CN1112583C - Digital radiation image forming type apparatus for investigating lorge guest materials - Google Patents

Abstract

The present invention belongs to the field of the application of nuclear technology, which comprises detection components, a translational driving mechanism, a signal processing system, an annular rotary scanning machine frame and a machine base thereof, etc., wherein the detection components, the translational driving mechanism and the signal processing system are composed of radiation sources of a gamma radioisotope of high specific activity, a shielding container of the radiation source, an irradiation chamber of the radiation source, a collimator and array detectors, and the detection components are arranged on the annular rotary machine frame. The present invention can conveniently obtain a projection image in any determined direction and a tomographic image of a specified part, and still use only one set of radiation sources, detectors and lossless detection devices of digital radiation imaging of a large object in an information system, and thereby, the detection sensitivity and the detection accuracy of the devices can be prominently enhanced.

Description

A large-scale object digital radiation imaging detection device

The invention belongs to the application field of nuclear technology, in particular to a digital radiation imaging detection device for large objects such as containers or missiles. It adopts high specific activity gamma radioactive isotope ray source (such as ⁶⁰ Co or ¹³⁷ Cs), array detector, circular rotating frame and translation dragging mechanism, etc., so that it can give the digital radiation projection map of the object along any direction in real time It can also obtain the tomographic radiation image of a designated part of the object according to the needs, so that the detection sensitivity and accuracy of the device can be significantly improved.

Existing container (large object) radiation imaging detection devices using electron accelerators, radioisotopes or X-ray machines as ray sources (such as Schlumberger of France, Heymann of Germany, British Aerospace Corporation, EG&G of the United States and China's The product information of Beijing Hualixing Technology Development Co., Ltd., etc. and the US patent 4785168 and Chinese patent applications 96102080.6 and 98101501.8) can basically meet the inspection requirements of the customs, but there are some defects:

First, the above-mentioned various devices can only provide radiation projection images in one or two fixed directions (horizontal and vertical) of the object under inspection. Once the device is built, neither the projection direction nor the number of projections (1 or 2) can be changed anymore.

Second, when it is necessary to provide projection images in two directions, two sets of ray sources, detectors and information systems must be provided, which will lead to a substantial increase in equipment costs.

Third, it can only provide radiation projection images but cannot obtain tomographic images of the object.

The above-mentioned defects quite seriously limit the inspection capability of the radiation imaging detection device for complex objects. For example, when the cargo in the container is complex and contains drugs, or when inspecting the internal defects of solid fuel in large missiles, it is urgently needed for the detection device to have the ability to obtain tomographic images and projection images in any direction, so that the detection The quality has been significantly improved.

The purpose of the present invention is to overcome the deficiencies of the existing container (large object) detection technology, to provide a projection image in any direction and a tomographic image of a designated position that can be easily obtained, and only one set of rays is still used. Source, detector and information system of large object digital radiation imaging non-destructive testing device, which can significantly improve the detection sensitivity and accuracy of the device.

The invention proposes a large object digital radiation imaging detection device, which includes a high specific activity gamma radioactive isotope ray source and its shielding container, an irradiation room, a collimator, an array detector, a translational drag mechanism and a signal processing system ; It is characterized in that it also includes a ring-shaped rotating scanning frame and its support, and the detection components composed of a shielded container with high specific activity gamma radioisotope ray source, an irradiation chamber, a collimator and an array detector are installed On the ring-shaped rotating frame, it rotates and scans synchronously or locates at a certain set position; the translational drag mechanism makes the object perform linear scanning motion at a uniform speed along the axis of the ring-shaped frame or locates at a designated position. When the detection part is positioned at a specified position by the circular rotating frame, the object is scanned in a uniform speed by the translational dragging mechanism to obtain the radiation projection image of the object along this direction. When the translational dragging mechanism makes the designated part of the object in the irradiated area, the circular rotating frame makes the detection part rotate and scan to obtain the radiation tomographic image of the part of the object.

The ray source used in the present invention is ⁶⁰ Co or ¹³⁷ Cs radioactive isotope with high specific activity and a linear dimension of only a few millimeters. The cobalt-60 flaw detector, which has been widely used in the industrial non-destructive flaw detection industry, has an activity of less than 24TBq and is the first choice. The array detector used is composed of multiple array detector units containing a certain number of detector elements arranged in sequence. The array detector unit is a high-pressure gas-filled array ionization chamber, a multi-wire proportional chamber, a Geiger counting tube array, and a scintillation array. One of the detectors or semiconductor array detectors. The rear of the array detector is provided with a shield (called a radiation "catch") to absorb radiation passing through the detector.

