FR3074905A1 - CORROSION TRACKING PROBE, CORROSION TRACKING SYSTEM, AND CORROSION TRACKING METHOD - Google Patents

Abstract

The invention relates to a corrosion monitoring probe (by measurement of reflectometry .The corrosion-monitoring probe (10) comprises a probe body (110) intended to be connected to a reflectometry measuring unit (20), to the minus a first longitudinal metal waveguide (120) The first waveguide (120) has at least a first and a second longitudinal portion (121, 122) succeeding one another along the probe body (110) and being sized to have a different corrodible thickness from each other, the first longitudinal portion (121) being the farthest portion of the probe body (110) from the first and second longitudinal portions (121, 122) and having a corrodable thickness less than that of the second longitudinal portion (122).

Description

CORROSION TRACKING PROBE, CORROSION TRACKING SYSTEM AND CORROSION TRACKING METHOD

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of monitoring of civil engineering works, storage places and objects stored in such storage places, and more specifically to the field of monitoring corrosion of elements metallic objects found in these same places and these same objects.

The invention thus relates to a corrosion monitoring probe, a corrosion system and a corrosion monitoring method.

PRIOR STATE OF THE ART

Currently, one of the only non-destructive methods of direct monitoring of the corrosion of metallic elements present in civil engineering works, such as buried storage places, consists in carrying out a reflectometry measurement along elements. of metallic structure of these civil engineering works, such as beams or reinforcements of these same civil engineering works.

Such a methodology, resulting from a method of measuring the humidity level in soils and other environments, and more generally known under the name temporal reflectometry or its acronym TDR for "Time Domain Reflectometry". As shown in particular by the works of W. Lui and his co-authors published within the framework of the conference “2nd International Symposium on TDR for Innovative Applications” in 2001, such a method consists in its application to the monitoring of corrosion in the works of civil and other engineering, to:

passing an electromagnetic wave, generally micrometric, along a metallic structure element, and detecting the reflections of this electromagnetic wave which appear along the structural element.

These reflections and their intensities are directly linked to the appearance of defects linked to corrosion and it is therefore possible from these reflections to trace a state of corrosion of this same metallic structural element and to the positions of these defects.

However, if such a methodology makes it possible to go back directly to a state of corrosion of the metallic elements found in a civil engineering structure or in objects stored in such a civil engineering structure, it does not make it possible to obtain a real precise measurement corrosion phenomena and their kinetics, this in a civil engineering structure or an object stored in such a civil engineering structure.

Note that this problem is particularly present in the context of radioactive waste storage. In fact, in the context of these applications, it is necessary to know the state of the metallic elements of the disposal cells and of waste packages, this over a period of time greater than 100 years, when they are not accessible to human operators for security reasons. It is therefore particularly necessary, for these applications, to develop a method for measuring corrosion which can be used in disposal cells and in waste packages. This method must be robust, interrogable from a distance and above all allow a reliable and quantitative measurement of corrosion.

STATEMENT OF THE INVENTION

The invention aims to solve this drawback and thus aims to provide a device allowing the monitoring of corrosion in an environment by allowing a precise measurement of corrosion phenomena and their kinetics this in a civil engineering work or a stored object. in such a civil engineering work.

To this end, the invention relates to a corrosion monitoring probe by measurement of reflectometry, the corrosion monitoring probe comprising:

- a probe body intended to be connected to a measurement unit by reflectometry, at least a first longitudinal metal waveguide, the first waveguide having at least a first and a second longitudinal portion following one another along the body of probe and being dimensioned to have a different corrodable thickness, the first longitudinal portion being the portion furthest from the probe body among the first and the second longitudinal portion and having a corrodable thickness less than that of the second longitudinal portion.

