Senior Nuclear Engineer
Confirmed on the employer's own hiring board on Nov 1, 2026. First seen by Alion on Aug 5, 2026. Antares Nuclear scores A on the Alion truth index.
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 with the ability to work effectively across disciplinary interfaces and identify data needs for validation, verification, qualification, and licensing activities
Experience planning and executing experimental programs to generate qualification data, including leveraging commissioning and power ascension campaigns to supplement analytical and modeling efforts
Understanding of fuel and materials irradiation effects, in-pile testing methodologies, and qualification approaches for advanced reactor systems and components
Experience developing qualification strategies for reactor components, fuels, and materials through a combination of analysis, testing, irradiation campaigns, and operational data collection
Culture
At 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:
Think 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
Obsess 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
Be 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”
Go 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
Operate in the Grey - Embrace nuance in pursuit of truth. Question every fundamental assumption
Equal Opportunity
Antares 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.
ITAR Requirements
To 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. Learn more about the ITAR here.