[en] For an advanced sodium-cooled fast reactor (named Japan sodium-cooled fast reactor: JSFR) a two-loop cooling system is designed by adopting a large-diameter piping system with high coolant velocity. The high-velocity piping system brings a flow-induced-vibration issue. To address this issue, experimental and analytical studies have been carried out to grasp flow-induced vibration characteristics in the piping. A flow-induced vibration evaluation methodology that was preliminarily verified with the experimental data tentatively indicated positive feasibility of the JSFR piping.This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in JSFR, in particular emphasizing on recent R and D activities that investigate unsteady elbow pipe flow. Experimental efforts have been made using 1/3-scale and 1/10-scale single-elbow test sections for the hot-leg pipe.First of all, experiments with water for the hot-leg piping were carried out using the 1/3-scale test section under rectified-flow conditions. The 1/10-scale experiment indicated no effect of pipe scale by comparison to the 1/3-scale experiment. The next experiment using the 1/3-scale test section was performed to investigate the effect of swirl flow at the inlet. Although the flow separation region was distorted at the downstream from the elbow, the experiment clarified that the effect of swirl flow on pressure fluctuation onto the pipe wall was not significant as shown. An additional experiment was intended to study the effect of elbow curvature. The experiments with water clarified that turbulence is weakened in an elbow with larger curvature than that of the JSFR. For cold-leg pipe experiments, a test section with triple elbows is necessary to simulate the JSFR pipe. Since the interference of multiple elbows should be investigated to understand turbulent flow in the cold-leg pipe geometry, 1/15-scale experiments with double elbows were carried out to compare the single-elbow experiment with the same scale. The experiment showed that flow in the first elbow influences a flow separation behavior in the second elbow. Simulation activities include Unsteady Reynolds Averaged Navier Stokes equation (U-RANS) approach with a Reynolds stress model using a CFD code and Large Eddy Simulation (LES) approach using in-house codes. A hybrid approach that combined with RANS and LES was also applied using a CFD code. Several numerical results appear in this paper, focusing on its applicability to the hot-leg pipe experiments. These simulations reasonably agreed with the experimental data using the 1/3-scale test section. The simulation also revealed that Reynolds number scarcely affects flow patterns and flow velocity distributions. The numerical results would be provided to the input data for the structural vibration evaluation of the piping