Development and verification of wall-flap-gate as tsunami inundation defence for nuclear plants

A wall-flap-gate is automatic watertight door, and it works by buoyancy without powered machineries and human operations. In the Tohoku Earthquake tsunamis, serious damages were caused by inundation from ventilators of outer walls in power plants. The wall-flap-gate is estimated to be effective in keeping sustainability of nuclear plants against extreme tsunamis. The present study examines the hydrodynamic characteristics of the wall-flap-gate by hydraulic model experiments and verifies its capability of flood prevention for nuclear plants through various prototype tests.The experimental results proved that the wall-flap-gate had sufficient strength, watertightness, and durability against tsunamis and that its motion was not disturbed by debris. The viability of the wall-flap-gate as an inundation defence structure for nuclear plants was confirmed through this study. As a result, practical wall-flap-gates are installing on Hamaoka nuclear power station in Shizuoka prefecture, Japan.