BWR transients simulation within the German nuclear plant analyzer (ATLAS)

The distributed computer architecture of the nuclear plant analyzer ATLAS (ATHLET Analysis Simulator) for a test control facility (TCF) including hardware configuration and software organization is briefly described. The application of ATLAS for the investigation of 'Station Blackout' transients with fine and coarse nodalization is described. This work was performed within the frame of the 'Safety Study for a German BWR', sponsored by the German Federal Minister for Research and Technology. These analyses were aimed to investigate the contribution of coolant from the feedwater line and feedwater tank to the core cooling during the automatic depressurization of the pressure vessel of a BWR. The availability of the relief valves and the flow resistance via the check valves in the feedwater line was varied. The utilization of the coolant available in the feedwater line and feedwater tank prolongs core cooling up to two and a half hours during a 'Station Blackout' transient due to the automatic depressurization. (orig.) (5 refs., 14 figs.)