Principal Engineer, Safety Methods

TerraPower LLC.; Bellevue (WA); On-site; USD 168,316 - 252,475; Full time

Benefits offered by this job

Competitive compensation

Discretionary incentive plan

Medical and wellness benefits

401k plan

21 days PTO

10 paid holidays

Relocation assistance

Professional development support

Job summary

TerraPower is seeking a Principal Engineer, Safety Methods in Bellevue, WA, to lead development, enhancement, and deployment of plant-scale thermal-hydraulic analysis methods for the Natrium reactor. You will improve modeling approaches and ensure robust predictions across operational and transient scenarios, reporting to the Manager, Plant Thermal Hydraulics Methods.

Responsibilities include developing closure models, performing steady-state and transient analyses, and driving method

Qualifications

• Degree in Mechanical, Nuclear, Chemical Engineering or similar field.
• 12+ years of experience in system-level thermal-hydraulic modeling and method development.

Responsibilities

• Develop plant-scale thermal-hydraulic analysis methods, including modeling strategies and closure models.

Skills

System-level modeling

Thermal-hydraulics

Analytical thinking

Technical communication

Mentoring

Education

Mechanical/Nuclear/Chemical Engineering degree

Tools

RELAP5-3D

GOTHIC

SAS

Python

MATLAB

Job description

TerraPower is a nuclear technology company based in Bellevue, Washington. At its core, the company is working to raise living standards globally through a more affordable, secure, and environmentally friendly form of nuclear energy along with innovations in medical isotopes to improve human health. In 2006, TerraPower originated with Bill Gates and a group of like-minded visionaries who evaluated the fundamental challenges to raising living standards around the world. They recognized energy access was crucial to the health and economic well‑being of communities and decided that the private sector needed to take action and create energy sources that would advance global energy deployment. TerraPower’s mission is to be a world leader in new nuclear technologies, while developing innovators and future leaders in the nuclear field. As a result, the company’s activities in the fields of nuclear energy and related sciences are yielding significant innovations in the safety and economics of nuclear power, hybrid energy and medical applications – all for significant human health benefits.

TerraPower is an Equal Opportunity Employer. We do not discriminate in hiring on the basis of sex, gender identity, sexual orientation, race, color, religious creed, national origin, physical or mental disability, protected Veteran status, or any other characteristic protected by federal, state, or local law.

Principal Engineer, Safety Methods

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.

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.

Key Qualifications and Skills

• 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.

Job Functions

• Motor Abilities: Sitting for extended periods, bending/stooping, grasping/gripping, fine motor control (hands)
• Physical exertion and/or requirements: Minimal, with ability to safely lift up to 25 pounds.
• Special Senses: Visual and audio focused work
• Work Conditions: Stairs, typing/keyboard, standard and/or sitting working environment of >8 hours/day
• Travel required 0‑10%

Job details

Salary Range: $168,316 - $252,475

Any salary offered within the posted salary band is based on market data and commensurate with the selected candidate’s qualifications and experience. This range is specific to Washington State.

• Competitive Compensation
• Salary, eligible to participate in discretionary short‑term incentive payments
• Comprehensive Medical and Wellness Benefits
  • Medical
  • Vision
  • Dental
  • Life and Disability
  • Gender Aff¬mation Benefits
• 401k Plan
• Generous Paid Time Off (PTO)
  • 21 days of annually accrued PTO
• Generous Holiday Schedule
  • 10 paid holidays
• Relocation Assistance
• Professional and Educational Support Opportunities

The application deadline for this role is August 5, 2026