Device for closing a drive casing pipe

The invention relates to a device for closing a pipe opening, opening upwards, of a drive casing pipe accommodating the control rod drive of a boiling water reactor, said device comprising a closure plug with a plug housing, opening downwards, a sealing element guided axially so as to be movable within the plug housing, which element has a sealing face providing a sealing contact with an annular counter face defining the pipe opening, a locking element provided to fix the plug housing on the drive casing pipe, and a spring, which is supported by the upper end thereof on the plug housing and by the lower end thereof on the sealing element and holds said element in a lower end position.