Thermal Hydraulics Behavior Around a Single Heated Rod With Adhesion Products of Sodium-Water Reaction

<jats:p>A safety assessment on Sodium-Water reaction in a steam generator (SG) of the SFBR is also one of significant issue. If a heat transfer tube is damaged by some reasons, the high pressure water or steam would leak into the sodium side as a high-temperature and high-corrosive sound-speed jet, and it might give rise to the ruptures of surrounding heat transfer tubes caused by overheating. On the suspicion of secondary failure of tubes, we need to understand the detail of heat transfer characterics on its surface. To grasp these phenomena mechanically and systematically, we studied in the case of low-speed jet. In our previous study, an experiment on the heat transfer between the tube and the jet was carried out by using a horizontal heated-rod and injecting argon gas-steam mixture (reaction gas) under the condition of low sodium temperature and low-speed gas jet [ICONE18-29388]. The result showed that the heat transfer between the rod and the reaction jet was decreased by the reaction products, adhered on the rod surface. But from the reasons of the sodium purity and the rod design, the correct adhesion condition was not declared. In the present study, we got over these problems. A simple method for purification of the used sodium which includes the reaction products was first established. Then the local heat transfer characteristics of the reaction jet were investigated with the more points of measuring temperature on the rod surface than the previous study by using the purified sodium. As soon as injecting the gas mixture into the sodium pool, the heat transfer to the rod surface was reproducibly decreased by the adhesion of the reaction products on it. In the first 10 second from the injection of the gas mixture, the local heat transfer at the lateral side of the rod was decreased obviously. About 10s later from the injection of the gas mixture, the heat transfer at the backward side also began to decrease. At the front side of the rod, the heat transfer was less affected by the chemical reaction. Thus, it was confirmed that the local heat transfer is closely influenced by the position of the adhesion products, and its products tend to adhere on the lateral and backward sides.</jats:p>