There are provided a generator internal pipe section that extends in the horizontal direction inside a steam generator; and a communication pipe section that is connected to the generator internal pipe section and is provided with a communication path, wherein one end of the communication path is connected to the pipe path at an upper end of a cross-section perpendicular to the flow direction of the cooling water in the pipe path and the other end of the communication path is positioned at the downside in the vertical direction in relation to one end of the communication path, and wherein one end side and the other end side of the communication path are connected at a position existing at the upside in the vertical direction in relation to one end.