Method for monitoring the condition of a tube sheet and a plurality of tubes in a steam generator

Abstract

Method (100) for checking a state of a tube sheet (41) and of a plurality of tubes in a steam generator (3), the method (100) comprising the following steps: acquisition (101) of at least two images by a movable image acquisition device inside the steam generator (3), one of the at least two images being acquired by the acquisition device in one position, and another of the at least two images being acquired by the acquisition device in another position, so that an image of the portion of the tube(s) (4) and / or of the tube sheet (41) is present in each of the at least two images acquired;determination (102) of the 3D coordinates, in a reference frame attached to the steam generator (3), of points on the tube(s) (4) and / or points on the portion of the tube sheet (41), from at least two acquired images, and from parameters representative of the tubes (4) and the tube sheet (41), the determination (102) of the 3D coordinates being carried out by computer-implemented photogrammetry. Figure 3;

Description

Title of the invention: Method for monitoring the condition of a tube sheet and a plurality of tubes in a steam generator

[0001] The present invention relates to the field of heat exchangers, and in particular to heat exchangers in a nuclear reactor.

[0002] It is known to perform television inspections in the secondary circuit, at the level of the tube plate of a heat exchanger, by means of a mobile device for acquiring images of the tubes passing through the tube plate and / or of the tube plate itself.

[0003] It is necessary to be able to size and characterize the sludge and / or other deposits observed during television inspections carried out in the secondary circuit in order to identify the presence of sludge and to check the condition of the plates.

[0004] The invention therefore aims to provide a solution to all or part of these problems.

[0005] To this end, the present invention relates to a method for monitoring the condition of a tube sheet and a plurality of tubes in a steam generator, the tubes passing through the tube sheet at a through-part of each tube, the method comprising the following steps: - acquisition of at least two images by a mobile image acquisition device inside the steam generator, one of the at least two images being acquired by the acquisition device in one position, and another of the at least two images being acquired by the acquisition device in another position, a portion of the through part of one or more tube(s) and / or a portion of the tube plate being present in the field of observation of the acquisition device in both positions, so that an image of the portion of the tube(s) and / or the tube plate is present in each of the at least two images acquired; - determination of the three-dimensional coordinates, in a reference frame attached to the steam generator, of points in the portion of the through part of the tube(s) and / or of points in the portion of the tube sheet, from the image of the portion of the through part of the tube(s) and / or of the tube sheet present in each of the at least two images acquired, and from parameters representative of the tubes and the tube sheet, the determination of the three-dimensional coordinates being carried out by computer-implemented photogrammetry.

[0006] According to one embodiment, the invention comprises one or more of the following features, alone or in a technically acceptable combination.

[0007] According to one embodiment, photogrammetry is implemented in real time as images are acquired.

[0008] According to one embodiment, the parameters representing the tubes include at least one of a spacing step between the tubes, a diameter of the tube(s), a position of the tube(s), a position of a line representing an intersection between a face of the tube plate and a plane defined by the tube(s).

[0009] According to one embodiment, the method further includes a step of determining one or more characteristics of a surface of the through part of the tube(s) and / or of a surface of the tube sheet through which the through part of the tube(s) passes, the characteristic(s) of the surface being determined from other parameters measured on the image of the portion of the through part of the tube(s) and / or of the tube sheet.

[0010] According to one embodiment, the other parameters measured on the image include at least one of a texture, a color, a groove formed by the acquisition device, and the characteristic(s) include at least one of a surface oxidation, a presence of gangue or mud, a presence of a powdery deposit, a presence of a migrating body.

[0011] For the sake of clarity, an embodiment and / or implementation of the invention is described with reference to the accompanying drawings, which represent, by way of non-limiting example, an embodiment or implementation of a device and / or method according to the invention. The same reference numerals in the drawings designate similar elements or elements with similar functions.

[0012] [Fig. 1] is a simplified representation of a pressurized water nuclear reactor with a steam generator.

[0013] [Fig.2] is a simplified representation of a steam generator of a pressurized water reactor.

