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.

Amentum is a Lot 1 delivery partner within the Decommissioning and Nuclear Waste Partners (DNWP) Framework, a major Sellafield programme worth up to £4.6 billion and running for up to 15 years. The framework is focused on safely accelerating decommissioning, remediation and high‑hazard risk reduction across one of the most complex nuclear sites in the world.

Our nuclear team supports the front‑end design, engineering, technical leadership and delivery expertise required across the DNWP portfolio. We are looking for individuals with high‑value expertise from across regulated and comparable sectors to who can work collaboratively, embrace new challenges and contribute to the mission of safely and efficiently delivering Sellafield’s decommissioning and nuclear waste objectives.

About the Opportunity

As a Senior Project Manager you will be responsible for planning, executing, and closing projects, ensuring they are completed on time, within budget, and meet stakeholder expectations.

You will conduct work alongside Delivery Leads, Package Managers, Engineers and with support from Administrators.

Employee will be expected to contribute to the delivery of social value in line with the DNWP framework, supporting positive outcomes for local communities. Voluntary engagement is supported, with up to 16 hours per full‑time equivalent allocated.

Key Responsibilities:

• Provide strategic leadership and oversight for multiple complex or high value projects, ensuring alignment with organisational objectives and client expectations.

• Take full accountability for end-to-end project delivery performance, including cost, schedule, quality, safety, and risk across assigned portfolios.

• Lead, mentor, and develop Project Managers and other delivery staff, providing professional guidance, performance management, and succession planning support.

• Act as the primary senior interface with clients, joint venture partners, regulators, and internal senior leadership, managing key relationships and escalation matters.

• Oversee the development, approval, and governance of project execution plans, ensuring consistent application of best practice project management methodologies.

• Provide assurance that robust project controls are in place, including programme management, cost control, risk and opportunity management, and change control processes.

• Review and challenge project budgets, forecasts, and schedules, ensuring early identification of risks, trends, and recovery actions where required.

• Sponsor and lead resolution of complex project issues, claims, disputes, and contractual matters, providing direction and support to project teams.

• Ensure effective governance, reporting, and compliance with corporate, client, and regulatory requirements, including health, safety, environmental, and quality standards.

• Support business development activities by contributing to bid strategies, tender reviews, estimates, and mobilisation planning for new work.

• Drive continuous improvement by capturing lessons learned, promoting innovation, and implementing improvements across projects and programmes.

• Provide leadership in safety culture, setting clear expectations, challenging behaviours, and ensuring safety excellence is embedded throughout all project activities.

• Represent the organisation as a senior leader, promoting Amentum values, professionalism, and a collaborative, high performance culture.

Essential Qualifications & Experience:

• Significant, minimum 10 years of experience in Project Management within a highly regulated and quality assured system in roles dependent upon engineering judgement.

• APM Chartered Project Professional and member of the Association of Project Management (APM) or PMI.

• Degree level qualification (2:1 minimum) in a relevant STEM subject.

• Previous experience of taking full accountability for end-to-end project delivery performance, including cost, schedule, quality, safety, and risk across assigned portfolios.

• Demonstrable experience in reviewing and challenging project budgets, forecasts, and schedules, ensuring early identification of risks, trends, and recovery actions where required.

• Superior interpersonal and leadership skills are required to enable effective interaction with clients, seniors and peers while working in a collaborative “Team” environment and able to build and maintain effective internal and external working relationships. 

• Strong organisational skills, attention to detail and quality are required along with a process improvement-oriented mindset.

• Previous experience of managing complex project issues, claims, disputes, and contractual matters, providing direction and support to project teams.

• Capable of effective multi-task working, identifying and managing priorities and working to challenging time scales.

• Experience embedding quality and safety practices.

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.

Compensation Details:

The compensation range or hourly rate listed for this position is provided as a good-faith estimate of what the company intends to offer for this role at the time this posting was issued. Actual compensation may vary based on factors such as job responsibilities, education, experience, skills, internal equity, market data, applicable collective bargaining agreements, and relevant laws.

Benefits Overview:

Our health and welfare benefits are designed to support you and your priorities. Offerings include:

• Health, dental, and vision insurance

• Paid time off and holidays

• Retirement benefits (including 401(k) matching)

• Educational reimbursement

• Parental leave

• Employee stock purchase plan

• Tax-saving options

• Disability and life insurance

• Pet insurance

Note: Benefits may vary based on employment type, location, and applicable agreements. Positions governed by a Collective Bargaining Agreement (CBA), the McNamara-O'Hara Service Contract Act (SCA), or other employment contracts may include different provisions/benefits.

Original Posting:

Amentum anticipates this job requisition will remain open for at least three days, with a closing date no earlier than three days after the original posting. This timeline may change based on business needs.

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.