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 currently recruiting a Senior / Principal Modelling Consultant (Nuclear Waste) to join our Waste Management and Disposal (WM&D) business. This position can be based at one of our key office locations – Harwell, London, Birchwood – or other locations may be considered, subject to business needs.
Our Waste Management, Disposal and Safety Case teams have played a leading role in research and assessment related to the safe management and disposal of radioactive waste for over three decades. We offer nationally and internationally recognised expertise in consultancy, modelling and laboratory work that supports the scientific and engineering foundations necessary for the safe and effective disposal of radioactive materials.
You will join a respected, multi-disciplinary team comprising chemists, physicists, geologists, engineers, and safety case specialists. Together, we deliver high-value technical programmes for UK and international clients including Nuclear Waste Services (NWS), the Nuclear Decommissioning Authority (NDA), site license companies, regulators, and overseas waste management organisations.
This position offers a unique opportunity to apply technical skills to meaningful and high-impact challenges. It is well suited to individuals seeking to develop their careers in a technically complex and commercially dynamic environment, working collaboratively with clients and colleagues on projects of national and international significance.
Key Responsibilities:
As a Senior/ Principal Modelling Consultant, you will play an integral role in delivering a wide range of desk-based consultancy projects for clients in the UK and internationally. Working within a collaborative and multidisciplinary team, you will contribute to both the technical delivery and ongoing development of our waste management and disposal capability.
Your responsibilities will include:
1. Providing technical input across a variety of disciplines relevant to radioactive waste management and disposal, including numerical and other types of complex modelling to support the safety case for future and existing disposal facilities in the UK and abroad. This could include groundwater flow and solute transport modelling; probabilistic and deterministic assessments of radionuclide release and contaminant migration; modelling of gas and two-phase flow; and assessment of engineered and natural barrier systems and their performance over long timescales.
2. Leading and coordinating technical work packages or small project teams, ensuring delivery to time, cost and quality requirements, and providing technical oversight and assurance of modelling outputs.
3. Interpreting client requirements and developing solutions that meet their objectives.
4. Contributing to the successful delivery of consultancy projects for clients such as radioactive waste producers, waste management organisations and regulators.
5. Supporting, mentoring and developing junior staff, including providing technical guidance, reviewing their work and contributing to their professional growth within the team.
6. Producing high-quality technical reports and presentations, communicating complex scientific information clearly to both specialist and non-specialist audiences.
7. Business development activities, including proposal writing and client engagement.
Requirements and Experience:
The successful candidate will demonstrate strong technical expertise, excellent communication skills, leadership potential (or experience) and a collaborative mindset, with a proven ability to deliver high-quality work in a multi-disciplinary and fast-paced environment.
Essential Criteria:
8. A degree in Earth sciences, physical sciences, engineering, or mathematics.
9. Experience in the development and application of numerical and/or complex environmental models.
10. Ability to evaluate complex systems and models, extract key safety insights, and present findings effectively.
11. Excellent written and verbal communication skills, with the ability to produce clear, accurate and well-structured technical documentation for diverse audiences.
12. Strong organisational and project delivery skills, including ability to manage competing priorities and deliver to time and budget.
13. Ability to work both autonomously and collaboratively in multidisciplinary teams.
14. Proven problem-solving ability and a creative, solutions-focused mindset.
15. A commitment to continuous learning and professional development.
16. Desire to contribute to the development of the company’s radioactive waste management and decommissioning strategy capability.
17. Ability to obtain Baseline Personnel Security Standard (BPSS) clearance.
Additional Criteria:
Experience in one or more of the following areas would be advantageous, but is not essential:
18. Environmental safety case development for radioactive waste disposal facilities.
19. UK nuclear regulatory frameworks and repository development programmes.
20. Experience developing groundwater flow and solute transport models both near surface and deep underground.
21. GoldSim (or similar tools) for contaminant transport simulation.
22. Geochemical modelling tools (, PHREEQC).
23. Scientific programming or scripting (, Python, MATLAB).
24. Coupled process modelling tools (, COMSOL, PFLOTRAN).
25. Engineered barrier system design and evaluation.
26. Experience supporting licence applications or regulatory review.
27. UK nuclear industry or radioactive waste management sector experience.
Successful candidates will be asked to complete a Baseline Personnel Security Standard Pre-Employment check and will be required to undergo various checks including Identity, Right to Work, Employment/Education History and Criminal Record. If you are unable to meet this and any associated criteria, then your employment may be delayed or rejected.
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.
Compensation Details:
GBP
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:
28. Health, dental, and vision insurance
29. Paid time off and holidays
30. Retirement benefits (including 401(k) matching)
31. Educational reimbursement
32. Parental leave
33. Employee stock purchase plan
34. Tax-saving options
35. Disability and life insurance
36. 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:
03/30/2026 - Until Filled
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 .