Technical Subject Matter Expert

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.

About the Opportunity

Amentum is the Design & Engineering partner within the Programme and Project Partners (PPP) framework at Sellafield — a 20-year strategic alliance delivering £7bn of major infrastructure projects.

We are seeking a Technical Subject Matter Expert (SME) to provide deep domain expertise and technical leadership across complex engineering programmes.

What You'll Be Doing:

• Act as the technical authority in your discipline, providing expert guidance across design, delivery, and assurance phases.
• Support project teams with specialist knowledge to resolve complex engineering challenges.
• Lead and contribute to technical reviews, design assurance activities, and risk assessments.
• Ensure compliance with regulatory standards, safety requirements, and industry best practices.
• Collaborate with internal and external stakeholders to ensure technical integration and alignment.
• Mentor engineers and contribute to the development of technical capability across the organisation.
• Influence strategy and decision-making through technical insight and evidence-based recommendations.

What We're Looking For:

• Recognised technical expert in a relevant engineering discipline, Chartered with a relevant institution.
• Extensive experience in regulated environments (e.g. nuclear, defence, infrastructure).
• Proven ability to lead technical assurance and solve complex engineering problems.
• Strong communication and stakeholder engagement skills.
• Experience supporting large-scale project delivery and multidisciplinary teams

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 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.

Amentum is proud to be an Equal Opportunity Employer. Our hiring practices provide equal opportunity for employment without regard to race, sex, sexual orientation, pregnancy (including pregnancy, childbirth, breastfeeding, or medical conditions related to pregnancy, childbirth, or breastfeeding), age, ancestry, United States military or veteran status, color, religion, creed, marital or domestic partner status, medical condition, genetic information, national origin, citizenship status, low-income status, or mental or physical disability so long as the essential functions of the job can be performed with or without reasonable accommodation, or any other protected category under federal, state, or local law. Learn more about your rights under Federal laws and supplemental language at Labor Laws Posters.