APPARATUS FOR CONTAINED DECONTAMINATION

Abstract

A decontamination apparatus for decontaminating an external surface is provided. The decontamination apparatus has a moveable platform and a containment structure mounted on the moveable platform. The containment structure has at least one aperture and a respective contact surface arranged around the perimeter of the aperture. The contact surface is arranged to make contact with the external surface to define a working volume, when the containment structure is positioned proximal to the external surface. The decontamination apparatus includes a decontamination device arranged to decontaminate the external surface. The decontamination device is arranged within the working volume and arranged to access the external surface through the at least one aperture. There is also a vacuum system for generating a partial vacuum in the containment structure to apply a suction force to the external surface.

Claims

1. A decontamination apparatus for decontaminating an external surface comprising: a moveable platform; a containment structure mounted on the moveable platform; wherein the containment structure comprises: at least one aperture; and a respective contact surface arranged around the perimeter of the at least one aperture; wherein the contact surface is arranged to make contact with the external surface to define a working volume, when the containment structure is positioned proximal to an external surface; a decontamination device arranged to decontaminate the external surface, wherein the decontamination device is arranged within the working volume and arranged to access the external surface through the at least one aperture; and a vacuum system for generating a partial vacuum in the containment structure arranged to apply a suction force to the external surface.

2. The decontamination apparatus as claimed in claim 1, wherein the contact surface is substantially continuous around the aperture.

3. The decontamination apparatus as claimed in claim 1, wherein the contact surface is flexible.

4. The decontamination apparatus as claimed in claim 1, wherein the containment structure comprises a hood that extends towards the contact surface; and wherein the hood comprises one or more walls having a concertina shape.

5. (canceled)

6. The decontamination apparatus as claimed in claim 4, wherein the hood is arranged to rotate the contact surface between a first plane and a second plane, wherein the first plane is not parallel to the second plane.

7. The decontamination apparatus as claimed in claim 1, wherein the vacuum system provides a suction barrier and/or a draw for the waste produced by the decontamination of the external surface.

8. The decontamination apparatus as claimed in claim 1, wherein the contact surface comprises one or more friction pads; and wherein the contact surface is arranged to hold the containment structure to the external surface via the one or more friction pads.

9. (canceled)

10. The decontamination apparatus as claimed in claim 1, wherein the moveable platform comprises a floating device.

11. The decontamination apparatus as claimed in claim 1, wherein the containment structure comprises a hatch or door to allow access to waste produced by the decontamination of the external surface.

12. The decontamination apparatus as claimed in claim 1, wherein the containment structure comprises a main body connected to the contact surface; and wherein the main body of the containment structure comprises a module for occupation by a human operator comprising shielding.

13. (canceled)

14. The decontamination apparatus as claimed in claim 1, wherein the decontamination device comprises a decontamination tool comprising one or more of: an ultra-high pressure hydro-demolition tool, a mechanical scabbling tool, a dry ice blasting tool, a grit blasting tool, a lasering tool, a nitro-jetting tool, a chemical removal tool and a high pressure water jetting tool.

15. The decontamination apparatus as claimed in claim 1, wherein the decontamination device is moveable relative to the containment structure.

16. The decontamination apparatus as claimed in claim 1, wherein the decontamination apparatus comprises a frame on which the controlled decontamination device is mounted.

17. The decontamination apparatus as claimed in claim 1, wherein the decontamination device is arranged to excavate or remove a layer of the external surface to at least a threshold depth into the external surface.

18. The decontamination apparatus as claimed in claim 1, wherein the decontamination apparatus comprises a plurality of contact surfaces and a plurality of hoods comprising the plurality of contact surfaces respectively, wherein each hood extends between the main body of the containment structure and the respective contact surface.

19. The decontamination apparatus as claimed in claim 1, wherein the contact surface comprises one or more hinges.

20. The decontamination apparatus as claimed in claim 1, wherein the decontamination apparatus comprises at least one sensor and/or detector for sensing and/or detecting a physical or chemical property associated with a contaminant in or on the external surface; and wherein the decontamination apparatus comprises a sensor and/or detector feedback system.

21. (canceled)

22. The decontamination apparatus as claimed in claim 1, wherein the decontamination apparatus comprises or is in communication with a control room for controlling operation of the decontamination device in the containment structure; and wherein the control room comprises control apparatus for controlling the components of the containment structure.

