Proposed guideline of flow-induced vibration evaluation for hot-leg piping of primary cooling system in sodium-cooled fast reactor. Supplemental interpretation

Japan Atomic Energy Agency (JAEA) has been conducting conceptual study of an advanced sodium cooled fast reactor (named Japan sodium-cooled fast reactor: JSFR) under the framework of Fast reactor Cycle Technology development (FaCT) project. The JSFR design adopts a two-loop cooling system that enables the scale merit to be significantly enhanced, thereby leading to reduction in the capital cost of the plant. Since the two-loop cooling system increases the primary coolant flow rate per loop, a large-diameter piping system is designed with high coolant velocity (9m/s) . To reduce thermal stress, the primary hot-leg piping with large diameter in JSFR is designed to be have thin wall. JSFR adopts an L-shaped short elbow, the curvature radius of which is equivalent to the piping diameter, for the hot-leg piping system in order to compact the reactor building volume. The turbulence generated by flow separation in the short elbow is predicted to be more severe than that in the long elbow. Such a turbulent flow, may raise a flow-induced vibration issue. It is necessary for designers to select appropriate design and suppress the flow-induced vibration as well as to evaluate and confirm the integrity of piping against the flow-induced vibration. JAEA has been developing a flow-induced vibration methodology applied to the JSFR piping under the FaCT project. As part of this development, flow pattern in the single-elbow pipe has been investigated with the measurements of fluid force induced by turbulent flow and of the flow-induced vibration response. The experimental results have been served to the development and vibration of the flow-induced vibration evaluation methodology. Based on these outcomes, JAEA has established a working group on a guideline of large-diameter piping flow-induced vibration evaluation under the JAEA's Thermal-Hydraulic Research Committee for creating the JAEA internal guideline. The first proposal of the guideline was summarized from the achievements of the working group activity. Since technical discussion has been made deeply in developing the guideline, this report summarizes technical background and understanding for the guideline. (author)