Abstract: Disclosed is a highly reliable weld repairing method to repair a crack defect in structures and apparatus inside pressure vessels of nuclear reactors, while preventing generation of new crack defects in the structures and apparatus during the repairing. These structures and apparatus are made of any of stainless steel and Ni-base alloys, and are irradiated with high energy corpuscular ray during operating period of the reactor. The repairing method includes the steps of eliminating a region of the structure or the apparatus including a portion having the crack defect, and executing spot welding at a surface of the region continuously or interruptedly in a manner so as to form a first welded layer in a manner that each of the spot welded spots is half-overlapped with adjacent welded spots. Additionally, welding for forming at least a second layer, on the first welded layer, so that the at least a second layer is not deeper than a weld penetration thickness of the first welded layer can be performed.

Abstract: An image processing welding control method comprises detection of isothermal pattern of a weld zone in the welding state through photographing the weld zone by an infrared camera; calculation of the area of the region defined by the isothermal line detected; comparison of the area with a standard area which is obtained in advance; control of welding heat input such that the area will be substantially the same as the standard area whereby a suitable welding heat is input the welding portion; detection of an asymmetric extent of said isothermal pattern; and controlling the torch position such that the asymmetric extent will be within a predetermined value, so that the torch will be strictly aligned with the welding groove center. This method enables two kinds of welding control methods, torch position control and welding heat input control, based on the same image information.

Abstract: A welding apparatus with monitor means including a welding torch having an electrode located in the vicinity of its forward end and supported at its rearward portion by a welding head for rotational movement about its longitudinal axis and back-and-forth reciprocatory movement along the longitudinal axis. The welding torch further includes an electric conductor covered at its outer periphery with an insulator and formed with a gas sump in the vicinity of the electrode. The electric conductor has defined therein a gas supply passageway for supplying gas shield gas, a bore for allowing an image guide and a light guide to extend therethrough, and a bore for allowing a fluid to flow therethrough to cool the electric conductor. The image guide and light guide have their forward ends located in the gas sump, so that they can command a view of outside through guide openings serving concurrently as gas ejecting ports for ejecting the shield gas therethrough.