FR3008794A1 - DEVICE FOR CONTINUOUSLY DETECTING LIQUID WATER INTO A DUCT, CIRCUIT COMPRISING A CONDUIT PROVIDED WITH SUCH A DEVICE AND METHOD FOR CONTINUOUSLY DETECTING LIQUID WATER IN THE CONDUIT - Google Patents

Abstract

Device for detecting (11) liquid water in a conduit (5) in which water predominantly circulates in the form of steam, the device (11) comprising: - means for sampling (14) water at a point sampling (15) of the conduit, - an analysis system (16) of water taken from the conduit (5), to detect a presence of liquid water. The sampling means (14) comprise continuous piping means (17) for channel water from the sampling point (15) to the analysis system (16).

Description

Device for the continuous detection of liquid water in a conduit, circuit comprising a conduit provided with such a device and method for the continuous detection of liquid water in the conduit The invention relates to the field of detection and detection quantization of a circulating element, and more particularly the quantification of liquid water in a withdrawal circuit, such as a circuit for withdrawing a turbine in a secondary circuit of a power plant.

There is for example a withdrawal circuit on the secondary circuit of nuclear power plants, but also thermal power plants, and generally on any circuit for producing electrical energy from water vapor. In such circuits, pressurized water is heated and vaporizes in a secondary circuit to recover energy by the expansion of the steam, for example by means of turbines. Draw-off circuits can then be placed at different points of the secondary circuit, in order to evacuate the liquid water produced by the expansion of the steam and to maintain satisfactory performance throughout the secondary circuit.

It is therefore important to know the amount of liquid water in the withdrawal circuits, in order to monitor the proper functioning of the energy production circuit. The importance of precise knowledge of the quantity of liquid water in the draw-off circuits is of a multi-faceted nature, as it allows, for example, the safety of installations, the respect of contractual values and the monitoring of the impact. on operation and maintenance. It is known to measure the amount of liquid water by injecting a tracer, that is to say a soluble and non-volatile product at the conditions of pressure and temperature in the withdrawal circuit. The conservation of the amount of tracer downstream of the injection point makes it possible to calculate, from the tracer concentration measurements in the circuit, either the moisture content or the flow rate of the single liquid phase. Two methods are generally used.

The first method is to inject a chemical tracer, and then to draw water from the withdrawal circuit. The sample is then analyzed in the laboratory. This method has the particular disadvantage that it does not allow continuous monitoring, and variations in the measurements, testifying for example of a change over time in the amount of liquid water, will be difficult to detect quickly. Indeed, samples and measurements are made on an ad hoc basis. In addition, the analysis is done in the laboratory, which can be time consuming.

The second method consists in injecting a radioactive tracer continuously. The measurement of the radioactivity on the withdrawal circuit makes it possible to obtain a measurement of the quantity of liquid water.

However, the use of a radioactive tracer is expensive because the amount of tracer involved is important. Indeed, the measurement of the amount of water in a withdrawal circuit enters a test campaign, each test lasting about one hour, during which all the withdrawal circuits of the secondary circuit to be verified are measured. In addition, a campaign is programmed for each particular operation of the plant, for example 100%, then 75%, and so on. Thus, a large number of sources of radioactive tracer are required. Such sources are expensive. In addition, such sources are difficult to obtain. Indeed, for reasons of environmental pollution and safety including plant personnel and stakeholders, the radioactive tracer used should have a short life.

However, since such sources are not on the measurement site, they must be transported. Their lifespan must therefore take into account the transport. A compromise is difficult to find. In addition, measurements by radioactive tracer are increasingly abandoned because of their difficulty of implementation in particular linked to increasingly stringent legislation in the field of the use of radioelements (supply, radiation protection, risk of releases in the environment, ...).

There is therefore a need for a new device for analyzing water vapor in a conduit, such as that of the secondary circuit, for detecting and measuring the presence of liquid water, overcoming the aforementioned drawbacks.

