Patent Number: 
Section: claims

1. A guide tube assembly for upper internals of a nuclear reactor arranged under water in a pit and a device for handling the guide tube assembly, the combination comprising:a) the guide tube assembly having an upper tube and a lower tube in each of which there are fixed horizontal guide plates arranged such that they are spaced apart in an axial direction, each guide plate including a central cavity and guide openings for guiding a rod cluster control assembly that controls reactivity in a core of the reactor, andb) the handling device including:a gripper including a tubular body;two opposing arms, constructed of symmetrically displaceable linkage assemblies, located at one end of the tubular body and moveable between a collapsed retracted position and an expanded deployed position, the arms bearing against a lower surface of a contacted guide plate when in the deployed position;a control member located at an opposite end of the tubular body for controlling the arms;an actuator rod axially slidable in the tubular body and connected at opposite ends thereof between the control member and the arm linkage assemblies for actuating the arms between the retracted and deployed positions;the length of the tubular body of the gripper being:greater than the distance between an upper end of the upper tube and a first guide plate of the lower tube; andless than the distance between the upper end of the upper tube and a third guide plate of the lower tube. 2. The device according to claim 1, wherein the tubular body has, at its second end, a bearing piece bearing against the upper end of the upper tube, the bearing piece supporting the control member. 3. The device according to claim 1, wherein the control member deploys the arms and displaces the arms toward the bearing piece. 4. The device according to claim 1, wherein the bearing piece, contacting the upper end of the upper tube, comprises, on its face, at least one elastic washer. 5. The device according to claim 1, wherein the control member comprises a load-limiting spring and is connected to the arms by a threaded assembly. 6. A guide tube assembly for upper internals of a nuclear reactor arranged under water in a pit and a device for handling the guide tube assembly, the combination comprising:a)the guide tube assembly having an upper tube and a lower tube in each of which there are fixed horizontal guide plates arranged such that they are spaced apart in an axial direction, each guide plate including a central cavity and guide openings for guiding a rod cluster control assembly that controls reactivity in a core of the reactor, andb)the handling device including:a gripper including a tubular body;two opposing arms, constructed of symmetrically displaceable linkage assemblies, located at one end of the tubular body and moveable between a collapsed retracted position and an expanded deployed position, the arms bearing against a lower surface of a contacted guide plate when in the deployed position;a control member located at an opposite end of the tubular body for controlling the arms;an actuator rod axially slidable in the tubular body and connected at opposite ends thereof between the control member and the arm linkage assemblies for actuating the arms between the retracted and deployed positions;the length of the tubular body of the gripper being:greater than the distance between an upper end of the upper tube and a first guide plate of the lower tube; andless than the distance between the upper end of the upper tube and a third guide plate of the lower tube;wherein the tubular body has, at its second end, a bearing piece bearing against the upper end of the upper tube, the bearing piece supporting the control member;wherein the control member deploys the arms and displaces the arms toward the bearing piece;and wherein the bearing piece, contacts the upper end of the upper tube, and includes on its face, at least one elastic washer;and further wherein the control member comprises a load-limiting spring and is connected to the arms by a threaded assembly.