(An) experimental study of the high pressure melt ejection from a reactor vessel

Abstract

In the present study, 1/25-th scale model of YGN 1\&2 reactor cavity is used to investigate the dispersal mechanism of the core debris from the reactor cavity during a high-pressure melt ejection scenario of the prostulated severe accident. Water is used as a low-temperature melt simulant while nitrogen and carbon dioxide are used to simulate the high-pressure primary system blowdown steam and hydrogen. The relations between the dispersed fraction of the water from the cavity model and the initial conditions of the pressure vessel are investigated. From the present study it has been found that the discharged water from the pressure vessel does not exit the reactor cavity model under its own momentum, but does exit by the driving force of the blowdown gas in YGN 1\&2 type reactor cavity model. The dispersed fraction of the water is dependent upon the initial conditions of the pressure vessel at the instant of the vessel failure. It is affected by the vessel breach size, the blowdown pressure, the driver gas density, and the Kutateladze number. However, the dispersed fraction of the water from the davity model is not significantly affected by initially stored amount of the water in the pressure vessel.