23. (canceled)

24. A decontamination apparatus for decontaminating an external surface comprising: a moveable platform; a containment structure mounted on the moveable platform; wherein the containment structure comprises: at least one aperture; and a respective contact surface arranged around the perimeter of the at least one aperture, wherein the contact surface is arranged to form a barrier with the external surface to define a working volume, when the containment structure is positioned proximal to an external surface; and a decontamination device arranged to decontaminate the external surface, wherein the decontamination device is arranged within the working volume and arranged to access the external surface through the at least one aperture.

25. A decontamination apparatus for decontaminating an external surface comprising: a containment structure, the containment structure comprising: at least one outer aperture; and a respective outer contact surface arranged around the perimeter of the at least one outer aperture; wherein the outer contact surface is arranged to form an outer barrier with the external surface to define a working volume, when the containment structure is positioned proximal to an external surface; and a decontamination device arranged to decontaminate the external surface, wherein the decontamination device is arranged within the working volume and arranged to access the external surface through the outer aperture, wherein the decontamination device comprises an inner aperture and an inner contact surface arranged around the perimeter of the inner aperture, wherein the inner contact surface is arranged to form an inner barrier between the external surface and the decontamination device, wherein the decontamination device comprises a decontamination tool, and wherein the decontamination tool is arranged to access the external surface through the inner aperture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0118] Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0119] FIG. 1 shows schematically a decontamination apparatus in accordance with an embodiment of the present invention;

[0120] FIG. 2 shows schematically a decontamination apparatus in accordance with another embodiment of the present invention;

[0121] FIG. 3 shows schematically an example of a platform for use with embodiments of the present invention;

[0122] FIG. 4A and FIG. 4B show examples of decontamination devices for use with embodiments of the present invention; and

[0123] FIG. 5 shows schematically a decontamination apparatus in accordance with an embodiment of the present invention having a hinged arrangement for fitting into a corner.

DETAILED DESCRIPTION

[0124] A significant challenge presented by nuclear power generation, is the safe storage and remediation of radioactive waste. Nuclear fuel pools or ponds provide one way of cooling and storing spent fuel rods. These ponds are filled with water and are typically lined with a thick concrete layer on the walls and floor. They provide immediate cooling for long enough so that short-lived isotopes are given time to decay, which reduces the ionising radiation emitted from the rods. The water and concrete provide adequate shielding (e.g. to protect workers at nuclear facilities) until the rods are sent elsewhere for dry storage or reprocessing.

[0125] One the most problematic fission products of Uranium-235 (used in fuel rods) is Caesium-137. It is highly water-soluble and has a half-life of approximately 30 years. Radionuclides, such as Caesium-137 and Strontium-90, may be released from the spent fuel rods into the pond water. Over time the water, contaminated with radioisotopes, absorbs into the surface layer of the concrete. This means that even when the spent fuel and water are removed, the remaining pond walls and floor will continue to be contaminated as the radionuclides become trapped within the porous concrete matrix.

[0126] When nuclear power facilities close, the spent fuel ponds require their concrete walls and floors to be remediated prior to final decommissioning and demolition. Both the contaminated water and the contaminated concrete should be removed from the site. Removing the contaminated concrete can be dangerous for the environment and the health and safety of nearby workers. Breaking or destroying the concrete, for example by water-jetting, allows the contaminated waste to become airborne and contaminated aerosols may be released into the surrounding environment, particularly for outdoor ponds.

[0127] FIG. 1 shows schematically a decontamination apparatus 1 in accordance with an embodiment of the present invention. Here, the decontamination apparatus 1 is being used to remove contaminated concrete from the surfaces (e.g. of the walls) of a spent fuel pond. The radiological goal for remediation of such spent fuel ponds is typically to reach R2 radiation zone levels (<25 pSv/hr) at a distance of 1 m. This may be achieved by removing (or in simple terms shaving) a layer of the external surface to be decontaminated.

[0128] In this embodiment shown in FIG. 1, the decontamination apparatus 1 comprises a containment structure, comprising a main body 6 and a hood 2 (i.e. defined by a corrugated or concertina-like tunnel), a decontamination tool and a platform 4.

