Nuclear Criticality Safety Engineer

Oak Ridge, TN | $145K–$180K | Hybrid | Relocation Assistance Available

Take ownership of criticality safety for the fuel lifecycle of the KRONOS MMR, a High-Temperature Gas-Cooled Reactor (HTGR) fueled by ceramic matrix TRISO fuel.

This role goes beyond performing individual calculations. You’ll establish and defend the criticality safety basis for out-of-core fuel operations spanning fresh and irradiated fuel handling, transportation, storage, qualification materials, test specimens, irradiation support, PIE activities, and material disposition.

Reporting jointly to the Reactor Fuel Design Manager and Reactor Design Manager, you’ll work across fuel design, performance, transportation, and qualification programs to ensure inherently safe configurations and rigorous nuclear quality standards.

• Own criticality safety analysis across handling, transportation, storage and qualification activities.
• Work directly with HALEU, TRISO fuel, graphite and ceramic moderation, and HTGR fuel configurations.
• Influence both fuel design and reactor design through a highly cross-functional role.
• Establish safety limits and controls for credible accident and upset scenarios.
• Apply advanced criticality methods using MCNP, SCALE/KENO, benchmark validation, bias and uncertainty, and sensitivity/similarity methods.
• Build qualification-grade safety documentation under rigorous NRC and nuclear QA requirements.

• Execute criticality safety analyses for fresh and irradiated fuel movement, including reactor-site transportation and inter-facility transfers.
• Define and validate geometric and moderation constraints for fresh-fuel and spent-fuel storage configurations.
• Model credible accident scenarios, including inadvertent moderation and geometric reconfiguration during handling events.
• Establish preventive and mitigative controls that maintain required subcritical margins.
• Partner with fuel design, fuel performance, and transportation teams to ensure handling equipment and transport casks maintain inherently safe configurations.
• Develop configuration-controlled criticality evaluations, validation reports, calculation packages, and operational limits in accordance with ASME NQA-1 and NRC requirements.
• Define and approve the criticality safety basis for HALEU-bearing qualification materials, fuel lots, test specimens, fabrication activities, packaging, shipments, irradiation support, PIE handling, and waste or residue disposition.

• Degree in Nuclear Engineering, Physics, or a related highly technical discipline.
• 5+ years of nuclear criticality safety experience, including authorship and independent defense of evaluations involving fissile-material processing, laboratories, storage, or transportation.
• Proficiency with industry-standard criticality safety codes such as MCNP and SCALE/KENO.
• Demonstrated experience establishing code validation, benchmark applicability, calculational bias and uncertainty, and subcritical margins using recognized critical experiments and sensitivity/similarity methods.
• Working knowledge of applicable ANSI/ANS-8 standards, double-contingency principles, criticality alarm and emergency-planning interfaces, and engineered and administrative controls.
• Experience analyzing enriched uranium and heterogeneous fuel configurations involving powders or kernels, TRISO particles, graphite or ceramic moderation, arrays, reflection, interaction, and credible upset conditions.
• Experience developing configuration-controlled evaluations and calculation packages under ASME NQA-1, 10 CFR Part 50 Appendix B, DOE, or equivalent nuclear software-quality requirements.