Senior Mechanical Engineer

Warrington, England, GB On-site Full-time Posted September 22, 2026
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Company Description

Today, Assystem is among the top three independent nuclear engineering firms worldwide. With over 60 years of experience in highly regulated sectors, the group supports public and industrial stakeholders in the execution of complex and strategic infrastructure projects, subject to high safety and security requirements. 

Assystem mobilizes 8,000 experts in 13 countries and intervenes across the entire project lifecycle, in engineering, project management and digital solutions.

Job Description

Senior Mechanical Engineer

Location: Warrington
Type: Staff / Contract (Inside IR35)

Role Description

🔧 The Mechanical Senior Engineer is required to deliver the mechanical work scope, including production and checking, reporting to a Principal Engineer.

🛠️ They will need to deliver detailed design work packs and supervise designers in the production of layout and detailed design drawings.

🚀 The project is in the latter stages of preliminary design with mock-up parts, with certain assemblies in final manufacturing and testing.

👷 The Mechanical Senior Engineer will be required to support the design through all project phases, testing, and execution of the parts required in this current phase.

🤝 They will work closely with the multi-discipline design team and plant-based team.

📋 The role includes guiding Mechanical Designers and Engineers in the production of detail drawings, sub-assemblies, GA, layout drawings, flow diagrams, and parts lists.

📐 May be required to produce calculations to verify detailed design and design substantiation.

📁 The production and compilation of technical files for machinery/UK CA compliance (e.g., RA’s, O&M manuals, etc.) will also be a requirement.

Qualifications

Essential Experience & Qualifications

✅ Experience of working within a highly regulated industry, preferably within the nuclear industry.
🛠️ Familiarity with ‘Design for Assembly’ within a nuclear facility.
📈 Ability to manage own workload and drive the completion of the work scope.
📘 Strong understanding of delivering mechanical designs in the nuclear sector.
📂 Experience in producing technical files (UK CA and machinery directive compliance).
🛡️ Knowledge of machining and fabrication manufacturing processes.
📊 Experience in producing and checking mechanical engineering calculations and deliverables.
🤝 Skilled in liaising with key stakeholders and other design disciplines.
✍️ Competent report writing skills for clear and concise findings.
⏳ Comfortable working under time and cost constraints.
💬 Excellent communication skills with team members and the Client.

Additional Information

Security clearance:

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.

NOTICE TO CANDIDATES ON RECRUITMENT FRAUD - We are committed to safeguarding candidates from fraudulent activity associated with our recruitment process. Please note that we will never offer specialist CV writing services, request payment or ask for sensitive personal information during the recruitment process.

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.

Market insight

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Frequently Asked Questions

Where is the Senior Mechanical Engineer job located?
This position is on-site in Warrington, England, GB.
Is this a full-time or part-time position?
This is full-time position.
How do I apply for the Senior Mechanical Engineer position?
Click the "Apply Now" button on this page to be redirected to ASSYSTEM's official application page. No account on Jooglee is required.
When was this job posted?
This job was posted on September 22, 2026 and is currently listed as active on Jooglee.
Who is hiring for this position?
ASSYSTEM is hiring for this role in Warrington, England, GB. Click "Apply Now" to visit their careers page.

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