The ring-shaped rotating frame of the present invention adopts two driving devices of stepping and continuous rotating motions to make the detection parts perform rotating and scanning motions to meet the needs of different image processing modes. The inner diameter of the annular rotating rack should be large enough so that large objects such as containers are always included in the fan-shaped radiation field.

The translational dragging mechanism of the present invention can adopt one of electric trolleys running on rails, roller conveyor belts, belt conveyor belts or chain plate conveyors to drag the object for translational scanning motion.

The specific content of the present invention is described in detail below in conjunction with accompanying drawing:

Referring to Fig. 1, " detection part " of detection device of the present invention is made of high specific activity ⁶⁰ Co or ¹³⁷ Cs gamma radioactive isotope source and its container (with shielding valve) 1, irradiation chamber and front collimator 2, rear collimator Straightener 3 and array detector 4. They are fixed together, and can rotate synchronously on the ring-shaped rotating frame 5 of the detection device, and can be rotated and positioned at a specified position, and can also perform a 360° rotational scanning movement. The rear of the array detector 4 has a shield (called a ray "catcher") for absorbing rays passing through the detector. The annular rotating frame 5 of the detection device is fixedly connected with the support 6, and the support 6 is firmly placed on the pre-embedded parts in the foundation. The inspected object 7 (container or large missile, etc.) is placed on the translation drag mechanism 8, which can perform uniform translation and scanning motion at a specified speed along the axis of the circular rotating frame, or move to a specified position and be moved by the circular rotating machine. Frame 5 to complete the rotary scanning motion. The dragging mechanism 8 can be an electric scooter traveling on a track as shown in the figure, or a roller conveyor belt or other transmission mechanisms.

When testing, the shielding valve on the ray source container 1 is opened to let the γ-rays pass through the irradiation chamber and the slit on the front collimator 2 and be collimated into a narrow fan-shaped beam. The sheet-shaped ray beam passes through the object 7 and then passes through the rear collimator 3 (for removing scattered rays) and enters the aligned array detector 4 . The main part of the radiation not absorbed by the detector will be blocked by the "catch" at the rear of the detector 4 so as not to have harmful effects on the surroundings.

When it is necessary to obtain the radiation projection image of the object along a certain direction, first order the "detection part" (composed of 1, 2, 3, 4, etc.) to be rotated and positioned at the corresponding position, and then the dragging mechanism 8 makes the object 7 move at a constant speed Pass through the narrow flake ray irradiation area, and simultaneously collect and process the signal output by the array detector. The radiation projection images corresponding to different directions of the object can be obtained by positioning the "detection component" in different directions. In Fig. 3, Fig. 4, Fig. 5 and Fig. 6, state diagrams of the detection device when the "detection part" is in different orientations are given.

When it is necessary to obtain a radiation tomographic image of a certain part of the object, first order the dragging mechanism 8 to move and place the part to be checked of the object in the narrow sheet-shaped radiation irradiation area, and then make the "detection part" on the ring-shaped rotating frame 5 Performing a 360° rotating scanning movement, and simultaneously collecting and processing the output signal of the array detector 4, the radiation tomographic image of the object at this part can be obtained. The signal processing system for accomplishing the above functions is a conventional technology, which will not be repeated here. In the process of obtaining the tomographic radiation image of the present invention, the large object remains still, and the "detection part" performs a rotary scanning motion. This is very beneficial for large objects that are difficult to rotate, such as containers or strategic missiles.

The ray source 1 adopts ⁶⁰ Co or ¹³⁷ Cs radioactive isotope source with high specific activity, and its active area is several millimeters in size, and its activity is less than 24TBq. For large objects, ⁶⁰ Co sources with high gamma ray energy are generally used. The specific activity and activity value of the ⁶⁰ Co source used in the present invention are basically consistent with the commercial gamma ray source device for flaw detection. The use of such a shaped product of the radiation source device with its own shielding container is conducive to improving the reliability of the operation of the detection device of the present invention.

The source container and the shielding valve 1 as well as the irradiation chamber and the front collimator 2 are all made of depleted uranium, lead, iron and other metals or their alloys. The collimating slit of the front collimator collimates the gamma rays emitted by the radiation source 1 into a narrow sheet as shown in Figure 1, and its opening angle in the direction perpendicular to the plane of the circular rotating gantry is 0.1° to 1.0°, while the opening angle in the plane direction of the circular rotating frame is not more than 90°.

