[en] Results of the ROSA-II tests simulating a loss-of coolant accident (LOCA) and the effects of an emergency core cooling system (ECCS) in a pressurized water reactor (PWR) are reported; test conditions and interpretations of the data in test runs 332, 413 and 425. Each test was carried out with a large double-ended cold leg break. Test parameters are ECC injection, pump operation and initial temperature difference across the core influencing the primary coolant system. (1) ACC injection causes the temporary condensation-depressurization initially, which influences the coolant flow in the core. Subsequently the depressurization decreases due to evaporation of ACC water. (2) Core is quenched mainly by LPCI water. (3) In pump operation after the break, the core cooling drops temporarily due to flow stagnation in the core. However, the water in the upper plenum is retained. (4) With large initial temperature difference across the core, the time from initiation of evaporation in the coolant of high initial temperature to initiation of evaporation in the coolant of low initial temperature increases. The discharge flow rate during this period becomes larger because of the low quality fluid or the subcooled water. The water in the primary system decreases rapidly. (author)