Patent Number: 043426204
Section: claims

1. A box to be inserted into a stationary nuclear fuel storage pool frame having a multiplicity of vertically extending polygonal openings, the box adapted for receiving a nuclear fuel assembly, comprising: a plurality of vertically extending metal plates arranged as an open ended polygonal container having a smaller cross-sectional area than the opening in the frame;  each plate having a flat portion forming the respective sides of the container and having an integral tab portion rigidly projecting outwardly from at least one longitudinal edge of the plate;  connecting means joining each tab to a tab of an adjacent plate to form a rigid container having a plurality of outwardly projecting ribs;  whereby the box may be slidingly inserted into the frame so that the ribs fit into the corners of the frame defining the opening. 2. The box insert of claim 1 wherein each plate has two tab portions extending over substantially the entire longitudinal length of the plate. 3. The box insert of claim 2 wherein the container is a square and each tab is angled at about 45 degrees to the flat portion of the plate. 4. The box insert of claims 2 or 3 wherein the adjacent tabs are connected at spaced intervals along their longitudinal dimension. 5. The box insert of claim 3 wherein each plate is made of stainless steel having a thickness in the range of about 0.050-0.065 inch. 6. The box insert of claims 3 or 5 wherein the flat portion of at least some plates has a layer of neutron absorbing poison material attached thereto. 7. The box insert of claim 6 wherein the thickness of the layer of poison material is less than about 0.090 inch. 8. In a rack for storing nuclear fuel in a pool area of a stationary facility including a frame having a plurality of perpendicular wall members defining a plurality of square openings and box inserts located within the openings for receiving assemblies to be stored, the improvement which comprises each box insert having a square, flat sided container portion for receiving the fuel assembly and having external ribs at the corners of the container portion, the ribs fitting slidingly into the inside corners of the openings whereby the container is maintained in predetermined, spaced relation from each wall defining the opening. 9. The improvement of claim 8 wherein the container is formed from four metal plates each having two tabs projecting at an angle from the flat surfaces thereof, the tabs of adjacent plates being connected to form the ribs. 10. The improvement of claim 9 wherein each tab is integral with and runs over substantially the entire longitudinal length of its respective plate. 11. The improvement of claim 10 wherein the plates are made of stainless steel having a thickness in the range of about 0.050-0.065 inches. 12. The improvement of claims 9 or 11 wherein the flat portion of at least some plates has a layer of neutron absorbing poison material attached thereto. 13. The improvement of claim 12 wherein the thickness of the layer of poison material is less than about 0.090 inch.