Study On Dynamic Characteristics Of Interaction Between Molten Aluminum Column And Water

With the rapid development of science and technology,the demand for various metal materials is increasing.While modern industry meets the demand for metal materials,the safety accidents have become one of the most important problems to be solved.In nuclear industry and metallurgical industry,the serious steam explosion may occur once the molten metal contacts with coolant under abnormal conditions,which endangers the safety of surrounding equipment and operators.In recent years,the steam explosion occurs frequently in the metallurgical industry.In addition,in the history of nuclear industry,there have been three serious safety accidents caused by steam explosion.As the interaction between high-temperature melt and coolant is a very complex process with many influencing factors,the controlling mechanism of this process has not be fully understood.At present,the accurate prediction of the occurrence of steam explosion accidents is not attained.Therefore,it is of great significance to study the phenomenon and mechanism of the Fuel-Coolant Interaction(FCI).The fragmentation and explosion behavior involving FCI process are studied by a self-developed experimental system.This process is photographed using a high-speed camera and the overpressure during the explosion is recorded in real time by a free-field pressure sensor.The chemical reactions associated with this process are understood through the analysis of products,and the influence of chemical explosion on steam explosion is studied.The main contents are summarized as follows:The interaction between molten aluminum column and cooling water is studied.The steam explosion may occur in the process of interaction between molten aluminum column and cooling water.There are two types of explosion: the local explosion and the complete explosion.With an increase in the temperature or the falling height of molten aluminum column,the probability of explosion increases.The overpressure peaks are recorded and analyzed under different experimental conditions.The released energy in the steam explosion and the energy conversion efficiency are calculated.The maximum values of the explosion energy,explosion overpressure and the energy conversion efficiency recorded in the experiment are143 k J,0.278 Mpa and 18.44% respectively.The oxide layer on the surface of aluminum and the surface tension maintaining its internal stable state are the main reason for the different explosion types in the process of interaction between molten aluminum column and cooling water.Meanwhile,the influence of temperature and falling height of molten aluminum column on the oxide layer and surface tension is evident.The experimental products are analyzed in detail.The solid products can be divided into three types by the external morphological characteristics,while gas products are mainly composed of hydrogen.The mass distribution of three kinds of metal products is analyzed.It is found that the kinds of products depend on the explosion type.The composition of the solid product is detected by the X-ray diffractometer,finding that the product is mainly composed of aluminum,alumina and aluminum hydroxide.The composition of the solid product also depends on the types of explosion indicating that the chemical reaction processes are different in the different explosion types.The gas products are collected in the experiment,finding that the gas collection volume depends significantly on the temperature,falling height and mass of molten aluminum column.With an increase in temperature of molten aluminum column,the volume of collected gas firstly increases but decreases afterwards.By contrast,the volume of collected gas increases with an increases in mass of molten aluminum column,but changes irregularly under different falling height of molten aluminum column.The generating hydrogen has a certain influence on the steam explosion.Specifically,the hydrogen will produce a certain disturbance on the interface of molten aluminum and cooling water,causing the deformation of the oxide layer.Then,the contact area between water and molten aluminum increases.Meanwhile,the aluminum oxide will also react with water to produce hydrogen under high temperature conditions.Without the protection of oxide film,the molten aluminum will be directly exposed to water,and react violently with water.