Numerical simulation of the emergency condenser of the SWR-1000

The SWR-1000 is a new innovative boiling water reactor (BWR) concept, which was developed by Siemens AG. This concept is characterized in particular b y passive safety systems (e.g., four emergency condensers, four building co ndensers, eight passive pressure pulse transmitters, and sir gravity-driven core-flooding lines). In the framework of the BWR Physics and Thermohydrau lic Complementary Action to the European Union BWR Research and Development Cluster, emergency condenser tests were performed by Forschungszentrum Jul ich at the NOKO test facility. Posttest calculations with ATHLET are presen ted, which aim at the determination of the removable power of the emergency condenser and its operation mode. The one-dimensional thermal-hydraulic co de ATHLET was extended by the module KONWAR for the calculation of the heat transfer coefficient during condensation in horizontal tubes. In addition, results of conventional finite difference calculations using the code CFX- 4 are presented, which investigate the natural convection during the heatup process at the secondary side of the NOKO test facility.