Experimental data of ROSA-III integral test run 706

RUN 706 in the ROSA-III program, which obtains information of the thermo-hydraulic phenomena of the coolant in a loss-of-coolant accident (LOCA) using a simulated test facility for assessment of the system computer code, simulates a 200% double-ended break at the inlet of a recirculation pump. Purpose of the test was to observe thermo-hydraulic behavior in the core under LOCA conditions in core heating without ECCS actuation. The primary initial conditions are steam dome pressure 7.17MPa, steam dome temperature 561K (saturation), lower plenum subcooling 12K, initial power 3.405MW and core inlet flow 36.2 kg/s. Recirculation pump power supply, main steam discharge flow and feed water flow were suspended instantaneously upon the break. Following are the experimental results. (1) Jet pump suction uncovering and lower plenum flashing occurred 8.5s and 17s, respectively, after the break. (2) Lower plenum flashing improved core cooling in the lower half of the heater rods. (3) Electric power supply to the heater rods was cut off 156s after the break to protect the rods. (4) Separate mixture levels were observed in the core and the lower plenum during blowdown. (author)