Senior Thermal-Hydraulics Systems Engineer — Equity & Impact

Valar Atomics; Los Angeles (CA); On-site; USD 150,000 - 230,000; Full time

Benefits offered by this job

Equity ownership

Unlimited PTO

Free daily meals

PPE stipend

High-impact startup

Career growth

Collaboration access

Ground-up impact

Job summary

Valar Atomics in the United States is seeking a Senior Thermal-Hydraulics Systems Engineer to lead 1-D and network modelling of reactor loops and power-conversion cycles using Flownex SE. You will develop integrated plant models capturing steady-state and transient behavior to guide design decisions.

You’ll size components, analyze transients, set modelling standards, and collaborate with CFD/FEA teams. The role emphasizes mentorship, documentation under NQA-1, and interaction with regulators

Qualifications

• Bachelor's degree or higher in Mechanical, Nuclear, Chemical or Aerospace Engineering with emphasis on thermodynamics, heat transfer or thermal-hydraulics.
• 5+ years of professional thermal-hydraulics / plant-systems analysis experience, including lead responsibility on integrated system or cycle models.
• Master’s degree (MSc/MEng) in Mechanical, Nuclear, Chemical or Aerospace Engineering preferred.
• Flownex SE expertise strongly preferred; otherwise depth in similar codes and willingness to adopt Flownex.
• Experience under nuclear or regulated quality programs (NQA-1, ISO 9001, 10 CFR 50 Appendix B) desirable.
• Scripting/automation of work within defined workflows and QA frameworks.

Responsibilities

• Build, run and maintain integrated Flownex SE network models of primary/secondary loops and power-conversion cycles for steady-state and transient analysis.
• Characterize and size components (pumps, compressors, heat exchangers, valves, turbomachinery) and evaluate cycle performance for Brayton and sCO₂ architectures.
• Analyze plant transients and control response and provide system boundary conditions to CFD/FEA streams.
• Produce calculation packages and system design-basis documentation under NQA-1; support safety analysis and interface with CFD/neutronics models.
• Lead verification and validation of system models, set modelling standards, and mentor junior analysts.
• Mentor engineers and train junior team members.
• Standardize Flownex modelling methods and templates; assist with scoping, estimating and scheduling systems work.

Skills

Mentoring

Leadership

System analysis

Thermal-hydraulics

Education

Bachelor's degree in Mechanical, Nuclear, Chemical or Aerospace Engineering

Master’s degree (MSc/MEng) in related field

Tools

Flownex SE

RELAP5

TRACE

GOTHIC

MELCOR

Modelica/Dymola

Aspen HYSYS Dynamics

GateCycle / Thermoflow

Job description

Valar Atomics in the United States is seeking a Senior Thermal-Hydraulics Systems Engineer to lead 1-D and network modelling of reactor loops and power-conversion cycles using Flownex SE. You will develop integrated plant models capturing steady-state and transient behavior to guide design decisions.

You’ll size components, analyze transients, set modelling standards, and collaborate with CFD/FEA teams. The role emphasizes mentorship, documentation under NQA-1, and interaction with regulators