Containment model library of the Apros process simulation software: an overview of development and validation work

The Apros CONtainment model library (ACON) is an add-on product of the Apros® (Advanced Process Simulation Environment) Nuclear software cooperatively developed by VTT and Fortum. ACON is suitable for comprehensive simulation of containment phenomena during nuclear reactor design basis accidents and, to some extent, severe accidents. The lumped parameter approach applied enables flexible modeling of various containment/compartment systems. ACON is a suitable tool for both safety analysis use and accurate training simulator purposes with real time calculation speed. The Apros containment model can be used fully separately, or a containment simulation can be coupled with other thermal-hydraulic calculation to create a complete simulation model of a power plant, including e.g. the reactor and turbine systems. Modeling of relevant engineering safety features is also included. The paper focuses on the modeling features of ACON and the related validation work which includes the calculations of nearly 50 experiments performed in various test facilities. The validation methodology is discussed and the validation calculations are summarized as a validation matrix. The paper provides a detailed presentation of selected validation cases, in which the main studied phenomena are related to general containment thermal-hydraulics, spray effects, blowdown modeling, steam condensation on a structure, steam stratification in containment, and ice melting with associated natural circulation flow. Finally, an example of applications is described. Severe accident containment phenomena are out of the scope of this paper. The results of the validation demonstrate that Apros can be used for analyses of containment thermal-hydraulic behavior including related aspects of engineering safety systems in various containment geometries.