{"id":231288,"url":"https://alion.io/job/antares-nuclear-inc-senior-nuclear-engineer","title":"Senior Nuclear Engineer","company":{"id":1877835,"name":"Antares Nuclear","domain":"antaresindustries.com","url":"https://alion.io/company/antaresindustries","size_band":"201-500","is_staffing_agency":false,"employer_type":"direct","is_intermediary":false,"listed_via":null,"ats_vendor":"Ashby","truth_index":{"grade":"A","score":90,"open_postings":5,"ghost_share":0,"stale_share":0.4,"repost_share":0,"time_to_fill_p50_days":54,"computed_at":"2026-11-04T06:34:25Z"}},"role":"Energy","role_family":"Energy","seniority":"senior","employment_type":"full_time","work_mode":"on_site","remote_scope":null,"remote_scope_basis":null,"remote_working_hours":null,"hiring_geo_confidence":"structured","locations":["Los Angeles, United States"],"countries":["US"],"hiring_countries":[],"hiring_countries_total":0,"salary":{"min":160000,"max":210000,"currency":"USD","period":"year","gross":null,"usd_annual":210000},"salary_estimate":null,"experience_years_min":null,"visa_sponsorship":false,"relocation_package":false,"has_equity":false,"technologies":[{"name":"MCNP","optional":false},{"name":"C++","optional":true},{"name":"Python","optional":true}],"status":"live","first_seen_at":"2026-08-05T17:14:41Z","employer_posted_date":"2026-08-05","last_verified_at":"2026-11-04T12:05:58Z","board_verified":true,"closed_at":null,"days_open":90,"trust":{"level":"ok","repost_count":null,"flags":[],"days_open":90},"description":"About Us\nAt 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.\nThe 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.\nAbout the Role\nAs 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.\nRoles and Responsibilities:\nYou will develop and provide expertise in a subset of the following:\n\nLead complex neutronics modeling and Multiphysics analysis\n\nResponsible nuclear engineer for design and integration of components as assigned\n\nMentor junior engineers\n\nDevelop and implement modeling and simulation methods and tools\n\nCoordinate validation and verification activities\n\nInterface directly with regulatory bodies for licensing and compliance\n\nSpearhead prototype testing and experimental campaigns\n\nLead 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\n\nIdentify 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\n\nBasic Qualifications:\nMaster's or Ph.D. in Nuclear Engineering, Physics, or related field\n\nDeep experience with and understanding of MCNP, Serpent, or SCALE\n\nExperience with Multiphysics simulations and methods (thermal-hydraulics, structural, heat transfer), reactor kinetics, safety analysis, or integrated systems modeling\n\nPreferred Skills & Experience:\nAdvanced programming proficiency (Python, C++, or similar)\n\nExperience designing or developing high temperature gas reactors, heat pipe cooled reactors, microreactors, TRISO fuel, or other advanced reactors\n\nStrong leadership and mentorship skills\n\nDemonstrated success in regulatory processes (DOE, NRC, DoD)\n\nPrevious experience at dynamic tech companies or startups\n\nExperience with advanced reactor transient and systems analysis tools such as SAM, AGREE, PARCS, or equivalent nuclear systems codes\n\nExperience with reactor commissioning, startup testing, power ascension testing, and operational readiness activities for nuclear systems\n\nDeep understanding of reactor shielding design, radiation transport analysis, and variance reduction methodologies, including experience with ADVANTG, MAVRIC, Attila4MC, or equivalent tools\n\nExperience performing integrated nuclear-thermal-mechanical analyses for reactor structures and components, including structural graphite, high-temperature steels, and other advanced reactor materials\n\nDemonstrated ability to maintain design margins and performance requirements across coupled neutronic, thermal, mechanical, materials, and operational domains\n\nStrong systems engineering mindset with the ability to work effectively across disciplinary interfaces and identify data needs for validation, verification, qualification, and licensing activities\n\nExperience planning and executing experimental programs to generate qualification data, including leveraging commissioning and power ascension campaigns to supplement analytical and modeling efforts\n\nUnderstanding of fuel and materials irradiation effects, in-pile testing methodologies, and qualification approaches for advanced reactor systems and components\n\nExperience developing qualification strategies for reactor components, fuels, and materials through a combination of analysis, testing, irradiation campaigns, and operational data collection\n\nCulture\nAt Antares, we like to specifically tie each role to our founding document’s set of values-here are the top five cultural values we think you should believe at your core to be successful:\nThink in Systems - Energy and Defense are complex ecosystems with numerous stakeholders with competing priorities, conflicting policies, perverse incentives, and emergent and path-dependent properties. First principles thinking alone is insufficient. Think probabilistically and then take action. “If you want to be certain, then you are apt to be obsolete.” Over-optimizing the components often degrades the system\n\nObsess over the End User - The customer and end user are often not the same. We will never build globally competitive commercial products if we lose sight of our end users and their entire interaction with the product life cycle\n\nBe Unconstrained by Convention - Our only limits are the laws of physics. Many, even experts, will say what we are working on is impossible. They said the same about SpaceX reusing rockets. Generationally impactful companies, by definition, must accomplish the seemingly impossible. If it were easy, it would have already been done. Never shy away from a solution because it has never been tried before, and never choose to do something because that's “how it's always been done”\n\nGo Where the Work Is - Never miss a chance to meet a customer, user, or stakeholder face to face, even if that means hopping on a plane. If you can’t make it, find a teammate who can channel your intentions and go in your place. Deep work can be done from anywhere, but we believe teams are built in person, and aim to maximize our time together\n\nOperate in the Grey - Embrace nuance in pursuit of truth. Question every fundamental assumption\n\nEqual Opportunity\nAntares is an Equal Opportunity Employer. Employment decisions are based solely on merit, competence, and qualifications, without regard to race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability, or any other legally protected status.\nITAR Requirements\nTo conform to U.S. Government export regulations, applicant must be a (i) U.S. citizen or national, (ii) U.S. lawful, permanent resident (aka green card holder), (iii) Refugee under 8 U.S.C. § 1157, or (iv) Asylee under 8 U.S.C. § 1158, or be eligible to obtain the required authorizations from the U.S. Department of State. 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