Features of Dendritic Oxide during Sodium Combustion

概要

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Liquid sodium is used as the coolant in fast reactors (FRs). It is a superior thermal medium, but its chemical reactivity with oxygen and water is very high. After the Monju sodium leak accident, a better physical and chemical understanding of the reaction phenomena was required from the viewpoint of the public acceptance of FRs. The purpose of this study is to understand the oxidation behavior of liquid sodium in detail, because it plays an important role in the continuation of the combustion process. The liquid sodium surface is covered with a thin oxide layer at the start of combustion. Generally, the surface oxide layer on the solid metal prevents further oxidation; however, dendritic sodium oxide is generated, and it grows on the oxide layer. This means that sodium can be supplied to the interface of the reaction without being blocked by the reaction products. As a result, the reaction continues spontaneously. Therefore, reaction products such as dendritic oxide have a significant influence on the overall reaction behavior. However, the precise roles of such products on the reaction have not been clarified in previous research. Understanding the role of the dendritic oxide in the reaction can be helpful for controlling sodium combustion phenomena, for example, the extinction process. Therefore, this study is a useful contribution to ensuring FR safety.
2011-12-01