Senior Principal Mechanical Engineer

Assystem; Bristol; On-site; GBP 60,000 - 80,000; Full time

Job summary

A global engineering leader is seeking a Senior Principal Mechanical Engineer in Bristol. This role involves leading design development for nuclear systems, conducting risk assessments, and ensuring compliance with regulatory standards. The ideal candidate will have a proven track record in team leadership and cooling water systems design. Applicants must be Chartered Engineers eligible for security clearance. The position offers a full-time commitment to impactful engineering in the nuclear sector.

Qualifications

• Strong leadership and communication skills with a focus on quality output.
• Proven experience in multidisciplinary team management for engineering projects.
• Ability to navigate regulatory environments and compliance in engineering.

Responsibilities

• Lead development of designs for nuclear systems and ensure technical compliance.
• Conduct DFMEA to identify risks early in the design phase.
• Coordinate between engineering teams and stakeholders for effective integration.

Skills

Team Leadership

Steam Cycle Modelling

Project Budgeting

Cooling Water Systems

Regulatory Knowledge

Requirements Capture

Systems Engineering

Subcontractor Management

Chartered Engineer

Security Clearance

Education

Chartered Engineer (CEng)

Job description

Company Overview

Assystem is a global leader committed to accelerating the energy transition. With 7,750 employees across 12 countries, we tackle the monumental task of switching to low‑carbon energy. Our 55+ years of experience in highly regulated sectors ensure we deliver top‑notch engineering, project management, and digital solutions.

Job Overview

Senior Principal Mechanical Engineer – Fusion and Modular Nuclear Business Unit

Location: Bristol, England, United Kingdom

Employment type: Full‑time

Responsibilities

• Lead and support the development of designs for the following systems: Personnel Airlocks, Main Equipment Access Hatch, Fuel Transfer Channel, Piping Penetrations, Electrical Penetrations, Specialist Nuclear Doors
• Conduct DFMEA (Design Failure Mode and Effects Analysis) to identify and mitigate potential failure modes early in the design process.
• Perform HAZID (Hazard Identification Study) to assess and document risks across the system.
• Complete and maintain Human Factors Checklists to ensure ergonomics and usability are considered in design decisions.
• Update and manage the project’s Risk Register to track, evaluate, and mitigate emerging risks.
• Design Package Production in line with requirements – oversee the creation of comprehensive design packages, ensuring alignment with project specifications, technical standards, and operational needs.
• Management of Interfaces – coordinate effectively between engineering teams, suppliers, and stakeholders to ensure seamless integration of cooling water systems with other reactor components.
• Preparation of Technical Specifications – develop clear, detailed technical specifications to guide procurement, fabrication, and installation of key cooling water system components.
• Collaborate with cross‑functional teams, including both new and existing FTEs and secondees across engineering and project functions.

Qualifications

• Multi‑Disciplinary Team Leadership – skilled in managing and coordinating diverse engineering teams.
• Steam Cycle Modelling Oversight – able to define modelling outcomes and ensure accurate implementation.
• Project Budget & Lifecycle Planning – experienced in budgeting and planning for full design lifecycles.
• Cooling Water Equipment Expertise – strong track record in designing and optimising cooling water systems.
• Regulatory & Compliance Knowledge – well‑versed in ONR, Environment Agency, and HSE regulations.
• Requirements Capture Experience – skilled in gathering and defining technical requirements.
• Systems Engineering Awareness – strong understanding of integrated design principles.
• Subcontractor Management – experienced in overseeing and coordinating subcontractors.
• Chartered Engineer (CEng) – professional accreditation in a relevant discipline.
• Security Clearance Eligibility – capable of obtaining SC clearance for secure projects.

Additional Information

• Excellent communication skills, written and oral.
• Strong leadership skills.
• Focus on delivering quality output to time and budget.
• Act with integrity and instil this in others.
• Has an appreciation of wider technical issues beyond own discipline.
• Ability to work with a high degree of independence, using own initiative and self‑motivation.
• Confident in a multi‑party, multi‑national environment.
• Ability to travel to Assystem offices and customer sites within the UK.
• To undertake work packages supporting major UK and international nuclear clients.

Due to the nature of work to be undertaken, applicants will be required to meet certain residency criteria in order to attain a minimum level of UK security clearance if not already security‑cleared to a minimum SC level.

We are committed to equal treatment of candidates and promote, as well as foster all forms of diversity within our company. We believe that bringing together people with different backgrounds and perspectives is essential for creating innovative and impactful solutions. Skills, talent, and our people’s ability to dare are the only things that matter! Bring your unique contributions and help us shape the future.