With such a corrosion measurement probe, the waveguide having portions of different corrodable thicknesses, each of these longitudinal portions will cause a reflection of the electromagnetic wave during a reflectometry measurement. Thus, when the corrosion is sufficient to have corroded the corrodable thickness of the first longitudinal portion, this corrosion can be identified by the absence of the reflection linked to the first longitudinal portion and by the detection of a shortening of the guide. wave corresponding to the removal of the first longitudinal portion. This applies identically to the second longitudinal portion. It is therefore possible to identify precisely with such a probe, when the corrosion has become sufficient to attack the thicknesses corresponding to the corrodable thicknesses of the first and the second longitudinal portion and therefore to deduce therefrom a state of corrosion and a corrosion rate. reliable.

Note, moreover, that such a probe is based on a reliable and robust measurement while allowing remote interrogation. It is therefore particularly suitable for applications to underground storage of radioactive waste.

The term “corrodable thickness” is understood above and in the rest of this document to mean a lateral dimension of metal of said longitudinal portion representing the minimum thickness of metal to be corroded in order to stop the electrical conduction along said portion. Thus, such a corrodable thickness can be, for example:

- for a portion having a circular section, the diameter of said circular section,

- for a portion having a square section, the length of one side of said square section,

- for a portion having a rectangular section, the width of said rectangular section,

- For a portion having a tubular shape, the thickness of the wall of said tubular shape.

The corrosion monitoring probe may also comprise at least a second waveguide, the second waveguide comprising at least a third and fourth longitudinal portion dimensioned to have a corrodable thickness different from each other, the third longitudinal portion being the most distant portion of the probe body from the third and the fourth longitudinal portion and having a corrodable thickness less than that of the fourth portion.

Such a second waveguide makes it possible to complete the measurement offered through the first waveguide, either to offer a redundant measurement, or to obtain a measurement of corrosion complementary to that permitted through the first waveguide.

The configuration of the third and fourth longitudinal portions along the second waveguide may be substantially identical to the respective configuration of the first and second longitudinal portions along the first waveguide, the third and the fourth longitudinal portion being dimensioned to have a corrodable thickness and an arrangement substantially identical to the corrodable thickness and the respective arrangement of the first and the second longitudinal portion on the first waveguide.

With such a second waveguide, the corrosion tracking probe makes it possible to provide a redundant corrosion measurement.

The configuration of the third and fourth longitudinal portions along the second waveguide may be different from the configuration of the first and second longitudinal portions respectively along the first waveguide, the third and the fourth longitudinal portions being dimensioned to have a corrodable thickness and an arrangement different from the corrodable thickness and the respective arrangement of the first and second longitudinal portions on the first waveguide.

With such a second waveguide, the corrosion monitoring probe makes it possible to provide a more precise measurement of corrosion since it is possible to identify four thicknesses of corrosion, namely those of the first to the fourth longitudinal portions.

The first waveguide may include at least one intermediate longitudinal portion disposed between the first and the second longitudinal portion.

Such an intermediate longitudinal portion offers a better distinction between the reflections corresponding to the first and the second portion without this having any significant influence on the transmission of the electromagnetic wave along the first waveguide, since this portion intermediate may have a relatively large thickness and therefore a low resistance.

The first waveguide may further include an extreme longitudinal portion extending the first longitudinal portion in a direction opposite to the probe body.

The first waveguide can be made of steel or cast iron.

The first waveguide can be produced in a steel selected from a grade P285NH steel and an API 5L grade X65 steel.

The first waveguide can be made from cast iron.

The first waveguide may have a rectangular lateral section, the width of said lateral section forming, for each of the first and the second longitudinal portion, the corrodable thickness.

Such a waveguide allows the waveguide to offer good conduction thanks to the length of its lateral section despite the small thickness linked to the thickness of corrosion. This results in a higher transmission of the electromagnetic wave during the measurement of reflectometry.

It will be noted that with such a first waveguide, the length of the rectangular lateral section is preferably greater than 10 times, or even 20 times, or even 50 times, the width of this same lateral section.

The invention also relates to a corrosion monitoring system comprising:

a corrosion monitoring probe, a reflectometry measuring unit, the corrosion monitoring probe being according to the invention.

Such a corrosion monitoring system benefits from the advantages linked to the invention.

