[en] The work which was performed by FZR within the BWR-CA is divided into three tasks: Implementation of two phase flow instrumentation, ATHLET calculations of NOKO experiments and approach for the optimization of passive components. Chapter two contains a description of the two phase flow measurement instrumentation developed by FZR in general and especially of the instrumentation of the single emergency condenser tube, which is installed in parallel to the emergency condenser test bundle. The experimental data should be used for the validation of the improved ATHLET condensation model. Because the evaluation of these experiments shows an undesired accumulation of non-condensable gases in front of the water level, some of the goals of the single tube measurements can't be met. Therefore there is a need for further single tube experiments with an improved instrumentation. On the other hand the results give valuable insights to the phenomena caused by non-condensables. In the second part of chapter two an improved two-phase flow instrumentation is suggested based on the collected experience and taking into account the detected problems. In chapter three ATHLET calculations of NOKO experiments are presented. Within the BWR-CA FZR had performed 10 post test calculations and an additional blind test calculation of NOKO experiments. The tests were selected by FZJ. The results of these calculations are presented and discussed. Basis of the comparison between computational and experimental data is the evaluation and the uncertainty analysis of the NOKO experiments, which were performed by FZR with the computer code CASH-(Computergestuetzte Auswertung und Unsicherheitsanalyse von NOKO Experimenten) Graphics. The fourth chapter deals with the optimization of the emergency condenser. This is desirable because this allows to decrease of the pressurized BWR surface and the possibility of leakages. An ATHLET calculation is performed for an optimized emergency condenser tube of a new material (Remanit). A detailed discussion of the thermal hydraulic yield proves the advantages for the suggested design. (orig.)