Patent ID: 8842799

Claim:
A jet pump disposed in a reactor pressure vessel of a boiling water reactor, the jet pump including an inlet mixer pipe connected to a riser pipe, and a diffuser pipe connected to the inlet mixer pipe to cause a forced circulation of coolant water in the reactor pressure vessel, the jet pump comprising: a slip joint structure connecting the inlet mixer pipe and the diffuser pipe to each other by inserting the inlet mixer pipe into an upper end opening of the diffuser pipe with a clearance left therebetween; and a self vibration damping structure configured such that when the clearance defined by an outer pipe wall of the inlet mixer pipe and an inner pipe wall of the diffuser pipe is widening or narrowing due to vibration of the inlet mixer pipe or the diffuser pipe, a flow path resistance inside a clearance flow path for pumped coolant water defined by the clearance is not smaller than a fluid inertia force all over the clearance flow path.