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US 2003/0191352 A1Published application
Method of applying foam reagents for radioactive decontamination
AssigneeNone recorded
InventorsDavid Bradbury, George Richard Elder
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AssigneeNone recorded
InventorsDavid Bradbury, George Richard Elder
Estimating the term…
A process for the chemical decontamination of a radioactive system or a system containing one or more radioactive components, which method comprises applying a chemical decontamination reagent to the radioactive system or the system containing one or more radioactive components in the form of a foam characterised in that a dynamic foam is caused to move through or around the system by means of a gas introduced into the system.
A process for the chemical decontamination of a radioactive system or a system containing one or more radioactive components, which method comprises applying a chemical decontamination reagent to the radioactive system or the system containing one or more radioactive components in the form of a foam characterised in that a dynamic foam is caused to move through or around the system by means of a gas introduced into the system.
A process as claimed in any one of the preceding claims wherein the gas is introduced through one or more inlets at the bottom of the system.
A process as claimed in any one of the preceding claims wherein the gas is compressed air.
A process as claimed in any one of the preceding claims wherein the system comprises an enclosed system of a nuclear plant.
A process as claimed in any one of the preceding claims wherein the introduction of gas into the liquid is controlled in order to maintain the foam filling the entire volume of the system.
A process as claimed in any one of the preceding claims wherein the system is provided with one or more exhaust means for the removal of gas.
A process as claimed in any one of the preceding claims where the foam is caused to form and collapse a plurality of times by starting and stopping the gas flow.
A process as claimed in any one of the preceding claims wherein the system is rinsed following the chemical decontamination by introducing rinse water at suitable points within the system.
Dependencies are inferred from the claim text.
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Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof: decontamination of the surface of objects…
Protection against x-radiation, gamma radiation, corpuscular radiation or particle bombardment
Term end not estimated
The present invention relates to a method of applying foam reagents for the radioactive decontamination of radioactive components.
The chemical decontamination of radioactive components is a now a well established procedure. Many components, particularly metallic ones, become contaminated with radioactive materials during the normal operation of a nuclear power plant or other nuclear facility. However, unless the component has been activated by a neutron flux, this contamination commonly occurs on the surface of the component only. Removal of the surface contamination can have significant benefits, and the process of doing this is generally referred to as “decontamination”. Specifically, when chemicals are used to remove the contamination from component surfaces the process is referred to as chemical decontamination.
The benefits of chemical decontamination include the reduction of radiation dose to people working on or close to, the component in question. More recently there are examples where the efficient decontamination of redundant components during decommissioning can allow the cleaned components to be released from radioactive materials controls so that they can be recycled or disposed of in a conventional manner. This not only has economic advantages, but benefits the environment as well through the recycling of valuable materials and the reduction in the volume of radioactive waste requiring disposal.
The present invention will be further described with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic representation of an apparatus for carrying out the present invention; and
FIG. 2 is a diagrammatic representation of the apparatus used in Examples 1 to 3 herein.
Referring to FIG. 1, an enclosure 5 contains the items 4 to be decontaminated. Items 4 and enclosure 5 may be one integral unit. The decontamination liquid 3 is introduced into the enclosure 5 and is aspirated with a gas from compressor 1 through inlets 2. The resulting foam rises within the enclosure 5 to cover the items 4 to be decontaminated. The foam is collapsed in the foam collapsing device 8. Gas exits from this device at 9 and the liquid is returned to enclosure 5 via 10. After completion of the decontamination procedure the liquid is drained through 7 and the system spray rinsed with water via inlets 6. The rinsings are also drained through 7.
FIG. 2 illustrates an experimental set up for demonstrating the method of the invention. The sample to be decontaminated 20 is placed in an inner container 11 positioned within an outer container 12. The inner and outer containers 11 and 12 are connected together by means of a hole 13. Liquid decontamination reagent 14 is introduced into both the inner container 11 and outer container 12. The reagent is foamed in situ by the introduction of air through the liquid. The foam so produced as shown at 15 rises to cover the sample 20 to be decontaminated. The foam spilled over the top lip 16 of the inner container 11 and collapsed to form a liquid which was returned in the space between the inner and outer containers.
A sample of boiler tube was obtained from a “Magnox” nuclear reactor. The sample was of a “finned” construction”. The sample was of a tubular construction of outer diameter of 3.0 cm with eight fins having an outer diameter of 4.5 cm disposed around the tube. The fin thickness was 1.0 mm and the fin pitch 3.0 mm.