The present invention therefore proposes, according to a first aspect, a device for detecting, and possibly quantifying, liquid water in a conduit in which water circulates, the device comprising: means for sampling water at a point of duct sampling, a water analysis system taken from the duct, to detect a presence of liquid water. In addition, the sampling means comprise means for continuously piping the conduit from the sampling point to the analysis system. Thus, water can flow continuously from the sampling point to the analysis system. The presence of tracer then indicates that liquid water circulates in the conduit. The device may further comprise an injector of a tracer of liquid water at a point of injection of the conduit, the analysis system being able to detect a presence of the tracer of liquid water. Thus, the amount of tracer injected being known, the flow of liquid water in the withdrawal can be calculated.

According to a particular embodiment, the analysis system comprises a microfluidic circuit, advantageously adapted to a continuous analysis. In addition, the microfluidic circuit, compact, can be easily transportable and implantable on an industrial site. The chemical components being consumed in small quantities in the microfluidic circuit, the continuous analysis can be done at a lower cost. Pollution problems with the substances used are also reduced.

The quilting means comprise a quilting capillary connecting a sampling pipe, connected to the sampling point, the analysis system, for injecting at least a portion of the water taken from the analysis system. Thus, the capillary makes it possible to make the transition between the conduit and the microfluidic circuit, despite the differences in the orders of magnitude of their size and respective flow rates. The sampling pipe comprises a so-called high point on which a vent is placed, the quilting capillary being placed on the sampling pipe at a determined distance from the high point, so as to form a hydraulic guard.

Advantageously, the liquid water detection device further comprises a regulator of the flow of water injected into the analysis system, so as to regulate the sampling rate, and for example to ensure that only liquid water is taken, in order to optimize the continuous operation of the analysis system, and to measure the amount of liquid water with increased reliability. In addition, the device for detecting liquid water may comprise, between the sampling point and the analysis system, at least one heat exchanger able to cool at least part of the water taken before it is injected into the system. analysis. Thus, the analysis system is preserved and the injection of water into the quilting capillary and then into the microfluidic circuit is facilitated. According to a preferred embodiment, the tracer of liquid water comprises a chemical tracer, that is to say non-radioactive, facilitating its handling and limiting the pollution of the external environment. Advantageously, the device further comprises: injection means in the analysis system of a probe of a tracer of liquid water present at the sampling point; means for mixing sampled water and the probe in the analysis system, means for analyzing the mixture comprising sampled water and the probe.

The injection of the probe makes it possible to reveal the presence of the tracer of liquid water in a simple and continuous manner. The device may comprise a regulator of the flow rate of the probe injected into the analysis system, in order to regulate the quantity of probe injected into the analysis system. For example, the probe comprises a fluorescent probe that reacts with the tracer, the system for analyzing the mixture comprising a device for optical analysis of the fluorescence of the mixture. Optical analysis lends itself particularly well to a continuous and real-time analysis, and allows to know the evolution over time of the tracer concentration, and thus also to know the evolution of the quantity of liquid water in the conduit.

According to one embodiment, the tracer comprises cesium, the fluorescent probe being chosen from among the components of the calixarene family. According to a second aspect, the invention proposes a circuit for withdrawing water from a turbine body of an electricity generating plant, comprising a hot water withdrawal duct for heating water from food. the plant, which circuit comprises a device for the continuous detection of liquid water as presented above. The device thus makes it possible to check the correct operation of the plant, in particular during the start-up tests of the power generation units. According to one embodiment, the withdrawal conduit is of predetermined diameter, and the device comprises a liquid water tracer injection means and a water sampling means to be analyzed, the injection means and the sampling being separated by a distance function of a multiple of said predetermined diameter, allowing good mixing between the tracer and the liquid water.

