Senior or Principal Mechanical Engineer

Contract Opportunity: Senior / Principal Mechanical Engineer Sellafield MSSS-OBLM Projects £51-£61 per hour (Inside IR35) Hybrid - 3 days per week in Warrington Sector: Nuclear | MSSS-OBLM Programme Are you an experienced Senior or Principal Mechanical Engineer looking to play a key role on one of Sellafield's most critical programmes? This opportunity sits within the MSSS-OBLM (Multi-Storey Seismic Stores - On-Balance Legacy Materials) projects, delivering essential mechanical engineering support to safety-critical, legacy nuclear infrastructure. You'll provide technical leadership and delivery assurance across task-based mechanical work packages, supporting the safe progression of complex designs within a highly regulated environment. The role offers a hybrid working model, balancing collaboration in Warrington with remote working flexibility. Key Responsibilities Deliver and manage mechanical engineering tasks across MSSS-OBLM project scopes Develop, review and approve designs, calculations, specifications, and technical documentation Ensure compliance with Sellafield engineering standards, nuclear safety requirements, and site licence conditions Support design reviews, optioneering studies, risk assessments, and HAZOPs Provide technical leadership, mentoring and assurance to junior engineers Collaborate closely with multi-disciplinary teams to achieve safe, efficient project delivery What We're Looking For Proven experience operating at Senior or Principal Mechanical Engineer level Background in nuclear or similarly highly regulated industries Strong technical capability across mechanical systems, structures, and process equipment Experience delivering task-based engineering packages to programme, cost and quality requirements Familiarity with Sellafield MSSS / OBLM design processes and standards (highly advantageous) SC clearance preferred or the ability to obtain Why This Role? Competitive £51-£61/hour (Inside IR35) Long-term opportunity on a high-profile Sellafield MSSS-OBLM programme Hybrid working with 3 days per week in Warrington Technically complex, safety-critical work with real national importance Opportunity to influence design decisions and support the next generation of engineers Apply now to bring your mechanical engineering expertise to one of Sellafield's most significant legacy infrastructure programmes