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
Job Info
* Job Title: Senior or Principal Mechanical Engineer
* Company: Highfield Professional Solutions Ltd
* Location: Carlisle, Cumbria
* Posted: Feb 12th 2026
* Closes: Mar 15th 2026
* Contract: Contract
* Hours: Full Time
Apply now to bring your mechanical engineering expertise to one of Sellafield's most significant legacy infrastructure programmes.
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