According to a third aspect, the invention provides a method for the continuous detection of liquid water in water vapor circulating in a conduit. The method comprises the following steps: / 1 / the continuous sampling of water at a sampling point of the conduit, / 2 / the continuous injection of at least a portion of the sampled water, in a system of analysis, / 3 / the continuous detection of liquid water. Continuous sampling allows continuous and real-time analysis to obtain a reliable measurement. In particular, the continuous sampling makes it possible to determine a maximum sampling rate, beyond which condensed vapor can be taken in addition to the liquid water. The step / 3 / of continuous detection of liquid water may comprise an operation of continuous injection of a probe into the analysis system, simultaneously with the injection step / 2 / of the part of water withdrawn. In addition, the flow rate of the probe and the flow rate of water injected into the analysis system are regulated according to each other to obtain a mixture comprising water taken from the sample and the probe in proportions determined according to of a desired sensitivity. Thus, the amount of probe injected is adapted to reveal the presence of tracer in the sample. According to a particularly advantageous embodiment, the probe injected into the analysis system forms a fluorescent complex with the tracer. The step of continuous detection of liquid water can then comprise the following operations: the excitation of the complex by a beam at a first wavelength and, simultaneously, the excitation of the complex or the probe in the system of analysis by a beam at a second wavelength different from the first wavelength; detecting the fluorescence of the excited complex as a voltage signal; synchronous detection on the voltage signal for the first wavelength; synchronous detection on the voltage signal for the second wavelength; the ratiometric measurement on the two signals resulting from the synchronous detections. The ratiometric measurement is defined as the quotient between the two signals resulting from the two synchronous detections, and thus makes it possible to obtain directly, without prior calibration or reference steps, the tracer flow rate, and therefore the flow rate of liquid water. In a variant, the probe injected into the analysis system again forms a fluorescent complex with the tracer of liquid water, and the step of continuous detection of liquid water comprises the following operations: the injection of a standard fluorescence distinct from the probe in the analysis system, the excitation of the complex in the beam analysis system at a first wavelength and, simultaneously, the excitation of the standard in the analysis system by a beam at a second wavelength different from the first wavelength; detecting the fluorescence of the excited complex and the fluorescence of the standard in the form of a voltage signal; synchronous detection on the voltage signal for the first wavelength; synchronous detection on the voltage signal for the second wavelength; the ratiometric measurement on the two signals resulting from the synchronous detections. The ratiometric measurement is defined as the quotient between the two signals resulting from the two synchronous detections. The standard then serves as an internal reference for the ratiometric measurement.

Of course, other advantages and characteristics of the invention will appear on examining the detailed description of possible embodiments, presented below, and the appended figures in which: FIG. 1 is a representation schematic of an overview of a secondary circuit of a power plant for producing electrical energy, - Figure 2 is a detailed view of a portion of the secondary circuit of the circuit of the circuit of Figure 1 in 3 is a diagram illustrating the concentration of a tracer in a sample as a function of the sampling rate; FIG. 4 is a diagrammatic representation of a device for detecting liquid water in the duct; of Figure 2; FIG. 5 is a schematic representation of an embodiment of an analysis system of the detection device; - Figure 6 is a schematic representation of a method for analyzing the sample. In Figure 1, there is shown schematically a power plant 1 for producing electrical energy comprising a steam generator 2, indicated by GV in the figure. In the case of a nuclear power plant for example, the steam generator acts as a heat exchanger between a primary circuit and a secondary circuit 3. More precisely, pressurized water circulates continuously in a conduit 4 of the secondary circuit 3. In a vaporization portion 5 comprising the steam generator 2, the heat of the primary circuit is transferred to the secondary circuit 3, for example by conduction. The temperature of the water in the vaporization portion 5 then increases to the point where the water is vaporized. In an energy recovery portion 6, the secondary circuit 3 comprises at least one turbine 7 placed on a main duct 4, and preferably comprises two turbines 7, 8 indicated by TURB in FIG. 1, placed in series, and connected to each other. to an alternator 9 indicated by ALT. For example, a first turbine 7 is called high pressure and a second turbine 8 is called low pressure.

