OECD International Standard Problem ISP-47 on containment thermal-hydraulics-Conclusions of the TOSQAN part

The main objective of the ISP-47 is to assess the capabilities of Lumped-Parameter and Computational Fluid Dynamics codes in the area of nuclear containment thermal-hydraulics. Three experimental facilities TOSQAN, MISTRA and ThAI were involved in this project. The present paper summarizes the specifications, the results and the conclusions obtained for the TOSQAN open benchmark exercise. Wall condensation, steam injection in air or air/helium atmospheres, and buoyancy were addressed under well-controlled initial conditions in the simple TOSQAN geometry. Detailed gas velocity and gas concentration (air, steam and helium) fields were obtained for the first time in such an exercise. It is found that the model predictions fit with a generally good accuracy the experimental results obtained during condensation steady-state conditions, but the flow conditions in the transition regime are not well reproduced by the calculations: some of the major transient phenomena are not always correctly modelled and if so, the transient evolutions or the levels of the concerned variables are not the same in the calculations and in the experiment. Furthermore, two kinds of measurements were specific for TOSQAN: boundary layer measurements and turbulence variables, which were addressed for the first time in such an exercise. It is concluded that more sophisticated modelling in CFD codes for the boundary layers should be developed and that turbulence variables should be addressed more intensively in further exercises.