Monitoring the optical density of an image during a radiographic examination

Abstract

A monitoring system (4) intended for use during radiographic inspection of a part (2) by ionizing radiation, said radiographic inspection using a radiographic film (13) and an emitting source (40) of incident photons to form an image (1) of the part on the radiographic film, the monitoring system (4) comprising: a measuring device (15) arranged to measure a quantity representative of the number of incident photons reaching the radiographic film (13); a processing unit (16) connected to the measuring device (15) and arranged to issue an alert when the quantity reaches a target value corresponding to an expected optical density level of the image of the part (2) formed on the radiographic film (13). [Fig. 4]

Description

Title of the invention: Monitoring the optical density of an image during radiographic examination

[0001] The present invention relates to radiographic control by ionizing radiation, implemented in the industrial field.

[0002] BACKGROUND OF THE INVENTION

[0003] Radiographic testing by ionizing radiation is a non-destructive testing technique, which is used in a large number of applications in different industrial sectors: nuclear, petrochemical, boiler making, aeronautics, etc.

[0004] This is a very effective technique for inspecting metal parts and thus for detecting defects in the parts, and for determining the risk of propagation of these defects. Radiographic inspection is also used to detect defects in welds (blobs, cracks, porosity, etc.).

[0005] Radiographic control uses a source that emits ionizing radiation, and a receiver which is generally a radiographic film but which can be a more complex device (electronics, camera, etc.).

[0006] The source of ionizing radiation is, for example, an X-ray generator (this is then called X-ray radiography), or a radioactive gamma ray source (this is then called gamma radiography). In the latter case, the source is, for example, a source of iridium-192 or selenium-75.

[0007] Thus, as the rays pass through the metal part, the radiation is absorbed to a greater or lesser extent depending on the thickness and density of the medium through which it passes. The radiation emerging from the part to be inspected then imprints a radiographic film which, after chemical development, produces a negative image of the part.

[0008] Today, such a control is carried out in the following way.

[0009] With reference to [Fig.1], the radiologist uses input data (step E1) to calculate the irradiation time (exposure time): step E2. In the case of checking a weld bead, this input data includes, for example, the expected thickness of the part and that of the weld bead.

[0010] The radiographic film is then placed on the part to be inspected (step E3). When the setup is complete, the radiologist activates the ionizing radiation source to irradiate the part (step E4). Once the irradiation time has elapsed, the radiologist deactivates the ionizing radiation source.

[0011] The radiologist then goes to the laboratory and develops the radiographic film (step E5). With reference to Figures 2 and 3, he obtains the negative image 1 of part 2 and weld bead 3. In the event that the quality of the radiogram If the result obtained is satisfactory, the radiologist can conclude whether or not there is a defect on part 2 and / or on weld bead 3 (step E6). The radiologist then writes up their report and gives it to their client (step E7).

[0012] The process that has just been described presents the following difficulties.

[0013] The input data used by the radiologist to assess the irradiation time correspond to estimates made by the radiologist. However, these estimates do not necessarily correspond to reality. For example, the weld bead 3 of part 2 may be thicker than expected. This excess thickness can lead to underexposure of the part. The radiologist therefore tends to increase the irradiation time, which, on the one hand, can lead to overexposure of the part (and therefore to a degradation of the image quality obtained), and on the other hand, presents a risk to the radiologist's health.

[0014] Furthermore, it is only during the development stage that the radiologist can determine whether the film has been underexposed or overexposed to ionizing radiation. In either case, the optical density of the image obtained of the part is unsatisfactory, and the radiographic examination is deemed unusable. The radiologist discovers the problem once they are in the laboratory, and therefore after they have left the site where the part is located. The examination must be repeated, which creates operational difficulties at the site, resulting in lost time, increased operating costs, and additional radiation exposure, however small, for the radiologist.

[0015] SUBJECT OF THE INVENTION

[0016] The invention aims to: - to improve the quality and accuracy of radiographic examinations; - to improve the efficiency and cost of these controls; - to reduce the impact of said controls on the health of radiologists. Summary of the invention

[0017] To this end, the invention provides a monitoring system intended for use during radiographic inspection of a part by ionizing radiation, said radiographic inspection using a radiographic film and a source emitting incident photons to form an image of the part on the radiographic film, the monitoring system comprising: - a measuring device, arranged to measure a quantity representative of a number of incident photons reaching the radiographic film; - a processing unit connected to the measuring device and configured to issue an alert when the quantity reaches a target value corresponding to an expected level of optical density of the image of the part formed on the radiographic film.