The water in vapor form is sent to the high pressure turbine 7 where it undergoes a first expansion, then on the turbine 8 low pressure where it undergoes a second expansion. The energy, for example electrical energy, is recovered in the alternator 9. In order for the energy production efficiency to be optimized for each turbine 7, 8, it is preferable for steam to be predominantly conveyed for each turbine 7. 8. For this purpose, a withdrawal circuit 10 is derived from the body of a turbine, for example the high pressure turbine 7, to recover the liquid water resulting from the expansion of the steam in the turbine 7 High Pressure, so that only dry steam, that is to say containing a proportion of liquid water with respect to steam below a fixed value, is sent to the turbine 8 Low Pressure. The drawdown circuit 10 comprises a withdrawal conduit 101, which joins a so-called food portion 102 of the main conduit 4, in which circulates so-called food water, mainly liquid, after expansion in the turbine 8, to feed the portion 5 Spraying. A condenser 104 may be placed on the food portion 102 in order to condense the remaining vapor phase remaining and ensure that it has only a liquid phase. The water of the withdrawal pipe 101 being at a temperature higher than that of the feed water, the withdrawal pipe advantageously comprises a heat recuperator 103 between the withdrawal pipe 101 and the food portion 102. The withdrawal conduit 101 is connected to the food portion 102 upstream of the heat recovery unit. In what follows, will be designated by "steam" water in vapor form, and "liquid" water in liquid form. We speak of "water" when it is indifferent to specify whether it is steam or liquid. In addition, in the following, the terms "upstream" and "downstream" are used with reference to the direction of flow of water in the secondary circuit 3. More broadly, these terms are used with reference to the direction of circulation any fluid in a corresponding conduit.

In order to detect a liquid in the withdrawal pipe 101, a device 11 for detecting liquid water makes it possible to continuously take water from the withdrawal pipe 101 and to analyze it continuously.

It is understood that a withdrawal circuit may also be placed to recover the liquid water from the turbine 8 Low Pressure. In addition, it is also understood that the detection device may be placed on any portion of the secondary circuit 3 for which it is useful to know the amount of liquid flowing therethrough.

A tracer is mixed with the liquid in the withdrawal pipe 101. In what follows, the term "tracer" any substance or element to highlight the presence of liquid in the secondary circuit 4. In particular, the tracer may be a very low volatile element under the conditions prevailing in the conduit 101 of racking, so that it does not mix with steam but only with the liquid. The tracer may be a radioactive element, but is preferably a non-radioactive chemical tracer. The elements of the alkaline family are particularly suited to the role of chemical tracer of liquid; among them in particular, cesium, whose safety vis-à-vis the components of the secondary circuit and operating parameters, such as conductivity, has been verified, can easily be used. More specifically, the tracer may be a salt whose cation is cesium. According to one embodiment, the tracer is naturally in the conduit 101 of withdrawal. It may be elements contained in water and steam such as oxygen or water conditioning elements of the secondary circuit, packaging made in particular to reduce the effects of corrosion. However, advantageously, the detection device 11 may comprise an injection point 12 on the conduit 101 connected to an injector 13, indicated by I NJ in FIG. 1, of the tracer, in order to allow, as will be seen below, to measure the amount of liquid in the withdrawal conduit 101.

The device 11 further comprises water sampling means 14, indicated by PREL in FIG. 1, at a sampling point 15 of the conduit 4, the sampling point being located downstream of the injection point 12 relative to in the direction of circulation of water in the pipe 101 of withdrawal.

The water flowing in the withdrawal pipe 101 is a mixture of liquid and steam. In practice, the percentage by mass of liquid flowing in the duct 101 of withdrawal is from a few% (percent) to about ten%. The flow, then two-phase, in the withdrawal conduit 101 is typically annular, that is to say that the liquid L is located on the wall of the conduit 101, while the steam V flows at a higher speed, in the center of the duct 101 (Figure 2). On the horizontal portions of the duct 101, the liquid, in the form of a dripping film, is located mainly on the lower generatrix of the duct 101, while in the elbows of the duct 101, the liquid film L is mainly formed on the extrados.

