Nuclear Fuel Performance Engineer

The Nuclear Fuel Performance Engineer will develop and validate models to predict TRISO fuel behavior in ZettaJoule’s High-Temperature Gas-cooled Reactor (HTGR) under normal operating and accident conditions. Key responsibilities include using BISON to model fuel coating stresses, particle failure probabilities, and fission product release; developing Python-based simulation automation; performing uncertainty and sensitivity analyses; and validating models against experimental data. The role also supports fuel qualification, safety analysis, NRC licensing documentation, and collaboration with fuel suppliers and national laboratories. Ideal candidate: A nuclear, materials, or mechanical engineer with hands-on TRISO fuel modeling experience in BISON, strong Python automation skills, and experience in nuclear fuel performance analysis and technical documentation. A minimum of 5 years of relevant experience with a bachelor's degree, 3 years with a master's degree, or a relevant PhD is required. Key screening priorities: Direct BISON/TRISO modeling experience, fuel failure and fission product transport analysis, Python workflow automation, and nuclear quality assurance experience.

Nuclear Fuel Performance Engineer

Location: Houston, TX, Bellevue, WA or Remote

Employment Type: Full Time

Reports To: Director, Safety and Thermal Hydraulics

About Us

We are a next-generation nuclear technology startup pioneering the commercialization of High-Temperature Gas-cooled Reactors (HTGRs) - a proven, safe, and transformative technology for delivering ultra-high-temperature heat and enabling a carbon-neutral future.

Our mission is to deploy the world’s first global fleet of Advanced Modular Reactors, redefining how clean energy powers industries, communities, and economies.

As a fast-growing company in its early stage, every team member — whether in engineering, program management, partnerships, operations, or business development — plays a direct role in shaping our technology, culture, and impact. You’ll join a collaborative, mission-driven team of internationally recognized experts and innovators working together to bring advanced nuclear energy to the world.

The Role

The Nuclear Fuel Performance Engineer will be a key contributor to ZettaJoule’s reactor design activities, responsible for predicting and demonstrating the performance of the TRISO particle fuel in our High-Temperature Gas-cooled Reactor (HTGR) during normal operation and accident conditions. Working at the intersection of core design, safety analysis, materials, and licensing, this role builds and runs BISON models to quantify coating-layer stresses, particle failure probabilities, and fission product release. The engineer develops the Python-based automation and calculation packages that support the fuel design basis, the mechanistic source term, and ZettaJoule’s fuel qualification strategy, and works closely with Reactor Physics, Thermal Hydraulics, Materials Engineering, and our fuel supplier to ensure that operating histories, fuel specifications, and material properties are applied correctly.

Key Responsibilities

• Perform BISON fuel performance analyses of TRISO fuel, from single particles to fuel elements, for normal operation, anticipated operational occurrences, and accidents (e.g., loss of forced cooling), and document results in formal calculation packages.
• Evaluate kernel and coating-layer behavior and quantify particle failure probabilities for mechanical and thermochemical failure mechanisms, including pressure vessel failure, IPyC cracking and debonding, kernel migration, and fission product attack on SiC.
• Model fission product diffusion and release from intact and failed particles through the fuel matrix and graphite, and provide release inputs to the mechanistic source term.
• Work with Reactor Physics and Thermal Hydraulics to define power, burnup, fast fluence, and temperature histories for normal operation and transients, and identify limiting fuel conditions across the core.
• Build and maintain Python automation for the fuel performance workflow — input generation, parametric studies, HPC job management, and post-processing — using version control and testing practices that keep analyses reproducible and auditable.
• Perform uncertainty quantification and sensitivity analysis (e.g., MOOSE Stochastic Tools Module, RAVEN, or Dakota) on fuel specifications, material properties, and operating conditions to establish defensible margins.
• Validate models against DOE AGR program and other irradiation, post-irradiation examination, and safety-testing data; benchmark against codes such as PARFUME; and identify data gaps that require additional testing.
• Work with the fuel supplier and Materials Engineering to review fuel specifications and product acceptance data, including as-manufactured defect fractions, and assess their impact on performance margins.
• Develop fuel design criteria and limits (e.g., temperature, burnup, and fluence), and support definition of specified acceptable system radionuclide release design limits (SARRDLs) with Safety Analysis and Licensing.
• Prepare fuel performance and fuel qualification content for licensing submittals, including the fuel performance evaluation model, consistent with NRC guidance such as NUREG-2246, and support ZettaJoule’s engagement with regulators.
• Manage analysis vendors and national laboratory collaborations, and perform independent review and verification of calculations, including qualification of BISON and in-house Python tools under a nuclear quality assurance program (10 CFR 50 Appendix B / NQA-1).

What You'll Bring

• BS in Nuclear Engineering, Materials Science, Mechanical Engineering, or a related field required; MS or PhD preferred.
• Minimum 5 years of nuclear fuel performance modeling experience with a BS, 3 with an MS, or a relevant PhD.
• Direct, hands-on experience modeling TRISO fuel in BISON, including its coating-layer material, failure probability, or fission product transport models.
• Proficiency in Python, with demonstrated experience automating simulation workflows (input generation, parametric studies, HPC job submission, and post-processing).
• Experience preparing formal calculation packages and technical reports, preferably under a nuclear quality assurance program.

Citizenship

U.S. citizenship or U.S. permanent resident status is required. Access to EAR-controlled and 10 CFR 810-governed nuclear technology requires authorization consistent with U.S. export control law.

Even Better

• Experience applying BISON TRISO analyses to the design or licensing of a TRISO-fueled reactor (e.g., HTGR, FHR, or heat-pipe microreactor).
• Experience with PARFUME or other TRISO codes, and familiarity with AGR program results.
• Experience coupling BISON with reactor physics or thermal-hydraulics codes (e.g., Griffin, Pronghorn, SAM).
• Experience developing MOOSE/BISON source code in C++ (e.g., custom material or failure models).
• Experience supporting NRC licensing of advanced reactor fuel, such as fuel qualification or mechanistic source term submittals.

Why Work for Us

Join an early-stage team bringing High-Temperature Gas-cooled Reactor (HTGR) technology to commercial deployment. Your analyses will directly shape the fuel design basis, the safety case, and the licensing path for the first fleet of Advanced Modular Reactors. You’ll work alongside internationally recognized experts in a role with real ownership and visible impact.

Compensation & Benefits

• Base salary: $140,000 – $185,000, based on experience and qualifications
• Equity and bonus: discretionary equity and bonus opportunities
• Health: medical, dental, and vision insurance
• Insurance: life and disability insurance
• Retirement: 401(k) retirement plan
• Time off: vacation, Sick and Holiday
• Flexibility: flexible hours and remote work options

EEO Statement

ZettaJoule is an Equal Employment Opportunity employer committed to diversity and inclusion.