Study on flow induced vibration evaluation for a large scale JSFR piping, 3; Pressure fluctuation characteristics in 1/3 scale hot-leg piping experiments under deflected inflow conditions due to UIS structures

Sago, Hiromi*; Shiraishi, Tadashi*; Watakabe, Hisato*; Xu, Y.*; Aizawa, Kosuke ; Yamano, Hidemasa   

A Japanese sodium-cooled fast reactor has adopted a two-loop cooling system. The reduced number of loops requires large-diameter piping and increased sodium velocity, raising a flow-induced-vibration issue. This paper describes a 1/3-scale experiments under deflected-flow conditions at the hot-leg piping inlet. Calculation of the flow in the reactor vessel (RV) suggested the deflection is generated by the upper internal structure (UIS) in the RV, and a UIS was partially modeled. We investigated the influence of the deflected flow on a size of a flow separation, the flow velocity distribution, and intensity of fluctuating pressure on the pipe wall. The deflect flow deformed the region of the flow separation. The 0% opening case yielded the result that the velocity distribution near the region of flow separation and its size differ from those in the other opening cases. We attribute it to the influence of the secondary flow induced by deflection.