The places where it is most likely to find liquid are therefore a priori known. Thus, the injection point 12 and the sampling point 15 are advantageously placed on the wall of the withdrawal conduit 101, preferably on the lower generatrix of the conduit 101, or on the extrados of a bend.

The injection point 12 is placed at a determined minimum distance from the sampling point 15, so that the tracer has time to mix perfectly uniformly with the liquid. For example, since the duct 101 of the withdrawal circuit 10 has a predetermined diameter D, the distance between the injection point 12 and the sampling point 15 is chosen as being a function of a multiple of the diameter D of the duct 101 of FIG. racking. In addition, the position of the injection point 12 with respect to the sampling point can take into account the presence of singularities related to the industrial framework, such as bends or valves, which promote mixing between the tracer and the liquid.

In order to detect the presence of a tracer, betraying the presence of liquid in the withdrawal pipe 101, the detection device 11 comprises a system 16 for analyzing at least part of the water taken from the pipe 101, in which the sampling means 14 inject at least a portion of the water sampled at the sampling point 12. More specifically, the sampling means 14 comprise means 17 for stitching water continuously from the conduit 101 withdrawing from the sampling point 15 to the analysis system 16, for continuously injecting at least a portion of the water taken from the analysis system 16. Thus, not only is water withdrawn continuously in the conduit 101 at the point of 15, but at least part of the water taken is also injected continuously into the analysis system 16. In other words, water flows continuously from the sampling point 15 to the sampling system. analysis 16. Preferably, the sampling rate, at the sampling point 15, must be adjusted so as not to collect steam. Indeed, in the case where the sampling rate is too high, the liquid film L flowing on the wall is broken, and steam V is mainly taken. The tracer concentration in the withdrawn water is then very low, and the measurement of the flow of water in the withdrawal is false. For this purpose, it is represented in FIG. 3 the tracer concentration Ct, determined in the analysis system 16, in the sampled water, as ordinates, as a function of the sampling flow rate Qp, on the abscissa. The concentration remains constant, indicating that only liquid is drawn until a maximum flow rate Qmax is reached. Beyond the maximum flow rate Qmax, the tracer concentration drops, indicating that the liquid film is broken and that steam is removed.

The maximum sampling flow rate Qmax is thus determined in a development step, prior to the measurement operations themselves, so as to obtain reliable measurements. Since only the evolution of the Ct concentration is necessary during the development step, and no quantification is required, the tracer whose Ct concentration is monitored may be a non-injected tracer, that is, that is to say, as seen above, a tracer naturally present in the duct 101 of withdrawal. In addition, the tracer, injected or not, used during the debugging step may quite be different from the tracer injected for the measurement.

During measurement operations, it may therefore be chosen a sampling rate lower than the maximum flow rate Qmax previously determined so as not to dilute the tracer in the water taken. Indeed, during measurement operations, it is essential to set a sampling rate lower than the maximum flow rate Qmax so that the tracer balance, which will then be performed, is correct. The sampling rate is, at the same time, preferably close to the maximum flow rate Qmax, so that the water sampling can be analyzed. Thus, only liquid L is taken, and by determining the dilution ratio of the tracer, it is possible to deduce the flow of liquid L in the conduit 101 In addition, unlike the devices of the state of the art the device 11 for detecting liquid water makes it possible to obtain rapidly the curve of FIG. 3 relating to the evolution of the concentration Ct of tracer as a function of the sampling rate Qp.