The rear collimator 3 is made of metals such as lead and iron or their alloys, the width of the collimating slit in the middle is equal to or slightly smaller than the pixel width of the array detector 4, and the collimating slit of the front collimator 2 is aligned Active area with radiation source 1. The rear collimator, like the array detector, can be made into an arc with the active area of the ray source as the center, and its arc length must ensure that the irradiation field defined by it and the array detector can completely contain the object. Of course, it is also feasible to make it into a straight line or a broken line.

The array detector 4 is composed of a number of array detector units containing a certain number of pixel detector elements arranged in sequence, and also forms an arc-shaped device (or in a straight line or a broken line) with the active area of the ray source as the center. The installation of the ray source 1, the front collimator 2, the rear collimator 3 and the array detector 4 is to make the collimated γ-rays accurately inject into the sensitive volume of each pixel detector element.

The function of the array detector 4 is to convert the γ-rays injected into its sensitive volume after passing through the object to be inspected into electrical signals. It is required to have high detection efficiency and sensitivity, be stable and reliable, and be able to withstand the vibration interference of the detection part when it is rotating and scanning. The preferred array detector that can meet this requirement is the "gas ionization type high-energy X, gamma radiation imaging array detector" described in Chinese patent ZL93102728.4. Other array detectors, such as multi-filament proportional chambers, proportional tubes or Geiger tube arrays, scintillation detector arrays or semiconductor detector arrays, etc., are also applicable objects.

After the output signal of the array detector is amplified, converted from analog to digital and collected, the digital radiation projection image or digital radiation tomographic image of the object is obtained by computer processing, which can be checked by the supervisor, and can be stored, printed, transmitted, archived, etc.

Annular rotating frame 5 is a large-scale rotating mechanism manufactured by conventional methods, which can make "detection parts" (comprising: ray source and shielding valve 1, irradiation chamber and front collimator 2, rear collimator 3, array detector 4 and connecting members, etc.) as a whole to rotate on it synchronously. One operation mode is to make the detection part rotate and locate at a certain specified position, and the other operation mode is to make the detection part perform 360° stepwise or continuous rotation. In the former operation mode, the detection device will obtain the radiation projection image of the object in the corresponding orientation, while in the latter operation mode, the detection device will obtain the radiation tomographic image of the object. The annular rotating frame 5 is firmly fixed on the pre-embedded parts in the foundation through the machine base 6 .

The drag mechanism 8 is a motion mechanism independent of the annular rotating frame 5 . It is used to drag the object along the axis of the circular rotating gantry to move in a straight line at a specified speed, or to move the specified part of the object to the sheet-shaped fan-shaped irradiation area of the ray. The former movement mode corresponds to the acquisition of radiation projection images, and the latter movement mode corresponds to the acquisition of radiation tomographic images. For very heavy object, dragging mechanism 8 can be selected the electric plate car that moves on preset track for use. The load of this type of drag mechanism can reach 40 tons or more, which can meet the detection needs of heavy and large objects such as fully loaded containers or giant missiles. For lighter objects (such as air containers), the dragging mechanism 8 can be selected roller type or other forms of conveyor belts. No matter what kind of dragging mechanism is selected, the parts in the irradiated area of sheet radiation should be as few and light as possible, so as to reduce the interference to the acquired radiation images. Since the thickness of the sheet-shaped irradiation area is only about 1 cm, this requirement is not difficult to achieve.

One of the outstanding advantages of the present invention is that during the process of obtaining the tomographic image, the object remains stationary while the "detection part" makes a rotational scanning movement. This is very necessary for objects that are not suitable for flipping, such as containers and large missiles.

Another outstanding advantage of the present invention is the use of a radioactive isotope ray source, which does not require power supply and is not accompanied by dangerous factors such as high voltage and strong microwaves, but can continuously and automatically emit gamma rays. This kind of ray source can be conveniently installed on the ring-shaped rotating frame and rotates along with the detection part. This is difficult for an accelerator-type detection system to achieve.

The invention is suitable for the non-destructive detection of large objects such as containers and missiles (including containers, container trucks, trucks, missiles or train carriages). One application is to detect air containers or container packages at airports, to exclude flammable and explosive items, and to ensure flight safety. Since the projected image in any direction and the tomographic image of the designated part can be obtained, it is very beneficial to find and judge suspicious objects. Another application is the inspection of solid fuel inside giant missiles for defects. In order to detect such defects, tomographic images of its various parts must be obtained. But, because this type of missile is bulky and very heavy, it is not suitable for rotating and moving. Therefore, it is the best choice to obtain the tomographic image of this type of missile with the device of the present invention in which the object does not move during inspection and the detection part performs rotating and scanning motion.