[0129] The hood 2 of the containment structure is arranged to be brought into contact with a wall 16 of a spent fuel pond (i.e. as shown in FIG. 1), and is supported by the (pontoon) platform 4. The platform 4 has a floating device (e.g. buoys or pontoons) 26 to help it to float on the water 18 and prevent it from colliding with the wall 16. The hood 2 has a contact surface 22 (at the distal end of the hood 2) that surrounds an aperture or hole of the containment structure. Within the hood 2 is a decontamination device 8 and a vacuum hose 12 connected to a vacuum system (not pictured).

[0130] A handrail 15 is provided for the safety of any operators or maintenance/repair workers who may need access to the main body 6 of the containment structure. Two gamma cameras 14a, 14b are mounted to the top of the main body 6 of the containment structure.

[0131] For an external surface 16 that is contaminated and needs to be decontaminated, the platform 4 and containment structure is assembled proximal to the external surface 16. It is appreciated that the containment structure could have any number of hoods and decontamination devices. However, here the decontamination apparatus has a single hood 2 and decontamination device 8. The face of the containment structure where the hood 2 and decontamination device 8 are located is arranged to face the external surface 16 to be decontaminated.

[0132] The concertina-like hood 2 may initially be folded up, close to the containment structure. On starting the decontamination process, the hood 2 is arranged to be deployed from the side of the main body 6 of the containment structure. Movement of the hood 2 may be remote-controllede.g. by a control system in a control room within the main body 6 or a control room remote from the decontamination apparatus 1, 3. Movement or deployment of the hood 2 involves extension of the hood 2, by unfolding, toward the external surface 16 to be decontaminated.

[0133] The corrugated nature of the hood 2 allows the hood 2 to bend in a number of directions. The hood 2 may therefore bend toward an external surface if necessarye.g. the floor of a spent fuel pond. This allows the decontamination apparatus 1 to increase the number of external surfaces that may be decontaminated with a single hood 2 and decontamination device 8.

[0134] When the hood 2 has been extended to make contact with the external surface 16, a barrier (e.g. seal) is formed between the contact surface 22 of the hood 2 and the external surface 16. The (suction) barrier (e.g. seal) is generated by a vacuum system (not pictured) being controlled to lower the pressure within the hood 2 via a vacuum hose 12.

[0135] The barrier (e.g. the outer barrier (e.g. the outer seal)) provided by the contact surface 22 of the hood 2 defines a (e.g. sealed) working volume within the containment structure, within which sits a decontamination device 8. The decontamination process is performed on the external surface 16 by operating the decontamination device 8 within this working volume.

[0136] The decontamination device 8 comprises a cover 9 having an inner contact surface 24 to provide an inner barrier, in addition to the outer barrier provided by the outer contact surface 22 of the hood 2. This further helps to prevent the release of waste into the surrounding environment. For example, the inner barrier (e.g. inner seal) may prevent the release of more solid/aggregate waste and the outer barrier (e.g. outer seal) may prevent the release of more of the aerosol waste.

[0137] The components (e.g. the hood 2, decontamination device 8, gamma cameras 14a, 14b) of the decontamination apparatus 1, 3 may be connected to a control system over one or more wired or wireless links. The operation of the decontamination device 8 is controlled via control lines 34a, 34b, 34c.

[0138] A support member 32 is used to mount the decontamination device 8 to the containment structure's main body 6, e.g. via a frame 302, 308 as shown in FIG. 4A or 4B. The support member 32 may be retractable or static and may comprise a vacuum hose (in addition to the main vacuum hose 12) for removing waste from within the decontamination device's cover 9. It can be seen that one of the control lines 34a connects to a decontamination tool 13 on a frame 11. The tool 13 is slidably mounted to the frame 11. The frame 11 provides a mechanism for moving the tool (e.g. horizontally and vertically) within the cover 9.

[0139] The vacuum hose 12 is arranged to remove aerosols from within the (e.g. sealed) working environment and transport them a short distance (e.g. between 0 m and 10 me.g. between 0.1 m and 5 m) to the main body 6 of the containment structure. This helps to prevent problems caused by transporting aerosols along long lengths of hosese.g. a build-up of dust may cause blockages in a longer hose.

[0140] The hood 2 (having a contact surface 22 forming the outer barrier) captures aerosols created by the decontamination (e.g. jetting) process. In this example, there is a separate vacuum system for the hood 2 and for the decontamination device 8. The vacuum system provided for the hood 2 creates a draw for the aerosol, and provides a barrier (e.g. seal) (and nominal adhesion) between the hood 2 and the external surface 16 (pond wall).

