Counterpart tests of SBLOCA on the effect of break location with the ATLAS. DVI nozzle versus cold-leg breaks

Results from two integral effect tests were compared to discuss the effect of break location between the direct vessel injection (DVI) nozzle and cold leg during the small-break loss of coolant accident (SBLOCA) scenario. One is the SB-DVI-09 test for a 6-inch (50% break area of a DVI nozzle) DVI line break and the other is the SB-CL-06 test for an equivalent break size of cold leg. Both counterpart tests were performed with the same control logic and initial/boundary conditions except for different break locations of the DVI line and cold leg. Experimental results showed that the maximum heater surface temperature increased more with the broken DVI nozzle (SB-DVI-09) than with the broken cold leg (SB-CL-06) due to the delayed and simultaneous occurrence of the loop seal clearing and the momentary decrease in the collapsed water level in the core region. (author)