Host: The Japan Society of Mechanical Engineers
Name : The 30th International Conference on Nuclear Engineering (ICONE30)
Date : May 21, 2023 - May 26, 2023
Self-actuated shutdown system (SASS) is one of the innovative technologies for application to an advanced-loop-type sodium-cooled fast reactor designed in Japan. SASS is a passive reactor-shutdown system that utilizes a Curie-point electromagnet (CPEM), which features the characteristic of loss in magnetism when the magnet temperature reaches the Curie point. A control rod with SASS is inserted into the core by gravity without recourse to any active shutdown system. To allow the SASS to effectively function, efficiently guiding high-temperature fluid from the fuel assembly to CPEM is important. Therefore, CPEM features a complicated shape such as having 45 fins, and a flow collector is installed upstream of CPEM to direct the flow from the fuel subassembly outlet to CPEM. In this study, a full-scale water experiment was performed to understand the flow field around CPEM and obtain data for code validation. The test section that simulated the structure from the fuel subassembly outlet to CPEM was mainly made of acrylic to enable flow visualization and particle image velocimetry (PIV) measurement. The flow velocity conditions were set from 0.26 m/s (Re = 48,000) to 1.55 m/s (Re = 280,000) at the fuel subassembly outlet. We confirmed from the PIV measurements that the flow from the subassembly outlet was directed to CPEM by the flow collector. The velocity at the inlet of the fins was approximately 60% of that at the fuel subassembly outlet. In addition, the velocity distributions around CPEM were almost the same regardless of Re number in the Re range in this study. Moreover, after passing through the flow collector, the dependence on the circumferential direction of the velocity distribution was almost eliminated. These experimental results were useful not only for understanding the flow field around CPEM but also for code validation.
