Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Fuel component
Patent
1996-07-22
1997-12-16
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Fuel component
G21C 3334
Patent
active
056993935
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a fuel assembly loading installation and, in particular, a fuel assembly loading installation for a pressurized water nuclear reactor.
BACKGROUND OF THE INVENTION
Pressurized water nuclear reactors include a core consisting of fuel assemblies of generally prismatic shape and having a length which is significant relative to their transverse dimension, e.g., of the order of four or more meters for assemblies having a square cross-section with sides of about 0.20 meters.
The fuel assemblies of pressurized water nuclear reactors consist of a framework forming housings for a set of fuel rods in parallel arrangements along the longitudinal direction of the assembly. The fuel rods are only very slightly shorter than the fuel assemblies, and their diameter is generally less than 1 cm.
The framework of the fuel assembly includes spacer grids perpendicular to the longitudinal direction of the assembly. These allow the fuel rods to be held in a regular array in the transverse planes of the assembly.
The spacer grids are spaced regularly along the longitudinal direction of the assembly and are fixed on guide tubes which substitute for certain fuel rods of the array of the assembly.
The spacer grids include cells in which fuel rods are held transversely by bosses and by springs placed opposite each other.
The framework of the fuel assembly is closed at its ends by two nozzles, one of which constitutes the bottom nozzle of the assembly, intended to rest on the lower support plate of the core and the other a top nozzle on which the upper plate of the core of the reactor comes to bear, after loading of the fuel assemblies.
The manufacture and mounting of the frameworks of the fuel assemblies, followed by the loading of the frameworks with fuel rods, is carried out in the factory. The fuel rods are to be introduced into the framework via one of the ends of the assembly which does not include its closure nozzle.
The fuel material of the assemblies which produces the neutron reactions in the nuclear reactor in operation is progressively consumed, so that it is necessary periodically to refuel the core of the reactor by replacing spent assemblies with new assemblies.
The fuel rods for loading the assemblies are to be introduced into their housings via one of the ends of the assembly and slid into the housings defined by the aligned cells of the spacer grids.
It has been proposed to carry out these loading operations by introducing the fuel rods one by manually one into their housings.
This manual operation is characterized by extremely long manufacturing times of the fuel assemblies, because of the large number of rods to a fuel assembly.
The fuel assemblies most commonly used in pressurized water nuclear reactors actually constitute arrays of rods with square unit cells which may, for example, include fourteen.times.fourteen or eighteen.times.eighteen cells intended to receive the fuel rods and the guide tubes fixed on the spacer grids. The fuel assemblies therefore generally include between two hundred and three hundred fuel rods which it is necessary to load into the framework.
In order to reduce the time for manufacture of the fuel assemblies, it may be advantageous to provide automatic installations for loading the fuel assemblies.
The new fuel rods which are loaded into the fuel assemblies are generally arranged in storage magazines including an array of housings which can be arranged in alignment with the housings of a fuel assembly framework to be filled with the new rods.
It has been proposed, for example, to carry out the loading by pushing the rods in order to slide them longitudinally, from a storage position inside the magazine to a position inside a housing of the framework defined by the spacer grids.
This operation can be carried out automatically under remote control but, because of the presence of guide tubes in certain positions of the array of housings of the assembly, it is necessary to provide a programming of the loading operations which takes into acc
REFERENCES:
patent: 4297776 (1981-11-01), Fogg
patent: 5251243 (1993-10-01), Nylund et al.
Picard Paul
Villeays Roland
Societe Franco-Belge de Fabrication de Combustibles FBFC
Wasil Daniel D.
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