[0018] Thus, the invention improves the quality and accuracy of radiographic inspections. Indeed, thanks to the measuring device, the representative value of the number of incident photons reaching the radiographic film, and therefore of the image's optical density, is known. Furthermore, the alert issued by the processing unit allows the photon-emitting source to be switched off at the opportune moment to obtain the expected optical density level of the part image. Consequently, the image of the part formed on the radiographic film conforms to expectations, and the film is neither underexposed nor overexposed in its area of ​​interest.

[0019] The efficiency is improved and the cost of radiographic control is reduced, as the radiologist is no longer required to perform said radiographic control again.

[0020] The radiologist therefore no longer needs to overexpose the room. This reduces the radiologist's exposure to ionizing radiation and thus reduces the impact of these controls on the radiologist's health.

[0021] A monitoring system as previously described is further proposed, in which the measuring device comprises a scintillating material arranged to produce scintillation photons from incident photons, and a photodetector arranged to count scintillation photons, the quantity being a number of scintillation photons.

[0022] A monitoring system as previously described is further proposed, in which the scintillating material is arranged so that, when the radiographic film is installed on the part, the scintillating material is positioned between the part and the radiographic film.

[0023] A monitoring system as previously described is also proposed, in which the scintillating material includes a portion of optical fiber.

[0024] A monitoring system as previously described is also proposed, in which the measuring device includes a gas ionization detector.

[0025] A monitoring system as previously described is also proposed, in which the gas ionization detector is a Geiger-Müller counter.

[0026] A monitoring system such as previously described is also proposed, in which the target value depends on a characteristic of the radiographic film.

[0027] We further propose a monitoring system as previously described, in which radiographic control is control by gammagraphy.

[0028] A monitoring system as previously described is also proposed, in which radiographic control is a control of a weld bead of the part.

[0029] A monitoring system as previously described is also proposed, in which the alert is an audible signal.

[0030] A reception system is also proposed comprising the monitoring system as previously described, and the radiographic film.

[0031] A receiving system as previously described is also proposed, further comprising a flexible device arranged to be installed on the part by surrounding it, the radiographic film and at least part of the measuring device being positioned on the flexible device.

[0032] A receiving system as previously described is further proposed, comprising a monitoring system as previously described, the receiving system further comprising a main pouch containing the radiographic film and a first secondary pouch fixed on an inner face of the main pouch located on the side of the part, the first secondary pouch being a pouch of an image quality indicator, the scintillating material being positioned in the first secondary pouch or in a second secondary pouch also fixed on the inner face of the main pouch.

[0033] A radiographic inspection method for a part is also proposed, using a monitoring system as previously described, the method comprising the following steps: install the emitting source; install the radiographic film on the part; use the emitting source to irradiate the room; stop the irradiation when the treatment unit issues the alert.

[0034] Other features and advantages of the invention will become apparent from the following description of a particular and non-limiting embodiment of the invention. Brief description of the drawings

[0035] Reference will be made to the attached drawings, among which:

[0036] [Fig. 1] [Fig. 1] is a diagram representing a prior art radiographic control method;

[0037] [Fig.2] [Fig.2] is a radiographic film, after development, obtained following the radiographic examination of a part;

[0038] [Fig.3] [Fig.3] is a perspective view representing said part for radiographic control;

[0039] [Fig.4] [Fig.4] is a perspective view of a surveillance system according to a particular mode of the invention, of a film, of the emitting source and of the part;

[0040] [Fig.5] [Fig.5] is a perspective view of a flexible device surrounding the part illustrated in [Fig.3] according to the invention;

[0041] [Fig.6] [Fig.6] is a schematic view of the monitoring system illustrated in the [Fig.4];

[0042] [Fig.7] [Fig.7] is a diagram representing a radiographic inspection method using the invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] With reference to [Fig. 4], the invention relates to a monitoring system 4 for use during radiographic inspection of a weld bead 3 of a part 2 by ionizing radiation. The radiographic inspection uses a radiographic film 13 and an incident photon emitting source 40 to form an image of the part 2 on the radiographic film 13.

[0044] The monitoring system 4 aims to ensure that the optical density of the image obtained corresponds to an expected level of optical density.

[0045] Optical density is a quantity that characterizes the degree of blackening of the radiographic film.

