Integral effect test results on the effect of asymmetric supply of feedwater during a station blackout transient of pressurized water reactor

Abstract The thermal–hydraulic integral effect tests were performed to investigate the effect of asymmetric active and passive secondary cooling on the primary cool-down performance during a prolonged station blackout. The A1.1 test was performed to simulate a prolonged station blackout with asymmetric secondary cooling through the delayed supply of auxiliary feedwater only to steam generator number 2 of ATLAS. The A1.2 test was performed to simulate a prolonged station blackout with asymmetric secondary cooling through the supply of passive auxiliary feedwater only to steam generator number 2 of ATLAS. In both tests, an asymmetric cooling pattern was clearly observed during the period when the auxiliary feedwater was supplied. The primary system pressure and temperature continuously decreased during the heat removal by active and passive auxiliary feedwater supply, which indicates that the active and passive auxiliary feedwater supply can efficiently remove the core decay heat during a prolonged station blackout transient.