Advanced Containment Models


Exitech’s Advanced Primary and Secondary Containment Environment Nodalized Thermodynamic simulation models provide detailed simulations of rooms and areas by using a nodalized thermodynamic solution coupled with detailed HVAC system simulation. The model includes transport of radioactive and component gases and is capable of producing realistic indications for normal and casualty scenarios.

Without a nodal solution secondary containment models cannot accurately simulate the localized response to normal and casualty conditions, resulting in a lack of fidelity and placing an additional demand on training staff to create realistic simulator scenarios.

During the model parameterization phase, nodalization is performed based on an analysis of arrangement drawings, HVAC drawings, piping isometric drawings, Engineering Calculations, and Piping and Instrumentation Diagrams. Nodal volumes are obtained from Engineering Calculations or are computed from arrangement drawings. Equipment arrangement is reviewed to determine nodal heat loads.

Nodal considerations include:

  • Non-equilibrium two-phase/superheat/subcooled thermodynamics
  • Independent hydrogen, oxygen, nitrogen, liquid, and steam mass balances
  • Energy balances for solid structures such as equipment, walls and floors
  • Dynamic heat transfer from plant equipment such as motors, piping and tanks
  • Convective and condensing heat and mass transfer from coolers and heaters
  • Detailed consideration of break flows
  • Saturated transfer processes such as evaporation, condensation and rainout
  • Convective and condensing heat and mass transfer from sprinkler flows
  • Gas pressure based on the ideal gas law and saturated steam relationships
  • Liquid level based on liquid volume and compartment physical properties
  • Liquid flow between nodes and sumps
  • Multiple radioactive gaseous specie balances
  • Multiple radioactive liquid specie balances
  • Multiple radioactive solid specie balances


Detailed HVAC models are coupled to the nodalized thermodynamic solution. These models employ a full set of mixing equations to allow proper transport of non-condensibles, water vapor, and activities.  HVAC models include consideration of the following components:

  • Condensing and convective coolers
  • Refrigeration units
  • Steam and electric heaters
  • Fans
  • Valves and dampers
  • Ductwork
  • Filters
  • Control systems


Exitech’s advanced primary and secondary containment models are able to meet the evolving training needs for your Plant Operators and Emergency Response Personnel and provide robust models to interface with higher fidelity Thermalhydraulic and BOP models