An opportunity has arisen for an experienced Senior Mechanical Design Engineer within pond mechanical handling experience to design rigs, tools and storage racks and support Design Substantiation and CA marking requirements to join the TDA Project Design Team. You should be a British Citizen and passport holder and not have worked outside the UK during the past 5 years. Candidates can start with BPSS security clearance whilst higher level clearance is being undertaken. This is a full time contract position inside IR35 with a requirement to spend a minimum of 3 days per week in the Whitehaven offices or Sellafield Site when required. This is an exciting opportunity to become part of an established team working on an emerging project at Sellafield. This role offers the chance to work in a dynamic and forward-thinking environment to deliver a project of national importance. The successful candidate will work closely with the Project Engineering Manager, multi-disciplinary project teams, and the Client on a fast-paced project. ROLE RESPONSIBILITIES Provide Lessons from Experience (LFE) and apply knowledge of plant constraints throughout the project delivery process. Produce NFR, feasibility studies, and Design Intent Reports (DIRs) to justify and support design decisions. Check and approve Mechanical design deliverables to ensure technical accuracy and compliance. Ensure plans, drawings, and quantities are accurate and suitable for engineering calculations. Manage and control design documentation, including drawings and technical specifications. Maintain configuration control of engineering deliverables and ensure effective integration with other disciplines. Liaise with other designers and stakeholders to ensure compliance with design and construction regulations. Provide regular progress reports and technical updates to the Mechanical Responsible Engineer (RE). Plan and prioritise work effectively, adapting to setbacks and resolving technical challenges as they arise. Use AutoCAD, Navisworks, and 3D scanning software proficiently to transfer accurate site data to the design team. Contribute technical knowledge and practical input to Design and Constructability Reviews. ESSENTIAL EXPERIENCE & QUALIFICATIONS Hold an HNC/HND in Mechanical Engineering (or equivalent qualification). Demonstrate strong plant knowledge and experience working within an operational environment. Have working experience using CIMAGE on the SL System. A positive can-do attitude, excellent communication and collaboration skills with the ability to work effectively across diverse project teams. Must hold appropriate Security Clearance (SC and British Sole National) and be a Sellafield pass holder.