Control rod drives

The present invention provides control rod drives of a BWR type reactor with a simple structure and reduced number of operation steps. Namely, an opening is disposed at the upper end of a control rod housing. A main body of control rod drives is inserted withdrawably from the opening. A wet-type electric motor or a hydraulically driven electric motor is disposed detachably at the lower end of the control rod housing. The rotational shaft of the electric motor is connected to a screw shaft of the main body of control rod drives by way of first and second connection members. With such a structure, (1) the structure is simplified and the number of steps is reduced, (2) since only the electric motor is disposed as equipment to be handled below the reactor pressure vessel, the device is simplified and requires no wide space, (3) as a result, the height for the installation of the reactor pressure vessel is reduced and accordingly, the height of the reactor is also reduced. (4) as a result, installation is reduced and earthquake resistance can be improved. (I.S.)