CS&A Principal Engineer

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.

⚛️ Project Overview – Box Encapsulation Plant (BEP)

TheBox Encapsulation Plant (BEP) is a major nuclear construction project atSellafield, Cumbria, forming a critical part of the Magnox Swarf Storage Silo (MSSS) Programme.

🏗️The Mission: Tackle one of Sellafield’s most hazardous legacy facilities by retrieving, treating and immobilising nuclear waste for safe, long-term storage.

☢️The Bigger Picture: The BEP may also support waste processing from other major decommissioning projects, including the First Generation Magnox Storage Pond and Pile Fuel Storage Pond.

We’re looking for an experiencedCivil, Structural & Architectural (CS&A) Engineering professional with a minimum of10 years’ nuclear experience, a strong technical background and the confidence to lead engineering activities within a regulated, quality-assured environment.

🎯 Key Responsibilities

• 👥Lead & Inspire – Provide leadership, technical guidance and support to the JV CS&A design and site engineering teams.
• 🤝Work with Sellafield – Report daily to the Sellafield CS&A Responsible Engineer (RE), maintaining strong communication and collaboration.
• 📐Design Assurance – Review, check and comment on CS&A design submissions, site modifications and technical documentation.
• ✅Engineering Approvals – Review, accept or reject design submissions and TQ/PP documentation, completing and submitting the required records through Sellafield Document Control.
• 🏗️Structural Design Oversight – Track structural detail design drawings, calculations and documents through toAs-Built status.
• 🔥Fire Strategy & Compliance – Support fire strategy reviews, including fire-rated service hanger supports, and engage with fire consultants on conventional and nuclear fire issues.
• 🛡️Safety Case Support – Contribute to safety case activities, including Design Justification Reports (DJRs).
• 🔄Multidisciplinary Collaboration – Resolve engineering challenges with the wider design team, Sellafield Capability and construction stakeholders.
• 📝Technical Governance – Support design reviews, engineering substantiation, risk reviews and Early Warning Notices (EWNs).

🏗️ External Works & Infrastructure

• 📏Design Review – Review external works design, including concrete slabs, surface water drainage and standard details.
• 🔗Interface Management – Assess interfaces between external works and the building envelope as construction progresses.
• 👷Construction Engagement – Work closely with the JV construction team and supply chain to resolve technical issues.
• ⚠️Risk Management – Attend weekly risk review meetings and support the management of emerging project risks and EWNs.
• 🚧Utilities & Infrastructure – Engage with Sellafield Site Utilities and Infrastructure Capability to secure alignment on contractor proposals before construction, where required.

📍 Site Presence & Location

• 🏢Warrington Office – Minimum of 3 days per week.
• ☢️Sellafield Site – Regular visits, ideally fortnightly, with site attendance generally weekly or at least once every two weeks.
• 🔍Site Walkdowns – Work alongside construction teams to identify, discuss and resolve CS&A engineering issues directly on site.
• 🤝Stakeholder Engagement – Build strong working relationships with Sellafield, JV construction teams, subcontractors and multidisciplinary engineering specialists.

Qualifications and experience

🚀 What You’ll Bring to the Role

• 🎓Qualified Engineer – Degree in Civil or Structural Engineering, or equivalent.
• 🏅Chartered Status – CEng accreditation with ICE (MICE) or IStructE (MIStructE).
• 🏗️Technical Excellence – Proven expertise across major projects, applying specialist engineering knowledge to deliver results.
• 🧭Strategic Vision – Experience shaping project and programme direction across a portfolio, providing expert guidance and insight.
• 👥Engineering Leadership – Ability to lead, inspire and drive excellence within an engineering function.
• ⚛️Nuclear Experience – Proven experience in the nuclear sector, including new-build and decommissioning projects, applying professional engineering judgement.
• 📐Design Expertise – Strong understanding of engineering design principles and their practical application.
• 📚Standards Knowledge – Working knowledge of relevant British Standards.
• 🗣️Communication Skills – Excellent written and verbal communication, with the ability to influence and engage stakeholders.
• 🚗UK Driving Licence – Full UK driving licence, or equivalent licence permitting you to drive in the UK.
• 🔐Security Clearance – Eligible to meet UK security clearance requirements.

**Security clearance**

This role requires the successful candidate to hold a minimum of a BPSS clearance without any caveats to that clearance.

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.