Patent Number: 046801596
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION A terminal storage container 11 of steel (FIGS. 1 and 2) includes a circular storage space 13 to accommodate the individual fuel rods 15 of several irradiated nuclear reactor fuel elements. The fuel rods 15 are tightly packed in four circular-segmental fuel-rod cans 17. These cans 17 are closed after being loaded. The fuel-rod cans 17 are placed in a cage 19 which is inserted into the circular storage space 13. When viewed in cross-section, this insert cage 19 includes a centrally located square shaft 21 from the corners of which diagonal partition walls 23 extend to the container inner wall 24 of the storage space 13. This results in the provision of four storage compartments 25 for receiving the fuel-rod cans 17. The fuel-rod cans 17 are of circular-segmental configuration. The rear walls 27 of cans 17 abutting the container inner wall 24 are curved and have a curvature corresponding to the curvature of the container inner wall 24. The radially extending sides 29 of the cans 17 are parallel to the partition walls 23. The inwardly facing wall 31 of each fuel-rod can is of a lattice configuration and extends parallel to a corresponding one of the sides of the square central shaft 21. A chamfer forms the transition between the radial sides 29 of the fuel-rod cans 17 and their curved rear wall 27. Each fuel-rod can 17 is capable of holding the fuel rods of two disassembled irradiated nuclear reactor fuel elements. Loading takes place with the can 17 lying on its rear wall 27. The latticed wall 31 is not yet set in place at this stage. The fuel rods are loaded into the can 17 through the opening. Following loading, the wall 31 is welded to the can. The loading opening of the terminal storage container 11 is closed by a stepped cap 33 (FIG. 1) which is fastened onto a suitable step 37 of the loading opening by means of threaded bolts 35. A seal (not shown) is placed between cap 33 and container 11. Another cap 41 is arranged on top of the screw-on cap 33 which is inserted into the loading opening and welded to the container wall 43. In the assembly shown in FIGS. 1 and 2, the terminal storage container 11 is placed into a shielded transport container 45. The loading opening of the shielded transport container 45 is closed by a closure cover 47 which is secured by threaded fasteners. A polyethylene layer 49 is inserted into the inner wall of the shielded transport container 45 for shielding neutrons. The shielded transport container 45 is equipped with carrying lugs 51 secured to its outer periphery. The loaded fuel-rod cans 17 are each equipped with a handling block 55 on the upper end faces thereof for the application of suitable lifting gear. Hold-down springs 57 bear with one end against the upper end surfaces 53 of the fuel-rod cans 17 and bear with the other end against the cover 33. The mode of operation of the arrangements described above will now be explained. The individual fuel rods 15 are loaded into the segmental fuel-rod cans 17 which are then closed. The fuel-rod cans 17 are then seized by the handling block 55 and placed into corresponding ones of compartments 25 of the insert cage 19. Hold-down springs 57 are placed on the upper end faces 53 of the fuel-rod cans 17. As the first cap 33 is fastened to the container 11, the springs will bear against the fuel-rod cans 17 thereby causing the fuel-rod cans 17 to be in constant abutment with the container bottom. The fuel-rod cans 17 lie against the container inner wall 24 with their curved rear walls 27 and a good heat transfer to the container body is thereby ensured. The empty square center shaft-like compartment 21 in the middle of the storage container 11 is loaded with fuel element structural parts 63 which were separated at the time of disassembly of the fuel elements. These parts include top and bottom pieces as well as the spacers including the control rod guide tubes. The fuel element structural parts are compacted. FIG. 3 shows the cross-section of a circular storage chamber 71 of a terminal storage container 73 in a modified embodiment. Inserted into the storage chamber 71 is a modified cage 75 which likewise has a square center shaft-like compartment 77 in the middle of the storage chamber 71. This square central shaft-like compartment 77 is held in position by pairs of partition walls (78, 79) which extend from the compartment corners and bear radially against the container inner wall 81. The partition walls (78, 79) of each pair are interconnected by a curved rear wall 83. Further pairs of partition walls (87, 89) extend from the center of the sides 85 of the square central compartment 77 to the container inner wall 81. The ends of the walls (87, 89) of each partition wall pair are connected by a short rear wall 91. The rear walls 83 and 91 of the partition wall pairs (78, 79) and (87, 89), respectively, are curved as shown and face the container inner wall 81. A circular-segmental fuel-rod can 93 is arranged between a pair of partition walls (78, 79) which extend from a corner of cage 75 and a pair of partition walls (87, 89) which extend from the center of a side 85 thereof. These fuel-rod cans 93 each have curved rear wall 95. The radial sides 97 of the fuel-rod cans 93 extend parallel to the adjacent pairs of partition walls (78, 79) and (87, 89). The inwardly facing wall 99 of the fuel-rod cans 93 is slightly curved. The embodiment of FIG. 3 shows eight fuel-rod cans 93 arranged in a circle. Each can 93 is capable of accommodating the fuel rods 101 of a single fuel element. The fuel-rod cans of this embodiment are loaded at the end face thereof. The cross-sections of the fuel-rod cans 93 are preferably identical in order not to complicate the front-loading procedure of the cans 93 and to be able to carry out the procedure without modification. Following loading, the upper end wall is welded to its fuel-rod can 93. For wet loading the fuel-rod cans 93, that is, for loading the same under water, a suction pipe 103 is provided in the circular storage space 81 so that the water can be removed from the container 73 following loading. FIGS. 4 to 6 illustrate another embodiment of the insert cage and the fuel-rod cans of FIG. 3. Like parts are assigned like reference numerals, with a prime being added. Inclined guides 105 are provided in the upper region on the radial sides 79' of each fuel-rod can 93'. These upper guides 105 cooperate with inclined engagement surfaces 106 provided in the adjacent partition walls of partition pairs (78', 79') and (87', 89'), respectively, of the insert cage 75'. At the lower end of the insert cage 75', outwardly extending inclined guide surfaces 109 are provided in the vicinity of the bottom of the storage container 73'. The guideways 105 and the guide surfaces 109 urge the fuel-rod cans 93' against the container inner wall 81' as they are being inserted. It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.