Cleaning and liquid contact with solids – Processes – Longitudinally traveling work of bar – strip – strand – sheet...
Reexamination Certificate
1999-10-08
2001-05-15
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
Longitudinally traveling work of bar, strip, strand, sheet...
C134S021000, C134S025100, C134S026000, C134S042000, C015S302000
Reexamination Certificate
active
06231682
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and a method for washing around rod elements, in particular for cleaning fuel elements in order to avoid the uncontrolled stripping of the impurities adhering to the surface of the cladding tubes of fuel elements, during the transport of the fuel elements, for example from the reactor pressure vessel to appropriately provided fuel element storage racks.
BACKGROUND OF THE INVENTION
After their period of use in the reactor, the spent fuel elements are extracted from the reactor and, before further processing, are first stored intermediately in a fuel element store. After the shutdown of the plant and the reduction in temperature, the impurities adhering to the surface of the cladding tubes of fuel elements, and designated in power station terminology as “crud”, come loose. This stripping effect is intensified when the fuel elements are being transported under water from the reactor pressure vessel to the fuel element storage racks or from the fuel element storage racks to the transport containers. During unloading under water, the previously flooded container is lowered into the unloading part of the store which is designed as a water pool. After the transport containers have been opened, the 4-5 metre long fuel elements are extracted from the container with the aid of underwater gripping tools, are inserted into cans and are introduced into the storage racks by means of a crane. The water serves as a shield and at the same time ensures an excellent view during unloading manipulations. On the other hand, however, as mentioned, because of its flow movement it also at the same time assists the effect of stripping the crud from the fuel elements, with the result that the fuel element storage pool becomes contaminated.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is, in order to avoid the uncontrolled stripping of the crud, to provide a device and a corresponding method, with the aid of which the fuel elements can be cleaned when being lifted out of the storage rack or the rack in the reactor pressure vessel. Since similar problems may arise with regard to other rod elements, such as, for example, filter cartridges in industrial uses, the object of the present invention is, in general, to provide a device and a method for washing around rod elements. The aim in this case is, in particular, to avoid contamination of the surroundings.
According to the invention, this object is achieved by means of a device and a method, such as are defined in the independent claims. Expedient developments are specified in the subclaims.
According to the invention, a device is provided which serves for washing around at least one rod element with at least one liquid and/or at least one gas, the device having at least the following elements:
a) at least one frame with a top side and an underside and with at least one first and at least one second circumferential portion for leading through the at least one rod element,
b) the frame having, in at least the second circumferential portion, at least one suction-extraction orifice for liquid and/or gas, and
c) the device having at least one discharge line for liquid and/or gas from the at least one suction-extraction orifice of the frame.
The rod element may, in this case, have any desired shape and any desired cross section. The frame must then be adapted, as appropriate, to this shape. The frame may at the same time consist of one or more parts which can be connected to one another or else separated from one another. The first and second circumferential portions of the frame are freely selected portions of the circumference of the frame. In the case of a rectangular frame, one circumferential portion may correspond approximately to one side of the rectangle, though the circumferential portion may also be composed of two, in particular mutually contiguous sides or of parts of a plurality of sides of the rectangle. The suction-extraction orifice in the second circumferential portion of the frame may be an orifice of any desired cross section which is connected to a suction device, so that liquid or gas can be suction-extracted. Suction extraction is carried out by suction means, for example a suction pump, which is separate from the frame or is connected to the frame. The liquid, or corresponding gas, serving for washing around are then removed via the discharge line. In use for nuclear power stations in which the fuel elements are handled under water, it is expedient to have an underwater suction appliance which is connected to the suction-extraction orifices. The liquid, or corresponding gas, used for washing around can be extracted from the surroundings of the frame, so that the washing-around action is brought about solely by the suction action of the suction-extraction orifices. In this case, in nuclear power stations, the water of the fuel element pool or storage pool is simply used as washing liquid.
In a preferred embodiment, however, the frame has, in at least the first circumferential portion, at least one outflow orifice for the at least one liquid and/or the at least one gas. At the same time, the device possesses a supply line for supplying the at least one liquid and/or the at least one gas to the at least one outflow orifice of the frame. There is therefore the possibility of guiding the at least one liquid and/or the at least one gas under an essentially freely selectable pressure, which is predetermined only by the prerequisites of the device, through the supply line to the at least one outflow orifice and of thereby causing the at least one liquid and/or the at least one gas to impinge onto the at least one rod element. Within the scope of the invention, a high pressure is usually advantageous for the washing-around efficiency. Moreover, this arrangement affords the advantage that the washing-around substance can be freely selected within particular limits, that is to say is not limited to the medium specifically present in the surroundings, for example air or water. Since the washing substance is suction-extracted again, it is possible to use even substances which are not to enter the surroundings, or not in overly large quantities, or which are to be recovered for economic reasons.
In nuclear power stations, washing around serves primarily for cleaning the surface of the fuel elements, as described above. In this case, pool water or make-up water is used for washing around. At the same time, an underwater sucker is preferably used for suction extraction.
Preferably, the frame surrounds the rod element completely, so as to ensure that the at least one rod element is washed round completely. Preferably, washing around the at least one rod element serves for cleaning the surface of the latter, and for reasons of efficiency this is expediently achieved by washing around the rod element with the at least one liquid and/or with the at least one gas as completely as possible. Complete surrounding by the frame does not mean, here, that the frame must consist of one part or of parts connected fixedly to one another. It is sufficient if there are no relatively large gaps between the frame parts, so that no relevant part of the rod element remains untreated, that is to say unaffected by make-up water.
In a further preferred embodiment, at least one sealing element is arranged on the top side and/or underside of the frame in such a way as to achieve sealing off relative to the rod element. As a result, when the at least one rod element is led through the frame, the fraction of loosened and actually suction-extracted constituents, for example the “crud”, is increased. This may be achieved simply by increasing the suction action in the more highly sealed-off regions surrounding the rod element. However, leading the rod element through this sealing element may also result in mechanical stripping of the rod element, by virtue of which loosely adhering impurity particles are detached from the surface of the rod element. It becomes apparent from this that “sealin
El-Arini Zeinab
Wood Phillips VanSanten Clark & Mortimer
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