Patent Number: 049884743
Section: summary

BACKGROUND OF THE INVENTION The invention concerns a process for repair of a nuclear reactor fuel assembly damaged at the periphery of a spacer support, which assembly consists of a bundle of longitudinally extended fuel rods, which are held in position by several grid-shaped interim spacer supports that are axially separated from one another, whereby each fuel rod passes through a cell of the spacer support formed by intersecting metal crosspieces arranged at the edge and is supported therein elastically. During loading or unloading of a reactor core with fuel assemblies, peripheral spacer support cells are occasionally damaged by catching against neighboring fuel assemblies. In order to eliminate such damage in the prior art, a fuel rod or a dummy fuel rod was re-inserted in position after removing or straightening the damaged metal crosspieces of the spacer support. In particular, if two or more spacer supports arranged one above the other are damaged and the metal crosspieces must be completely removed, the insufficient support leads to a swinging of the fuel road and thus this rod or the neighboring fuel rod can be easily damaged. If one wishes to avoid such swinging, according to the state of the art, all rods of the fuel assembly must be withdrawn in a time consuming way, and then be inserted into a new fuel assembly frame consisting of the spacer support, guide and end pieces. In addition to loss of time here there is also the danger that the fuel rods will receive excessive cracks during withdrawal and reinsertion, and in addition, the spacer support may be damaged. Therefore, the objective is to create a process of the type given above, but in which swinging can be avoided. SUMMARY OF THE INVENTION This objective is solved according to the invention by the fact that, after removing the damaged metal crosspieces, a holding component contacting the fuel rod is joined to the spacer support. By this means, it is possible to attach the fuel rod relative to the spacer support, so that undesired swinging movements are avoided. If a dummy fuel rod (dummy) is inserted into the cell instead of a fuel rod, then, in a preferred embodiment of the process, the holding component is inserted into a snap ring groove. In this way, any shifting of the holding component relative to the rod, which is beyond the play required for heat-expansion equilibration, is avoided. The holding component for realization of the process is a metal strip partially embracing the circumference of the fuel rod or dummy fuel rod, which strip has a projection that can be joined to the spacer support on each of its free ends. Thus the rod is held by simple means in a swingless manner in as precise a way as in an intact spacer support. The projections on the free ends of the holding component are formed elastically, so that the rod can assuredly be axially displaced for purposes of a heat expansion equilibration in addition to offering a reliable installation of the rod on the remaining metal crosspieces of the spacer support. A jut-out piece formed elastically and turned toward the rod supports this means and also assures a better contact of the fuel rod with the coolant. If a corner cell is damaged, the projections preferably engage in slots of the two remaining pieces, whereas if a non-corner cell is damaged, three crosspieces remain, so that in that case, a direct hanging of the holding component on the crosspieces is preferably produced. For insertion of a dummy fuel rod, a configuration of a holding component may be used which is characterized by the fact that the holding component is embodied in the form of a split pin (cotter) whose arms are formed elastically and on the free ends of which are found projections, whereby after passing through a borehole or a slot of the dummy fuel rod, the projections can engage in the spacer support. This configuration crates a holding component which cannot fall off since passing through an opening, which may be a bore or a slot, produces a firm hold with the elastically loaded arms, which take on a larger diameter than the borehole behind the borehole, and in this way, it cannot fall out of the borehole as a result of an unintentional loosening of the locking device with the spacer support. An undesired rotation of the holding component in the cooling cycle of the nuclear reactor installation is thus not possible. In order to simplify the mounting of a holding component in combination with a dummy fuel rod, a longitudinal groove is provided in the region of the snap ring groove of the dummy fuel rod in order to create a place for a mounting tool.