Radiation detection apparatus

Abstract

A radiation detection apparatus is disclosed. In one arrangement, the apparatus comprises: a detector configured to detect radiation from a surface, wherein the detector is positioned such that radiation from the surface is incident on the detector; and a radiation shield, comprising a static wall and a moveable door, wherein the static wall contains a recess configured to accommodate the moveable door, wherein the moveable door is positionable within the recess, and wherein the moveable door is configured to be actuated between a closed position completely covering the recess and an open position leaving at least a portion of the recess uncovered, wherein the radiation shield is positioned such that the moveable door prevents the radiation from being incident on the detector when in the closed position, and does not prevent the radiation from being incident on the detector when in the open position.

Description

RADIATION DETECTION APPARATUSField

[0001] The present invention relates to a radiation detection apparatus. More particularly, embodiments of the present invention relate to a system able to detect contamination entrained in concrete in a submerged environment. The system may be used to determine the category of waste that a surface belongs to, and the depth to which the contamination ingresses throughout a structure.Background

[0002] Characterisation of contamination in cementitious material is of major importance to the development of a comprehensive decommissioning strategy in nuclear environments. Cementitious material constitutes a significant fraction of the total radioactive waste expected to be generated, and subsequently stored, as part of decommissioning. Concrete is a naturally porous material and particularly permeable to certain radioactive species. Due to the nature of this process, the contamination levels will typically be highest at the surface, decreasing as a function of depth. This results in physical boundaries where the activity concentration changes from Intermediate Level Waste, to Low Level Waste, and subsequently Very Low Level Waste. Higher level waste is more expensive to process and dispose of, and so a thorough understand of these boundary locations enables the waste to be segregated and disposed of more efficiently.

[0003] A frequent challenge associated with nuclear facilities is the in-situ measurement of entrained radioactivity within the walls of nuclear fuel storage ponds. These facilities are found in many power and reprocessing facilities, where fuel is stored to cool down following its use in a reactor. The concrete pond linings absorb the nuclide species contained in the water, which are a result of corrosion of the fuel cells stored within it. The water hygroscopically penetrates the concrete lining and areas of high contamination can build up in defects of the lining, i.e. cracks and holes. The penetration of radioactivity will be limited in depth, dependent on the material and is unlikely to be uniform.

[0004] Although several existing methods allow for waste to be correctly classified, these methods require the pond to be dewatered so that samples can be taken. This is impractical in a lot of circumstances, and creates significant additional hazards as the potentially contaminated surfaces are exposed to workers due to the removal of the water which acts as a shield. Equally, these methods can suffer from a reduction in accuracy due to thepresence of other radioactive sources leading to background radiation impacting the measurement. In view of the above, there exists a need for an apparatus that is capable of being remotely deployed in both wet and highly contaminated nuclear environments.Summary

[0005] According to an aspect of the invention, there is provided a detector configured to detect radiation from a surface, wherein the detector is positioned such that radiation from the surface is incident on the detector; and a radiation shield, comprising a static wall and a moveable door, wherein the static wall contains a recess configured to accommodate the moveable door, wherein the moveable door is positionable within the recess, and wherein the moveable door is configured to be actuated between a closed position completely covering the recess and an open position leaving at least a portion of the recess uncovered, wherein the radiation shield is positioned such that the moveable door prevents the radiation from being incident on the detector when in the closed position, and does not prevent the radiation from being incident on the detector when in the open position.

[0006] When measuring the contamination entrained in concrete, it is important to ensure that the estimation is as accurate as possible. Background radiation values that are not emitted by the surface being estimated may lead to an estimate that is higher than the actual value. The amount of background radiation is especially high when the detector is used to measure the contamination entrained in a surface that is submerged. The use of a radiation shield allows for a measurement of the background radiation to be taken. The measurement for the background radiation can then be subtracted from the measurement taken from the surface to provide a more accurate measurement for the true value of the contamination entrained in the surface. A more accurate estimation of the contamination is therefore provided, without the need to dewater the environment or take samples from the surface being measured.

