Comparative assessment of condensation models for horizontal tubes

The condensation in horizontal tubes plays an important role e.g. for the d etermination of the operation mode of horizontal steam generators of VVER r eactors or passive safety systems for the next generation of nuclear power plants. Two different approaches (HOTKON and KONWAR) for modeling this proc ess have been undertaken by Forschungszentrum Julich (FZJ) and University f or Applied Sciences Zittau/Gorlitz (HTWS) and implemented into the 1D-therm ohydraulic code ATHLET, which is developed by the Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) mbH for the analysis of anticipated and abnorm al transients in light water reactors Although the improvements of the cond ensation models are developed for different applications (VVER steam genera tors - emergency condenser of the SWR1000) with strongly different operatio n conditions (e.g. the temperature difference over the tube wall in HORUS i s up to 30 K and in NOKO up to 250 K, the heat flux density in HORUS is lip to 40 kW/m(2) and in NOKO up to 1 GW/m(2)) both models are now compared an d assessed by Forschungszentrum Rossendorf FZR e.V. Therefore past test cal culations of selected HORUS experiments were performed with ATHLET/KONWAR a nd compared to existing ATHLET and ATHLET/HOTKON calculations of HTWS. It c an be seen that the calculations with the extension KONWAR as well as HOTKO N improve significantly the agreement between computational and experimenta l data.