Thermo-hydraulic behavior of fluid in pressure vessel during blowdown

Thermo-hydraulic behavior of fluid in pressure vessel during blowdown was experimentally investigated with the Facility for the Blowdown Behavior of Integrated Type Marine Reactors. The dimensions of the pressure vessel used for the experiments were 284mm ID and about 1700mm height. 34 experiments were conducted with various combinations of following parameters: three orifice diameters (25.4, 12.7 and 6.4mm), three initial saturation pressures of fluid (50, 40 and 30kg/cm 2g), three break positions (upper, middle and lower), two liquid levels, and two volume numbers (with and without internals). Pressures in pressure vessel, differential pressures between upper and lower nozzles, and void fractions at vertically 6 points in pressure vessel were measured during blowdown. A computer code (BLODAC-IV) was developed to analyse the single volume blowdown characteristics. The code includes so-called bubble gradient model for the steam distribution in water and some input parameters. The experimental results of pressures, void fractions and falling speed of liquid level were compared with the calculational results, and the combinations of the values of input parameters were determined so that the results of calculations fit well for the experimental results. The blowdown characteristics and the combinations of input parameters were explained by the newly derived experimental results of void distributions in water. (auth.)