Flow damper, pressure accumulation and water injection device, and nuclear power equipment

A flow damper 34 provided with a cylindrical vortex chamber 35, a low-flow-rate pipe connected to a peripheral plate 35C of the vortex chamber 35 along a direction tangential thereto, a high-flow-rate pipe connected to the peripheral plate 35C at a prescribed angle in relation to the low-flow-rate pipe, an outlet pipe connected to an outlet formed in the center of the vortex chamber 35, and a pressure equalizing pipe 50 having ends 50A connected to portions of the peripheral plate 35C on both sides of the outlet that are closer to the low-flow-rate pipe and high-flow-rate pipe connection portions than positions opposing each other across the outlet, wherein the pressure equalizing pipe 50 is disposed such that at least a portion thereof is positioned above a top plate 35A of the vortex chamber 35, and a hole part 51 for gas release is formed at the uppermost part 50D of the pressure equalizing pipe 50.