Mechanical System Design Engineer – Nuclear Island

Do you want to contribute to the development of a new energy technology that can safely turn nuclear waste into emission-free energy? Are you excited about working in a hands-on deep tech start-up team that aims to make a huge impact? Do you like complex challenges? Then, we might be just the company you are looking for

We are looking for a Mechanical System Design Engineer – Nuclear Island to join an innovative and international team.

About the client

Our client designs and creates frontier technology for Molten Salt Reactors (MSR). They currently have a team of ~40 spread across Amsterdam and Lyon, all working together to develop nuclear power solutions. They are in the development phase and aim to solidify their design through analyses, experiments, simulations, and partnerships.

The primary location of the role will be in Lyon.

Your mission

As a Mechanical System Design Engineer – Nuclear Island you will advance the reactor design by strong cross-functional teamwork. You will deliver the design of specific reactor (sub)systems and components and interact with subcontractors and suppliers. Based on your engineering background you can develop a strong technical understanding of the reactor concept which allows you to execute short term engineering activities in line with our long-term mission.

You have a strong content on nuclear technology, mechanical system engineering, with thorough technical background and experience on nuclear process system, heating/cooling system, knowledge on nuclear safety (knowledge of ISO 15288) and combine this with excellent teamwork, people and stakeholder management and communication skills.

This role is based in Lyon.

Responsibilities

• Work together with a larger team of technical engineers to progress the reactor design.
• Work in cross-functional workstreams in the development program (typically a project-based team of ~3-6 engineers from different disciplines such as nuclear engineering, core physics, thermal hydraulics, chemistry)
• Work on one or more assigned (sub)systems / components, towards quarterly priorities in line with the long-term program deliverables.
• Define, validate and verify (functional) requirements for the system, optimize the design to deliver on those requirements, and manage trade-offs in the design envelope. (e.g., reliability, performance, lifetime, costs) while continuously ensuring maximum safety.
• Initiate projects with our expert engineers that support you with analyses, validation, verification and qualification.
• Inspect the market on different technologies and different suppliers
• Select, qualify and manage external contractors that support you in your mission.
• Deliver system documentation, prepare design reviews, and ensure system integration.
• Build documentation and presentation to enable licensing discussion with safety authorities.
• Conduct engineering work for these workstreams (e.g., component and system design, computer models and analyses to simulate safety and performance)
• Support program management by coordinating meetings, communicating with external partners, and leading specific projects.
• Work very closely with your team leader (Nuclear Island System Lead), the program office, COO, CTO, and the rest of the teams in Lyon and Amsterdam
• Report to the System Lead, in the COO line

Qualifications and Experience

• Experienced multidisciplinary engineer with 7+ years in nuclear system design (liquid or gas process systems).
• Knowledge and understanding of these disciplines are mandatory to succeed in the role: mechanical, neutronic, chemistry (corrosion), thermodynamic, structural
• Mechanical design expertise, particularly in piping and pumps
• Proficiency in 3D modeling software like SolidWorks, CATIA, or AutoCAD
• Industrial experience, including production chains
• Ideally nuclear project background, covering commissioning, safety, design, and installation
• Skills in system design, operation, system sizing, and piping stress calculations
• Strong strategic and technical skills: connects design drivers to requirements, roadmaps, and objectives in complex projects.
• Excellent stakeholder management, ownership, and adaptability in fast-paced environments, with experience in scale-ups or new designs.
• Pioneer mindset, quick learner, and potential leader in complex topics.
• Master's degree in engineering; fluent in English (French/Dutch a plus).
• Willing to travel between Lyon and Amsterdam.

Gintare Juozapaviciute