The invention further relates to a method for monitoring corrosion in a given medium from a corrosion monitoring system according to the invention, the method comprising the following steps:

supply of the corrosion monitoring system,

- installation of the corrosion monitoring probe in the given environment,

- carrying out a reflectometry measurement along at least the first waveguide from the corrosion monitoring system,

- research from the result of the measurement of any reflections corresponding to the first and the second longitudinal portion,

- deduction of corrosion greater than a first threshold and a second threshold if no reflection corresponding to the first and second portions respectively is identified.

Such a method makes it possible to benefit from the advantages linked to the use of a corrosion monitoring probe according to the invention.

The first and second thresholds can correspond respectively to either the corrosion thickness of the first and the second portion, or to the corrosion thickness of the first and the second portion divided by two.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments, given for purely indicative and in no way limiting, with reference to the appended drawings in which:

FIG. 1 illustrates a corrosion monitoring system according to the invention, said system comprising a corrosion monitoring probe according to a first embodiment of the invention, FIG. 2 graphically illustrates an example of reflectometry measurement obtained with a corrosion monitoring system as illustrated in FIG. 1, FIG. 3 illustrates a corrosion monitoring probe according to a second embodiment of the invention in which the corrosion probe comprises two metal waveguides, FIG. 4 illustrates a corrosion monitoring probe according to a second embodiment of the invention in which first and second longitudinal portions are separated from one another by an intermediate portion.

Identical, similar or equivalent parts of the different figures have the same reference numerals so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with one another.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 1 illustrates a corrosion monitoring system 1 for monitoring corrosion in a civil engineering structure, such as an underground storage facility for radioactive waste, or an object stored in a civil engineering structure, such as 'a waste package.

It will be noted that if the present description mainly relates to the application to underground works for the storage of radioactive waste and to the waste stored in such a work, the invention nevertheless applies to all types of civil work and or of stored object. in such works, the skilled person being able to apply the present teaching to such civil works and / or objects.

Such a corrosion monitoring system 1 comprises:

a corrosion monitoring probe 10, a reflectometry measurement unit 20.

The corrosion monitoring probe 10 comprises:

a probe body 110 intended to be connected to a measurement unit by reflectometry 20, a first longitudinal metallic waveguide 120.

The probe body 10, in order to allow its connection to the reflectometry measurement unit 20, comprises a connector, not shown, such as a coaxial connector. Of course, as a variant, the probe body 10 may include another type of connector without departing from the scope of the invention, this connector being capable of transporting an electromagnetic wave used to perform a reflectometry measurement. According to another possibility of the invention, the probe body can also comprise a cable, such as a coaxial cable, capable of being connected to the measurement unit by reflectometry 20 and of transporting an electromagnetic wave used for carrying out a measurement reflectometry.

The probe body 10 comprises an internal conductor making it possible to connect a core of the coaxial connector to the first waveguide 120.

The first waveguide 120 has a first, second and fifth longitudinal portion 121, 122, 123 which follow one another along the probe body and are dimensioned to have a corrodable thickness different from each other.

The first, second and fifth longitudinal portion 121, 122, 123 follow one another in this order along the first waveguide 120 in the direction of the body of the probe 110, so that the first longitudinal portion is the longitudinal portion the most distant among the first, second and fifth longitudinal portions 121, 122, 123. The first longitudinal portion 121 has a corrodable thickness less than those of the second and fifth longitudinal portions 122, 123. The second longitudinal portion 122 has a thickness corrodable lower than that of the fifth longitudinal portion 123.

According to an advantageous possibility of the invention, the first waveguide 120 has a rectangular section. In such a configuration, the width of the lateral section of each of the first, second and fifth longitudinal portion 121, 122, 123 forms the corrodible thickness of said longitudinal portion 121, 122, 123. According to this possibility the length of the section lateral of the first, second and fifth longitudinal portion may be equal. As a variant, the length of the lateral section of the first, second and fifth longitudinal portion 121, 122, 123 may be different in order to obtain, at each transition between longitudinal portion 121, 122, 123, a more pronounced reflection of the electromagnetic wave emitted by the reflectometry measurement unit 20.

