Senior Principal Mechanical Engineer — Fusion & Nuclear

Assystem; Warrington; Hybrid; GBP 90,000 - 120,000; Full time

Benefits offered by this job

Holiday bonuses

Ongoing training

Employee committee

Internal promotion culture

Hybrid work 1-2 days remote per week

Job summary

Assystem is seeking a Senior Principal Mechanical Engineer to join its Fusion and Modular Nuclear unit in the UK. You will lead designs for cooling water systems and related reactor components, driving DFMEA/HAZID activities and managing interfaces across engineering teams and suppliers.

This role requires Chartered Engineer status, SC clearance eligibility, and the ability to work in a hybrid environment with some UK travel.

Qualifications

• Multi-disciplinary leadership across engineering teams.
• Experience in steam cycle modelling and diagnostics.
• Budgets and lifecycle planning for complex design projects.
• Expertise in cooling water systems within nuclear contexts.
• Knowledge of ONR, Environment Agency, HSE regulations.
• Skills to capture and define technical requirements.
• Strong systems engineering mindset.
• Experience managing subcontractors and suppliers.

Responsibilities

• Lead and support the development of designs for personnel airlocks, main equipment access hatch, fuel transfer channel, piping and electrical penetrations, and nuclear doors.
• Conduct DFMEA to identify and mitigate potential failure modes early in the design process.
• Perform HAZID to assess and document risks across the system.
• Complete and maintain Human Factors Checklists to ensure ergonomics are considered in design decisions.
• Update and manage the project’s Risk Register to track, evaluate, and mitigate risks.
• Oversee design package production to ensure alignment with project specs and standards.
• Coordinate interfaces between engineering teams, suppliers, and stakeholders for cooling water system integration.
• Prepare technical specifications for procurement, fabrication, and installation of key cooling water components.
• Collaborate with cross-functional teams including both FTEs and secondees across engineering and project functions.

Skills

Multi-disciplinary leadership

Steam cycle modelling

Budget & lifecycle planning

Cooling water systems

Regulatory compliance

Requirements capture

Systems engineering

Subcontractor management

CEng

SC clearance eligibility

Job description

Assystem is seeking a Senior Principal Mechanical Engineer to join its Fusion and Modular Nuclear unit in the UK. You will lead designs for cooling water systems and related reactor components, driving DFMEA/HAZID activities and managing interfaces across engineering teams and suppliers.

This role requires Chartered Engineer status, SC clearance eligibility, and the ability to work in a hybrid environment with some UK travel.