[0007] In an embodiment, the radiation detection apparatus further comprises a first casing, comprising an opening located at the distal end of the first casing, and a first flange located at the distal end of the first casing extending outwards from the centre of the casing. The radiation detection apparatus also comprises a second casing, comprising an opening located at the proximal end of the second casing and a second flange located at the proximal end of the second casing extending outwards from the centre of the casing, wherein the first flange is positioned directly against the second flange. The casing ensures that the internal components of the detector are protected from potential damagedue to exposure to radioactive water. The casing can also be easily decontaminated after the apparatus is used. Additionally, assembly, repair, and maintenance of the apparatus is easier in comparison to using only a singular casing.

[0008] In an embodiment, an O-ring is positioned in between the first flange and the second flange to form a watertight seal between the first casing and the second casing. The use of an O-ring further improves the waterproofing of the casings, by providing a seal between where the two casings are joined together. Water is therefore prevented from making ingress between the two casings and the components contained within the casing are protected from possible water damage.

[0009] In an embodiment, the radiation detection apparatus further comprises a third casing. The second casing further comprises an opening located at the distal end of the second casing, and a third flange located at the distal end of the second casing extending outwards from the centre of the casing. The third casing comprises an opening located at the distal end of the third casing, an opening located at the proximal end of the third casing, and a fourth flange located at the proximal end of the third casing extending outwards from the centre of the casing. The third flange is positioned directly against the fourth flange and the detector is connected to an external computing device by a cable which passes through the opening located at the distal end of the third casing . The use of a third casing allows a cable to exit the apparatus without creating an opening that allows water to ingress within the casing. The internals of the casing are therefore protected from potential damage to exposure to radioactive water.

[0010] In an embodiment each component is located in a separate casing . Providing each casing in a separate component means that, should a component fail, the casing containing that component can be removed and replaced with a new casing containing a working component. The entire apparatus therefore does not have to be replaced when a component is not functioning correctly. Equally, maintenance on the apparatus can be easily carried out, as each component can be accessed in isolation, for example, to perform testing on the component. The use of a modular design therefore allows for a more easily repairable and maintainable apparatus.

[0011] In an embodiment, the second casing contains an amplifier connected to the detector, wherein the amplifier is a component and is configured to amplify a detector signal produced by the detector. Amplifying the raw signal received from the detector before the signal is transmitted outside of the apparatus allows for the effects of noisewhen transmitting low amplitude signals over long distances to be reduced. The length of a cable connecting the apparatus to any external components can then be increased, allowing for the apparatus to be used at greater depths and over larger distances.

[0012] In an embodiment, the first casing and the second casing have different outer dimensions. Any internal components contained within the first casing and the second casing are in contact with opposing inner surfaces of the first casing and the second casing respectively. Providing a casing that is in contact with the internal components such that the external size of the casing is minimised reduces the size and weight of the apparatus. The apparatus can therefore be more readily manoeuvred when in use. Equally, the internal components can be held securely to prevent possible damage caused by movement within the casing.

[0013] In an embodiment, the moveable door and static wall both comprise an outer waterproof layer at least at the interface between the recess and the moveable door. In an embodiment, the moveable door and recess are shaped so that radiation traversing the interface between the moveable door and the static wall is directed away from the detector, such that the detector does not detect the radiation. In an embodiment, the moveable door is tapered. Including a waterproof layer prevents the moveable door and static wall from being damaged by the water. The waterproof layer is less effective at shielding against radiation than the moveable door and static wall. The waterproof layer therefore provides a path that radiation can follow. Shaping the moveable door and the static wall so that the radiation is directed away from the detector ensures that the radiation does not impact the detector, improving the effectiveness of the radiation shield. A tapered shape ensures that any path through the waterproof layer is directed away from the detector, to prevent an impact upon the measurement.

[0014] In an embodiment, the first housing further comprises a first side plate and a second side plate extending in substantially opposing directions. Each side plate includes a foot configured to prevent the radiation shield from contacting a surface when the detector faces the surface. The apparatus may be used to measure materials that have a rough or porous surface, such as concrete. Direct contact between the radiation shield and the surface would damage the radiation shield over time, reducing its effectiveness. Preventing contact using the first and second side plates prevents damage to the radiation shield. The feet themselves can also be easily replaced should they be damaged. The long-term reliability of the device is therefore improved.