[0014] [Fig.3] is a schematic representation of the sequence of steps of the process according to one embodiment of the invention

[0015] The steam generators 3 are located in the reactor building 14 of a nuclear power plant; the main components of a nuclear power plant are shown, by way of example, in [Fig. 1]. The reactor building 14 houses a primary circuit comprising a vessel 8 and a reactor core 7, as well as a pump 6 and a pressurization device 5, arranged to heat and circulate the water 1 of the primary circuit. The water 1 of the primary circuit flows along tubes 4 positioned inside a steam generator 3, so as to heat the water 2 of the secondary circuit at the steam generator 3 until the steam required for to rotate the turbines of one or more electricity generators 9; the water in the secondary circuit then condenses in a condenser 10 of the secondary circuit which is cooled by a cooling fluid 13 from a cooling circuit. A pump 13 circulates the water in the secondary circuit to return it to the steam generator 3.

[0016] Figure 2 illustrates an example of a steam generator 3, inside which a bundle of tubes 4 of the primary circuit are inserted. Starting from the lower part of the steam generator 3, an inlet 42 from the reactor and a return 43 to the reactor are shown. The steam generator 3 is an enormous pressure cooker inside which thousands of tubes are inserted (for example, between 4,000 and 5,000, depending on the type of power plant), through which the water from the primary circuit passes, heating and vaporizing the water from the secondary circuit inside a water box 40 formed of one or more substantially cylindrical rings that form the structure and walls of the heat exchanger 3: in Figure 2, a lower ring 39, a middle ring 38, a conical ring 36, and an upper ring 34 are thus shown as examples.The tubes 4 of the primary circuit tube bundle rest on a tube sheet 41 and are held in place by means of spacer plates 44 which are spaced apart from each other, for example, about 1 m, along the height of the steam generator. A casing 37 of the tube bundle 4 encloses the tube bundle inside the heat exchanger 3. The upper part of the heat exchanger 3 includes a steam dome 30 with a steam outlet 31 to the turbine; before exiting, the generated steam passes through a steam space 33 including, in particular, a coarse separator 35 and a fine separator 32.

[0017] By way of example, the total height of a steam generator 3 is approximately 22m, its weight is 400 tonnes and its diameter is 3.5m. It is positioned vertically in the reactor building 14. Depending on the type of power plant, 3 or 4 steam generators 3 may be located in a reactor building 14.

[0018] During operation, through phenomena not yet modeled, deposits, called sludge, form on the plates of the steam generator 3. This sludge is of different types and causes, on the one hand, a decrease in the efficiency of the steam generator 3 and, on the other hand, thermo-hydraulic and vibratory phenomena that create fatigue in the tubes, potentially leading to rupture.

[0019] Television inspections are carried out in the secondary circuit, on these plates, to identify the presence of sludge and to check the condition of the plates, using a mobile image acquisition device.

[0020] With reference to [Fig.3], the method 100 according to the invention will now be described.

[0021] The method 100 aims to control a state of a tube sheet 41 and of a plurality of tubes in a steam generator 3, the tubes passing through the tube sheet 41 at the level of a through part of each tube.

[0022] Process 100 comprises the following steps: - a first acquisition step 101 of at least two images by a mobile image acquisition device inside the steam generator 3, one of the at least two images being acquired by the acquisition device in one position, and another of the at least two images being acquired by the acquisition device in another position, so that a portion of the through part of one or more tube(s) 4 and / or a portion of the tube plate 41 are present in the field of observation of the acquisition device in both positions; thus, an image of the portion of the tube(s) 4 and / or the tube plate 41 is present in each of the at least two images acquired. - a second step of determining 102 the three-dimensional coordinates, in a reference frame attached to the steam generator 3, of points of the portion of the through part of the tube(s) 4 and / or of points of the portion of the tube plate 41, from the image of the portion of the through part of the tube(s) 4 and / or of the tube plate 41 present in each of the at least two images acquired, and from parameters representative of the tubes 4 and of the tube plate 41, the determination 102 of the three-dimensional coordinates being carried out by computer-implemented photogrammetry.

[0023] Optionally, photogrammetry is implemented in real time as images are acquired by the mobile acquisition device.

[0024] According to an example of implementation of the method 100 according to the invention, the parameters representing the tubes 4 include at least one of: a spacing step between the tubes 4, a diameter of the tube(s) 4, a position of the tube(s) 4, a position of a line representing an intersection between a face of the tube plate and a plane defined by the tube(s) (4).

