Thermohydraulics Safety Analysis Engineer

Deep Fission is a nuclear technology company pioneering the development of a revolutionary deep borehole pressurized water reactor. They are seeking a Thermal-Hydraulic Engineer to develop and maintain reactor system models, execute analyses, and contribute to documentation for NRC licensing. The role requires independent work and collaboration across engineering disciplines to support the advancement of their nuclear technology.

Responsibilities:

• Develop, run, and interpret steady-state and transient system-level T/H simulations using codes such as RELAP5, RELAP5-3D, TRACE, RETRAN, or MOOSE
• Perform design-basis analyses including non-LOCA transients, loss-of-flow, station blackout (SBO), and reactivity-initiated accidents (RIA), with mentorship available for less familiar event types
• Build and maintain reactor system nodalization models; perform steady-state benchmarking against design data and code-to-code comparisons
• Conduct sensitivity studies and post-process simulation results using Python, MATLAB, or equivalent scripting tools
• Support V&V activities for T/H system codes in accordance with applicable regulatory requirements and NQA-1 quality assurance standards
• Develop and maintain analysis procedures, calculation packages, and QA documentation consistent with licensing-grade standards
• Assist in the development and application of Deep Fission’s safety analysis methodology, including licensing basis event identification and acceptance criteria
• Prepare clear, well-organized technical analysis reports and calculation packages suitable for internal design reviews and NRC licensing submittals
• Support preparation of safety analysis report (SAR) sections and responses to NRC Requests for Additional Information (RAIs) under the direction of senior staff
• Contribute to licensing basis documentation as the design and safety basis evolves through the regulatory process
• Coordinate with reactor physics, systems engineering, mechanical design, and licensing teams to maintain technical alignment across the design and safety basis
• Participate in design reviews, safety review committee activities, and in-person technical workshops
• Support nuclear safety culture and contribute to technical discussions in both internal and regulatory forums as your experience and confidence grow

Requirements:

• 2–5 years of professional or research experience in nuclear or mechanical engineering, applying thermal-hydraulic analysis methods in a nuclear, research, or closely related technical environment
• Bachelor's degree in Nuclear Engineering, Mechanical Engineering, or a closely related technical field
• Demonstrated hands-on experience — professional or research — with at least one T/H system code applicable to light water reactor analysis: RELAP5, RELAP5-3D, TRACE, RETRAN, or MOOSE
• Working knowledge of reactor system nodalization, steady-state benchmarking, and transient simulation for LWR applications
• Familiarity with NRC regulatory requirements for nuclear safety analysis (e.g., 10 CFR Part 50); direct professional experience is preferred but academic exposure is acceptable
• Working awareness of nuclear quality assurance principles (e.g., 10 CFR 50 Appendix B, NQA-1) as applied to engineering calculations and technical documentation
• Ability to produce clear, well-organized technical documentation; some experience contributing to licensing-grade calculations or NRC submittals is a plus
• Comfortable working independently and across disciplines in a virtual and hybrid team environment
• Must be a U.S. person eligible to meet DOE Export Control requirements under 10 CFR 810
• Ability to travel up to 20%
• Master's degree or Ph.D. in Nuclear Engineering or Mechanical Engineering
• Experience contributing to a safety analysis or T/H methodology program at a reactor vendor, national laboratory, utility, or nuclear engineering consultancy
• Exposure to NRC licensing submittals — topical reports, RAI responses, or ACRS interactions — in any capacity
• Familiarity with uncertainty quantification methods (e.g., CSAU, ASTRUM, or statistical analysis approaches) for best-estimate T/H analyses
• Familiarity with advanced reactor designs, SMRs, or novel reactor concepts (e.g., underground siting, microreactors, Generation IV designs); exposure to 10 CFR Part 53 or emerging 10 CFR Part 57 licensing pathways is a meaningful plus
• Proficiency with Python or MATLAB for scripting, post-processing, and model automation
• Exposure to AI-enabled engineering platforms or modern simulation toolchains