[0015] In an embodiment, the moveable door is actuated between the closed position and the open position using a hydraulic system. In an embodiment, the hydraulic system uses demineralised water as a hydraulic fluid. As the apparatus is intended to operate in an active nuclear environment, it is important that the apparatus has a low risk of failure, and will not cause any chemical contamination even when failure does occur. Demineralised water can be used as the hydraulic fluid. Demineralised water will have no repercussions to the pond environment, meaning that the apparatus does not present a risk, even if failure does occur. Specifically, there is no risk of chemical incompatibility with the fuel housings. There is also low risk of long term damage being caused by a leak.Brief introduction to the drawings

[0016] Embodiments of the disclosure will be further described by way of example only with reference to the accompanying drawings.

[0017] Figure 1 is a schematic side view of an example apparatus with the radiation shield located in the open position

[0018] Figure 2a is a schematic showing the cross section of the moveable door from the example apparatus shown in Figure 1.

[0019] Figure 2b is a schematic showing a front view of the static wall from the example apparatus shown in Figure 1.

[0020] Figure 3a is a schematic showing a front view of the example apparatus shown in Figure 1, with the moveable door located in the closed position.

[0021] Figure 3b is a schematic showing a front view of the example apparatus shown in Figure 1, with the moveable door located in the open position.

[0022] Figure 4 is a schematic showing a cross section of a side view of the example apparatus shown in Figure 1.

[0023] Figure 5 is a schematic showing a cross section of a top view of the example apparatus shown in Figure 1.Detailed description

[0024] Various examples of a system for detecting readings of radiation entrained in concrete are described below with reference to the figures.

[0025] As depicted in Figure 1, the radiation detection apparatus 1 comprises a detector 14 configured to detect radiation from a surface. The detector may be configured to detect radioactive emissions in the range of 20 - 2000 keV. Optionally, the detector 14 is a spectrometer. Optionally, the detector 14 is a cadmium zinc telluride spectrometer. The detector 14 is positioned such that radiation from the surface is incident on the detector 14. Readings taken by the detector can be used to characterise the radiation emitted by cementitious material for the purposes of radioactive waste categorisation and segregation.

[0026] The apparatus 1 additionally comprises a radiation shield 40 configured to shield the detector 14 from radiation. The radiation shield 40 may be configured to shield the detector 14 from at least x-ray and gamma-ray radiation. The radiation shield 40 may be specifically configured to block radiation with an energy range of between 0 to 1500 keV. The radiation shield 40 comprises a static wall 44 and a moveable door 42 (alternatively called a plug), as depicted in Figure 2a and 2b. The static wall 44 contains a recess 48 configured to accommodate the moveable door 42. The moveable door 42 is positionable within the recess 48.

[0027] The moveable door 42 is configured to be actuated between a closed position and an open position, as shown in Figure 3a and 3b. Figure 3a shows the moveable door 42 in a closed position completely covering the recess 48. Figure 3b shows the moveable door 42 in an open position leaving at least a portion of the recess 48 uncovered. Although the figures show the moveable door 42 moving vertically upwards and downwards, the moveable door 42 could instead move in alternate directions, such as horizontally.Equally, the moveable door 42 could comprise multiple parts configured to be actuated away from each other. When the moveable door 42 is moved vertically, the closed position may be called the down position, and the open position may be called the up position. Optionally, when the moveable door is actuated into the open position, the movable door is locked in the open position to prevent movement until the moveable door is further actuated out of the open position and when the moveable door is actuated into the closed position, the movable door is locked in the closed position to prevent movement until the moveable door is further actuated out of the closed position. The moveable door may be prevented from moving by locking the movable door into position. For example, the shield can be locked in the closed position, so that the moveable door 42 stays in place when moving to a new position to take measurements. Equally, locking the moveable door 42 in the open position prevents the moveable door 42 from temporarily blocking a portion of the detector due to movement while a measurement is being taken.

[0028] The radiation shield 40 is positioned such that the moveable door 42 prevents x-ray and gamma-ray radiation from being incident on the detector 14 when in the closed position, and does not prevent the radiation from being incident on the detector 14 when in the open position. In the embodiment shown in Figure 3a and 3b, the detector 14 is positioned behind the recess 48, such that radiation is able to pass through the recess 48 and be incident upon the detector 14. When the moveable door 42 is positioned in the closed position, the moveable door 42 is located between the detector 14 and any radiation emitted by a surface. The moveable door 42 and the static wall 44 form a shield that ensures there is no unshielded path that radiation emitted from a surface can take to reach the detector 14.

