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An important component in the safety systems of atomic power stations is equipment for localizing accidents in which the primary loop is depressurized and steam is blown into special bubbling units with cold water. It is necessary to prevent rupture of the bubbling units and damage to the nozzles. In the present work, the physical features of bubbling are investigated to elucidate the factors responsible for such problems.The experimental apparatus is shown in Fig. I. The steam is prepared in a 0.12-m 3 vessel equipped with monitoring and control sensors: TKhK thermocouples (accuracy class 0.5) and an I~DM manometer (limit of measurement 0-I MPa, accuracy class 0.5). Two 3.15-kW U-tube electric heaters are connected to the line through a switch controlled by a signal corresponding to the pressure in the heaters.The steam produced in the vessel is sent to the experimental cell through a flexible corrugated pipe 4 (of Du 15 and Ru 10 MPa type) screened from heat losses by asbestos tape. The experimental cell is an open cylindrical shell (diameter 0.3 m, height 0.4 m) with a lateral outlet of diameter 125 mm and length 80 mm fitted with a viewing window of thickness 5 mm at the flanged joint. The floor of the shell is covered with black microporous rubber (thickness 5 mm) to eliminate glare in photographing the process and to reduce the influence of pressure waves reflected by the floor. In addition, it seals the lower flange joint of the experimental cell.Steam is introduced in the cold water through an attachment made of coaxially welded tubes (internal diameter 32 and 10 mm; see view I-I in Fig. 1) ensuring air insulation to prevent condensation of the steam before reaching the nozzle; the attachment has an M6 x 0.75 threaded adapter for connecting nozzles of different size. For convenience in measuring the flow rate of the steam and varying the spatial position of the nozzle with respect to the pressure sensor, the attachment is fitted on a rotary mount. The steam flow rate is measured by a mass-based method using a 0.001-m 3 measuring volume and laboratory scales with an error of 0.01 g. Pressure oscillations in the experimental cell are determined by means of a DD-10 inductional sensor operating with an IVP-2 secondary unit that permits the measurement of pressure oscillations of amplitude up to 1.5 MPa and frequency up to 1 kHz in accuracy class 0.2. The sensor has a sealed input, which allows it to be moved in the water volume in the immediate vicinity of the nozzle. The temperature of the cold water in the vessel is measured by a TKhK thermocouple; the measurement accuracy is monitored by means of a mercury-in-glass thermometer with a range of 0-120~ and an error of 0.5~ The saturated-steam temperature is monitored from the pressure in the vessel.High-speed processes are recorded on a K121 light-beam oscillograph (in combination with an N117 oscillograph connected to MI012 galvanometers of type 40 and 300) in the frequency range extending up to the working frequency of the galvanometer (in the present case,...