Patent Number: 
Section: claims

1. An apparatus for containing radioactive materials having a residual heat load comprising:a body having an inner surface that forms a cavity for receiving radioactive materials, the cavity having an open top end and a dosed bottom end, the cavity having a horizontal cross-sectional profile having a perimeter formed by the inner surface of the body;a basket formed of a plurality of intersecting plates positioned in the cavity, the basket comprising a plurality of cells, the basket having an outer surface;a plurality of spacers having a top surface, a bottom surface, an outer surface, and an inner surface forming a central passageway, the spacers arranged in a stacked assembly within the cavity the basket extending through the central passageways of the spacers of the stacked assembly; andwherein an entirety of the outer surface of the basket is in conformal surface contact with the inner surfaces of the spacers. 2. The apparatus of claim 1 further comprising:the plurality of spacers having a substantially constant horizontal cross-section from the top surface to the bottom surface, the spacers arranged in the stacked assembly within the cavity so that the top and bottom surfaces of adjacent spacers are in surface contact with one another so as to form a spacer-to-spacer interface; andmeans for maintaining the spacers of the stacked assembly in alignment. 3. The apparatus of claim 1 wherein one or more of the spacers are keyed to maintain alignment of the stacked assembly. 4. The apparatus of claim 1 wherein an entirety of the outer surfaces of the spacers is in conformal surface contact with the inner surface of the body. 5. The apparatus of claim 1 further comprising:a lid enclosing the open top end of the cavity,each of the spacers comprising a passageway extending from the top surface to the bottom surface;wherein when arranged in the stacked assembly, the passageways of the spacers form a downcomer extending from a top plenum of the cavity to a bottom plenum of the cavity; andwherein the downcomer has a substantially constant horizontal cross-sectional area from the top plenum to the bottom plenum. 6. The apparatus of claim 1 wherein the stacked assembly comprises a top end and a bottom end, the stacked assembly having a substantially constant horizontal cross-section from the top end to the bottom end. 7. An apparatus for containing radioactive materials having a residual heat load comprising:a body comprising an inner surface that forms a cavity for receiving radioactive materials, the cavity having an open top end and a closed bottom end;a basket positioned in the cavity and comprising a plurality of cells, the basket having a horizontal cross-sectional profile having an external perimeter formed by an outer surface of the basket;a plurality of ring structures having a top surface, a bottom surface, an outer surface, and an inner surface forming a central passageway, the ring structures arranged in a stacked assembly within the cavity so that the top and bottom surfaces of adjacent ring structures in the stacked assembly are in direct surface contact with one another, each of the ring structures having a horizontal cross-sectional profile having an internal perimeter formed by the inner surface of the ring structure and an external perimeter formed by the outer surface of the ring structure; andwherein the basket extends through the central passageways of the ring structures so that an entirety of the external perimeter of the basket is in conformal surface contact with the internal perimeters of the ring structures. 8. The apparatus of claim 7 wherein each of the ring structures is constructed of a material having a first coefficient of thermal expansion and the body is constructed of a material having a second coefficient of thermal expansion, the first coefficient of thermal expansion being greater that the second coefficient of thermal expansion. 9. The apparatus of claim 8 wherein each of the ring structures comprise a plurality of passageways extending from the top surface to the bottom surface, and the passageways of the ring structures form a plurality of downcomers extending from a top plenum of the cavity to a bottom plenum of the cavity when arranged in the stacked assembly, each of the plurality of downcomers having a substantially constant horizontal cross-section from the top plenum to the bottom plenum. 10. The apparatus of claim 8 further comprising:a first plurality of cutouts provided at a top of the basket so that the cells are in spatial communication with each other, thereby forming a top plenum;a second plurality of cutouts provided at a bottom of the basket so that the cells are in spatial communication with each other, thereby forming a bottom plenum; andeach of the ring structures comprising a plurality of passageways extending from the top surface to the bottom surface, the passageways of the ring structures forming a plurality of downcomers extending from the top plenum to the bottom plenum when arranged in the stacked assembly; andwherein each of the plurality of downcomers has a substantially constant horizontal cross-section from the top plenum to the bottom plenum. 