A method and apparatus for removing from the tube sheet and transfer tubes of a nuclear steam generator sludge deposits which occur from the use of all volatile treatment water chemistry. A continuously activated suction apparatus maintains at a low level the water/sludge inventory on the tube sheet. A high pressure first water lance is oscillated and stepped inwardly along the central tube lane of the generator to dislodge the sludge from the tube plate and heat exchange tubes. After this lance has been stepped inwardly to a predetermined position, a low pressure second water lance is activated and periodically advanced to a position just short of the first lance and functions both to dislodge sludge and to form a water barrier which prevents redeposition of sludge in the clean area. The flows from both lances combine to produce a high flow of water-suspended sludge which flows across the top of the tube sheet to the annulus of the steam generator where it is removed by the suction apparatus without any redeposition. Suction dams are placed in the vicinity of the suction apparatus in order to increase the efficiency of the removal of the water-entrained sludge by suction.

The high-pressure lance is shiftably mounted in a bearing bush which is swingably mounted in a base which is to be secured over an opening in the wall of the steam generator. On the base are mounted a revolving cylinder which can swing the bearing bush to-and-fro over 180.degree. and a cylinder-piston unit which can shift the lance. A pneumatic control mechanism couples the lance either by means of clamping-cylinders to the bearing bush during its swinging or by means of another clamping cylinder to the piston of the cylinder-piston unit during its shifting.

A device for removing a cladding material from a bottom portion of a control rod guide tube of a nuclear reactor. A rotor tube is removably mounted in a housing of a control rod drive of the nuclear reactor and has at least its forward end portion hydraulically insertable into the bottom portion of the control rod guide tube through an opening located in a lower portion of the control rod guide tube for inserting the control rod drive. The rotor tube is provided at the forward end portion thereof with a foldable rotary brush and cleaning water supply nozzles. A rotary drive shaft is extending through the rotor tube for rotating the rotary brush. The cladding material deposited on the bottom portion of the control rod guide tube that has become radioactive can be readily and positively removed therefrom with a small volume of water while enabling the risk of exposure to radiation to be minimized at a time the operation of cleaning the bottom portion of the control rod guide tube is performed.

A steam generator for a nuclear power station in which the flow of secondary fluid is deflected and distributed by a block articulated on a fixed horizontal pivoting spindle, such as to retain maintenance access to the tube place by tooling introduced through orifices in the outer casing, and to eliminate dead zones difficult to access for cleaning and servicing the tubes.

A sludge collection system for a vertically oriented nuclear steam generator is provided with an upwardly open chamber for receiving separated liquid and incoming feedwater that contain sludge particulates. A plurality of sludge collecting containers are positioned within the chamber and include a top rim encompassing an opening leading into the interior of each container. Generally flat perforated covers are positioned over each container such that a gap is formed between the cover and the adjacent top rim. Particulate material in the water entering the container can settle within the container because of relatively stagnant conditions. Sludge agitation and removal means are provided for remotely cleaning the containers. The sludge collection system components are sized to permit retrofitting this system into existing steam generators.