Thermal Hydraulics Engineer in , us

About the Company
We’re partnering with a well-funded, early-stage nuclear energy startup based in

San Francisco

. The company is focused on developing next-, compact reactor systems designed for scalable, cost-predictable deployment across large energy applications such as data centers, industrial heat, and grid-scale power.
Backed by significant private funding and operating in a true builder/startup environment, the team is mission-driven, fast-moving, and deeply committed to tackling complex, first-of-a-kind (FOAK) engineering challenges. This is an opportunity to join at an early stage and play a key role in shaping both the technology and the organization.
This is a remote role with travel as needed.
Role Overview
We are seeking a

Thermal Hydraulics Engineer

with nuclear industry experience to support the modeling and simulation of advanced reactor systems, including normal operation and transient/accidental scenarios. This individual will contribute to the design, analysis, and optimization of high-performance nuclear systems in a highly collaborative, hands-on startup environment.
Key Responsibilities
Lead

accident scenario modeling

and safety analysis using system-level codes
Analyze

thermal-hydraulics performance

under steady-state and transient conditions
Perform

CFD modeling and simulation

to support reactor and system design efforts
Collaborate cross-functionally with reactor design, systems, and safety teams
Contribute to the development and validation of modeling methodologies
Support design decisions through quantitative simulation insights
Required Qualifications
Professional experience with

system codes and accident modeling tools

(RELAP, MELCOR, or equivalent)
Strong understanding of

thermal-hydraulics and fluid dynamics

principles
Professional engineering experience applying CFD and thermal-fluid analysis
Hands-on experience with

CFD tools

(Star-CCM+ ; other packages acceptable)
Ability to work onsite in a fast-paced, startup environment
Demonstrated ability to learn new technical domains and solve complex engineering challenges
/ Nice-to-Have Qualifications
Industry experience in nuclear engineering
Experience with

nuclear-specific CFD applications
Experience coupling CFD and FEA analyses for thermal-mechanical design challenges
Experience modeling heat exchangers, steam generators, or similar thermal-fluid systems
Exposure to

core design / reactor physics tools

(CASMO, SIMULATE, or equivalent)
Experience with

fuel performance modeling

(FRAPCON, BISON, or similar)
Experience supporting work performed under NRC regulatory frameworks or licensing processes
Familiarity with

cost modeling or techno-economic analysis
Broader systems-level understanding of reactor design
Experience working in startup, high-growth, or fast-paced engineering environments
Experience with both computational modeling and experimental/testing programs
What We're Looking For (Culture & Mindset)
Strong communicator who collaborates effectively across highly technical teams
Proven

grit, resilience, and determination

—comfortable tackling ambiguous, high-difficulty problems
Strong interest in working on

first-of-a-kind (FOAK) hard-tech projects
Curious, continuous learner who can quickly develop expertise in new technical areas
Builder mentality: takes ownership, moves with urgency, and thrives in early-stage environments
Committed to technical excellence while balancing speed, execution, and practical engineering outcomes
Motivated by the opportunity to help reshape the future of energy
Compensation
Competitive salary based on years of experience
Healthcare & dental fully covered by the company. Vision Available.
Equity