[0141] Where the external surface 16 is a spent fuel pond wall (as in FIG. 1), the pond water may be removed incrementally during the decontamination process. This advantageously allows the water to continue to provide some shielding during decontamination.

[0142] The pond water 18 is incrementally removed (e.g. via a pumpnot pictured) and the water level is consequently lowered in increments, e.g. 700 mm at a time. As the water is lowered by a certain distance (e.g. 700 mm) 20, the floating platform 4 is automatically lowered the same distance 20. After the water has been reduced by a certain distance, e.g. by 700 mm, the decontamination device 8 is again moved into contact with to the external surface 16 and the decontamination tool within the cover 9 works to remove a layer of the external surface 16.

[0143] While the decontamination tool works on the external surface, no water is removed from the pond and the platform 4 stays at a constant level. This gives the decontamination device 8 enough time to work horizontally (or in two directionse.g. horizontally and vertically) to remove a layer of the external surface within the working volume, e.g. up to a depth of 28 mm.

[0144] A jet of high-pressure water may be used to abrade concrete fines and aggregatee.g. without damaging reinforcing bars or other cast-in steel items in the external surface (pond wall) 16. A high flow rate vacuum system captures and removes the water and solids from the work surfacee.g. via the vacuum hose 12 within the hood 2 or another vacuum hose located within the cover 9 of the decontamination device 8 (e.g. within the support member 32).

[0145] During decontamination, a layer of the external surface (e.g. to a depth of approximately 28 mm) may be removed from the external surface 16 by the decontamination device 8. This may involve the use of a shaving methode.g. by an ultra-high pressure hydro-demolition remotely operated vehicle.

[0146] Approximately 99% of radioactive Caesium is in the first 25 mm of the external surface of a spent fuel pond. By removing up to 28 mm of the external surface, the hazard may be removed to a safe level.

[0147] The containment structure may be modular and, in some examples, a module for waste (solids) collection may be housed in the modular containment structure's main body 6. Water treatment systems may also be contained within the main body 6 so that pH neutral water may be routed back into the pond.

[0148] The decontamination tool 13 or device 8 and/or surrounding hood 2 may be driven horizontally along the external surface 16 using a linear tracking system (e.g. at a certain tracking speed). The depth of penetration into the external surface 16 by the decontamination tool 13 or device 8 may be controlled by the tracking speed (i.e. the movement of these components). This may be controlled remotely and/or automatically based on captured data. For example, the plastic scintillator radiation (gamma) detectors 14a, 14b may monitor the scabbled wall behind the hood 2. Radiometric data may be collected and related to the position of the jetting operations and may be used to generate a dose map of the external surface (e.g. pond wall) 16.

[0149] The gamma cameras 14a, 14b may monitor the external surface (e.g. behind the hood 2) and this data can be used to adjust the tracking speed (e.g. speed of horizontal movement of the decontamination device) to achieve the required depth of penetration into the external surface 16. The gamma cameras 14a, 14b may alternatively be located within the hood 2 or even within the cover 9 of the decontamination device 8.

[0150] FIG. 2 schematically shows another embodiment of the decontamination apparatus. FIG. 2 has substantially all the features of FIG. 1. The difference between the decontamination apparatus 101 shown in FIG. 2 and the embodiment shown in FIG. 1 is that the floating pontoon platform 4 has been replaced by a mechanically moveable platform 104. Supporting the platform 104 is a scissor lift 105 which is mounted to the floor 130.

[0151] In FIG. 2, the pond is dry (e.g. already dewatered) and the moveable platform support (scissor lift) 105 is mounted on the pond floor 130. The moveable platform support 105 allows for vertical movement of the platform 104. The platform 104 may be modular (as shown in FIG. 1), however, in this example, the platform 104 is comprised of one solid block of concrete. The thick concrete platform provides radiological shielding for devices/electronics and potential operator(s) above the platform or within the containment structure.

[0152] The decontamination apparatus 101 shown in FIG. 2, is useful for decontaminating external surfaces (e.g. 116) where there is no water for the platform to float on, for example, for decontaminating walls or floors of a building or drained spent fuel ponds.