[0029] The radiation detection apparatus 1 is designed to operate in a nuclear pool that is currently in operation. The nuclear pool will therefore contain contaminated water, as well as fuel cells. The proximity of the fuel and pond water to the measurement location causes background radiation that may reduce the accuracy of the measurement, leading to the radioactive surface being incorrectly characterised. The strength of this background radiation may dramatically change depending on the position of the fuel and activity levels of the pond water. The present invention overcomes this through taking an initial measurement of the background radiation before taking a measurement of the radiation emitted by a surface.

[0030] When the detector 14 is moved into a position to take a reading of a surface, the moving wall 42 is first moved into the closed position. The radiation shield 40 is configured to prevent at least x-ray and gamma-ray radiation from the surface from being incident upon the detector 14. Small amounts of background radiation is able to penetrate the shield, and so a measurement of the background radiation coming through the shield can be taken. The moving wall 42 can then be raised into the open position and a second measurement taken. The second measurement will have the radiation from the exposed surface elevated due to the moving wall 42 no longer being present, in addition to the previously measured background radiation. Subtracting the closed position measurement from the open position measurement allows for an isolated measurement of the radiation emitted from the surface only to be achieved. The radiation shield therefore allows for a non-invasive measurement of entrained radioactive contaminants to be taken, without any requirement to dewater the pond or take samples from the concrete.

[0031] Optionally, the apparatus 1 further comprises a collimator configured to substantially prevent radiation not emitted by the surface from being incident on the detector 14. The detector 14 may be located within the collimator such that radiation emitted from other sources are incident on the collimator rather than the detector. One example of a possible source would be other parts of the surface that are not currently being measured. A specific reading of the section of the surface that the detector 14 is positioned in front of can be taken. The collimator therefore helps reduce radiation from other sources from impacting the measurement, meaning that a more accurate measurement is achieved. The collimator may be positioned using a collimator cup 15 and a collimator plug 16 to prevent movement of the collimator.

[0032] The collimator may include an opening that allows for the detector located within to be connected to other components. The routing for the connecting cable may bend, to minimise any potential reduction in collimation towards the detector, by preventing a single, unshielded, path through the cable.

[0033] A spectral analysis technique may be performed on the data recorded with the detector 14. A non-intrusive picture of the penetration of contamination within a concrete surface can be provided through this technique. The detector 14 may be essentially uncollimated, with the radiation shield 40 removing background radiation to ensure that the spectrum recorded is that of the surface being analysed. The system therefore has a rapid deployment that produces zero airborne contaminants during a survey, enabling large areas to be scanned relatively quickly and minimising the time spent by workers in the contaminated area.

[0034] A characterisation of the contamination of the surface can be generated based on the principle that for a given source of radiation, the x-ray and y-ray spectrum varies significantly as additional attenuating material is positioned between the radiation source and the detector. A database of simulated spectra generated using high precision models may be used. A detailed comparison of spectral features between calibrated simulations and real measurement enables high precision depth profiles to be generated.

[0035] In an arrangement, the radiation detection apparatus further comprises a first casing 10 (also called a waterproof housing), comprising an opening located at the distal end of the first casing 10. The first casing 10 also comprises a first flange 12 located at the distal end of the first casing 10 extending outwards from the centre of the casing. The firstflange 12 may extend at substantially 90 degrees from the body of the casing. Alternatively, the first flange 12 may extend at an angle relative to the body of the casing.

[0036] The radiation detection apparatus further comprises a second casing 20, comprising an opening located at the proximal end of the second casing and a second flange 22 located at the proximal end of the second casing 20 extending outwards from the centre of the casing. The first flange 12 is positioned directly against the second flange 22. The first flange 12 and the second flange 22 may be joined together using a plurality of fasteners 52. The first casing 10 and the second casing 20 prevents water ingress and therefore allows for sensitive components, such as the detector 14, to be protected from contamination and water damage due to exposure to the water contained within the pool. Any part of the apparatus exposed to contaminated material must undergo a decontamination procedure after use. The casing ensures that none of the sensitive internal components require decontamination, which may cause damage.

