An Experimental Investigation of Boiling of Water in a Vertical Tube

Abstract

  In order to realize a quick mass production of PuO₂/UO₂ (MOX) particles via vaporization of Pu/U mixed nitrate solution, an innovative denitration process is required. In this process, one of the important problems is the safety control of radioactive materials in the solution. However, it is known that violent boiling (i.e., geysering) of liquid sometimes occurs in a long, heated vessel. In this study, we experimentally examined the boiling characteristics of water in a vertical glass tube with a closed lower end opening to an upper plenum at the top. In our experiments, we measured the transient statistic water pressure and the water temperature at four elevations along the glass tube. The effects of the water temperature of the upper plenum and heat input into the water on the boiling of water were investigated. Flow visualization shows that the bubbles are first formed on the heater surface, and then they detach and start to rise in the water. They suddenly coalesce and form a large slug bubble in the test tube. Measurements of local water temperatures showed that in the case of violent boiling, the temperatures and pressure fluctuate at the same frequency.