Definition of non-stationary flow rate of coolant on efflux out from a high-pressure vessel

The blow-out process of the boiling coolant at NPP circuit disintegration is investigated. The quantitative dependences at the blow-out of the boiling coolant from a vessel, in particular, the non-stationary flow rate an experimentally determined. The experimental installation is a high pressure vessel with the height of about 2 m and with the diameter of 309 mm with two lines of pipe branches through which the outflow goes, and the disintegration device to initiate spontaneous leakage flow. The flow diameter was varied by the installation of limiting diaphragms in the pipe branches. The vapor content during coolant boiling has been determined by γ-scanning along the vessel axis. For recording the pressure dynamics quick-response tensometric sensors were used, temperature was measured by chromel-copel thermopairs in three points. The blow-out velocity of the boiling coolant is determined according to the dynamics of the pressure change and coolant temperature in the vessel volume, and on the vapor content change and water residue in the vessel. It is stated that the pressure in the vessel sharply falls at the spontaneous outflow of water underheated to the saturation temperature, the coolant boiling takes place and its main losses are at the stage of outflow after boiling-up. The blow-out type of the boiling coolant does not practically depend on the initial pressure, and is determined by the coolant underheating to the saturation temperature. The hole diameter and the pipe branch position affect the blow-out character of the boiling coolant