Patent Number: 039487237
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to liquid metal cooled nuclear reactors, particularly to equipment for handling nuclear fuel assemblies, and more particularly to an apparatus for isolating a particular reactor core position for easy insertion and withdrawal of fuel assemblies at that position. 2. Description of the Prior Art In any nuclear reaction which is intended to operate over an extended period of time, such as a reactor which is to be utilized for the generation of electrical power, the reactor facility should be constructed for removal and disposal of used or "spent" fuel elements and for recharging or refueling of the reactor with new or unused fuel elements. One particular problem which has been encountered with sodium-cooled fast reactors has been accurately locating the fuel subassembly to be removed. This problem comes about because of the relatively small size of the typical fuel assembly and the tight packing of these assemblies within the core region. It is further compounded by the fact that sodium is not transparent and thus the assemblies cannot be visually located. Another problem brought about by the tight packing of the fuel assemblies in the core is that of preventing the accidental withdrawal of adjacent assemblies when a desired assembly is being pulled from the core. Also, again due to the tight packing it is desirable to have some means for maintaining the core positions, from which an assembly has been withdrawn, open to facilitate the inserting of a new assembly in its place. SUMMARY OF THE INVENTION The present invention overcomes the prior art problems recited above by providing a device which is installed through the reactor closure head prior to refueling. The apparatus includes two separate sections, the handling plug/spreader assembly and the floor valve. The handling plug is a wedge shaped segment with an opening through it to permit passage of the refueling apparatus. During installation in the reactor the opening is closed by a shield plug, which is removed after the floor valve is installed. The handling plug with the spreader assembly attached replaces an identically shaped control rod island in a rotating plug in the reactor head. The handling plug when in place in the reactor serves as part of the reactor containment boundary to prevent contamination of the reactor room atmosphere during installation of the floor valve. The core spreader assembly consists of an elongated shroud attached to and extending downward from the handling plug and carrying at its lower end a radially floating, hexagonal spreader or camming tube. The attachment of the camming tube to the shroud is a self-adjusting universal type coupling that permits the tube to move radially to compensate for misalignment as the tube is inserted into the core. Mechanisms are provided to rotate the camming tube for angular alignment purposes and to translate it linearly for insertion into and withdrawal from the core. The upper end of the camming tube serves as a guide for leading the handling machine into alignment with the chosen subassembly. The floor valve sits on top of the handling plug and interconnects it with the fuel handling machine. It is basically a gate valve provided with shielding to protect operating personnel during handling of spent subassemblies.