Abstract: A method of obtaining a leakproof connection between a metallic tube having a leak and a metallic sleeve extending over the leak, includes expanding the sleeve being formed of a material having given strength values against an inner wall surface of the tube being formed of a material having strength values greater than the given values. In order to bridge a gap due to spring-back without the aid of an additional component of a shape memory alloy, a sleeve material having strength values lower than those of the material of the tube is used. A leakproof connection is obtained as the result of the greater spring-back of the tube.

Abstract: A method and an apparatus for testing, repairing or exchanging nozzles of the bottom of a reactor pressure vessel include inserting individual shielding containers into the reactor pressure vessel. Shafts pass through a shielding container and water-filled cartridges can be inserted into the shafts. Tubes for receiving probes of an in-core instrumentation are embedded into bottom plates of the remaining shielding containers and into bottoms of the cartridges. After removing a cartridge, a carrier for working tools can be introduced into the shaft. In this way the radioactive loading is considerably reduced by the probes inside or outside the reactor pressure vessel.

Abstract: After some time incipient cracks may occur in nozzles welded directly into a reactor pressure vessel cover for guiding a control rod, which make it necessary to exchange the nozzles. A method is provided for exchanging the nozzles which changes the structure of the cover little during removal and accomplishes low-stress installation. According to the method, the nozzles are installed with prestressing. An annular surface is introduced from the inside of the cover coaxially to the through-bore and a supporting surface is introduced from the outside of the cover, which surfaces serve for applying the prestressing force and arresting the same.

Abstract: A metallic sleeve for bridging a leakage point on a pipe is expanded onto the inner wall surface of the pipe with the aid of an expansion technique. During the expansion process, a gap of approximately 5 to 10 .mu.m occurs between the pipe and the sleeve due to the elastic resilience of the deformed materials. In order to prevent leakage through this gap, the peripheral surface of the end regions of the sleeve carry a component made of a shape-memory alloy which forms a seal between the sleeve and the pipe when a given temperature is reached. The sleeve is used primarily during the repair of heat exchanger tubes.

Abstract: A metallic sleeve for bridging a leakage point on a pipe has a predetermined wall thickness and requires relatively large expansion forces. In order to reduce spring-back after expansion has been completed, the sleeve is of multi-layer construction. The individual layers may be applied one after the other, and the wall thicknesses of all of the layers together correspond to the predetermined wall thickness of the metallic sleeve. The outer surface of each layer has a surface roughness with a profile depth of up to 0.1 mm and the surface hardness of the outer surfaces is greater than the surface hardness of the pipe and of the inner peripheral surfaces of the individual layers.

Abstract: In devices for the ultrasonic testing of a head screw inserted into a component, a skew position of an ultrasonic probe with respect to the screw head leads to inaccurate test results. In order to achieve precise test results independently of the position of the screwing-in axis, at least one ultrasonic transducer is disposed in a cradle-mounted centering piece of the ultrasonic probe. An adaptor of the centering piece is located nearer to the screw head than the ultrasonic transducer. The adaptor is matched to the configuration of the screw head. In order to achieve a centering connection with the screw head, the ultrasonic probe can be moved about its axis and in the axial direction. The device is principally to be used to test screws in the core baffle of a nuclear reactor vessel.

Abstract: Closure plugs have heretofore been required in an apparatus for stabilizing an unstable tube of a heat exchanger with a weakened wall region, in addition to providing a stabilizer. Furthermore, differing inside diameters can often not be bridged with the spreading range of the stabilizer. A rod which is fitted with two axially spaced-apart cam discs is provided in order to achieve not only a vibration-free stabilization but a simple sealing as well. Each cam disc has a spreading sleeve which engages over it. Once the spreading sleeve has been pressed against the inner wall of the tube by a relative rotation of the rod, the sleeve-shaped end of the rod is expanded by rolling or is welded in the tube sheet.