Senior Nuclear Engineer

About Us At Antares, our long-term mission is to make clean energy abundant from Earth to the Asteroid Belt. We’re fueled by the belief that advanced nuclear energy can strengthen our military, solve the climate crisis, elevate global living standards, and expand humanity's presence in outer space. To achieve our mission, we’re building mass-producible, inherently safe, deployable microreactors that can be used terrestrially, underwater, and in space. The Antares team hails from SpaceX, the White House, the Pentagon, the Department of Energy, MIT, Rigetti Computing, General Atomics, Relativity Space, Ursa Major, and National Laboratories like Idaho, Oak Ridge, Los Alamos, and Savannah River. Antares has raised over $600M in venture capital from top-tier investors and has hundreds of million-dollars on contract with the military services, NASA, and the Department of Energy. About the Role As a member of the nuclear engineering team, you will become the responsible engineer for a key component of the Antares reactor design such as reactivity controls and instrumentation, radiation shielding, fuels, materials, thermal hydraulics, safety, or licensing. The ideal candidate has a mix of industry and academic experience, and has worked in a team-oriented environment to mature nuclear concepts. While you may have a specialty, you’re not afraid to operate as a generalist in a growing organization. Roles and Responsibilities: You will develop and provide expertise in a subset of the following: Lead complex neutronics modeling and Multiphysics analysis Responsible nuclear engineer for design and integration of components as assigned Mentor junior engineers Develop and implement modeling and simulation methods and tools Coordinate validation and verification activities Interface directly with regulatory bodies for licensing and compliance Spearhead prototype testing and experimental campaigns Lead cross-disciplinary integration efforts across neutronics, thermal-hydraulics, structural mechanics, materials, and reactor operations to ensure design margins are maintained across all Figures of Merit (FOMs) and safety-critical performance metrics Identify and define validation, verification, qualification, and testing requirements across engineering disciplines, including opportunities to leverage startup, commissioning, and power ascension testing data for model development and design maturation Basic Qualifications: Master's or Ph.D. in Nuclear Engineering, Physics, or related field Deep experience with and understanding of MCNP, Serpent, or SCALE Experience with Multiphysics simulations and methods (thermal-hydraulics, structural, heat transfer), reactor kinetics, safety analysis, or integrated systems modeling Preferred Skills & Experience: Advanced programming proficiency (Python, C++, or similar) Experience designing or developing high temperature gas reactors, heat pipe cooled reactors, microreactors, TRISO fuel, or other advanced reactors Strong leadership and mentorship skills Demonstrated success in regulatory processes (DOE, NRC, DoD) Previous experience at dynamic tech companies or startups Experience with advanced reactor transient and systems analysis tools such as SAM, AGREE, PARCS, or equivalent nuclear systems codes Experience with reactor commissioning, startup testing, power ascension testing, and operational readiness activities for nuclear systems Deep understanding of reactor shielding design, radiation transport analysis, and variance reduction methodologies, including experience with ADVANTG, MAVRIC, Attila4MC, or equivalent tools Experience performing integrated nuclear-thermal-mechanical analyses for reactor structures and components, including structural graphite, high-temperature steels, and other advanced reactor materials Demonstrated ability to maintain design margins and performance requirements across coupled neutronic, thermal, mechanical, materials, and operational domains Strong systems engineering mindset w