[0037] Nuclear fuel storage ponds are subject to rigorous material restrictions to ensure chemical compatibility with the fuel housing stored within. Accordingly, the materials selected for the casings must pose little to no risk of interacting with the fuel element housings. Equally the casing must be able to withstand prolonged radiation doses and decontamination using pressure jets without degradation. Finally, the casing must not impact the spectroscopic capabilities of the sensor housed within. Examples of possible materials used for the casings include PEEK (polyether ether ketone), ABS (acrylonitrile butadiene styrene), and stainless steel. The first casing 10 and the second casing 20 may be made using predominantly PEEK. The fixings may be made using predominantly stainless steel. The housing may be waterproof up to a depth of 10 meters.

[0038] The first casing 10 may use a thin, low-density material for the proximal surface. Radiation emitted from the surface being measured is therefore able to penetrate the material easily and be detected by the detector 14 located within.

[0039] Alternatively, the first casing 10 and the second casing 20 may not comprise a first and second flange, with a fastener 52 instead being located within the body of the casings themselves. Removing the flanges reduces the amount of material required to manufacture the first casing 10 and the second casing 20.

[0040] Further alternatively, the apparatus 1 may comprise only a single combined casing.A singular casing is simpler to manufacture in comparison to multiple casings, and doesnot require some form of fixing mechanism to join multiple parts together. Equally, a singular casing does not have the possibility of allowing water to ingress through a joint and into the casing.

[0041] The use of a first casing 10 and a second casing 20 allows for easier assembly of any internal components and electronics, as each casing can be assembled in isolation before being combined. The apparatus 1 is also made more repairable, as the internals of the apparatus can be more readily accessed to make replacements or repairs. Equally, should one of the casings themselves be damaged, the undamaged casing can be reused.

[0042] Optionally, an O-ring 28 is positioned in between the first flange 12 and the second flange 22 to form a watertight seal between the first casing 10 and the second casing 20. The O-ring 28 and flanges work in combination to ensure that a waterproof seal is formed between the first casing 10 and second casing 20. Contaminated water is therefore prevented from ingress between the first flange 12 and the second flange 22. Components contained within the apparatus 1 are therefore protected from possible damage caused by exposure to water or radiation. Figure 4 shows one possible position of the O-rings between the first flange 12 and the second flange 22.

[0043] The first casing 10 may further comprise one or more standing feet 17, as shown in Figure 2. The standing feet 17 are located at the bottom of the apparatus 1, and extend below the apparatus 1. The standing feet 17 prevent the apparatus 1 from impacting with the bottom of a nuclear pool directly, which could cause damage to the casing of the apparatus 1. The standing feet 17 further allow for the apparatus 1 to be deployed using a flat platform, as the standing feet 17 prevent the apparatus 1 from rolling. The first casing 10 may further comprise a lift shackle 18, as shown in Figure 1. The lift shackle 18 allows for the apparatus 1 to be easily mounted to a deployment system that is then used to position the apparatus against a surface. Examples of possible deployment systems include attachment to the end of a pole, to positionable frames, and to a robotic arm. The apparatus 1 can therefore be positioned without requiring the operator to approach the contaminated water. The operator is therefore protected from exposure to high levels of radiation.

[0044] In an arrangement, each component is located in a separate casing. Optionally, the detector 14 is a component and is located with the first casing 10. Positioning only a single component within each casing further increases the repairability of the apparatus, as eachcasing can be swapped out should the component contained within develop a fault and require replacement.

[0045] In an arrangement, the first casing 10 and the second casing 20 have different outer dimensions and any internal components contained within the first casing and the second casing are in contact with opposing inner surfaces of the first casing 10 and the second casing 20 respectively. The first casing 10 and second casing 20 are sized such that there is substantially no gap between the casing and the component located within the first casing 10 or second casing 20. The dimensions of the first casing 10 and second casing 20 are therefore such that any component located within a casing is secured within by the pressure of the casing. There is no gap between the internal components and the casing meaning that the internal components are not able to move around. Should the internal components move, they may become damaged or defective. The size of the casing therefore increases the reliability of the apparatus. Equally, the size and mass of the system is reduced, meaning less materials are required to manufacture the apparatus 1. Mounting and manoeuvring the apparatus 1 is also more straightforward due to the reduced mass of the apparatus. Alternatively, larger casings that do not keep the components secure could be used, which would allow for the components to be more easily accessed and positioned within the casing.

