Current status of the COCOSYS development

The simulation of a severe accident propagation in containments of nuclear power plants is required to investigate the consequences of severe accidents and the effectiveness of potential counter measures under conditions as realistic as possible. For this purpose, GRS developed the containment code system (COCOSYS). The main objective is to provide a code system based on mechanistic models for the simulation of all relevant phenomena, processes and plant states during severe accidents in the containment of LWRs, also covering the aspects of design basis accidents. In this paper the current status of the COCOSYS development will be presented, especially pointing out the new features. Among other things the COCOSYS system has been used in the past for the design and installation of catalytic recombiner systems in German LWR plants. According to the experience gained by validating COCOSYS, for example on HDR Experiment E11.4, and the increased requirements to calculate local effects on hydrogen distribution the need for a sophisticated nodalisation of the containment and for the comprehensive simulation of specific system components will be underlined. (orig.)