Senior Principal Mechanical Engineer

Assystem GmbH; Warrington; Hybrid; GBP 65,000 - 85,000; Full time

Benefits offered by this job

Attractive social benefits

Ongoing training opportunities

Holiday bonuses

Job summary

Assystem GmbH is seeking a Senior Principal Mechanical Engineer for its Nuclear division in Warrington, UK. Join a pioneering Small Modular Reactor (SMR) program where you will lead a team focusing on critical cooling water systems vital for reactor operations.

This permanent role requires strong leadership skills and track record in nuclear engineering. Benefits include social perks, career opportunities, and a hybrid work model.

Qualifications

• Proven expertise in leading projects from Front-End Engineering Design through to execution.
• Skilled in managing and coordinating diverse engineering teams.
• Strong track record in designing and optimizing cooling water systems.
• Experienced in budgeting and planning for full design lifecycles.
• Well-versed in ONR, Environment Agency, and HSE regulations.

Responsibilities

• Lead and mentor a team of engineers on cooling water systems.
• Define rigorous safety and performance criteria for reactor operation.
• Oversee the creation of comprehensive design packages.
• Coordinate effectively between engineering teams and stakeholders.
• Develop clear technical specifications for key cooling water components.

Skills

Leadership skills

Cooling water system design

Regulatory compliance knowledge

Systems engineering

Project budget planning

Excellent communication

Education

Chartered Engineer (CEng)

Job description

# Senior Principal Mechanical Engineer* Nuclear* Permanent /* Warrington* United Kingdom* 11/06/26* On site* ShareI apply##Today, Assystem is among the top three independent nuclear engineering firms worldwide. With over 60 years of experience in highly regulated sectors, the group supports public and industrial stakeholders in the execution of complex and strategic infrastructure projects, subject to high safety and security requirements. Assystem mobilizes 8,000 experts in 13 countries and intervenes across the entire project lifecycle, in engineering, project management and digital solutions.## Job Description **Join the Fusion and Modular Nuclear Business Unit!** Take on a pivotal role in shaping the future of clean energy by establishing, leading, and managing the Cooling Water Island engineering team within a groundbreaking Small Modular Reactor (SMR) development program. Drive the development of a high-performing team, overseeing the design, integration, and execution of critical cooling water systems essential to reactor operation. Play a key role in defining technical strategies, ensuring regulatory compliance, and collaborating across multidisciplinary teams to deliver innovative, high-efficiency engineering solutions that will help revolutionize nuclear power.**Your mission:*** Leadership of the Engineering Activities of the Cooling Water Team – Lead and mentor a team of engineers, driving technical excellence, innovation, and collaboration to deliver critical cooling water systems for the Small Modular Reactor (SMR) program.* Development of Safety and Functional Requirements – Define and establish rigorous safety and performance criteria, ensuring compliance with industry regulations and best practices to support safe and reliable reactor operation.* 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.* Maintain Equipment Lists and Schedules – Track, update, and manage critical equipment inventories and project schedules to ensure timely delivery and smooth execution of engineering activities.* Management of Risk and Opportunity – Proactively identify potential risks and opportunities, implementing strategies to mitigate challenges and optimize system performance, cost-effectiveness, and overall project success.**Why Join the Community of Switchers?*** Over 55 years in nuclear engineering.* Ranked among the top 3 largest nuclear engineering companies.* Attractive social benefits, including an engaging Employee Committee and holiday bonuses.* Ongoing training with numerous career opportunities.* 70% of our managers are promoted internally!* Hybrid work: 1-2 days remote per week.## My profile* FEED to Detailed Design Experience – Proven expertise in leading projects from Front-End Engineering Design through to execution.* Multi-Disciplinary Team Leadership – Skilled in managing and coordinating diverse engineering teams.* Steam Cycle Modelling Oversight – Ability 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 optimizing 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.**Attributes:*** Excellent communication skills, written and oral* Strong leadership skills* Focus on delivering quality output to time and budget* Act with integrity and instils this in others* Has an appreciation of wider technical issues beyond own discipline – Understands interdisciplinary challenges and their impact on projects.* Ability to work with a high degree of independence, using their own initiative and self-motivation – Proactive and capable of managing tasks autonomously.* Confident in a multi-party, multi-national environment – Comfortable working with global teams and diverse stakeholders.* Ability to travel to Assystem offices and customer sites within the UK* To undertake work packages supporting major UK and international Nuclear Clients – Contributes to high-profile nuclear projects with global impact.**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.****NOTICE TO CANDIDATES ON RECRUITMENT FRAUD – We are committed to safeguarding candidates from fraudulent activity associated with our recruitment process. Please note that we will never offer specialist CV writing services, request payment or ask for sensitive personal information during the recruitment process.**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.