PURPOSE: To permit more miniaturization and obtain a circulating pump integrated type heat exchanger free of maintenance, by a method wherein the heat exchanger is provided with a solenoid pump, discharging primary system cooling agent in a lower plenum part to a primary system outlet nozzle through a double cylindrical discharging tube, formed by an insulating shroud and a pump casing.

CONSTITUTION: A solenoid pump 41, positioned at the inside of an insulating shroud 28 and mounted at the lower end of a pump casing 29, is arranged in a space at the center of the bundle of pipes of heat transfer tube 25. The suction port 41a of the solenoid pump, the discharging port 41b of the same, an annular flow passage 41c and an annular coil 41d are shown in a diagram. In this constitution, a motor for driving the pump above a heat exchanger 27 is eliminated, therefore, the height of the circulating pump integrated type heat exchanger is reduced by a height corresponding to the height of the motor whereby the miniaturization of the heat exchanger may be contrived. On the other hand, the solenoid pump does not necessitate maintenance different from a mechanical pump as has been employed in a prior art.