Patent Number: 053176073
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a crack removal tool. More specifically, this invention relates to a crack removal tool which utilize EDM techniques and which are suitable for removing cracks which appear within conduits, nozzles and the like, such as are found in nuclear reactor related structures. 2. Description of the Related Art During inspection of certain types of nozzle penetrations in pressurized water nuclear reactor heads, cracks may be discovered in weld areas of one or more nozzles. Access to these defects is severely hindered by the presence of thermal sleeves which are welded in place in nozzles and which prevent access with tooling. Accordingly, it is extremely difficult to effect repairs. SUMMARY OF THE INVENTION It is an object of the present invention to provide cutting and removal tools or heads which simplify the removal and repair of cracks which tend to develop in nozzle penetrations and similar types of conduiting which are used in nuclear reactors and the like type of environments. In brief, the above object is achieved through the use of EDM (electro discharge machining) heads which were developed so as to permit the cutting and partial removal of a thermal sleeve so as to expose a cracked area to permit defect blending within the head penetration In brief, the above object is achieved through the use of a tool system which features an EDM crack removal head which can be positioned within the nozzle or thermal sleeve and then oscillated in vertical and horizontal directions to enable precise material removal, leaving a surface free from cracks and in a condition for rewelding if required. In the event that a crack is found in a surface which is covered by a thermal sleeve, a small specialized EDM cutting head which can be delivered from an under side of the reactor head, and which has the ability to pass through the ID of the thermal sleeve, is used to cut the thermal sleeve and allow a portion of the sleeve to be removed. The crack can then be readily removed using the crack removal type of head. The use of the tooling system according the present invention enables repair of cracked nozzles in PWR heads from the underside, thus eliminating a costly need to remove a control rod drive mechanism and associated hardware from a reactor. More specifically, a first aspect of the present invention resides in a tool for use with conduiting, comprising: an elongated shaft structure; first and second support members disposed on the shaft structure which engage an inner wall of a conduit when actuated; cutting head means, supported on the shaft structure between the first and second support members, for performing a cutting operation on an inner wall of the conduit, the cutting head means including a movable cutting electrode and first servo means for selectively moving the electrode member laterally outwardly with respect the shaft structure; and second servo means, operatively connected with the cutting head mean for selectively displacing the cutting electrode in at least one of first and second rotational directions. A second aspect of the present invention resides in a crack removal tool comprising: an elongate shaft structure; first and second inflatable members disposed on the shaft structure; a crack sensor supported on the shaft structure at a location between the first and second inflatable members; a crack removal head supported on the shaft between the first and second inflatable members at a predetermined distance from the crack sensor, the crack removal head including a removal electrode and electrode servo means for selectively displacing the removal electrode radially with respect to an axis of the shaft structure; and head servo means for selectively displacing the crack sensor and the crack removal head with respect to the first and second inflatable members and for causing the crack removal head to undergo rotation about the axis of the shaft structure in at least one of first and second rotational directions. A third aspect of the present invention resides in a sleeve cutting tool comprising: an elongate shaft structure; first and second inflatable members disposed on the shaft structure; a cutting head supported on the shaft between the first and second inflatable members, the cutting head including a cutting electrode and cutting electrode servo means for selectively displacing the cutting electrode radially with respect to an axis of the shaft structure; and cutting head servo means for selectively displacing the cutting head in at least one of first and second rotational directions. A fourth aspect of the present invention resides in a crack removal system comprising: a crack removal tool which comprises: a first elongated shaft structure; first and second selectively actuatable support members disposed on the shaft structure; a crack sensor supported on the shaft structure at a location between the first and second support members; a crack removal head supported on the shaft between the first and second support members at a predetermined distance from the crack sensor, the crack removal head including a crack removal electrode and a first servo means for selectively displacing the crack removal electrode radially with respect to an axis of the shaft structure; and second servo means for selectively axially displacing the crack sensor and the crack removal head with respect to one of the first and second support members and for causing the crack removal head to undergo rotation about the axis of the shaft structure in at least one of first and second rotational directions. A fifth aspect of the present invention resides in a crack removal system further comprising: a sleeve cutting tool which comprises: a second elongate shaft structure; third and fourth selectively actuatable support members disposed on the second shaft structure; a cutting head supported on the shaft between the third and fourth support members, the cutting head including a cutting electrode and third servo means for selectively displacing the cutting electrode radially outwardly with respect to an axis of the second shaft structure; and fourth servo means for selectively causing the cutting head to undergo rotation about the axis of the shaft structure in at least one of first and second rotational directions. A further aspect of the present invention is presented in a method of repairing cracks in a nozzle in which a sleeve is fixedly disposed, comprising the steps of: inserting sleeve cutting tool into the sleeve; activating support means which engages the inner wall of the sleeve and which maintains the sleeve cutting tool in a predetermined position within the sleeve; cutting through the sleeve using the sleeve cutting tool in a manner which allows a portion of the sleeve to be removed; removing the portion of the sleeve; inserting a crack removing tool into the portion of the nozzle wherein the sleeve has been removed; activating support means on the crack removing tool to support the crack removing tool in the nozzle; using a crack detecting sensor to locate the position of a crack in the nozzle; moving the crack detecting sensor away from the location at which the crack is detected and moving a crack removal head into position opposite the location whereat the crack was detected; and removing portion of the inner wall of the nozzle using the crack removal head.