Principal Process Engineer, Fuel Cycle

About Helion We are a fusion power company based in Everett, WA, with the mission to build the world's first fusion power plant, enabling a future with unlimited clean electricity. Our vision is a world with clean, reliable, and affordable energy for everyone. Since Helion's founding in 2013, we have raised over $1 billion from long-time investors such as Sam Altman, Mithril, and Capricorn Investment Group as well as new investors SoftBank and Lightspeed to propel us forward. Our last prototype, Trenta, completed 10,000 high-power pulses and reached plasma temperatures of 100 million degrees Celsius (9 keV). We are now operating Polaris, our next prototype on the path to the world's first fusion power plant. This is a pivotal time to join Helion. You will tackle real-world challenges with a team that prizes urgency, rigor, ownership, and a commitment to delivering hard truths – values essential to achieving what no one has before. Together, we will change the future of energy, because the world can't wait. What You’ll Be Doing: You will be at the forefront of designing the world’s first continuous fusion fuel cycle – an opportunity to redefine the future of clean energy for the modern world. This role operates at the intersection of process design, system integration, and program strategy, owning the performance, scalability, and operability of the fuel cycle across its full lifecycle. You'll work collaboratively with Engineering, Science, R&D, Operations, and Leadership, serving as a technical authority focused on setting design direction, resolving first-of-a-kind engineering challenges, and delivering critical systems for an integrated, closed-loop fuel cycle. You will report to the Fuel Cycle Manager and work onsite at our Everett, WA office. You Will: - Own delivery of major fuel cycle systems from concept through integration, including process design, procurement, installation, and commissioning - Define plant-level fuel cycle philosophy and tradeoffs, including operational approach, throughput, energy usage, holdup inventories, and safety across fuel cycle systems - Utilize first-principles analysis, modeling, and rigorous simulation tools to evaluate steady-state, dynamic, and fault scenarios to ensure design operability - Set technical direction for and guide detailed design of process equipment (e.g., columns, reactors, membranes, heaters, exchangers, pumps, and piping) across ambient, high-temp, cryogenic, and vacuum conditions - Develop and maintain core engineering design deliverables (PFDs, P&IDs, H&MBs, HAZOPs, and sizing calculations), ensuring technical rigor and consistency across the program - Drive cross-functional alignment across Science, R&D, EHS, Fuel Cycle Operations, and Plant Engineering to deliver a cohesive and scalable fuel cycle - Lead high-level design reviews as the decision authority, resolving complex technical issues and ensuring alignment with program goals - Ensure technical rigor and alignment of detailed engineering work across team process designs (e.g., columns, reactors, membranes, cryogenic and vacuum systems) - Mentor and develop senior engineers, establish engineering best practices, and shape team capability and technical standards - Represent Helion as a technical authority in external engagements, communicating fuel cycle architecture, design decisions, and program direction through industry forums, conferences, and publications Required Skills: - Bachelor’s or Master’s degree in Chemical Engineering, Mechanical Engineering, Nuclear Engineering, or related field; advanced degree preferred - 12+ years of experience in chemical process design, translating process concepts into first-of-a-kind hardware - Deep technical expertise in transport phenomena (mass, heat, and momentum), thermodynamics, and reaction engineering applied to complex process systems - Decomposition of complex problems into fundamental physical principles, process objectives, and operational constraints to devel