Indeed, from the techniques of laboratory sample analysis of the state of the art, obtaining this curve requires several point samples and several analyzes. In addition, due to the punctual nature of the measurements of the state of the art, the determination of the maximum flow rate Qmax lacks precision. On the contrary, the device 11 for detecting liquid water makes it possible in a short time to accurately determine the maximum flow rate Qmax increasing the reliability of the measurement. According to a particularly advantageous embodiment, the analysis system 16 comprises a microfluidic circuit 18. By "microfluidic" is meant here a system of which at least one characteristic dimension is less than one millimeter. Thus, in this case, the microfluidic circuit 18 of the analysis system 16 comprises channels 19, for example of rectangular section, the largest dimension is of the order of two hundred microns. The use of a microfluidic circuit 18 advantageously makes it possible to carry out a continuous analysis. Indeed, by the continuous nature, conventional methods of measurement by chromatography or using a mass spectrometer are excluded. The microfluidic circuit 18 makes it possible to implement techniques adapted to the continuous nature, as will be seen below. In addition, the dimensions of the microfluidic circuit 18 make it possible to obtain a liquid water detection device 11 of limited size, easily transportable and easily implantable at the industrial site, in particular near the secondary circuit 4.

In order to inject water from the withdrawal pipe 101, the diameter of which is approximately 50 centimeters into the channels 19 of the microfluidic circuit 18, the sampling means 14 advantageously comprise a sampling pipe 20, connected to the conduit 101 at the sampling point 15, and the stitching means 17 comprise a stitching capillary 21, connecting the sampling tube 20 to the microfluidic circuit 18 of the analysis system 16. The stitching capillary 21 is in practice under the shape of a pipe of one or several hundred microns in inner diameter, and allows the water to make the transition between the sampling pipe 20, whose dimensions are of the order of a few millimeters, and the Channels 19 of the microfluidic circuit 18. Thus, only a small fraction of the water taken from the sampling pipe 20 is sent into the microfluidic circuit 18. The rest of the water taken can be direct returned to the effluent treatment plant.

Controllers of flow rates make it possible to control the flow of water towards the analysis system 16. For example, a first valve 22 is placed on the sampling pipe 20, between the quilting capillary 21 and the sampling point 15, so that to adjust the flow of water taken from the conduit 101, for example compared to the maximum flow rate Qmax, determined in the previous step of focusing. Instead of the first valve 22, but preferably in combination, a second valve 23 may be placed on the quilting capillary 21, in order to control the flow of water sent to the analysis system 16. The flow in the sampling pipe 20 is very different from the flow rate in the quilting capillary 21. In addition, in order to guarantee the circulation of the water from the sampling point 15 to the microfluidic analysis circuit 18, the pressure at the inlet the stitching capillary 21 must be sufficiently high.

A hydraulic guard 24 can then be formed on the sampling pipe 20, downstream of the inlet of the stitching capillary 21 on the sampling pipe 20, to impose a determined pressure at the inlet 25 of the stitching capillary 21. this effect, downstream of the inlet 25 of the stitching capillary 21, the sampling pipe 20 forms an S. More precisely, the stitching pipe 21 comprises, from the sampling point 15 on the conduit 101, a portion 26 substantially linear, and extending in a vertical direction. The vertical direction is taken here with reference to the natural orientation of FIG.

The terms "above" and "below" will also be used with reference to the natural orientation of FIG. 4, it being understood that in FIG. 4, in the vertical direction, the withdrawal conduit 101 is at above the microfluidic circuit 18 of the analysis system 16.

The substantially linear portion 26 of the sampling pipe 20 is extended, beyond the inlet 25 of the stitching capillary 21, by a first bend 27 at 180 °, in turn extended by a second bend 28 at 180 °. The second bend 28 then has a point 29 said high, on which is placed a vent 30, open at atmospheric pressure. A predetermined height h is defined between the high point 29 on the second bend 28 and the inlet 25 of the tapping capillary 21 on the sampling pipe 20, the high point 29 being above the inlet 25 of the capillary. The height h of the water column is then calculated to increase the pressure at the inlet 25 of the quilting capillary 21, so as to promote the passage of water to the microfluidic circuit 18 of the analysis system. 16.

The flow regulators 22, 23 may also assist in regulating the inlet pressure of the stitching capillary 21. Other means, such as diaphragms, may also be employed to assist in regulating the pressure.

