Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Fuel component
Patent
1984-01-19
1987-06-09
Kyle, Deborah L.
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Fuel component
376272, 29723, 414146, G21C 1932
Patent
active
046719210
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process, installation and device for compacting flexible, oblong objects, particularly fuel pencils of a nuclear reactor.
In enriched uranium nuclear reactors, the fissile matter is known to be constituted by pellets of uranium oxide stacked in metal cans closed at each end to form what is called "fuel pencils". These are assembled together in large numbers (for example 264), with a certain number of tubes not containing fuel, to form a fuel element. The fuel elements are disposed in the reactor to form the core thereof.
Once the required specific burn-up is attained, the irradiated fuel elements are withdrawn from the reactor and immersed for several months in a nearby pond in order to cool and lose the major part of their radioactivity. They are then evacuated to an appropriate site and stored in some manner (pond, storage packaging, etc...) whilst awaiting possible re-processing.
Both for transport and storage, in order to save space, it is advantageous to dismantle the fuel elements and to re-assemble the fuel pencils compactly in bundles, i.e. in a more or less compact assembly of oblong, rectilinear objects which are parallel to one another over their whole length. In fact, inside a fuel element, the fuel pencils, which have an outer diameter of the order of 9.5 mm for example, are disposed in a lattice of square meshes whose sides are of the order of 12.6 mm. This results in a section of the fuel element virtually double that corresponding to a compact lattice.
It will be readily appreciated that dismantling of the fuel elements, and more particularly the constitution of bundles of pencils and introduction thereof into appropriate containers, presents difficulties since these pencils are very long (about 4 m) with respect to their small diameter (9.5 mm).
To overcome this difficulty, a method which may be envisaged at the present time would consist in taking the pencils from inside a fuel element row by row (17 pencils at a time, for example) and in disposing these pencils horizontally on vibrating tables which form a V surface an d which compact the pencils in the point of the V. The bundle of triangular section thus obtained is then pushed into a container, likewise of triangular section. The main disadvantages of such a method, apart from requiring a complex and expensive installation, are that it is slow (only 17 pencils out of the 264 contained in a fuel element are taken at a time) and that one can be sure only after vibration that the pencils will be absolutely parallel to one another. In fact, by reason of their great length, and therefore of their considerable longitudinal flexibility, adjacent pencils may interlace with one another to such an extent that they cannot be returned parallel to one another by vibration. In such a case, the bundle could not penetrate in the triangular container.
It is an object of the present invention to overcome all the drawbacks mentioned above. It relates to a process, installation and device for compacting objects of great length and of small transverse dimensions, with a view to disposing them in a container reliably, repetitively and rapidly, with the result that the portion ofthe section of the latter occupied by the transverse sections of said objects is maximum. It is applied more particularly, but not exclusively, to the handling and compacting of fuel pencils with a view to placing them in containers, whatever the purpose of such an operation (final storage, intermediate storage, transport, etc...).
To this end, according to the invention, the process for forming a bundle, i.e. an assembly of oblong, approximately rectilinear objects converging at one end, more or less compact, of oblong objects of small transverse dimensions, such as fuel pencils for nuclear reactors, said objects constituting, prior to the change of arrangement, an assembly in which they occupy parallel, transversely spaced apart positions, is noteworthy in that:
a plurality of guiding tubes are arranged substantially parallel to the same directio
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patent: 4511499 (1985-04-01), Meuschke et al.
patent: 4537741 (1985-08-01), Christiansen et al.
patent: 4548347 (1985-10-01), Christiansen et al.
Kyle Deborah L.
Societe pour les Transports de l'Industrie Nucleaire Transnuclea
Wasil Dan
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