Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Storage container systems for new and/or irradiated core...
Patent
1996-09-05
1998-02-03
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Storage container systems for new and/or irradiated core...
G21C 1907, G21F 5012
Patent
active
057152896
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a rack for nuclear fuel assemblies, constituted by a plurality of very long contiguous cells, each of which being capable of holding a fuel assembly or the rods of several fuel assemblies following consolidation.
These racks are intended for the storage or transport of fuel assemblies which may or may not be in shielded containers; they are particularly suitable for irradiated fuel, but are also perfectly suited for use with new fuel; they can be used in dry or wet media, for example when storing fuel in the cooling pool or during their temporary storage in cement structures, or even during final storage by burial in geological strata.
STATE OF THE ART
A number of racks with cell-like construction are known for nuclear fuel assemblies. They must simultaneously carry out the following three functions: or in the presence of water in the liquid or gaseous state (the water can contain neutrophages, for example boron based); retain the geometry of the rack when filled with assemblies and prevent deterioration of the fuel rods during normal use (handling, transport...), (ii) control the criticality by retaining the geometry of the rack even under accidental conditions (severe shock and drops) in accordance with the current rules.
The racks are sometimes designed to provide complementary shielding against radiation, for use in certain applications.
A number of types of rack have been developed for use with assemblies used in different reactor types: light water (PWR, BWR, VVER . . .), graphite (UNGG, MAGNOX, AGR, RBMK, . . .), heavy water (CANDU . . .), fast neutron, research reactors . . .
The cell walls in those racks are generally made from a combination of several materials, each carrying out at least one of the three functions cited above.
The principal materials used are generally stainless steel or aluminium (or their alloys) for mechanical strength, aluminium or copper (or their alloys) for heat transfer, boron compounds (such as B4C based glasses), or copper, aluminium or stainless steel alloys containing boron to control criticality. The criticality function can also be carried out by using spaces in the cell walls of the rack which are of suitable thickness and fill or empty with water simultaneously with the cells containing the fuel medium.
The walls are often constituted by: materials sandwiched together, each layer carrying out at least one of the functions; or (generally profiles) made from these materials; in one wall between the cells, a succession of base components of different materials can be seen in the longitudinal direction, each carrying out at least one of the functions. An arrangement such as this is illustrated in French patents FR-A 2 627 622 and FR-A-2 650 113 .
In these patents, the juxtaposed base components constituting the walls between the cells are profiles of a standard material which are regularly Juxtaposed and interlocked perpendicular to the axis of the cells and held in position relative to each other; these profiles may be of stainless steel, aluminium alloy, copper, etc. . . to carry out the mechanical strength and heat transfer functions, the criticality function being carried out by rods of neutrophage neutron absorbing material inserted in the walls and/or by identical shaped profiles of neutrophage material inserted in the lattice.
FIG. 6 of French patent FR-A-2 627 622 , for example, shows walls between the cells which are constituted by a juxtaposition of notched strips which cooperate with each other to interlock the strips and fix them relative to each other, producing cells which resemble separators for bottles in boxes. This juxtaposition alternates strips of neutrophage material (to carry out the criticality function) and standard material strips (to carry out the mechanical strength and heat transfer functions). This rack is designed not to deform under accidental severe conditions such as those described in the IAEA (International Atomic Energy Agency) rules governing the transport of radioactive material.
REFERENCES:
patent: 4203038 (1980-05-01), Takahashi et al.
patent: 5032348 (1991-07-01), Blum et al.
Kirchner Bernard
Malesys Pierre
Transnucleaire S.A.
Wasil Daniel D.
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