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 a condition of a tube plate and a plurality of tubes in a steam generator

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

[0002] It is known to carry out 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 to identify the presence of sludge and check the condition of the plates.

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

[0005] To this end, the present invention relates to a method for monitoring a condition of a tube plate and a plurality of tubes in a steam generator, the tubes passing through the tube plate at a through portion 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 tubes 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 acquired images; - determination of the three-dimensional coordinates, in a reference frame attached to the steam generator, of points of the portion of the through-part of the tube(s) and / or of points of the portion of the tube plate, from the image of the portion of the through-part of the tube(s) and / or of the tube plate present in each of the at least two acquired images, and from parameters representative of the tubes and of the tube plate, the determination of the three-dimensional coordinates being carried out by photogrammetry implemented by computer.

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

[0007] According to one mode of implementation, the photogrammetry is implemented in real-time real as the images are acquired.

[0008] According to one embodiment, the parameters representative of the tubes comprise at least one of a spacing pitch between the tubes, a diameter of the tube(s), a position of the tube(s), a position of a straight line representative of 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 comprises 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 plate crossed by the through-part of the tube(s), 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 plate.

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

[0011] For a better understanding, an embodiment and / or implementation of the invention is described with reference to the attached drawings representing, by way of non-limiting example, an embodiment or implementation respectively of a device and / or a method according to the invention. The same references in the drawings designate similar elements or elements whose functions are similar.

[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 reactor at pressurized water.

[0014] [Fig.3] is a schematic representation of the sequence of steps of the process according to an 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.l]. 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 circulates 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 producing the water vapor necessary to turn the turbines of one or more electricity generators 9; the water of the circuit The secondary circuit then condenses in a condenser 10 of the secondary circuit which is cooled by a cooling fluid 13 of a cooling circuit. A pump 13 circulates the water in the secondary circuit to bring it back to the steam generator 3.

[0016] [Fig. 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, and a return 43 towards, the reactor are shown. The steam generator 3 is an enormous pressure cooker inside which thousands of tubes are inserted (for example between 4000 and 5000, depending on the type of power plant), through which the water of the primary circuit passes, which heats and vaporizes the water of the secondary circuit inside a water box 40 formed of one or more substantially cylindrical rings which form the structure and the walls of the heat exchanger 3: in [Fig. 2] are thus shown by way of example a lower ring 39, a middle ring 38, a conical ring 36 and an upper ring 34.The tubes 4 of the tube bundle of the primary circuit rest on a tube plate 41 and are held by means of spacer plates 44 which are spaced apart from each other, for example by approximately 1 m, over the height of the steam generator. A casing 37 of the tube bundle 4 envelops the tube bundle inside the heat exchanger 3. The upper part of the heat exchanger 3 comprises a steam dome 30 with a steam outlet 31 towards the turbine; before exiting, the generated steam passes through a steam space 33 comprising in particular a coarse separator 35 and a fine separator 32.

[0017] For 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, due to 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 reduction in the efficiency of the steam generator 3 and, on the other hand, thermo-hydraulic and vibratory phenomena which create fatigue in the tubes which can lead to rupture.

[0019] Television inspections are carried out in the secondary circuit, on these plates, to identify the presence of sludge and 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 plate 41 and a plurality of tubes in a steam generator 3, the tubes passing through the tube plate 41 at a through portion of each tube.

[0022] The method 100 comprises the following steps: - a first step 101 of acquiring 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 tubes 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 of the tube plate 41 is present in each of the at least two acquired images. - a second step 102 of determining 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 photogrammetry implemented by computer.

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

[0024] According to an exemplary implementation of the method 100 according to the invention, the parameters representative of the tubes 4 comprise at least one of: a spacing pitch between the tubes 4, a diameter of the tube(s) 4, a position of the tube(s) 4, a position of a straight line representative of 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 of 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 plate 41 crossed by the through-part of the tube(s) 4, 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 of the tube plate 41.

[0026] Even more particularly, the other parameters measured on the image comprise at least one of: a texture, a color, a furrow formed by the acquisition device, and the characteristic(s) comprise at least one of: oxidation of the surface, a presence of gangue or mud, a presence of a powdery deposit, a presence of a migrating body.

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

[0028] The texture in an image is presented as a flat area of ​​variations in brightness levels, and / or colors. The variations in brightness level in the image are representative of variations in flatness of the observed surface, the color variations being furthermore representative of variations in the oxidation level. Thus, it is for example possible 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 makes it possible to deduce an oxidation rate, the “texture” parameter measured on the image makes it possible to deduce a uniformity rate of the oxidation of the surface derived from a rate of variation of the color, as well as a flatness rate of the surface derived from a rate of variation of a brightness, and the 3D reconstruction makes it possible to quantify the flatness defects more precisely.

Claims

Claims

1. A method (100) for monitoring a state of a tube plate (41) and a plurality of tubes in a steam generator (3), the tubes passing through the tube plate (41) at a through portion of each tube, the method (100) comprising the following steps: - acquiring (101) 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, a portion of the through portion of one or more tubes (4) and / or a portion of the tube plate (41) 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) (4) and / or of the tube plate (41) is present in each of the at least two acquired images; - 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 photogrammetry implemented by computer.

2. The method (100) of claim 1, wherein the photogrammetry is implemented in real time as the images are acquired.

3. Method (100) according to one of claims 1 or 2, in which the parameters representative of the tubes (4) comprise at least one of a spacing pitch between the tubes (4), a diameter of the tube(s) (4), a position of the tube(s) (4), a position of a straight line representative of an intersection between a face of the tube plate and a plane defined by the tube(s) (4).

4. Method (100) according to one of claims 1 to 3, further comprising a step of determining (103) one or more characteristics of a surface of the through part of the tube(s) (4) and / or a surface of the tube plate (41) crossed by the through part of the tube(s) (4), 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 of the tube plate (41).

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

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