Patent Number: 055263844
Section: claims

1. Fuelling machine for fuel assemblies for the core of a nuclear reactor, inside a reactor vessel having an open upper end in a cavity of the reactor, including horizontal guide means arranged above the reactor vessel, a carriage mounted movably on the guide means, a tubular external shaft, fastened on the carriage with its axis vertical, a cylindrical internal mast mounted in a coaxial arrangement and so that it can move axially inside the external shaft, by virtue of guide elements and means for displacing the internal mast axially of the external shaft, said displacing means being carried by the carriage, wherein the guide elements for the internal mast include at least two straight beams provided with means for fastening in an axial direction on the exterior surface of the external shaft, at least two sets of rollers which can rotate about axes perpendicular to the axial direction of the external shaft and of the internal mast being mounted on each of said beams, spaced apart from one another in the axial direction, the external shaft including a through opening for passage of each of the sets of rollers of each of the beams, inside the external shaft in order to guide the internal mast. 2. Fuelling machine according to claim 1, wherein the rollers of each of the sets of rollers are rotationally mounted on a support which is solidly attached to the beam and extends perpendicularly to the axial direction of the beam and is capable of passing with clearance inside an opening in the external shaft. 3. Fuelling machine according to claim 2, including two guide elements arranged at 180.degree. from one another about the axis of the external shaft, so that the rollers of each of the sets of rollers are arranged symmetrically with respect to an axial plane of the external shaft. 4. Fuelling machine according to claim 3, wherein the mobile internal mast includes guide rails including plane straight tracks interacting with the rolling surfaces of the rollers of the sets of rollers in order to guide axial displacement of the mobile mast. 5. Fuelling machine according to claim 1, wherein the means for removably fastening each of the beams on the external shaft include at least one positioning stud solidly attached to an axial end part of the beam and engaging in an opening in a support foot solidly attached to the external shaft, and at least one threaded fastening stud to be screwed into a tapped sheet externally fastened on the external shaft and including a part for engagement in an opening passing through an end part of the beam, opposite the positioning stud. 6. Fuelling machine according to claim 5, wherein the means for removably fastening each of the beams include two positioning studs and two fastening studs. 7. Fuelling machine according to claim 1, wherein the straight beams of the guide elements each include a handling ring. 8. Fuelling machine according to claim 6 or 7, wherein the external shaft includes, above each of the lower support feet of a beam of a guide element, a guide wall which is flared upwards in the form of a funnel in order to guide the end part of the beam including the positioning stud and for engaging the positioning stud in the opening in the support foot, during positioning of the guide element on the external shaft.