EXPERIMENTAL INVESTIGATION ON THERMAL-HYDRAULICS BEHAVIOR DURING A STATION BLACKOUT TRANSIENT IN A PRESSURIZED WATER REACTOR

摘要

Considering the high-lighted safety concerns on the high risk multiple failures, a series of tests with a thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation) was performed. In this study, the most conservative SBO transient and a more realistic SBO transient were simulated in the SBO-01R and the SBO-02 tests, respectively. The main objectives of these tests were not only to provide physical insight into the system response of the APR 1400 during the SBO transients but also to produce an integral effect test data to validate a safety analysis code. In most nuclear power plants (NPPs), a turbine-driven auxiliary feedwater system was designed to remove the decay heat during the early period of an SBO transient. In the SBO-01R test, however, supply of turbine-driven auxiliary feedwater to steam generators was not considered from a conservative point of view. On the other hand, turbine-driven auxiliary feedwater was supplied to both steam generators in the SBO-02 test. From the present SBO-01R and SBO-02 experimental results, it could be confirmed that the supply of turbine-driven auxiliary feedwater plays a key role in maintaining the natural circulation flow during a SBO transient. An efficient heat removal through the supply of auxiliary feedwater to steam generators prevented the inventory discharge through opening of POSRV and the primary system became stable condition without any excursion of core wall temperature.