[0046] In an arrangement, the apparatus 1 further comprises a third casing 30. The second casing 20 further comprises an opening located at the distal end of the second casing 20, and a third flange 24 located at the distal end of the second casing 20 extending outwards from the centre of the casing. The opening at the distal end of the second casing 20 may allow for a cable 34 to pass out from the second casing 20, as shown in Figure 4. The third casing 30 comprises an opening located at the distal end of the third casing 30, an opening located at the proximal end of the third casing 30, and a fourth flange 32 located at the proximal end of the third casing extending outwards from the centre of the casing. The third flange 24 is positioned directly against the fourth flange 32. The openings may allow for a cable 34 to pass into the third casing 30, and then to exit the third casing 30 after passing through it. The detector 14 is then connected to one or more external computing devices by the cable 34 which passes through the opening located at the distal end of the third casing 30. The external computing devices may be an external multi channel analyser and / or a computer.

[0047] Connecting the apparatus 1 to an external computing device means that measurements taken by the detector 14 can then be stored or processed further. As an alternative to a physical connection, some form of memory could be located within the apparatus 1 that is later accessed, to remove the need for a cable 34. However, the use of a cable 34 allows any data produced by the apparatus 1 to be analysed or processed in real time. A cable 34 also allows for the apparatus 1 to be externally powered and controlled. The size and complexity of the apparatus 1 is also reduced. Including a hole through which the cable 34 exits the apparatus 1 provides a possible point for contaminated water to enter the apparatus 1. The third casing 30 may therefore act as a waterproof plug that prevents ingress of water through the hole that the cable 34 exits the casing through. The apparatus 1 is therefore further waterproofed, and the internal components are protected from potential damage due to exposure to water and / or radiation.

[0048] As shown in Figure 4, the third casing 30 may be coupled to, a potting agent 36 that acts as a cable plug, around the third casing 30. The potting agent 36 may be substantially conical, and surrounds the cable such that water is prevented from entering the apparatus interior.

[0049] Optionally, an O-ring 38 is positioned in between the third flange 24 and the fourth flange 32 to form a watertight seal between the second casing 20 and the third casing 30. The O-ring 38 operates in combination with the flanges to produce a greater level of waterproofing than would be achieved by either feature in combination.

[0050] The apparatus may comprise further casings with further flanges. These further flanges may comprise additional O-rings located between them. The further casings may comprise additional components.

[0051] In an arrangement, the second casing 20 contains an amplifier 26 connected to the detector 14. The amplifier 26 is a component and is configured to amplify a detector signal produced by the detector 14. The amplifier 26 may be positioned within the second casing 20, as shown in Figure 4. The amplifier 26 may be connected to an external computing device using a cable 34. Optionally, the amplifier 26 may be a pre-amplifier. Optionally, a further amplifier may be later included. The further amplifier may be located outside of the apparatus 1. The amplifier 26 may be configured to receive the output of the detector 14, and to then amplify the raw signal before the signal is further transmitted outside of the apparatus 1. The amplified signal may then be transmitted to the further amplifier for further amplification or processing to be performed. When transmitting lowamplitude signals over a long distance, the impact of noise in the signal can become more pronounced. The use of an amplifier 26 to amplify the detector signal means that the signal can then be transmitted over a longer distance without the presence of the noise impacting the signal. The apparatus 1 is therefore able to be used at a greater depth and with less repositioning of any external hardware. When the apparatus is used in an active nuclear environment, such as a nuclear pool currently storing fuel, the external hardware is usually positioned at a distance of at least 10 meters away. The accuracy of any measurement taken by the apparatus 1 is therefore increased.

[0052] Alternatively, the apparatus 1 may not contain an amplifier 26. The lack of an amplifier 26 allows for the size of the apparatus 1 to be reduced, or for another component to be included instead.

[0053] In an arrangement the radiation shield 40 comprises tungsten. Optionally, the radiation shield 40 substantially comprises tungsten, as shown in Figure 3a. Optionally, the radiation shield further comprises a layer of copper 47 and / or a layer of tin 45. The layers are positioned within the radiation shield such that they prevent radiation from being incident upon the detector 14 when the radiation shield is in the closed position. As shown in Figure 3a, the layers may form a rear surface of the moving wall 42. The combination of these materials forms an effective radiation shield that prevents radiation emitted from the surface being measured from being incident upon the detector 14. Alternatively, different materials could be used to form the radiation shield 40, or in different combinations.

