Patent Number: 042591538
Section: summary

The present invention relates to fuel recharging devices of nuclear reactors and, more particularly, to devices for the removal of fuel assemblies and cans for rods of the control and safety system from the core of a nuclear reactor, primarily, a fast reactor with liquid metal coolant. There is known a device for the removal of fuel assemblies and cans of the control and safety system from the core of a nuclear reactor, comprising a hollow bar, wherein there is arranged a grip intended to interact with the head of a fuel assembly. The grip is coupled to the hollow bar by a means which makes it possible for the grip to move along the bar's axis. This type of fuel recharging device is the commonest in the existing nuclear reactors. Devices for the removal of fuel assemblies from nuclear reactor cores, provided with grips to grip fuel assemblies by their heads, make it possible to grip and withdraw from the nuclear reactor core any of densely packed fuel assemblies. In high-power fast reactors, fuel assemblies and cans of the control and safety system are exposed to a powerful integrated fast-neutron flux which causes swelling and affects the mechanical properties of the materials of fuel assemblies arranged in the reactor core. The high temperature of the liquid metal coolant in the core also causes deformations and affects the mechanical properties of the materials of fuel assemblies. A change in the geometrical parameters of fuel assemblies may cause jemming of the tails of fuel assemblies in collector holes (sockets) of the core. If in an attempt to remove a fuel assembly jammed in its socket, the latter is gripped by the head, there is the danger that the fuel assembly may break in the middle, because it is precisely the middle of a fuel assembly that has the highest temperature and is exposed to the highest integrated fast-neutron flux, while the reactor is in operation. It is an object of the present invention to provide a device for the removal of fuel assemblies and cans of the control and safety system from the core of a nuclear reactor, which would make it possible to withdraw from the reactor core even such fuel assemblies that are jammed in their sockets, without destroying the assemblies. The foregoing object is achieved by providing a device for the removal of fuel assemblies and cans of the control and safety system from the core of a nuclear reactor, comprising a hollow bar, wherein there is arranged a grip adapted for axial movement along the bar's axis and intended to interact with the head of a fuel assembly to be removed, which device is characterized, according to the invention, by that the internal diameter of the hollow bar makes it possible for the bar to envelop elements being removed, while at the end of the bar, which faces the element being removed, there is mounted an auxiliary grip intended to interact with the outer surface of the element being removed, the length of the bar being sufficient for the auxiliary grip to reach the end of the element being removed, while the main grip is on the head of the element, which is at the opposite end of that element. It is advisable that a sleeve member be fitted over the hollow bar, which would envelop the auxiliary grip and be adapted for axial movement relative to the hollow bar, and that the sleeve member be provided with openings in a number corresponding to that of the jaws of the auxiliary grip, each of said openings being arranged opposite one jaw of the auxiliary grip and having profiled surfaces to interact with external profiled surfaces of the jaws of the auxiliary grip. It is desirable that both the hollow bar and the sleeve member be provided with at least one longitudinally extending slot having a length not less than that of elements to be removed, the location and width of the slot being determined by the shape, size and arrangement of elements in the reactor core. The proposed device for the removal of fuel assemblies and cans of the control and safety system from the core of a nuclear reactor rules out breaking jammed fuel assemblies and cans of the control and safety system in the course of their removal from the reactor core, which is due to the fact that fuel assemblies and cans are gripped by their lower portion which is to a lesser extent exposed to the effects of high temperatures and the integrated fast-neutron flux. The provision of longitudinal slots in the hollow bar and the sleeve member makes it possible for the auxiliary grip to reach the lower end of an element being removed even if some of the adjacent element are jammed.