Senior Systems Engineer - Defence

Location: UK (Hybrid – minimum 3 days per week on-site)

Sector: Nuclear / Defence / Highly Regulated Infrastructure

Employment Type: Permanent / Staff

About the Role

Assystem is seeking an experienced Senior Systems Engineer to join its expanding Defence & Decommissioning business unit. This role will support major UK nuclear and defence programmes, working across mechanical, electrical, and process systems within complex, safety‑critical environments. You will play a key role in defining system architecture, managing requirements, and ensuring system‑level integrity across the full project lifecycle, from concept through to delivery and verification. This position is ideally suited to a systems engineer with experience in highly regulated industries such as nuclear, defence, or aerospace, who is comfortable operating in multi‑disciplinary engineering teams and driving structured systems engineering approaches.

Key Responsibilities

• Define, manage, and maintain system requirements across complex engineering programmes
• Develop and maintain system architectures, functional breakdowns, and interface definitions
• Manage and coordinate system interface control across mechanical, electrical, and process disciplines
• Produce and maintain requirements specifications using structured engineering tools (e.g. DOORS)
• Develop functional and behavioural system models using Model-Based Systems Engineering (MBSE) tools (e.g. Capella)
• Ensure traceability of requirements through design, verification, and validation activities
• Work closely with discipline engineers to ensure system‑level coherence and integration
• Support technical reviews, design assurance activities, and systems verification planning
• Contribute to systems engineering governance, processes, and best practice development
• Provide systems thinking leadership across multidisciplinary engineering teams

Key Requirements

• Experience in a complex, highly regulated industry (Nuclear, Defence, Aerospace, Energy, etc.)
• Strong understanding of systems engineering principles and systems thinking
• Experience working with multi-disciplinary engineering systems (mechanical, electrical, process)
• Ability to define and manage system requirements and interfaces
• Experience working within structured engineering lifecycles
• Nuclear industry experience
• Use of IBM DOORS (requirements management)
• Experience with MBSE tools such as Capella or similar
• Familiarity with INCOSE or British Systems Engineering standards
• Systems engineering training or formal qualification

Qualifications

• Degree in Engineering, STEM, or equivalent demonstrable experience
• Systems Engineering certification or training (desirable)

Security & Compliance

• Must be eligible for Security Clearance (SC minimum)
• Sole UK National status required
• Must be willing to work hybrid with minimum 3 days per week on site

About Assystem

Assystem is a global engineering and project delivery organisation focused on accelerating the transition to low‑carbon energy. Operating in highly regulated sectors for over 55 years, we are a trusted partner to major nuclear and defence programmes worldwide. We combine engineering expertise with digital innovation to deliver complex infrastructure safely, efficiently, and sustainably.