Patent Number: 048266515
Section: description

Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a cross section of a portion 1 of a reactor building, the remainder of which is not shown. A storage or spent fuel pit 2 contains two storage racks 3. A partition 4 has a non-illustrated floodgate or sluice, which during operation of the reactor plant closes off a lead through, penetrator or transition 7 and separates the storage pit 2 from a flooding or reactor pit 5 located above a reactor vessel 6. FIG. 1 shows a reactor plant that has been shut down, so that the reactor vessel 6 is open. Both the storage pit 2 and the flooding pit 5 are filled with neutron-shielding liquid or water 9, 9a across the lead through 7 that is several meters thick, up to a level indicated at reference numeral 8. A compensator 10 which extends between the flooding pit 5 and a flange 11 of the opened reactor vessel 6, prevents the water from escaping downward. If a fuel assembly 12 from the storage rack 3 in the storage pit 2 is to be inserted into a grid position 13 of a core supporting structure 24 of the reactor vessel 6 shown in FIGS. 2 and 4, then a refueling or fuel assembly changing machine 14 takes such a fuel assembly 12 from the rack 3 and moves with the fuel assembly through the lead through 7 between the storage pit 2 and the flooding pit 5. A television camera 17 is disposed in a stationary manner on a holder 16 in guide rails 15 for the removed floodgate. As soon as the refueling machine 14 has reached the position represented in phantom, the position of a carrier element or base 18 of the fuel assembly 12 appears in a monitor 19 shown in FIG. 3. Specifically, the monitor shows what is picked up by the camera, that is a central portion 20 of the lower surface of the fuel assembly carrier 18. A central tube 21 of the fuel assembly carrier serves as a reference point. The desired position of the central tube and therefore of the fuel assembly along with a nominal or reference axis axis 22, is stored in a memory in propelling or driving equipment and also appears on the monitor. The driver of the refueling machine causes the nominal or reference axis 22 to coincide with the axis 23 of the central tube 21 and thus compensates for the deviation between the desired and actual positions of the fuel assembly carrier. The grid position 13 of the core supporting structure 24 of FIG. 4, which is shown on a larger scale in FIG. 4a, shows the actual position of the fuel assembly carrier in broken lines. A lowering of the fuel assembly in the direction of an arrow 25 before the deviation was corrected would complicate or impede the mounting of the fuel assembly 12 and would thus make insertion into the grid position more difficult. However, if a correcting movement of the refueling machine 14 is first performed in the direction of arrows 26, 27, until the reference axis 22 coincides with the axis 23 of the central tube 21 as shown in FIG. 3, then the refueling machine 14 can insert the fuel assembly 12 into the grid position 13 without danger, as shown in solid lines in FIG. 4. Bowing is expressed in a misalignment between a head piece or top 28 and the carrier element 18 of the fuel assembly 12; the nominal or rated size of the travelling movement of the refueling machine is calibrated by using the position of the head piece 28 and must be corrected with respect to the position of the carrier element 18. A fuel assembly shown on a larger scale in FIG. 5, measuring approximately 4207 mm in total length and 217 mm on a side, with a total weight of approximately 683 kg, must be inserted without danger into the grid of the reactor vessel, as shown in FIG. 2. A substantial advantage of the novel loading method is a time saving of several days in reloading the entire core, with the result that the nuclear reactor plant is more quickly available for use. A torsion-proof test gauge, having similar contours to a fuel assembly, serves to set the camera position and the reference axis of the fuel assembly. It can be positioned either in the lead through 7 or at any point in the storage pit. The foregoing is a description corresponding in substance to German Application No. P 36 06 997.3, dated Mar. 4, 1986, the International priority of which is being claimed for the instant application, and which is hereby made part of this application. Any material discrepancies between the foregoing specification and the aforementioned corresponding German application are to be resolved in favor of the latter.