According to this same possibility, the length of the lateral section of the first waveguide 120 is greater than 10 times, or even 20 times, or even 50 times, the width of this same lateral section. In other words, the first waveguide 120 has a planar shape.

The first waveguide 120 is made of a corrodible metallic material, preferably ferrous. It will thus be noted that the first waveguide 120 is preferably made of steel which can be, in a particularly advantageous manner, a steel selected from a steel grade P285NH and a steel API 5L grade X65 (in particular of the MS SAWL type). According to another advantageous possibility of the invention, the first waveguide 120 can be made of cast iron.

It will be noted that the corrodable thicknesses of each of the first, second and fifth portions are chosen as a function of the expected corrosion rate and of the period of monitoring of the civil structure and / the object during which the corrosion must be monitored. Thus, for example, for an expected corrosion rate of lpm / year and a monitoring period of more than 10 years, the corrodable thicknesses can be selected between 5 pm, that is to say 5 years of corrosion, and 5 mm, that is to say 50 years.

Of course, such a shape of the first waveguide 120 is given only by way of example which, if it is particularly advantageous for applications for monitoring corrosion in underground storage for the storage of nuclear waste and / or a waste package stored therein is by no means limiting. Thus, the first longitudinal waveguide 120 may also have a circular, square or even tubular side section without departing from the scope of the invention.

The reflectometry measurement unit 20 is adapted to: generate an electromagnetic wave, preferably micrometric, and transmit it to the corrosion monitoring probe 10 to which it is connected;

measuring the electromagnetic waves resulting from the multiple reflections which take place in the corrosion monitoring probe 10, in other words for carrying out a reflectometry measurement in the corrosion monitoring probe 10 and more precisely along the first waveguide 120 .

According to an advantageous possibility of the invention, the reflectometry measurement unit 20 can also be configured for:

- from the result of the measurement of the electromagnetic waves resulting from the multiple reflections which take place in the corrosion monitoring probe 10, detect any reflections 201, 202, 203 corresponding to the first, the second and the fifth longitudinal portion 121,122,123,

- deduction of corrosion greater than a first threshold, a second threshold and a third threshold if no reflection corresponding to the first, second and fifth longitudinal portions 121, 122, 123 respectively is identified.

The first, second and third threshold may correspond respectively to the respective corrosion thickness of the first, second and fifth portion 121, 122, 123. According to another convention and according to the configuration of the waveguide The first, second and third threshold may correspond respectively to the respective corrosion thickness of the first, second and fifth portion 121,122,123 divided by two.

Thus, such a corrosion monitoring system 1 allows the implementation of a corrosion monitoring process comprising the following steps:

supply of the corrosion monitoring system 1,

- installation of the corrosion monitoring probe 10 in the given medium,

- carrying out a reflectometry measurement along at least the first waveguide 121 from the corrosion monitoring system 1,

- detection, from the result of the measurement, of any reflections 201, 202, 203 corresponding to the first, the second and the fifth longitudinal portion 121, 122, 123,

- deduction of corrosion greater than a first threshold, a second threshold and a third threshold if no reflection corresponding to the first, second and fifth longitudinal portions 121, 122, 123 respectively is identified.

FIG. 2 provides an example of reflectometry measurements according to the invention in order to explain the principle of the invention. Thus, according to the principle of the invention, the reflectometry measurement unit 20 emits an electromagnetic wave and transmits it to the corrosion monitoring probe 10. The graph in FIG. 2 thus illustrates the variation of the electrical reflection signal , in arbitrary unity, over time. A reflection is identifiable on this graph by a change in slope of the electrical reflection.

We can see on this graph that the electromagnetic wave has a first reflection 201 at the interface between the probe body 110 and the first waveguide 120, then a second, third and fourth reflection 202, 203, 204 aux interfaces respectively between the fifth longitudinal portion 123 and the second longitudinal portion 122, between the second longitudinal portion 122 and the first longitudinal portion 121 and between the first longitudinal portion 121 and the medium in which the corrosion monitoring probe 10 is located.