Preferably, at least one heat exchanger 31 is placed between the sampling point 15 and the analysis system 16, in order to cool the withdrawn water. In fact, the water taken from the secondary circuit 4 is at a temperature that is so high that it risks damaging the equipment of the analysis system 16. Thus, a heat exchanger 31 can be placed on the sampling pipe 20, upstream of the inlet 25 of the quilting capillary 21. When steam is accidentally taken off, the heat exchanger 31 also causes the condensation of the water, so that in the analysis system 16, and more precisely in the microfluidic circuit 18, the water is in liquid form only, facilitating the flow of water in the microfluidic circuit 18, while avoiding damage to the equipment of the analysis system 16. The manipulation of the analysis system 16 by the operators is also easier.

According to a preferred embodiment, the detection device 11 comprises injection means 33 of a tracer specific probe, that is to say reacting in the presence of the tracer. More specifically, a part of the water taken from the withdrawal pipe 101 is continuously injected into the microfluidic circuit 18. The probe is also injected into the microfluidic circuit 18, where it mixes with water.

Chevrons may be formed on the channels 19 of the microfluidic circuit 18 to form a chevron mixer and promote mixing between the water and the probe. The mixture comprising water, in which the tracer is present, and the probe is then analyzed.

An embodiment of the continuous detection of the tracer by the probe is described below, wherein the probe is a fluorescent probe, i.e. it reacts with the tracer to form a mixture, or complex, capable of emitting fluorescence when excited by a source of photons. For example, when the tracer is cesium, the probe can be chosen from the components of the calixarene family. Cesium is complexed by the calixarene molecule. When the complex is excited, it then emits photons, which can be detected by an optical analysis device 39, to reveal the presence of cesium. The microfluidic circuit 18 comprises two inlets 34, 35, in this case a first inlet 34, connected to the quilting capillary 21 and through which water taken from the duct 101 is injected into the microfluidic circuit 18, and a second inlet 35 connected to the injection means 33 of the probe.

The injection means 33 of the probe may then comprise a reservoir 36 of the probe, a reservoir 37 of compressed gas, and possibly a pressure reducer 38. Upstream of the probe reservoir 36, the propellant gas is compressed in the reservoir 37 of gas, and is expanded in the expander 38 before being sent into the tank 36 probe. The probe is thus driven by the gas to be injected into the microfluidic circuit 18. A flow regulator, such as a valve 23 ', makes it possible to adjust the injected probe flow rate. Similarly, the second valve 23 mentioned above, placed on the quilting capillary 21, makes it possible to adjust the amount of water injected. Thus, the probe and the water can be injected simultaneously into the microfluidic circuit 18. It is also possible to control the relative amounts of water and probe injected into the microfluidic circuit 18. In particular, the probe flow and the flow of water injected into the analysis system 16 are regulated one against the other to obtain a mixture comprising water taken and the probe in proportions determined according to a desired sensitivity, such as the relative concentrations of probe and tracer provide the desired reaction. For example, the flow rates will be chosen so that the amount of probe injected into the microfluidic circuit 18 is substantially equal to the amount of water injected.

The length of the microfluidic circuit 18 can be chosen to ensure an effective mixture between the injected water and the probe as well as a complete reaction between the tracer and the probe, for example to form a complex. For example, the length of the microfluidic circuit 18 is ten cm (centimeter) and is of constant section. For this purpose, the channels 19 of the microfluidic circuit 18 are folded into a coil, for example to form crenellations or any other similar form. The microfluidic circuit 18 comprises, at an end opposite the two inputs 34, 35, a substantially rectilinear terminal portion, forming a measurement segment 40. The microfluidic circuit 18 makes it possible to consume only small quantities of probe, allowing continuous analysis on long periods of time without causing problems with potentially polluting discharges or high costs.

In addition, the amount of tracer used is proportional to the amount of probe, so that again thanks to the microfluidic circuit 18, the amounts of tracer consumed are low. The risks of tracer discharges into the environment are therefore less restrictive because of the small quantities.

