meet and exceed our clients’ requirements. Reporting to the Lead Engineer and Project Manager, you’ll play a crucial role in steering project success—from concept design through to delivery—ensuring technical excellence, timely delivery, and compliance with industry standards.

Your missions:

🎯 Provide technical leadership and direction to project teams.

🎯 Supervise and mentor junior engineers through well-defined work packages.

🎯 Deliver high-quality technical documentation, design reports, and LTQR packs.

🎯 Communicate progress, risks, and solutions effectively to stakeholders.

🎯 Collaborate closely with clients and subject matter experts across various disciplines.

🎯 Identify and proactively manage technical risks and opportunities.

🎯 Drive the development and verification of mechanical and structural engineering designs.

🎯 Ensure compliance with safety and regulatory frameworks, including nuclear safety where applicable.

Why join the community of Switchers?

As one of the Top 3 Nuclear Engineering companies in the world, Assystem offer a competitive benefits package which includes:

💥25 days of annual leave + bank holidays

💥8% company pension contributions

💥Healthcare cash-plan to get money back on dental, medical, physical care

💥Employee assistance programme including 24/7 access to free mental health support, virtual gym classes and more

💥Get professional and industry membership fees paid for.

Qualifications

Essential Qualifications/Skills to be successful:

💡 Minimum 2:1 BEng in Mechanical Engineering (or equivalent). Master’s degree preferred.

💡 Proven engineering experience in regulated industries (e.g., nuclear, defence, oil & gas).

💡 Proficient with design and modelling tools such as Revit, Inventor, AutoCAD, and/or CATIA.

💡 Strong mathematical foundation; MathCAD experience desirable.

💡 Familiarity with MBSE and the full design cycle from concept to manufacture.

💡 Experience working with engineering standards and regulations (PED, PUWER, LOLER, etc.).

💡 Exposure to Hazard and Risk Assessments (HAZOP, HAZID, FMEA, etc.).

Desirable Qualifications/Skills:

💡 Chartered status or working towards chartership is advantageous.

💡 Understanding of FEA and experience with ANSYS, CAESAR, or Flow Master is a plus.

💡 Understanding of functional safety (BS EN 61508 / 61511).

💡 Knowledge of NEC 3/4 contracts and risk identification.

💡 Strong understanding of pipework and system components.

💡 Experience engaging with supply chains and specifying equipment.

💡 Adaptable and comfortable managing shifting project scopes and concurrent system developments.

Apply now and take the next step in your engineering career!

Additional Information

Due to the nature of work to be undertaken applicants will be required to meet certain residency criteria in order to attain a minimum level of UK security clearance if not already security cleared to a minimum SC level.

Sole British National is desirable.

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.