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: Neutron absorber rods are mounted with their upper ends in bores formed in a mounting device and the absorber rods are movable within guide tubes of a nuclear reactor fuel assembly. A holding device is firmly attached to a fixed location of the storage pit. The holding device has holder tubes for absorber rods. In order to replace the absorber rods, the mounting device with the neutron absorber rods is placed and locked in the holding device, the mounting device is disconnected from at least one neutron absorber rod to be replaced, the mounting device with any neutron absorber rods still attached to it is removed from the holding device, the disconnected neutron absorber rods remaining in holder tubes of the holding device are removed for storage, new neutron absorber rods are placed in the empty holder tubes and the mounting device with any neutron absorber rods still connected to it are placed in the holding device and the mounting device is connected to the new neutron absorber rods.

Abstract: An apparatus for inspecting fuel assemblies, includes a water container, a receptacle disposed in the container for securing bases of fuel assemblies vertically disposed in said container, a beam, a plurality of fingers engaged by the beam, measuring probes supported on the fingers, and a guiding device disposed in the container and accurately positioned relative to the receptacle for guiding the beam laterally toward the fuel assemblies for inserting the measuring probes in a given direction into spaces between cladding tubes of fuel rods of the fuel assemblies, each of the fingers being movable relative to the given insertion direction after striking an obstacle.