Thermal-Hydraulics Engineer

Your mission

You will work at the heart of our reactor development, using modelling, simulation and experiments to understand how our systems behave and to guide the engineering choices we make. Your work will cover a broad range of questions, from the behaviour of individual components to the interaction of thermal-hydraulics with the wider reactor system.

You will work closely with colleagues in system engineering, nuclear safety, neutronics, chemistry, mechanics and other areas of expertise. Together, you will translate complex physical behaviour into practical design decisions.

Your expertise will matter not only because of the analyses you perform, but because of the judgement you bring to the project. We are looking for someone who knows when a question requires sophisticated modelling, when a pragmatic engineering approach is sufficient, and when an assumption needs to be challenged.

You will also help us close the loop between simulation and reality. You will contribute to defining experiments, tests and prototypes that allow us to validate our models, challenge our assumptions and demonstrate that our innovations work outside the computer.

Depending on the stage of the technology, your work may support our non-nuclear Pilot, the Pioneer nuclear demonstrator or the future FOAK and NOAK reactor designs.

This is an opportunity to have a real impact on the development of a novel nuclear technology while helping build the thermal-hydraulics capability of a growing deep-tech company.

This role is based in Amsterdam, Netherlands or Lyon, France.

• Own and deliver thermal-hydraulics analyses that support important reactor and system design decisions.
• Translate engineering questions and system requirements into appropriate thermal-hydraulic models, simulations and analyses.
• Select the right modelling approach and computational tool for each problem, balancing accuracy, complexity, available data and project needs.
• Perform high-quality CFD and system-level thermal-hydraulic studies and critically assess the results.
• Analyse thermal-hydraulic behaviour across different levels of the reactor design, from components and systems to integrated reactor behaviour.
• Investigate relevant reactor transients and the interaction between thermal-hydraulics and other physical phenomena, including neutronics.
• Work with system engineers to assess and improve the design of thermal-hydraulic systems and components, including heat exchangers, pumps and related equipment.
• Develop and improve modelling methodologies and tools that strengthen Thorizon's engineering capabilities, building computational workflows involving data preparation, simulation, post-processing and, where appropriate, coupling between different tools and physical models.
• Contribute to the verification and validation of computational tools and models used to support design and safety decisions following high standards like ASNR guide 28 and the execution of the thermal-hydraulic validation programme, including work performed with external research and engineering partners.
• Help identify where experiments, tests or prototypes are needed to increase confidence in the technology.
• Review technical work produced internally and externally and challenge assumptions, methods and conclusions where appropriate. Support the technical specification and management of external specialists, engineering contractors and suppliers.
• Provide technical guidance to colleagues and share your knowledge and good practices with the wider engineering team.
• Participate in technical exchanges with regulators and external experts when thermal-hydraulics is relevant to the project.
• Contribute to international initiatives and technical networks in thermal-hydraulics and advanced nuclear technology, including relevant IAEA and Euratom activities.
• Keep up with developments in modelling techniques, computational tools, experimental methods and thermal-hydraulics applied to advanced nuclear systems.
• Work across different project teams and contribute to building a strong and collaborative thermal-hydraulics capability at Thorizon.

• Master’s degree in nuclear engineering, mechanical engineering, fluid mechanics, heat transfer, applied mathematics, or a related technical discipline.
• PhD in nuclear engineering, fluid mechanics, heat transfer, numerical methods, or a related field is an advantage.
• Around 8 years or more of relevant professional experience in thermal-hydraulics, CFD, reactor engineering, or a closely related field.
• Strong hands-on experience with CFD methods, including RANS, LES and/or DES.
• Professional experience with CFD tools such as OpenFOAM, STAR-CCM+ or Fluent.
• Experience with thermal-hydraulic system codes such as SPECTRA, CATHARE, TRACE or ATHLET.
• Strong command of numerical methods and modelling approaches, with the ability to select an appropriate level of modelling for the engineering question at hand.
• Experience designing, developing or using complex computational…