[0046] During the examination of the film, which takes place after the film has been developed and during which a densitometer is used, the optical density F) is such that: [°047] D = log^

[0048] where is the light incident on the image and It is the light transmitted by the image during the examination.

[0049] The optical density of the image depends on the intensity of the radiation reaching the film during the radiographic inspection.

[0050] Part 2 here is a tubular part, and for example a piping elbow of the safety injection circuit (RIS) connected to the primary circuit of a reactor in a nuclear power plant.

[0051] The incident photon emitting source 40 is here a radioelement, that is to say, a radioactive source 40 emitting gamma radiation, housed in a gamma radiograph 5. In this case, the radiographic inspection is therefore a gamma radiography inspection. To perform the inspection of part 2, the gamma radiograph 5 is extended by an ejection sleeve 6, allowing the transport of the radioactive source 40, initially housed in the gamma radiograph 5, to the irradiation nozzle 7. The ejection sleeve 6 is thus connected at one end to the gamma radiograph 5. At a second end, opposite the first, the ejection sleeve 6 is connected to the irradiation nozzle 7.

[0052] With reference to [Fig.5], a receiving system 41 is used which here includes the radiographic film 13 and the monitoring system 4.

[0053] The receiving system 41 here includes a flexible device 8. The flexible device 8 includes a strap 9. The strap 9 is here a fabric strap. Furthermore, the flexible device 8 includes a clip buckle having a male part 10 located at one end of the strap 9 and a female part 11 located at a second strap end 9. The flexible device 8 is intended to surround the part 2 to be controlled.

[0054] The receiving system 41 also includes a main pouch 12. The main pouch 12 is attached to the strap 9 (for example, by gluing or sewing). The main pouch 12 contains at least one radiographic film 13, one or more filters, and one or more blocking screens. All these elements are stacked in the main pouch 12, forming different "sandwich" layers.

[0055] The radiographic film 13 conforms to ISO 11699-1, which classifies systems for films used in industrial radiography. The radiographic film 13 is selected by evaluating the expected image quality level 1 of part 2. In this case, the radiographic film 13 is manufactured by Agfa. Agfa manufactures at least seven types of radiographic films 13, which, in ascending order of speed and grain size, are: D2, D3, D4, D5, D6, D7, and D8. The closer the radiographic film type 13 is to type D2, the higher the image quality level 1 of part 2. Type D2 therefore allows for the radiography of small parts 2 with high precision. Furthermore, the closer the radiographic film type 13 is to type D8, the faster the image 1 is acquired. The D8 type therefore allows for the control of 2 large parts.

[0056] With further reference to [Fig. 5], the flexible device 8 includes an image quality indicator 14 (IQI). The image quality indicator 14 comprises a first secondary pocket 30 in which are positioned a plurality of wires of calibrated thickness made of the same material as the part to be inspected. By analyzing the image 1 obtained after development of the radiographic film 13, a radiologist can determine the image quality level 1 by identifying the wire with the thinnest thickness.

[0057] The first secondary pouch 30 is glued to an inner face of the main pouch 12 and is therefore positioned between the part 2 and the radiographic film 13 when the flexible device 8 is installed on the part 2. Here, by "inner face" is meant a face intended to be applied to the part 2, and by "outer face" is meant a face opposite to the inner face.

[0058] With reference to figures 4 to 6, the monitoring system 4 comprises a measuring device 15 and a processing unit 16.

[0059] The measuring device 15 is arranged to measure a quantity representative of a number of incident photons reaching the radiographic film 13. The measuring device 15 comprises a scintillating material 17, a means of transporting scintillation photons 18, and at least one photodetector 19.

[0060] Here, the scintillating material 17 is a first portion of optical fiber and the scintillation photon transport means 18 is a second portion of optical fiber.

[0061] The first optical fiber portion 17 is arranged to transform the incident photons from the emitting source 40 into scintillation photons. The second optical fiber portion 18 is arranged to carry the scintillation photons to the photodetector 19.

[0062] When the flexible device 8 is installed on part 2, the first portion of optical fiber 17 is positioned between part 2 and the main pouch 12 (and therefore between part 2 and the film 13).

[0063] Here, the first portion of optical fiber 17 is positioned in a second secondary pouch 31, which is also fixed to the inner face of the main pouch 12, for example by gluing.

[0064] The second optical fiber portion 18 extends in line with the first optical fiber portion 17 and runs to the photodetector 19.

[0065] In one embodiment, the first portion of optical fiber 17 is a photonic crystal fiber and the second portion of fiber 18 is made of plastic or silica.

