Estimation of heat transfer coefficient and flow characteristics on heat transfer tube in sodium water reaction

In a steam generator of FBR, a high pressured water flows inside of heat transfer tubes and exchanges its heat with sodium through the tubes. When a tube fails, water would leak into sodium, and react with sodium (Sodium Water Reaction; SWR). This reaction occurs rapidly and accompanies a high temperature jet. The jet has possibilities to cause a secondary failure of neighboring tubes. With regard to the secondary failure caused by deterioration of tube material due to high temperature (overheating rupture), quantification of heat transfer from fluid to the tube is important perspective of safety evaluation. The SWR experiments with SWAT-1R test facility was performed at Japan Atomic Energy Agency (JAEA). In the experiment, the SWR was produced by feeding water vapor from one tube toward a test section of pin bundle with 43 tubes. Thermo couples (T/Cs) were installed and temperature transient was measured in a certain tube near the reacting zone. In the present study, the heat transfer coefficient on the heat transfer tube has been investigated numerically based on the experimental temperature. Furthermore, we also have made an investigation of the flow characteristic on the heat transfer tube, taking into account the variation of the heat transfer coefficient. (author)