Thus, if only three reflections are detected, it can be deduced that the probe, and therefore the metallic elements found in the civil engineering structure or the object being monitored, have been subjected to corrosion greater than or equal to that corresponding to the corrosion thickness of the first portion 121.

Likewise, if only two reflections are detected, the corrosion is greater than or equal to that corresponding to the corrosion thickness of the second portion 122. If only one reflection is detected, the corrosion is greater than or equal to that corresponding to the thickness of corrosion of the fifth portion 123.

FIG. 3 illustrates a corrosion monitoring probe 10 according to a second embodiment in which the corrosion monitoring probe 10 also comprises a second waveguide 130. A corrosion monitoring system 1 according to this second embodiment differs from a corrosion monitoring system 1 according to the first embodiment only in that the corrosion monitoring probe 10 includes the second waveguide 130.

As illustrated in FIG. 3, the second waveguide comprises a third, a fourth and a sixth longitudinal portion 131,132,133 which follow one another along the probe body 110. The third, fourth and sixth longitudinal portion 131, 132, 133 dimensioned to have a corrodable thickness different from each other.

The third, fourth and sixth longitudinal portion 131, 132, 133 follow one another in this order along the second waveguide 130 towards the body of the probe 110, so that the third longitudinal portion is the most longitudinal portion distant among the third, fourth and sixth longitudinal portion 131, 132, 133. The third longitudinal portion 131 has a corrodible thickness less than that of the fourth and sixth longitudinal portions 132, 133. The fourth longitudinal portion 132 has a lower corrodable thickness to that of the sixth longitudinal portion 133.

According to a first possibility of this second embodiment illustrated in FIG. 3, the first and the second waveguide have similar configurations. In other words, the third, fourth and sixth longitudinal portions 131, 132, 133 have an arrangement and a dimensioning, that is to say a thickness of corrosion, along the second waveguide substantially identical to respectively the first, second and fifth longitudinal portions 121, 122, 123. In this way the first and second waveguides make it possible to provide redundant monitoring of corrosion.

According to a second possibility, not illustrated in this second embodiment, the first and the second waveguide have different configurations. In other words, the third, fourth and sixth longitudinal portions 131, 132, 133 have an arrangement and a dimensioning, that is to say a thickness of corrosion, along the second waveguide substantially different from those of the first, second and fifth longitudinal portions 121, 122, 123. In this way, the third, fourth and sixth longitudinal portion 131, 132, 133 make it possible to provide a fourth, a fifth and a sixth corrosion threshold distinct from the first, second and third corrosion thresholds provided by the first waveguide 120. It will be noted that it is possible to distinguish the reflections along the first and the second waveguide 120, 130 by the separate arrangement between the portions of the first and second waveguide 120,130.

FIG. 4 illustrate a corrosion monitoring probe 10 according to a third embodiment in which each of the longitudinal portions 121, 122, 123, 131, 132, 133 are separated by an intermediate portion 124, 134. A monitoring system for corrosion 10 according to this third embodiment differs from corrosion monitoring system 10 according to the second embodiment in that an intermediate portion 124, 134 is provided between each of the longitudinal portions 121, 122, 123, 131 , 132, 133.

Such intermediate portions 124, 134 make it possible to extend each of the longitudinal portions 121, 122, 123, 131, 132, 133, and thus improve the detection sensitivity, without increasing the resistance of the waveguide which could cause attenuation. too much of the electromagnetic wave. What is more, such an intermediate portion 124,134 makes it possible to increase the weight exerted on a longitudinal portion to which said intermediate portion is attached and can thus promote a rupture of said longitudinal portion due to the brittleness brought by corrosion.

It will be noted that, according to one possibility of this third embodiment illustrated in FIG. 4, and in order to favor a rupture of the longitudinal portions 121, 131 extremes of the first and of the second waveguide 120, 130, that is to say say the first and the third portion 121, 131, each of the first and the third portion can be extended by an extreme longitudinal portion 125,135.

