Patent Number: 055047882
Section: summary

FIELD OF THE INVENTION The present invention is directed to the field of nuclear power plant inspection devices. In particular, the present invention is directed to the field of nuclear power plant steam generator inspection. BACKGROUND OF THE INVENTION Nuclear power plants typically contain three major components as shown in FIG. 1: a reactor which produces superheated water which is transported to one or more steam generators; and a power turbine, driven by the steam, which generates electrical power. The superheated water is transported to the steam generator by a tube sheet. The tube sheet in a nuclear steam generator typically forms a pair of tube members or tube rows separated by a lane, and held together by a plurality of support plates, separated at periodic intervals. The height of each tube row may exceed thirty-two feet, and include six to eight or more support plates, each separated horizontally at three to six foot intervals. In the steam generator, the tube sheets carrying the superheated water are quenched with cool water, which generates the steam which drives the turbine. The water exits through a plurality of access ports situated at the bottom of each lane. This procedure for generating steam presents several problems. First, the water used to quench the tube sheet is supplied directly from adjacent rivers or reservoirs. Such water often has impurities or chemicals which may pierce or corrode both the steam generator tubes and the support plates. Periodic inspections of nuclear steam generators are required for obvious safety reasons connected to their operation, and steam generator cleanliness has been a problem due to such pipe corrosion and damage. The highly corrosive environment of the steam generator is particularly problematic for many of the older nuclear reactors in service throughout the world. Heretofore, the tubes and support plates of these steam generators were inaccessible from visual inspection. Information was gathered by complicated systems which could not adequately inspect all sections of the tubes and support plates. Because of the highly radioactive environment and the heat of the pipes, direct human inspection has typically been restricted to between three and five minutes per man per six month period. This time period does not provide an ample opportunity for the careful inspection for corrosion, holes and leaks. It is particularly difficult to inspect within the narrow lanes and the tubes at the support plates, because of the heat, radioactivity and narrowness of the lanes separating the tube sheet members and the small access ports. There are a number of issued patents directed to mechanical steam generator inspection and repair devices. U.S. Pat. No. 4,673,027 for example, discloses a device for inspecting and repairing the tubes of a nuclear reactor steam generator. The device includes a manipulator which is insertible in the chamber and which may be locked onto the tube sheet for supporting remotely controlled and monitored inspection instruments in tools. The manipulator includes a support leg which is adjustable in length in an axial direction, a main arm connected to and movable relative to the support leg and an equipment carrier which is connected to the main arm. U.S. Pat. No. 4,653,971 discloses a device for selectively positioning a tool carried by a vehicle which moves on a perforated plate, while the device utilizes an elbow which swings a telescoping arm in the position. Similarly, U.S. Pat. No. 4,945,979 discloses an improved robotic arm for effecting a tube plugging operation. The system also includes an elbow control mechanism. U.S. Pat. No. 4,205,939 discloses an apparatus for remotely repairing the tubes in a steam generator. The device includes a boom pivotally mounted on a column and a system for rotating the column and the boom therewith. The disclosed device further includes a tool which is operable on the tubes. U.S. Pat. No. 4,231,419 discloses a manipulator for inspecting and repairing the tubes of heat exchangers. An inspection arm is inserted and removed through a lead-in nozzle and a swivel arm carries an extendable and retractable mouthpiece carrier with a mouthpiece which can be aligned into the tube openings. Finally, U.S. Pat. No. 4,919,194 discloses a method of positioning a robot for inspecting and maintaining operations within a nuclear plant. While each of the above mechanism has been utilized to inspect and/or repair nuclear power steam generators and include the use of robotic manipulators or arms, none have been successfully utilized to inspect the outer diameter of the steam tube bundle or the support plates None of the above devices can enter the 1", 2", 4", or 6" diameter apertures situated proximate to the tubes The device disclosed in U.S. Pat. No. 4,673,027, for example, is described as entering the steam generator through a manhole, typically called the primary channel head. There has been a long felt need for a steam generator tube sheet and support plate inspection system which can be inserted through the access ports of the steam generator, and which can be used to thoroughly inspect the tubes and support plates situated within the lanes between the tube rows. There further has been a long felt need for a support plate inspection and cleaning device which facilitates the inspection and cleaning of the rear of a steam generator and which may be insertable through the smallest access ports in the steam generator. SUMMARY OF THE INVENTION In view of this long felt need and in accordance with the present invention, a support plate inspection device and method for inspecting within the lanes separating the tube sheets of a nuclear steam generator are disclosed. The device of the present invention facilitates the inspection of the tube sheet and support plates of a nuclear steam generator and particularly inspection within the lanes situated between the tubes. In a preferred embodiment, the device comprises a boom means for extending into an access port of a steam generator and into a lane separating two rows of tube members, said boom means being uprightable within said lane; and video camera means attached to said boom means for inspecting the tubes and support plates within said lane. In a more preferred embodiment, the present invention is directed to a support plate inspection device comprising first boom coupled by a rotatable connector to a second boom, said first and second booms being insertable through the access port of a steam generator and into a lane between two rows of tubes, said rotatable connector facilitating the rotational movement of said second boom such that said second boom can be held upright through said tube lane and adjacent to the tubes and support plates of a steam generator, the second boom having a charge coupled device (CCD) video camera attached thereto such that said second boom and CCD video camera can be uprighted and positioned adjacent to the support plates in a steam generator such that the tubes and support plates can be examined by said CCD video camera. In more preferred embodiments, the second boom comprises a plurality of telescoping members which can extend a length of up to approximately 32 feet, the height of a standard steam generator tube. The CCD video camera is preferably mounted to a pan and tilt means which is under the control of a remote joy stick. The CCD video camera also preferably includes an auto-focus mechanism. In yet more preferred embodiments, the present invention includes means for cleaning the tubes and support plates. The present invention is also directed to a method for inspecting the support plates and tube sheet of a nuclear steam generator. The method comprises the following steps: inserting boom means through an access port of said generator and within a lane separating two tube sheets, said boom means having a CCD video camera attached thereto; and uprighting said boom means within said lane such that said CCD video camera may be held adjacent to said tube sheet and support plates such that said tube sheet and support plates can be inspected by said CCD video camera. These and other advantages and features of the present invention will become apparent from the detailed description which follows.