Senior Mechanical Engineer (DJR Mark ups)
Confirmed on the employer's own hiring board on Oct 25, 2026. First seen by Alion on Jul 18, 2026. Amentum scores B on the Alion truth index.
At Amentum, we're not just solving problems; we're engineering the future. Our team is driven by an unyielding commitment to innovation, integrity, and collaboration, tackling some of the most significant challenges in science, security, and sustainability. If you're passionate about making a real impact and want to be part of a community that values ethical excellence, this is the place where your ambition can thrive.
Here, we believe that success comes from continuously pushing boundaries and working together to deliver on our promises. We embrace challenges with confidence and are dedicated to creating a secure and vibrant future for all. We’ll inspire and empower you to deliver your best work so you can evolve, grow and succeed - today and into tomorrow.
We offer an exciting range of opportunities to develop your career within a supportive team who always strive to do the right thing for our people, clients and communities.
People are our greatest asset, and we offer a competitive package to retain and attract the best talent. In addition to the benefits you’d expect, UK employees also receive free single medical cover and digital GP service, family-friendly benefits such as enhanced parental leave pay and free membership of employee assistance and parental programmes, plus reimbursement towards relevant professional development and memberships. Work-life balance and flexibility is a key focus area for us. We’re happy to discuss hybrid, part-time and flexible working hours, patterns and locations to suit you and our business.
The Opportunity
Amentum is the Design and Engineering partner for Sellafield under the PPP (Programme and Project Partners). This is a 20-year arrangement to deliver ~£7bn of major projects. We are looking to recruit high value expertise from across regulated and comparable sectors to work in a collaborative environment. PPP is delivering major projects, site wide improvements and provision of supporting services.
The Project
The SIXEP Continuity Plant, being delivered by the Programme and Project Partners (PPP) at Sellafield, will ensure the site's existing Site Ion Exchange Effluent Plant (SIXEP) facility can continue its vital work for decades to come. The newbuild SCP facility will play a vital part in Sellafield's purpose to create a clean and safe environment for future generations
The Role
We are now looking to recruit a Senior Mechanical Engineer To lead a small team (3 or 4 people) on the detailed design, support to manufacturing and implementation, of several significant plant modification packages (PMP’s) within the SIXEP facility on Sellafield site.
The nature of the designs is primarily related to process piping systems and includes both coaxial and single-skin piping design with active connections to the existing SIXEP plant, plus associated shielding, supports and valves.
The existing design team has already completed considerable work on these packages. However, as Senior Mechanical Engineer, you will be expected to consider functionality, manufacturability, constructability and maintainability of all packages. You will also be expected to support the technical authoring and presentation of the various PMP packages.
As Senior Mechanical Engineer, you will also be responsible for keeping the design activities on track, updating schedules where necessary and managing the resources to deliver on time.
As a Senior Mechanical Engineer, responsibilities could include:
leading a small team in the design and delivery of complex mechanical engineering packages.
Experience of working within a highly regulated industry
Must be conversant with the relevant engineering standards for delivery of high integrity piping installations and associated equipment.
Familiar with nuclear containment and shielding principles/design.
Must have experience in working with schedules to track activities and provide regular updates to project management.
Experience in Nuclear Design Justification Report (DJR)/Engineering substantiation production/checking
As a Senior Mechanical Engineer, you will already have experience of:
Checking of engineering drawings up to and including manufacturing maturity.
Checking of engineering documentation such as risk assessments, outline installation method statements, calculations and operation & maintenance manuals
Our Culture
Our values are built on a strong foundation of safety, integrity, and respect for every individual. People are at the heart of our mission, and we believe in supporting one another through a culture of care and collaboration.
We strive to create a workplace where everyone feels they belong and can thrive. Supporting mental wellbeing and fostering a sense of connection are essential to how we work.
When we embrace different perspectives and work together, we become more innovative, more agile, and more successful.
We partner with VERCIDA, for greater online accessibility please visit www.vercida.com to view and access our roles. As a Disability Confident employer, we will interview all disabled applicants who meet the minimum criteria for a vacancy. We welcome applications from candidates who are seeking flexible working and from those who may not meet all the listed requirements for a role.
If you require further support or reasonable adjustments with regards to the recruitment process (for example, you require the application form in a different format), please contact the team.