[0054] In an arrangement, as shown in Figure 3a, the moveable door 42 and static wall 44 both comprise an outer waterproof layer 46 at least at the interface between the recess 48 and the moveable door 42. The waterproof layer 46 prevents the corrosion of the tungsten layer due to prolonged immersion within water. Including this layer at the recess 48 between the two components prevents potential damage from compromising the integrity of the radiation shield 40. The waterproof layer may be made from waterproof plastic. The waterproof layer may cover the entirety of the static wall 44 and the moveable door 42.

[0055] In an arrangement the moveable door 42 and recess 48 are shaped so that radiation traversing the interface between the moveable door 42 and the static wall 44 is directed away from the detector 14, such that the detector 14 does not detect the radiation. The use of a waterproof layer creates regions of lower density within the radiation shield 40. Astraight line path from the surface to the detector 14 that passed only through the waterproof layer would create a shine path that did not correctly shield the radiation. Directing the radiation away from the detector 14 reduces or even prevents this effect by ensuring any shine path is not in the direction of the detector 14 and is instead towards a region that will have little to no effect on the measurement.

[0056] In an arrangement, the moveable door 42 is tapered. Optionally, the moveable door 42 may be wedge shaped, as shown in Figure 3 and Figure 5. A tapered shape, such as a wedge, is simple to manufacture, while still ensuring that any possible shine path is directed to a region that has no effect on the measurement. Alternative shapes can be used, such as an octagonal shape. These shapes may be harder to manufacture.

[0057] The moveable door 42 may be actuated between the closed position and the open position using a hydraulic system 54. The hydraulic system 54 may be attached to one or more tubes that convey the hydraulic fluid to and from the apparatus. The hydraulic system 54 may use demineralised water as a hydraulic fluid. The apparatus 1 may be deployed in an environment that still contains nuclear material. The environment must therefore not become contaminated with foreign chemicals, as this could have a negative effect on the nuclear material stored within the pond. Should the hydraulic system 54 malfunction, demineralised water will not have a negative impact on the pond’s environment. The apparatus therefore does not present a risk to the pond’s environment, even in the case of failure.

[0058] Alternatively, other methods of actuating the moveable door 42 may be used. For example, a motor may be used. A motor may be smaller than a hydraulic system 54, and will also not require an external connection to function, meaning that the apparatus 1 is then more versatile and is able to be quickly deployed. A motor may also allow for more precise positioning of the moveable door 42.

[0059] The hydraulic system 54 may be connected to the moveable door 42 by a rod inserted into the top of the moveable door 42, as shown in Figure 4. The hydraulic system 54 may then actuate the hydraulic rod to adjust the position of the moveable door 42. The hydraulic system 54 may include a 30mm stroke hydraulic cylinder, which is able to actuate between a closed position and an open position. When in the open position, the moveable door may be in a position 30mm away from the closed position. The hydraulics may maintain a pressure of around 15 bar to ensure that the door remains in a fixed position.

[0060] In an arrangement, the first housing further comprises a first side plate 56 and a second side plate 56 extending in substantially opposing directions. Each side plate includes a foot 58 configured to prevent the radiation shield from contacting a surface when the detector faces the surface. The apparatus 1 is designed to be used to measure porous materials, such as concrete. The surface of the radiation shield 40 may become damaged due to repeated impacts with surfaces, reducing the effectiveness of the radiation shield 40. This is especially true if the radiation shield 40 includes a waterproof layer, as the layer may be damaged and no longer provide protection. As shown in Figure 1, the feet protrude past the radiation shield 40, preventing the radiation shield 40 from contacting the surface. The radiation shield 40 is protected from potentially being damaged. The feet 58 are easily replaceable, ensuring that the apparatus 1 can be easily reused. The feet 58 provide the further benefit of ensuring that the detector 14 is always positioned at the same distance from the surface, which would not be the case if the apparatus 1 was only positioned next to the surface by eye, with no form of guide. The consistency of measurements taken by the apparatus 1 is therefore increased. The feet 58 may be configured to protrude approximately 1 mm in front of the radiation shield 40.

[0061] The side plates 56 may extend horizontally from the first housing 10, as shown in Figure 3a and 3b. Alternatively, the side plates may extend vertically from the first housing 10. More than two side plates 56 may be used. For example, three side plates 56 or four side plates 56 may be used.