11. The apparatus of claim 8 wherein the first coefficient of thermal expansion is at least 20 percent times greater than the second coefficient of thermal expansion. 12. The apparatus of claim 7 further comprising:the cavity having a horizontal cross-sectional profile having a perimeter formed by the inner surface of the body; andan entirety of the external perimeters of the ring structures is in conformal surface contact with the perimeter of the body. 13. The apparatus of claim 7 wherein each of the ring structures is a unitary structure. 14. An apparatus for containing radioactive materials having a residual heat load comprising:a body comprising an inner surface that forms a cavity for receiving radioactive materials, the cavity having an open top end and a closed bottom end;a basket comprising a plurality of cells positioned in the cavity, the basket having an outer surface;a plurality of ring structures having a top surface, a bottom surface, an outer surface, and an inner surface forming a central passageway, the ring structures arranged in a stacked assembly within the cavity; andthe basket extending through the central passageways of the ring structures so that an entirety of the outer surface of the basket is in conformal surface contact with the inner surface of the ring structures. 15. The apparatus of claim 14 wherein each of the ring structures is a unitary structure. 16. The apparatus of claim 14 further comprising:the ring structures having a substantially constant horizontal cross-section from the top surface to the bottom surface, the ring structures arranged in the stacked assembly within the cavity so that the top and bottom surfaces of adjacent ring structures in the stacked assembly are in direct surface contact with one another and the stacked assembly has a substantially constant horizontal cross-section along its entire height; andmeans for maintaining the ring structures of the stacked assembly in alignment. 17. The apparatus of claim 14 wherein an entirety of the outer surfaces of the ring structures is in conformal surface contact with the inner surface of the body. 18. The apparatus of claim 14 further comprising:the cavity having, a horizontal cross-sectional profile having a perimeter formed by the inner surface of the body;each of the ring structures having an external perimeter formed by the outer surface of the ring structure; andwherein the perimeter of the cavity is circular, and wherein the external perimeter of the basket is of a shape that is not circular. 19. An apparatus for containing radioactive materials having a residual heat load comprising:a body comprising an inner surface that forms a cavity for receiving radioactive materials, the cavity having an open top end and a closed bottom end;a basket comprising a plurality of cells positioned in the cavity, the basket having an outer surface;a plurality of ring structures having a top surface, a bottom surface, an outer surface, and an inner surface forming a central passageway, the ring structures arranged in a stacked assembly within the cavity; andthe basket extending, through the central passageways of the ring structures so that a first clearance exists between the inner surfaces of the ring structures in the stacked assembly and the outer surface of the basket at ambient temperature, the first clearance circumferentially surrounding the basket; andwherein upon radioactive materials having, a residual heat load being positioned in the basket, the residual heat load from the radioactive materials causes the basket to expand so that an entirety of the outer surface of the basket is in conformal surface contact with the inner surfaces of the ring structures and the first clearance is eliminated. 20. The apparatus of claim 19 further comprising:a second clearance between the inner surface of the body and the outer surfaces of the ring structures in the stacked assembly at ambient temperature, the second clearance circumferentially surrounding the stacked assembly; andwherein upon positioning, the radioactive materials having a residual heat load in the basket, the residual heat load of the radioactive materials causes the ring structures to expand so that an entirety of the outer surfaces of the ring structures is in conformal surface contact with the inner surface of the body and the second clearance is eliminated. 21. The apparatus of claim 20 wherein the plurality of ring structures are constructed of a material having a first coefficient of thermal expansion and the inner surface of the body is constructed of a material having a second coefficient of thermal expansion, the first coefficient of thermal expansion being greater that the second coefficient of thermal expansion.