Thermohydraulics Safety Analysis Engineer

Deep Fission is a nuclear technology company pioneering the development of a revolutionary deep borehole pressurized water reactor. We recently completed a private placement financing and Alternative Public Offering and are now operating as a public company while maintaining our startup agility and innovation focus. S.

Nuclear Regulatory Commission (NRC), we are executing our next phase of growth as we advance our groundbreaking nuclear technology toward commercial deployment. Job Summary We are looking for a Thermal-Hydraulic Engineer with 2–5 years of experience to join our T/H Group as a hands-on technical contributor. You will own the development and maintenance of reactor system models, execute steady-state and transient analyses, support code validation and benchmarking activities, and contribute directly to the documentation and analysis packages that underpin our NRC licensing program.

This is not a support role. You will be expected to produce analysis work independently, coordinate across engineering disciplines, and grow your scope as the program matures. You will work alongside experienced nuclear safety and licensing engineers who will provide technical guidance, but the expectation is that you bring enough foundational depth to execute real work from day one.

Key Responsibilities

Thermal-Hydraulic Analysis 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.

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.

Licensing Documentation 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.

Coordination Collaboration 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.

Required Skills Experience 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.