[0153] FIG. 3 shows schematically a platform that may be used with embodiments shown in FIGS. 1 and 2. In FIG. 3, the platform 204 is modular and comprises three concrete blocks 204a, 204b, 204c. A gangway 240 (ramp) is provided to allow access to the platform 204. This is useful particularly when the external surface is a pond wall (e.g. 16, 116), as the platform 204 may otherwise be difficult to access. A grooved layer 248 on top of the platform 204 and gangway 240 prevents them from being slippery when walked on.

[0154] FIGS. 4A and 4B show decontamination devices which may be used in the decontamination apparatus shown in FIGS. 1 and 2.

[0155] In FIG. 4A, the decontamination device 301 comprises a cover 303. The cover 303 surrounds the decontamination tool (not shown) and is slidably mounted to a frame 302. In operation, the cover 303 (and decontamination tool within) is held against an external surface to be decontaminated (within the containment structure of the decontamination apparatus of FIG. 1 or 2).

[0156] The tool and cover 303 may be translated along the frame 302 (e.g. either horizontally or vertically) at a speed determined by a tracking system. The tracking system may change the speed of the tool based on the depth of external surface that must be removed. This speed may also depend on the decontamination technique used. In this example, the decontamination device 301 is arranged to use the technique of robotic hydro-demolition where the tool comprises a water jet. The water is delivered through the hose 305 to be released from the tool at very high pressures/flow rates.

[0157] The decontamination device 306 shown in FIG. 4B is another example of a decontamination (e.g. robotic hydro-demolition) device. In contrast to the decontamination device 301 shown in FIG. 4A, the decontamination device 306 of FIG. 4B allows for both horizontal and vertical movement.

[0158] For example, the horizontal movement of the whole device 306 (including the decontamination tool and its surrounding cover 307) is achieved by moving a vehicle 310 on which the decontamination tool is mounted. The vehicle 310 has a motorised continuous track 309. The continuous track 309 increases the footprint size and therefore the stability of the decontamination device 306. The vertical movement of the decontamination tool and its surrounding cover 307 is achieved by moving the tool and cover 307 along the frame 308 to which it is slidably mounted.

[0159] Preferably, an ultra-high pressure dry-hydro-scabbling tool is used to perform the decontamination. Such ultra-high pressure (e.g. greater than 3000 bar) pump systems are advantageous as they use a fraction of the water volume used by conventional hydro-demolition systems.

[0160] FIG. 5 shows a simplified schematic of a further embodiment of the present invention, in which the contact surface 422 of the hood 402 comprises a friction pad 433 and a hinge mechanism 435. The decontamination apparatus 434 shown in FIG. 5, is shown with the hood 402 connected to the main body 406 of the containment structure. In this example, the external surface 416 to be decontaminated includes a corner. The hinge mechanism 435 of the friction pad 433 allows the flexible contact surface 422 to be manipulated into the shape required for providing a barrier (e.g. seal).

[0161] The addition of a hinged friction pad 433 at the contact surface allows the hood 402 to fit within the corner of the external surface 416 (pond wall) and helps to ensure that the contact surface 422 forms a secure barrier (e.g. seal). The decontamination apparatus of FIG. 1 or 2 may include a contact surface as shown in FIG. 5.

[0162] The waste produced from typical decontamination techniques (e.g. water jetting and scabbling), is often highly contaminated. Existing decontamination techniques typically result in considerable aerosol effluence and without the barrier (e.g. seal) provided by the decontamination apparatus described herein, would release highly contaminated airborne waste into the surrounding environment. This would cause recontamination of the surfaces that are being decontaminated and would also spread toxic or hazardous contaminants around the local environment.

[0163] Embodiments of the present invention address at least some of the issues described above. Such issues are especially associated with dry decontamination techniquese.g. namely the generation of airborne dust (or aerosols) and the transportation of the dust via long lengths of hose. Further, the decontamination apparatus according to the invention provides additional shielding and protection from the contaminants.

[0164] It will be appreciated by those skilled in the art that although the invention has been illustrated by describing embodiments in relation to decontaminating the walls and floors of spent fuel ponds which may be contaminated with radioactive materials, it is not limited to these embodiments, and the invention can be used in any other suitable contexte.g. for surfaces contaminated with toxic chemicals, asbestos, biologically active materials and hazardous waste. Furthermore, many variations and modifications are possible, within the scope of the accompanying claims.