[0066] The monitoring system 4 also includes a housing 20. The housing 20 integrates the photodetector 19 and the processing unit 16. The second portion of optical fiber 18 therefore runs between the flexible device 8 and the housing 20.

[0067] The photodetector 19 is arranged to count the scintillation photons produced by the scintillation material 17 and carried by the second portion of optical fiber 18. When a scintillation photon from the second portion of optical fiber 18 is detected by the photodetector 19, the latter converts it into an electrical signal. The measuring device 15 therefore acts as a scintillation detector and makes it possible to measure a quantity representative of the number of incident photons reaching the radiographic film 13. In this case, the quantity is therefore a number of scintillation photons.

[0068] The processing unit 16 is connected to the photodetector 19 of the measuring device 15 and is configured to issue an alert when the representative quantity of a number of incident photons reaching the radiographic film 13 reaches a target value. The target value corresponds to an expected optical density level of the image 1 of the part 2 formed on the radiographic film 13.

[0069] The target value may depend on a characteristic of the radiographic film. This characteristic is, for example, the type of film (D2, D3, D4, etc.).

[0070] The processing unit 16 is arranged to receive each electrical signal emitted by at least one photodetector 19.

[0071] In one embodiment, the processing unit 16 comprises at least one processing component 21 (for example, a processor, a microcontroller, a programmable logic circuit, etc.), at least one memory, and at least one warning device 22. The processing component 21 processes the data from the The photodetector 19 determines the number of incident photons reaching the radiographic film 13. The target value, mentioned previously, is determined based on the expected optical density level of the image of the part. The processing of the target value is performed by the processing component 21. When the target value is reached, the processing unit 16 activates the alarm device 22. In this case, the alarm device 22 includes a device for emitting an audible signal, for example, a beeper.

[0072] The processing unit 16 is therefore located away from part 2 and therefore does not receive ionizing radiation 23. This position helps to limit the aging, under the effect of radiation, of the electronic components of the processing unit 16. For example, the processing unit 16 is located about one meter away from part 2 thanks to the second portion of optical fiber 18 which therefore measures about one meter in length.

[0073] It is understood that the use of the scintillating material 17 and therefore of the second portion of optical fiber 18 which carries the scintillating photons, makes it possible to move away the electronic components performing a plurality of measurements during the control of the part 2.

[0074] When the receiving system 41 is installed on part 2, the flexible device 8 surrounds part 2 and the radiographic film 13 is positioned on one first side of part 2 while the irradiation tip 7 is positioned on a second side of part 2, opposite the first side.

[0075] Furthermore, as we have seen, the scintillating material 17 is located between the part 2 and the film 13. This arrangement allows said first portion of optical fiber 17 to produce scintillation photons from the incident photons reaching the radiographic film 13.

[0076] The second portion of optical fiber 18 extends the first portion 17 and runs to the housing 20, so as to transport the scintillation photons so that they may be detected by the photodetector 19.

[0077] A radiographic inspection method for a part 2, using a monitoring system 4, will now be described with reference to [Fig.7].

[0078] The incident photon emitting source 40 is installed (step E10). By "installed" it is meant that the irradiation tip 7, connected to the gammagraph 5 via the sheath 6, is placed on the part 2 to be radiographed.

[0079] The flexible device 8 is installed on part 2 (step El 1). As a result, the image quality indicator 14 (IQI) and the scintillating material 17 are interposed between part 2 and the radiographic film 13.

[0080] Then, the emitting source 40 of the gammagraph 5 is used to irradiate part 2 (step E12). The ionizing radiation 23 will therefore pass through part 2 and reach the radiographic film 13.

[0081] Irradiation of part 2 is stopped when the processing unit 16 issues an alert (step E13). During the irradiation of part 2, the scintillation material 17 transforms the incident photons into scintillation photons. The scintillation photons are detected by the photodetector 19, which converts them into one or more electrical signals. The electrical signals are then processed by the processing unit 16, which, when the target value characteristic of an expected optical density level of the image 1 is reached, issues an alert via the alert device 22. The radiologist can then stop the irradiation of part 2 by returning the source to the safe position.

[0082] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0083] A reception system comprising both the film and the monitoring system has been described here. However, these may be two separate systems. The radiologist can thus, to perform the inspection, be equipped with the film, which he installs on the specimen, and the monitoring system, which he positions appropriately to monitor the optical density of the image.

