In Japan Atomic Energy Agency (JAEA), a study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius has been conducted. Flow-induced vibration in the elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this study, applicability of the Unsteady Reynolds Averaged Navie-Stokes equations (U-RANS) approach with the Reynolds Stress Model (RSM) using a commercial CFD code to the flow through the short-elbow under high Reynolds number condition was examined for the 1/10 scaled water experiment simulating the hot-leg piping of the JSFR. As a result, the time-step dependency is observed in flow structure.