Abstract: A bundle of individual measuring lines extends through the cover of a reactor pressure vessel, the bundle extending into a tubular mounting having a multiplicity of extending tubes through which the individual lines of the bundle extend. In each tube the line is passed through a sleeve slidably inserted in the tube and having an inner portion soldered to the line and an outer portion welded to the tube's outer end. The length of the sleeve and tube between the soldered and welded joints is made sufficient to prevent the heat of welding from effecting the soldered joints. Each line can be removed from its tube by cutting away the welded joint and removing the line with its sleeve from the tube. The line can be reinstalled by returning the sleeve to its tube and making a new welded joint with the sleeve spacing its soldered connection with the line far enough to prevent the welding heat from affecting the soldered joint between the sleeve and the line.