OECD/NEA ROSA project experiment on steam condensation in PWR horizontal legs during large-break LOCA

Takeda, Takeshi ; Otsu, Iwao ; Nakamura, Hideo  

Separate-effect experiment simulating steam direct-contact condensation on emergency core cooling system (ECCS) water in PWR cold legs during reflood phase of large-break LOCA was conducted in OECD/NEA ROSA Project using the Large Scale Test Facility (LSTF). A new test section was furnished in the downstream of the LSTF break unit horizontally attached to the cold leg. Significant condensation of steam appeared in a short distance from the simulated ECCS injection point, and the steam temperature in the test section decreased immediately after the initiation of the ECCS water injection. Total steam condensation rate estimated from the difference between steam flow rates at the test section inlet and outlet was in proportion to the simulated ECCS water mass flux until the complete condensation of steam. Clear images of high-speed video camera were successfully obtained on droplet behaviors through the viewer of the test section, especially for annular mist flow.