Note that if in the three embodiments described above each of the waveguides 120, 130 of the corrosion monitoring probe 10 has three longitudinal portions, the invention is not limited to this only possibility. Thus, it is also possible, without departing from the scope of the invention, for each waveguide 10 to have a number of longitudinal portions different from three, this number possibly being, for example equal to 2 or greater than 3 or even 5.

Claims (10)

1. Corrosion monitoring probe (10) by measurement of reflectometry, the corrosion monitoring probe (10) comprising: - a probe body (110) intended to be connected to a reflectometry measurement unit (20), at least a first longitudinal metallic waveguide (120), the corrosion monitoring probe (10) being characterized in that that the first waveguide (120) has at least a first and a second longitudinal portion (121, 122) succeeding each other along the probe body (110) and being dimensioned to have a corrodable thickness different from one of the other, the first longitudinal portion (121) being the portion furthest from the probe body (110) among the first and second longitudinal portions (121,122) and having a corrodable thickness less than that of the second longitudinal portion (122) . 2. corrosion monitoring probe (10) according to claim 1 further comprising at least a second waveguide (130), the second waveguide (130) comprising at least a third and fourth longitudinal portion (131 , 132) dimensioned to have a corrodable thickness different from each other, the third portion (131) being the portion furthest from the probe body (110) among the third and fourth longitudinal portions (131, 132) and having a corrodable thickness less than that of the fourth portion (122). 3. Corrosion monitoring probe (10) according to claim 2, in which the configuration of the third and of the fourth longitudinal portion (131, 132) along the second waveguide (130) are substantially identical to the respective configuration of the first and the second longitudinal portion (121, 122) along the first waveguide (120), the third and the fourth longitudinal portion (131, 132) being dimensioned to have a corrodable thickness and an arrangement substantially identical to the corrodable thickness and to the respective arrangement of the first and the second longitudinal portion (121, 122) on the first waveguide (120). 4. The corrosion monitoring probe (10) according to claim 2, in which the configuration of the third and of the fourth longitudinal portion (131, 132) in the second waveguide (130) are different from the respective configuration. the first and second longitudinal portions (121,122) in the first waveguide (120), the third and fourth longitudinal portions (131, 132) being dimensioned to have a corrodable thickness and an arrangement different from the thickness corrodible and the respective arrangement of the first and the second longitudinal portion (121,122) on the first waveguide (120). 5. Corrosion monitoring probe (10) according to any one of claims 1 to 4, in which the first waveguide (120) comprises at least one intermediate longitudinal portion (124) disposed between the first and the second longitudinal portion (121,122). 6. corrosion monitoring probe (10) according to any one of claims 1 to 5, wherein the first waveguide (120) further comprises an extreme longitudinal portion (125) extending the first longitudinal portion (121 ) in a direction opposite to the probe body (110) 7. corrosion monitoring probe (10) according to any one of claims 1 to 6, wherein the first waveguide is made of steel or cast iron 8. corrosion monitoring probe (10) according to any one of claims 1 to 7, wherein the first waveguide (120) has a rectangular side section, the width of said side section forming, for each of the first and the second longitudinal portion (121,123) the corrodable thickness. 9. Corrosion monitoring system (1) comprising: a corrosion monitoring probe (10), a reflectometry measuring unit (20), the monitoring system being characterized in that the corrosion monitoring probe is according to any one of claims 1 to 8. 10. Method for monitoring corrosion (1) in a given medium from a corrosion monitoring system (1) according to claim 9, the method comprising the following steps: supply of the corrosion monitoring system (1), - installation of the corrosion monitoring probe (10) in the given environment, - carrying out a reflectometry measurement along at least the first waveguide (121) from the corrosion monitoring system (1), - detection, from the result of the measurement, of any reflections (202, 203) corresponding to the first and the second longitudinal portion (121, 122), - deduction of corrosion greater than a first threshold and a second threshold if no reflection corresponding to the first and second longitudinal portions (121,122) respectively is identified. S.64091