Thermal Hydraulics Analysis Engineer - Nuclear

ALTEN is a global engineering and technology consultancy operating across over 35 countries worldwide. We partner with industry leaders across sectors including Aeronautics, Aerospace, Defence, Naval, Automotive, Energy, Rail, IT and many more to deliver innovative engineering solutions that drive technological advancement & support sustainable transformation.

Our teams of passionate and agile engineers work on cutting-edge projects that shape the future of technology and sustainability. At ALTEN, we empower talented engineers to innovate, solve complex challenges, and deliver impactful solutions that build tomorrow’s world—today.

Join us and start building tomorrow’s world today!

As a Thermal Hydraulics Analysis Engineer , you will join Derby  team to support our activities within the Nuclear sector. 

You will play a key role in supporting the LOCA fault analysis team, contributing to the delivery of detailed design and GDA Step 3 for advanced nuclear reactor systems.

This role focuses on Loss of Coolant Accident (LOCA) and steam generator tube rupture analyses, using system thermal hydraulics codes to support reactor safety cases and design validation.

You will be working within a highly regulated, safety-critical environment, contributing to the development and assessment of PWR (Pressurised Water Reactor) systems.

• Location: Derby 
• On Site: 1 day / Remote 
• Clearance: BPSS 
• Experience Level: 5-10 

Key Responsibilities:

• Perform LOCA fault studies analysis, supporting ongoing safety and design assessments.
• Conduct thermal hydraulics simulations using tools such as RELAP5-3D, CATHARE, or equivalent.
• Analyse PWR water systems behaviour using 0D, 1D, or CFD modelling approaches.
• Support analysis of steam generator tube rupture faults and related transient scenarios.
• Provide technical input into reactor island system design and safety case development (GDA Step 3 E3S case).
• Interpret simulation results to inform design decisions and safety justifications.
• Collaborate with multi-disciplinary engineering teams to ensure alignment with nuclear safety requirements.
• Contribute to technical documentation and safety case authoring where required.
• Perform advanced thermal analysis and flow simulations using Flowmaster.
• Carry out pressure drop, heat transfer, and system performance calculations.
• Develop and validate models to support complex system designs.
• Collaborate with cross-disciplinary engineering teams (mechanical, systems, safety, and integration).
• Ensure all work is delivered to the highest technical and regulatory standards.
• Contribute to design reviews, technical reports, and project milestones.

Required Skills:

• Strong background in thermal hydraulics and fluid system analysis.
• Experience with system thermal hydraulics codes (e.g. RELAP5-3D, CATHARE).
• Knowledge of PWR technology and nuclear reactor systems.
• Experience in fluid simulations, particularly thermal hydraulics (preferred over general thermofluids).

Required Qualifications:

• Bachelor’s or Master’s degree in Mechanical Engineering, Aerospace Engineering, or related discipline or equivalent military experience.

Desirable Skills:

• Experience in LOCA (Loss of Coolant Accident) analysis.
• Familiarity with nuclear safety case development and regulatory frameworks.
• Experience with CFD tools for thermal-fluid analysis.
• Coding or modelling experience related to PWR system behaviour.

Why join us? 

We bring together entrepreneurial, tech-driven people to deliver innovative solutions for leading companies.

At ALTEN, you’ll work on exciting projects, supported by ongoing learning, mentoring, and clear career development tailored to your goals.

Join a passionate team and help build tomorrow, today.

In short you get: 

• A personalised career path and a rewarding management style 
• A huge diversity of engineering projects and industries
• Private Medical Insurance
• Cycle & Tech Scheme 
• Employee assistance programme
• Life insurance & Pension Scheme
• Social atmosphere, regular gatherings & team buildings
• Flexible way of working (role dependent)

We are proud to support the Armed Forces Covenant & actively encourage applications from members of the Armed Forces community, including veterans, reservists, service leavers, and military spouses/partners. We recognise the value of military skills and experience and are committed to ensuring that no applicant is unfairly disadvantaged during our recruitment and selection processes. 

ALTEN is committed to fostering a diverse and inclusive workplace and values the strength that comes from a global mix of backgrounds and perspectives. We welcome applications from all suitably qualified candidates, regardless of background or protected characteristics under the Equality Act 2010. If you require any reasonable adjustments during the recruitment process, please let us know. 

This role may require you to have or be willing to go through Security Clearance. As part of the onboarding process candidates will be asked to complete a Baseline Personnel Security Standard; details of the evidence required to apply may be found on the government website Gov.UK. If you are unable to meet this and any associated criteria, then your employment may be delayed, or rejected . Details of this will be discussed with you at interview.