Brief description of the drawings:

Fig. 1 is an axonometric view of the large object digital radiation imaging detection device of the present invention.

Fig. 2 is a side view of the large object digital radiation imaging detection device of the present invention.

Fig. 3 is a state diagram of the detecting part of the detecting device according to the present invention when it is in the vertical direction.

Fig. 4 is a state diagram when the detection part of the detection device of the present invention is in the horizontal direction.

Fig. 5 is a state diagram of the detection part of the detection device of the present invention when it is in the direction of +45°.

Fig. 6 is a state diagram of the detection part of the detection device of the present invention when it is in the -45° direction.

The present invention designs an embodiment of a detection device suitable for containers, which is described in detail as follows in conjunction with the accompanying drawings:

The overall structure of this embodiment is shown in FIG. 1 . The large-scale object digital radiation imaging detection system (abbreviated as "detection system") of the present embodiment consists of a ⁶⁰ Co ray source and its container and shielding valve 1, irradiation chamber and front collimator 2, Rear collimator 3, array detector and trap 4, machine base 6, track plate vehicle drag mechanism 8, signal acquisition and processing system, etc. The ray source is selected from the market-supplied stereotyped product - ⁶⁰ Co flaw detector, with an activity of 300 Curie (11TBq), and comes with a shielded container that meets the relevant safety standards of the International Atomic Energy Agency. Both the irradiation chamber and the front collimator are made of lead. The rear collimator is made of iron. The array detector is the detection device described in Chinese patent ZL93102728.4, the cross-sectional size of the pixel ionization chamber is 1×1 cm, and there are 512 channels in total. The size of the active area of the ray source is a cylinder with a diameter of 6mm and a length of 6mm, and the distance from its center to the front surface of the array detector is 6m. The inner diameter of the annular rotating frame 5 is 5.5m, and the outer diameter is 8m. The detection component can perform stepwise (for example, one step per degree) rotational movement on the circular rotating frame, or perform continuous uniform rotational movement. The load of the track plate vehicle drag mechanism 8 can reach 40 tons, and the uniform linear motion speed is 5～40 cm/s. The detection device is suitable for detecting standard containers with a width and height of 2.5m, and can also be used to detect missiles with a diameter not greater than 3m.

When acquiring radiation projection images in any direction, this device can find iron wires with a diameter of 2.5mm or iron sheets with a thickness of 0.7mm behind a 100mm iron plate, and can still observe heavy absorbers such as lead blocks behind a 240mm iron plate . When obtaining tomographic images, the detection index is closely related to the shape, size, material, structure, etc. of the object, and it is expected to find millimeter or submillimeter-level defects.

Claims (7)

1. A digital radiation imaging detection device for large objects such as containers, including a high specific activity gamma radioactive isotope ray source and its shielding container, an irradiation room, a collimator, an array detector, a translational drag mechanism, and a signal processing system etc., its structure is characterized in that: it also includes an annular rotating scanning frame and its base, and the detection components composed of the said radiation source and its shielding container, the irradiation room, the collimator and the array detector are installed on the said annular On the rotating frame, it rotates and scans synchronously or locates at a set position; the translation and drag mechanism makes the object perform uniform linear scanning motion along the axis of the ring frame or locates it at a designated position; the said ray source It is a high specific activity ⁶⁰ Co or ¹³⁷ Cs radioactive isotope with a line length of only a few millimeters. The back of the array detector has a shield to absorb the rays passing through the detector. 2. The detection device according to claim 1, characterized in that the high specific activity ⁶⁰ Co ray source used is a cobalt-60 flaw detector, and its activity does not exceed 24TBq. 3. The detection device according to claim 1, wherein the array detector is composed of a plurality of array detector units comprising a certain number of detector elements arranged in sequence, and the array detector unit is a high-pressure air-filled array One of ionization chamber, multi-filament proportional chamber, Geiger counter array, scintillation array detector or semiconductor array detector. 4. The detection device as claimed in claim 1, characterized in that, said back collimator is the same as the array detector, and is made into an arc with the radiation source active area as the center of the circle, and its arc length will ensure that it is the same as the array detector. The irradiation field defined by the array detector can completely contain the object. 5. The detection device according to claim 1, characterized in that, said circular rotating frame adopts two driving means of stepping and continuous. 6 . The detection device according to claim 1 , wherein the translational dragging mechanism is one of electric trolleys running on rails, roller conveyor belts, belt conveyor belts or chain plate conveyors. 7 . 7. The detection device according to claim 1, characterized in that the object to be detected is a container, a container truck, a truck, a missile or a train carriage.

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