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Estimation of Heat Transfer Coefficient and Flow Characteristics on Heat Transfer Tube in Sodium-Water Reaction

In the steam generator of a sodium-cooled fast reactor, high-pressure water flows inside heat transfer tubes while liquid sodium flows on the shell side. Heat is exchanged through the tube wall. When the tube fails, water vapor leaks into the sodium stream, and a sodium-water reaction is initiated. This reaction occurs rapidly and generates a high-temperature jet. It then becomes possible for neighboring tubes to experience a secondary failure due to overheating. With regard to the secondary failure, an estimate of heat transfer from fluid to the tube is important for safety evaluation. In the present study, a numerical analysis has been carried out to determine the heat transfer coefficient from temperature data obtained in a sodium-water reaction experiment. By updating the heat transfer coefficient, an inverse problem of heat transfer has been solved in the analysis based on the result of the SWAT-1R experiment. It is found that the heat transfer coefficient fluctuates largely during the reaction. The heat transfer coefficient is affected by the flow characteristics. Hence, we characterize the flow pattern near the heat transfer tube at typical periods in the phenomenon progression.