[0084] It has been described here that the scintillating material is positioned between the part to be inspected and the film. The scintillating material can also be positioned behind the film.

[0085] More generally, the measuring device can be arranged to measure a quantity representative of the number of incident photons passing through the radiographic film. This quantity is in fact also representative of the number of incident photons reaching the radiographic film (these two numbers of photons are in fact very close).

[0086] Although here a flexible device is used to fix the main pouch and the optical fiber to the part to be radiographed, these elements could be fixed to the part in a different way.

[0087] The alert is not necessarily an audible alert. It could be a visual alert, or a message communicated to the radiologist by any type of means of communication. For example, if the communication is wireless, the processing unit incorporates a wireless communication module.

[0088] The processing unit could be purely analog.

[0089] It has been described here that the image quality indicator is integrated into a first secondary pocket and the glitter material into a second secondary pocket. It would also be possible to integrate the glitter material into the first secondary pocket.

[0090] Although here the measuring device comprises a scintillating material and at least one photodetector, the measuring device may be different. It could, for example Understanding a gas ionization detector. The gas ionization detector could be a Geiger-Müller counter.

[0091] Furthermore, the measuring device could also include a scintillating material emitting scintillation photons, a photomultiplier (PM) amplifying the number of scintillation photons and an electronic counting device measuring the representative magnitude of a number of incident photons reaching the radiographic film.

[0092] Although here the invention relates to the radiographic control of a part, the invention could also be applicable to a search for corrosion, or a search for foreign body in a pipe.

Claims

Demands

1. A monitoring system (4), intended for use during a radiographic inspection of a part (2) by ionizing radiation (23), said radiographic inspection using a radiographic film (13) and an emitting source (40) of incident photons to form an image (1) of the part on the radiographic film, the monitoring system (4) comprising: - a measuring device (15), arranged to measure a quantity representative of a number of incident photons reaching the radiographic film (13); - a processing unit (16) connected to the measuring device (15) and arranged to issue an alert when the quantity has reached a target value corresponding to an expected optical density level of the image (1) of the part (2) formed on the radiographic film (13).

2. Monitoring system (4) according to claim 1, wherein the measuring device (15) comprises a scintillating material (17) arranged to produce scintillation photons from incident photons, and a photodetector (19) arranged to count scintillation photons, the quantity being a number of scintillation photons.

3. Monitoring system (4) according to claim 2, wherein the scintillating material (17) is arranged so that, when the radiographic film (13) is installed on the part (2), the scintillating material (17) is positioned between the part (2) and the radiographic film (13).

4. Surveillance system (4) according to any one of claims 2 or 3, wherein the scintillating material (17) comprises a portion of optical fiber.

5. Monitoring system (4) according to claim 1, wherein the measuring device comprises a gas ionization detector.

6. Monitoring system (4) according to claim 5, wherein the gas ionization detector is a Geiger-Müller counter.

7. Monitoring system (4) according to any one of the preceding claims, wherein the target value depends on a feature of the radiographic film (13).

8. Monitoring system (4) according to any one of the preceding claims, wherein the radiographic control is a gamma-ray control.

9. Monitoring system (4) according to any one of the preceding claims, wherein the radiographic control is a control of a weld bead (3) of the part (2).

10. A monitoring system (4) according to any one of the preceding claims, wherein the alert is an audible signal.

11. Receiving system (41) comprising the monitoring system (4) according to any one of the preceding claims, and the radiographic film (13).

12. Receiving system (41) according to claim 11, further comprising a flexible device (8) arranged to be installed on the part (2) by surrounding it, the radiographic film (13) and at least a part of the measuring device (15) being positioned on the flexible device (8).

13. Receiving system (41) according to claim 12, comprising a monitoring system (4) according to claim 2, the receiving system further comprising a main pouch (12) containing the radiographic film (13) and a first secondary pouch (30) fixed on an inner face of the main pouch (12) located on the side of the part (2), the first secondary pouch being a pouch of an image quality indicator (14), the scintillating material (17) being positioned in the first secondary pouch (30) or in a second secondary pouch (31) also fixed on the inner face of the main pouch (11).

14. A radiographic inspection method for a part (2), using a monitoring system (4) according to any one of claims 1 to 10, the method comprising the following steps: - installing the emitting source (40); - installing the radiographic film (13) on the part (2); - using the emitting source (40) to irradiate the part (2); - stopping the irradiation when the processing unit (16) issues the alert.

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