Principal Engineer, Thermal Hydraulics - Remote
About the Role
We are looking for a Principal Engineer to own the computational thermal-hydraulics methods layer: computational two-phase flow and heat transfer, subchannel and CFD-coupled models, and reactor safety code development adapted to the cruciform geometry together with the software that implements them and the verification, validation, and uncertainty quantification that make them defensible to the NRC. This is a builder's role on a small, growing team where methods development and licensing application sit close together.
Key Responsibilities
- Develop computational two-phase flow and heat transfer methods for the HCF geometry — flow, pressure, void, and CHF/DNB distribution in helical, self-spacing bundles where conventional closure relations do not transfer.
- Contribute to reactor safety code development and adaptation (system codes such as TRACE and RELAP5-3D, and subchannel codes such as VIPRE) — constitutive relations, closure models, and geometry treatments for non-cylindrical fuel, supporting LOCA and Chapter 15 analysis.
- Build and maintain analysis software (C++/Fortran/Python) to engineering- and licensing-grade standards, including theory manuals, user documentation, and software requirements/design records.
- Implement coupled subchannel–CFD models to inform closure relations and resolve lobe-scale and rod-to-rod phenomena that one-dimensional methods cannot capture.
- Lead verification and validation — method of manufactured solutions, code-to-code comparison, and validation against separate-effects and integral-effects data — under an NQA-1 quality framework.
- Own the methodology development for the thermal-hydraulic safety case: sensitivity analysis, statistical methods, and the propagation that feeds time-at-temperature and best-estimate-plus-uncertainty LOCA evaluations.
- Contribute to a formal LOCA PIRT exercise and the downstream code-modification roadmap, translating ranked phenomena into prioritized methods development.
- Collaborate across the TH team (subchannel, system-code, CFD) and with national-lab and university partners.
Required Qualifications
- PhD in Nuclear Engineering or a closely related field, plus 10 years of relevant experience.
- Demonstrated development of reactor thermal-hydraulics or reactor safety software — subchannel, system-code, or CFD — including the mathematical modeling, implementation, and documentation.
- Strong foundation in computational two-phase flow and heat transfer, including boiling heat transfer and CHF/DNB physics.
- Strong scientific computing: C/C++, Fortran, and Python; modern build/version-control/testing practice (git, CMake, unit testing).
- Experience with code verification and validation methodology.
Preferred Qualifications
- Reactor safety system-code experience (TRACE, RELAP5-3D, or equivalent) and subchannel code development (VIPRE/COBRA-class), including coupling to commercial CFD (e.g., STAR-CCM+).
- Uncertainty quantification and sensitivity analysis — polynomial chaos, Gaussian-process/surrogate modeling, or nonparametric (order-statistics) methods — applied to long-running simulation models.
- Familiarity with PWR safety analysis, Chapter 15 events, and the LOCA evaluation-model framework (CSAU/EMDAP, 10 CFR 50.46).
- Experience working to an NQA-1 quality program.
- Bubble-dynamics, microlayer, or boiling-closure research background.
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