Principal Engineer, Safety Methods

TerraPower LLC.•Bellevue, WA

9d•$153,862 - $205,149•Onsite

About The Position

This role supports the development, enhancement, and deployment of plant‑scale thermal‑hydraulic analysis methods and models for the Natrium reactor. Reporting to the Manager, Plant Thermal Hydraulics Methods, the principal engineer supports the creation, improvement and qualification of advanced system-level modeling approaches that enable accurate, robust prediction of plant behavior across operational and transient scenarios. The position requires expertise in system‑level thermal‑hydraulics, thermal‑fluids behavior, and the formulation of computational methods and closure models that represent complex reactor phenomena.

Requirements

Degree in Mechanical, Nuclear, Chemical Engineering, or similar field, with 12+ years of experience in system‑level thermal‑hydraulic modeling and method development for nuclear or complex energy systems.
Demonstrated experience in developing or improving analysis methods, including numerical scheme development, closure model formulation, and stability/accuracy optimization strategies.
Experience performing system‑level thermal‑hydraulic analyses using tools such as RELAP5‑3D, GOTHIC, SAS, or equivalent, with the ability to extend or tailor modeling approaches within these frameworks.
Strong foundation in thermal‑fluids and reactor system behavior, including complex thermal‑hydraulic phenomena relevant to advanced reactor designs.
Experience in sensitivity analyses and model gap identification that support method development priorities.
Familiarity with scientific programming and workflow automation (e.g., Python, MATLAB).
Familiarity with NQA‑1 quality assurance for modeling workflows, including documented methodologies, configuration control, and model traceability.
Strong analytical thinking, clear technical communication, and the ability to support multiple method development efforts in parallel.
This position is subject to qualification requirements in accordance with ANSI/ANS 3.1. Candidates must meet the minimum education and experience criteria applicable to the role, including relevant nuclear industry experience where required. Verification of data will be part of the hiring process.

Responsibilities

Develop plant‑scale thermal‑hydraulic analysis methods, including modeling strategies, numerical approaches, and closure models.
Perform steady-state and transient system‑level analyses to characterize model behavior, assess method performance, and define method fidelity requirements.
Develop and maintain method qualification plans, including numerical verification, applicability envelopes, and performance characterization.
Formulate and integrate closure models and correlations (e.g., heat transfer, pressure drop, mixing, component-level physics) into existing analysis frameworks.
Identify modeling gaps and drive method enhancement priorities using Phenomena Identification and Ranking Table (PIRT), sensitivity studies, and multi-physics needs.
Develop automated workflows and tools for model setup, execution, post‑processing, and repeatable method application.
Collaborate with test engineering to define data needs that inform method development (not for validation purposes, but to guide model formulation and closure development).
Document modeling methodologies, assumptions, method applicability, and numerical performance for design processes and licensing‑support activities.
Work across disciplines to ensure thermal‑hydraulic methods integrate effectively with plant design, safety analysis, and coupled simulation workflows.
Apply and improve TerraPower’s SQA and NQA‑1 modeling practices, ensuring traceability, configuration control, and reproducibility of methods.
Mentor junior engineers in numerical method development, system modeling, and modern computational analysis practices.