Operation conditions of the emergency condenser of the SWR1000 Original Research Article

Siemens AG is developing the innovative boiling water reactor concept SWR1000. New features are the passive safety systems (e.g. emergency condenser, building condenser, passive pressure pulse transmitter). For the experimental investigation of the emergency condenser effectiveness, the NOKO test facility has been constructed at the Forschungszentrum Jülich. The facility has an operating pressure of 10 MPa and a maximum power of 4 MW. The emergency condenser test bundle consists of eight tubes and is fabricated with planned geometry and material of the SWR1000. In more than 200 experiments, the emergency condenser capacity was determined as a function of pressure, water level and concentration of non-condensables in the pressure vessel, as well as of pressure, water level and temperature in the condenser. For the evaluation of the NOKO experiments, the program system CASH-Graphics (Computergestützte Auswertung und Unsicherheitsanalyse) was developed. This evaluation is the basis for the determination of the operation conditions of the emergency condenser. Post-test calculations of NOKO experiments were performed with an improved version of ATHLET. To calculate the heat transfer coefficients during condensation in horizontal tubes, the module KONWAR has been developed and implemented in ATHLET. KONWAR is based on the flow regime map of Tandon and includes several semi-empirical correlations for the determination of the heat transfer coefficients. The comparison between calculations and experiments shows a good agreement.