Evaluation Report on CCTF Core-I Reflood Tests Cl-18 (Run 37) and Cl-8 (Run 17). Investigation of the Effect of Water Remaining in the Loop Seal Section on Reflood Behavior

摘要

The loop seal experiments, Cl-18 and Cl-8, were conducted in the Cylindrical Core Test Facility (CCTF). For these experiments, the saturated water was filled in four loop seal sections to the elevation of 1.5 m from the bottom of them prior to the experiment initiation in order to simulate the remaining water in the loop at the initiation of a reflood phase during a loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). The results of the loop seal experiment, Cl-18, was mainly discussed in this report because, in the other loop seal experiment, Cl-8, the core power was prematurely turned off during the transient of it. The significant steam penetration through the broken loop seal section initiated at 32 seconds after flood, and most of the filled water was blown away until 65 seconds. Before that time, the core water accumulation was suppressed due to the water seal in the loop seal section. The turnaround temperature was higher than that for the Cl-5 which was conducted under no filled water in the loop seal section. The driving force of the steam penetration is the difference of the differential pressures in the downcomer and the core. The driving force was equal to the pump-side water head at the initiation of the steam penetration. The ECC injection rate affected the water accumulation in the downcomer and controlled the timing of the initiation of the steam penetration. (Atomindex citation 15:059465)