Senior/Principal Fluids System Design Engineer

Company Description Hadron Energy specializes in Micro Modular Reactor (MMR) development, design, and research based in the San Francisco Bay Area. As a leading MMR developer, Hadron Energy is building factory-produced, transportable microreactors that provide 24/7 carbon-free power for data centers, government facilities, industrial sites, and remote communities. Our mission is to create a brighter, healthier, and more equitable energy future. Role Description This is a full-time role for a Senior or Principal Fluids Engineer, based in the San Francisco Bay Area or Remote. The position is ideal for candidates with strong mechanical engineering and fluids system design fundamentals, and deep technical expertise in the design and analysis of fluids systems in light water reactor applications, who are passionate about advancing safe, scalable nuclear technology. You will work closely with our cross-functional team to lead the design, sizing, and analysis of fluid systems and equipment in the MMR. The role focuses on primary and secondary loop fluid mechanics, heat exchangers, pumps, valves, and piping networks, ensuring that all hardware meets product requirements as well as rigorous nuclear industry codes and standards in a fast-paced startup environment. Responsibilities Lead the design and analysis of primary, secondary, and auxiliary fluid systems, including sizing of pumps, valves, heat exchangers, and piping networks. Develop P&IDs, PFDs, functional requirements, system descriptions, and equipment specifications for fluid systems. Perform single-phase and two-phase sizing studies and flow analyses, including hydraulic loss calculations, pressure transient evaluations, and net positive suction head (NPSH) studies. Develop and execute sizing studies for heat transfer characterization. Perform trade studies to optimize safety, simplicity, reliability, cost and schedule while meeting system requirements and interface needs. Support planning of fluid system design activities to advance each system to Final Design. Perform rigorous peer reviews and contribute to QA documentation per ASME NQA-1 and engineering procedures. Mentor junior engineers and serve as a technical point of contact for fluid systems and thermal-hydraulic component engineering. Required Qualifications and Skillsets Bachelor's, Master's, or PhD in Mechanical Engineering, Nuclear Engineering, Chemical Engineering, or a closely related field. Minimum 8 years (Senior) / 12+ years (Principal) of relevant experience in fluid system design engineering, thermal-hydraulic component design, or power plant fluid systems. Experience designing and analyzing light water reactor fluid systems. Strong fundamental understanding of single-phase and two-phase fluid mechanics, convective heat transfer, boiling, and natural circulation. Demonstrated experience designing and analyzing pumps, valves, heat exchangers, and piping networks. Hands-on proficiency with system-level thermal hydraulic analysis. Working knowledge of ASME B31.1 / B31.3, ASME Section III, ASME OM, TEMA, and applicable NRC SRP / RG guidance for fluid systems. Experience working under stringent quality assurance programs such as ASME NQA-1, MIL-Q-9858A, or ISO-9000. Exceptional technical writing and oral communication skills; ability to clearly translate analytical results into design decisions. A high degree of integrity, a desire to foster teamwork, and a passion for solving the complex challenges of clean energy.