Patent Number: 050842285
Section: claims

1. Sealing device for an instrumentation column penetrating a head of a pressurized-water nuclear reactor vessel, inside a tubular follower fastened in a penetration opening of said head and projecting inwardly and outwardly from said head, having a tubular bearing unit fastened to an end of said follower situated outside said head and in its extension, in which a leaktight bearing area is provided for said instrumentation column traversing a bore of said tubular bearing unit and of said follower, and means for pulling on one end of said instrumentation column projecting outwardly from said bearing unit and resting on an end of said bearing unit, wherein said bearing unit has an end part in which is provided said bearing area of said instrumentation column and on which said pulling means of said instrumentation column rests, consisting of two successive sections in an axial direction, (a) a first section being fastened to an outer end of said follower and having an outer, peripheral annular throat and at least three openings traversing said first section in an axial direction so as to open into said throat;  (b) a second section superposed on said first section and having openings in an extension of said openings of said first section and said bearing area of said instrumentation column;  (c) a mounting piece consisting of two half-rings being introduced into said throat of said first section and comprising tapped openings in the extension of said openings of said first and second sections in assembled position where screws are introduced into coinciding openings of said first and second sections and screwed into said tapped openings of the mounting piece so as to assemble said first and the second sections, a sealing strip being placed therebetween. 2. Sealing device according to claim 1, wherein said means for pulling on an end of said instrumentation column consists of an annular pressure plate arranged about the upper part of the thermocouple column projecting above the upper surface of the upper section of the bearing unit, a traction ring with two parts which can be engaged laterally into a throat machined in the upper part of said thermocouple column, and at least three compression screws engaged in tapped holes axially traversing the compression plate and bearing with their heads against a bearing surface of the second section opposite the first section. 3. Sealing device according to claim 2, wherein each of said compression screws has, about its head, a washer having a deformable locking part intended to enter a cavity of the upper surface of said second section in order to lock the screw against rotation. 4. Sealing device according to claim 1, wherein the compression plate has through openings enabling access to the heads of the screws for assembling said first and second sections. 5. Sealing device according to claim 1, wherein said pulling means has four screws arranged at 90.degree. about an axis of said thermocouple column and about the penetration of said head of said vessel. 6. Sealing device according to claim 1, comprising four screws for assembling said first section and said second section of the upper part of said bearing unit. 7. Sealing device according to claim 1, wherein said first section is unitary, with a tubular mounting element of said bearing unit at the end of said follower situated outside said head of said vessel.