[0062] An embodiment of the present invention is expected to achieve a significantly higher spatial resolution than alternate methods, with the depth of a point source of radioactive contamination being ascertainable with a 1 mm accuracy up to a depth of at least 50 mm.

Claims

Claims1. A radiation detection apparatus, comprising: a detector configured to detect radiation from a surface, wherein the detector is positioned such that radiation from the surface is incident on the detector; and a radiation shield, comprising a static wall and a moveable door, wherein the static wall contains a recess configured to accommodate the moveable door, wherein the moveable door is positionable within the recess, and wherein the moveable door is configured to be actuated between a closed position completely covering the recess and an open position leaving at least a portion of the recess uncovered, wherein the radiation shield is positioned such that the moveable door prevents the radiation from being incident on the detector when in the closed position, and does not prevent the radiation from being incident on the detector when in the open position.

2. The radiation detection apparatus of claim 1, further comprising: a first casing, comprising an opening located at the distal end of the first casing, and a first flange located at the distal end of the first casing extending outwards from the centre of the casing; a second casing, comprising an opening located at the proximal end of the second casing and a second flange located at the proximal end of the second casing extending outwards from the centre of the casing, wherein the first flange is positioned directly against the second flange.

3. The radiation detection apparatus of claim 2, wherein an O-ring is positioned in between the first flange and the second flange to form a watertight seal between the first casing and the second casing.

4. The radiation detection apparatus of claim 2 or claim 3, further comprising a third casing, wherein: the second casing further comprises an opening located at the distal end of the second casing, and a third flange located at the distal end of the second casing extending outwards from the centre of the casing; the third casing comprises an opening located at the distal end of the third casing, an opening located at the proximal end of the third casing, and a fourth flange located at the proximal end of the third casing extending outwards from the centre of the casing;the third flange is positioned directly against the fourth flange; and the detector is connected to an external computing device by a cable which passes through the opening located at the distal end of the third casing.

5. The radiation detection apparatus of claim 4, wherein an O-ring is positioned in between the third flange and the fourth flange to form a watertight seal between the second casing and the third casing.

6. The radiation detection apparatus of any of claims 2 to 5, wherein each component is located in a separate casing.

7. The radiation detection apparatus of claim 6, wherein the detector is a component, and wherein the detector is located within the first casing.

8. The radiation detection apparatus of claim 6 or claim 7, wherein the second casing contains an amplifier connected to the detector, wherein the amplifier is a component and is configured to amplify a detector signal produced by the detector.

9. The radiation detection apparatus of any of claims 2 to 8, wherein the first casing and the second casing have different outer dimensions and wherein any internal components contained within the first casing and the second casing are in contact with opposing inner surfaces of the first casing and the second casing respectively.

10. The radiation detection apparatus of any of claims 1 to 9, wherein the moveable door and static wall both comprise an outer waterproof layer at least at the interface between the recess and the moveable door.

11. The radiation detection apparatus of claim 10, wherein the moveable door and recess are shaped so that radiation traversing the interface between the moveable door and the static wall is directed away from the detector, such that the detector does not detect the radiation.

12. The radiation detection apparatus of claim 11, wherein the moveable door is tapered.

13. The radiation detection apparatus of any of claims 1 to 12, wherein the first housing further comprises a first side plate and a second side plate extending in substantially opposing directions, and wherein each side plate includes a foot configured to prevent the radiation shield from contacting a surface when the detector faces the surface.

14. The radiation detection apparatus of any of claims 1 to 13, wherein the detector is a cadmium zinc telluride spectrometer.

15. The radiation detection apparatus of any of claims 1 to 14, wherein the moveable door is actuated between the closed position and the open position using a hydraulic system.

16. The radiation detection apparatus of claim 15, wherein the hydraulic system uses demineralised water as a hydraulic fluid.

17. The radiation detection apparatus of any one of claims 1 to 16, further comprising a collimator configured to substantially prevent radiation not emitted by the surface from being incident on the detector.

18. The radiation detection apparatus of any one of claims 1 to 17, wherein the radiation shield comprises tungsten.

19. The radiation detection apparatus of claim 18, wherein the radiation shield substantially comprises tungsten.

20. The radiation detection apparatus of claim 19, wherein the radiation shield further comprises a layer of copper and / or a layer of tin, wherein the layers are positioned within the radiation shield such that they prevent radiation from being incident upon the detector when the radiation shield is in the closed position.

Images