Patent Number: 
Section: claims

1. A leakage testing device for testing leakage of a nuclear fuel assembly by sipping, comprising:a collection assembly configured to close an upper end of a cell of a storage rack for storing at least one nuclear fuel assembly discharged from a nuclear reactor, so as to prevent water contained in the cell from escaping via the upper end of the cell, and to collect products containing possible fission products released by a nuclear fuel assembly contained in the cell, wherein the collection assembly comprises a tube extender configured to be arranged at the upper end of the cell while extending the cell upward, a bell-shaped cover configured to cap the extender. 2. The leakage testing device according to claim 1, wherein a lower edge of the cover surrounds the extender while being located at a lower level than that of an upper edge of the extender. 3. The leakage testing device according to claim 1, wherein the extender and the cover are secured to one another so as to be able to be handled jointly. 4. The leakage testing device according to claim 1, wherein the cover has a pyramidal or conical shape converging upward. 5. The leakage testing device according to claim 1, wherein the cover comprises at least one tap to feed a pressurized gas below the cover. 6. The leakage testing device according to claim 1, further comprising a control assembly separate from the collection assembly and connected to the collection assembly, the control assembly being configured for the analysis of products collected by the collection assembly to detect the possible presence of fission products. 7. The leakage testing device according to claim 1, further comprising a heating unit configured to be arranged in the bottom of a cell and to support a nuclear fuel assembly received in the cell. 8. The leakage testing device according to claim 1, further comprising a bubbling device configured to loosen fission product bubbles from the nuclear fuel assembly. 9. A method for testing leakage of a nuclear fuel assembly, comprising:leakage testing the nuclear fuel assembly by the leakage testing device as recited in claim 1 by sipping while the nuclear fuel assembly is stored in the cell of the storage rack. 10. The leakage testing method according to claim 9, further comprising collecting products using the collection assembly, and analyzing collected products to detect possible fission products released by the nuclear fuel assembly contained in the cell. 11. The leakage testing method according to claim 10, further comprisingarranging the extender at the upper end of the cell to extend the cell upward, the extender being capped by the bell-shaped cover. 12. The leakage testing method according to claim 9, further comprising testing leakage of several nuclear fuel assemblies arranged in respective cells of the same storage rack, by moving the collection assembly successively from one of the cells to the other in order to test leakage of the nuclear fuel assemblies. 13. The leakage testing method according to claim 9, further comprising heating the nuclear fuel assembly in the cell. 14. The leakage testing method according to claim 13, wherein the heating is performed using a heating unit attached at the bottom of the cell.