The TeamAs part of the Engineering organization, Models & Simulations develops advanced analytical models that support engineering design, performance prediction, and system optimization. The team enables informed decision-making through computational analysis and simulation.
The Role The Senior Thermal-Hydraulics Systems Engineer leads system-level (1-D / network) thermal-hydraulics modelling of the reactor's primary and secondary loops, balance of plant and power-conversion cycles using Flownex SE. Within the ModSim Engineering Group, the role builds and validates integrated plant models that capture steady-state performance and transient behavior - start-up and shutdown, load changes, loss-of-flow and trip scenarios - and that inform component sizing, control philosophy and cycle optimization (Brayton and supercritical-CO₂). The engineer defines the systems-modelling approach, reconciles Flownex results with CFD-derived coefficients and supplier data, and translates system analyses into engineering decisions and inputs for the wider design and safety effort.
Key Responsibilities - Build, run and maintain integrated Flownex SE network models of primary/secondary loops, balance of plant and power-conversion cycles for steady-state and transient analysis.
- Characterize and size components (pumps, compressors, heat exchangers, valves, turbomachinery) and evaluate cycle performance and optimization across Brayton and sCO₂ architectures as required.
- Analyze plant transients and control response (start-up/shutdown, load-follow, loss-of-flow, trips) and provide system boundary conditions to the CFD and FEA streams while consuming their loss/heat-transfer coefficients.
- Produce calculation packages and system design-basis documentation under NQA-1; provide inputs to safety analysis and interface with detailed CFD models and neutronics power distributions.
- Lead verification and validation of system models, set systems-modelling standards, support regulator/customer reviews, and mentor junior systems analysts.
- Mentor engineers and train junior team members
- Standardize Flownex modelling methods, component libraries and templates, and support the Stream Lead in scoping, estimating and scheduling systems work.
Basic Qualifications - Bachelor's degree or higher in Mechanical, Nuclear, Chemical or Aerospace Engineering with emphasis on thermodynamics, heat transfer or thermal-hydraulics systems.
- 5+ years of professional thermal-hydraulics / plant-systems analysis experience, including lead responsibility on integrated system or cycle models.
Preferred Skills and Experience - Master's degree (MSc/MEng) or higher in Mechanical, Nuclear, Chemical or Aerospace Engineering with emphasis on thermodynamics, heat transfer or thermal-hydraulics systems.
- Flownex SE expertise strongly preferred; otherwise demonstrable depth in a comparable systems/transient code (RELAP5, TRACE, GOTHIC, MELCOR, Modelica/Dymola, Aspen HYSYS Dynamics, Thermoflow / GateCycle) with willingness to adopt Flownex.
- Strong applied thermodynamics, heat transfer, and fluid mechanics; closed-loop power-cycle design (Brayton, supercritical-CO₂).
- Heat-exchanger thermal/hydraulic design and rating; turbomachinery and pump performance characterization; control-system representation.
- Transient and dynamic simulation, including reactor thermal-hydraulics and decay-heat / natural-circulation scenarios.
- Property libraries / equations of state (e.g., CoolProp / REFPROP) and helium, molten-salt, sodium, or CO₂ working fluids a strong plus.
- Experience under a nuclear or regulated quality programme (NQA-1, ISO 9001, 10 CFR 50 Appendix B) and exposure to NRC/ASME environments.
- Scripting/automation of work within defined workflows and quality assurance frameworks.
- Track record of mentoring and leading technical systems analysis within a team.
What We Offer - Competitive base salary
- Equity ownership in a rapidly growing advanced energy company
- Comprehensive medical benefits
- Unlimited PTO
- Free daily lunch and dinner provided onsite
- Generous PPE stipend
- High-impact startup environment with significant ownership and autonomy
- Opportunities for rapid career growth and internal advancement
- Direct collaboration with experienced operators, engineers, and industry leaders
- The opportunity to help build and scale transformative energy technology from the ground up
Salary$151,000-$185,000 USD
