Senior TH 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. With strategic partnerships in place, strong private and public investment, and active engagement with the U.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

Deep Fission is seeking an experienced Senior Engineer to support performance of thermal-hydraulic (T/H) and nuclear safety analyses in support of the design development and licensing of its first-of-a-kind underground pressurized water reactor (PWR). The reactor concept utilizes standard LEU fuel assemblies and conventional PWR thermal-hydraulic conditions, uniquely sited approximately one mile underground. This role sits within the Thermal-Hydraulics Group and represents a key technical contributor to the reactor’s safety analysis program.

The successful candidate will bring hands-on experience with DOE or NRC accepted system-level codes and analysis methodologies applied to licensed PWR applications. In addition to performing design-basis and beyond-design-basis transient and accident analyses, this engineer will help shape Deep Fission’s overall safety analysis and licensing strategy, support code validation and verification (V&V) activities, and develop the reactor system models used for analysis. Because Deep Fission is an early-stage company, this role requires adaptability and a willingness to take on responsibilities across the broader engineering and licensing program as the project evolves.

Key Responsibilities

• Perform design-basis and beyond-design-basis thermal-hydraulic analyses, including non-LOCA transients, reactivity-initiated accidents (RIAs), loss-of-flow, and station blackout (SBO) scenarios.
• Develop, maintain, and benchmark reactor system models using T/H codes in accordance with applicable regulatory requirements and quality assurance standards.
• Support the development and execution of the Code Validation and Verification (V&V) program, including the preparation of V&V reports and uncertainty quantification in support of NRC licensing submittals.
• Contribute to the development of Deep Fission’s overall safety analysis methodology and licensing strategy, including selection of analysis codes, determination of licensing basis events, and definition of acceptance criteria.
• Prepare and review safety analysis documentation including design-basis accident analyses, safety analysis reports (PSDA/DSA or PSAR/FSAR sections), technical specifications bases, and responses to regulator questions and requests for information.
• Ensure effective coordination with reactor physics, systems, mechanical, 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.
• Promote a proactive nuclear safety culture and advocate for Deep Fission and its technology in technical and regulatory forums.
• Perform additional tasks as requested by management, which may include supporting construction, procurement, startup testing, and operational licensing activities as the project matures.

Required Skills & Experience

• 7+ years of experience performing nuclear thermal-hydraulic and safety analyses in a licensed nuclear application environment.
• Bachelor’s degree in Nuclear Engineering, Mechanical Engineering, or a closely related technical field.
• Demonstrated proficiency in one or more NRC-accepted T/H system codes applied in licensed PWR applications, including RETRAN, RELAP5 (or RELAP5-3D), TRACE, and/or GOTHIC.
• Experience developing and executing reactor system models for design-basis LOCA and non-LOCA analyses, including model development, nodalization, and steady-state benchmarking.
• Working knowledge of NRC regulatory requirements applicable to safety analysis, including 10 CFR Part 50, Appendix K, the Revised Acceptance Criteria (Best-Estimate LOCA), and associated regulatory guides.
• Familiarity with nuclear quality assurance requirements (e.g., 10 CFR 50 Appendix B, NQA-1) and their application to safety analysis and software V&V.
• Proven ability to prepare and review technical documentation intended for NRC review, including safety analysis calculations, topical reports, or FSAR sections.
• Ability to work effectively in a virtual and hybrid team environment with multiple interfaces and stakeholders.
• Must be a U.S. person eligible to meet DOE Export Control requirements under 10 CFR 810.

Desired Skills & Experience

• Master’s degree or Ph.D. in Nuclear Engineering or Mechanical Engineering.
• Licensed Professional Engineer (PE) in a relevant discipline.
• Direct experience supporting NRC licensing submittals, including topical report preparation, RAI responses, and/or ACRS interactions.
• Experience developing or contributing to a safety analysis methodology program at a reactor vendor, utility, or nuclear engineering firm.
• Familiarity with uncertainty quantification methods (e.g., CSAU, ASTRUM, or similar statistical approaches) for best-estimate T/H analyses.
• Experience with first-of-a-kind nuclear designs, SMRs, or novel licensing pathways (10 CFR Part 52 or emerging 10 CFR Part 53 framework).
• Proficiency with scripting tools (Python, MATLAB) for model automation, post-processing, and sensitivity studies.
• Experience with AI-enabled engineering platforms and modern simulation toolchains.

Key Competencies

• Technical Depth – Advanced understanding of thermal-hydraulic phenomena in light water reactor systems, including two-phase flow, critical heat flux, natural circulation, and reactor transient behavior.
• Licensing Acumen – Ability to translate regulatory requirements into defensible analysis approaches and documentation that will withstand NRC scrutiny.
• Strategic Thinking – Capacity to help define and advance Deep Fission’s safety analysis and licensing approach at both the technical and programmatic level.
• Adaptability/Resilience – Ability to thrive in an early-stage, resource-constrained environment, adjusting priorities and scope as the project evolves.
• Organizational – Experience functioning within structured engineering programs with multiple engineering disciplines, subcontractors, and regulatory stakeholders.
• Communication – Demonstrated ability to clearly convey complex technical concepts in written reports and verbal presentations to both internal teams and external regulators.

Our Commitment: 

Deep Fission is an equal opportunity employer committed to building a diverse and inclusive workplace. We welcome applicants from all backgrounds who share our passion for advancing clean nuclear energy and creating a sustainable future. We do not discriminate on the basis of race, color, creed, religion, ancestry, age, sex, marital status, national origin, disability, veteran status, or any other characteristic protected by applicable law.