[0025] More particularly, the method 100 according to the invention further comprises a step 103 for determining one or more characteristics of a surface of the through-part of the tube(s) 4 and / or of a surface of the tube sheet 41 through which the through-part of the tube(s) 4 passes, the characteristic(s) of the surface being determined from other parameters measured on the image of the portion of the through-part of the tube(s) 4 and / or the tube sheet 4L

[0026] More specifically, the other parameters measured on the image include at least one of the following: a texture, a color, a groove formed by the acquisition device, and the characteristic(s) include at least one of the following: a surface oxidation, the presence of gangue or mud, the presence of a powdery deposit, the presence of a migrating body.

[0027] Color can indicate the degree of oxidation of the surface of the tubes or plate. For example, a carbon steel plate, which, when not altered by oxidation, has a color ranging from dark gray to white, will be brown or orange when oxidized. Thus, by knowing the nature of the material of the object observed in the image, it is possible to deduce a characteristic such as "surface oxidation" from the parameter "color".

[0028] Texture in an image appears as a flat pattern of variations in brightness levels and / or colors. Variations in brightness levels in the image represent variations in the flatness of the observed surface, while variations in color are further representative of variations in the oxidation level. Thus, it is possible, for example, to deduce from the "texture" parameter a characteristic such as "uniform oxidation of the surface" or "non-uniform oxidation of the surface".

[0029] In addition, the reconstruction of the coordinates in three dimensions makes it possible to quantify the flatness defects of the surfaces.

[0030] Thus, the "color" parameter measured on the image allows us to deduce an oxidation rate, the "texture" parameter measured on the image allows us to deduce a surface oxidation uniformity rate derived from a color variation rate, as well as a surface flatness rate derived from a brightness variation rate, and the 3D reconstruction allows us to quantify flatness defects more precisely.

Claims

Demands

1. A method (100) for monitoring the condition of a tube sheet (41) and a plurality of tubes in a steam generator (3), the tubes passing through the tube sheet (41) at a through-section of each tube, the method (100) comprising the following steps: - acquiring (101) at least two images by an image acquisition device inside the steam generator (3), one of the at least two images being acquired by the acquisition device in one position, and another of the at least two images being acquired by the acquisition device in another position, a portion of the through-section of one or more tubes (4) and / or a portion of the tube sheet (41) being present in the field of view of the acquisition device in both positions, such that an image of the portion of the tube(s) (4) and / or the tube sheet (41) is present in each of the at least two images acquired;the method (100) being characterized in that the image acquisition device is mobile and in that the method comprises a step of: - determination (102) of the three-dimensional coordinates, in a reference frame attached to the steam generator (3), of points of the portion of the through part of the tube(s) (4) and / or of points of the portion of the tube plate (41), from the image of the portion of the through part of the tube(s) (4) and / or of the tube plate (41) present in each of the at least two acquired images, and from parameters representative of the tubes (4) and of the tube plate (41), the determination (102) of the three-dimensional coordinates being carried out by computer-implemented photogrammetry.

2. Method (100) according to claim 1, wherein photogrammetry is implemented in real time as images are acquired.

3. A method (100) according to any one of claims 1 or 2, wherein the parameters representing the tubes (4) include at least one of a spacing step between the tubes (4), a diameter of the tube(s) (4), a position of the tube(s) (4), a position of a line representing an intersection between a face of the tube plate and a plane defined by the tube(s) (4).

4. A method (100) according to any one of claims 1 to 3, further comprising a step of determining (103) one or more characteristics of a surface of the through portion of the tube(s) (4) and / or of a surface of the tube plate (41) through which the through portion of the tube(s) (4) passes, the characteristic(s) of the surface being determined from other parameters measured on the image of the portion of the through portion of the tube(s) (4) and / or of the tube plate (41).

5. Method (100) according to claim 4, wherein the other parameters measured on the image include at least one of a texture, a color, a groove formed by the acquisition device, and wherein the feature(s) include at least one of a surface oxidation, a presence of gangue or mud, a presence of a powdery deposit, a presence of a migrating body.

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