Finally, the reaction in the channels 19 of the microfluidic circuit 18 between the probe and the tracer is faster, thanks to the effects specific to microfluidic systems.

Measurement costs are thus greatly reduced. According to one embodiment, the optical analysis device 39 comprises a first source of photons 41, possibly a second source of photons 41 'located symmetrically with the first source 41 with respect to the measurement segment 40, optical sensors 42. indicated by CAP in FIG. 5 and an analysis station 43 of the signal generated by the sensors 42. The photon source 41 is placed at the entrance of an optical fiber 44 which guides the excitation light towards the segment 40 measure. This may for example be a laser diode, emitting a coherent light beam 45 set at a wavelength adapted to excite the mixture comprising the water sampled and the probe. A light-emitting diode emitting around a wavelength corresponding to the absorption maximum of the tracer-probe complex is also suitable. For example, in the case where the tracer is cesium and the probe is a molecule of the family of calixarenes, the excitation wavelength may be 365 nm (nanometers). The collection direction of the emission of the fluorescence 46 is for example perpendicular to the direction of the excitation beam. By placing the optical sensors 42 along the substantially rectilinear measuring segment 40 of the microfluidic circuit 18, the optical sensors 42, which may for example comprise a fluorescence collecting optical fiber 46, receive the fluorescence 46, and send a signal to the Analysis station 43. Optionally, the signal passes through an amplifier 47, indicated by AM PL in FIG. 5. The analysis station 43 can then in turn transmit a signal indicating the presence or absence of a tracer.

Optionally, the analysis station 43 determines the amount of liquid L flowing in the withdrawal circuit 10 by analyzing the intensity of the fluorescence 46 of the mixture comprising the injected water and the probe. Indeed, by basing the analysis of the mixture comprising water and probe on the tracer concentration, the higher the tracer concentration in the microfluidic circuit 18, the higher the intensity of the fluorescence 46 is. Since the tracer has only been mixed in the withdrawal conduit 101 with the liquid L, by determining the concentration of tracer in the water taken, it is possible to determine the level of liquid L with respect to the vapor V in the the secondary circuit 4.

For example, to be able to determine the rate of liquid, only liquid must be taken. As described above, the sampling rate can be adjusted by means of a flow regulator 22. Thus, from the diagram of FIG. 3, the sampling rate is adjusted to be lower than the maximum flow rate Qmax, so that only liquid is removed. Then, a tracer is injected at the injection point 12, according to a known predetermined concentration and flow rate, so that the amount of tracer is a known parameter. The tracer is then diluted in the liquid L in the conduit 101, and the more liquid there is in the conduit, the greater the dilution will be important. The measurement of the concentration of tracer in the withdrawn water then makes it possible, by applying the principle of the conservation of the material, to calculate the flow of liquid in the conduit 101. According to one particular embodiment, the optical analysis device 39 comprises two photon sources 48, 49, each emitting a beam at a given wavelength: a first source 48 emits at a wavelength corresponding to the excitation wavelength of the mixture comprising the tracer and the probe, then forming for example a tracer-probe complex, a second source 49 emits at a wavelength corresponding to the excitation wavelength of the probe, or at an excitation wavelength of tracer-probe complex different from the first source 48.

For example, when the tracer is cesium introduced in salt form such as cesium iodide, and the probe is a calixarene molecule, the first source 48 can emit at a wavelength of 365 nm (nm) and the second source 49 at 310 nm (nanometer) these two wavelengths corresponding to two distinct excitation wavelengths of the complex. The two sources 48, 49 are implemented simultaneously. For example, each source 48, 49 is placed at one end of an optical fiber 44, 50 guiding the excitation light towards one of the two ends of the portion 40 of the microfluidic circuit and each emits a beam 51, 52 in the same direction, that is towards the other direction. Thus, at each instant, it is the same sample in the measurement segment 40 which receives the two beams 51, 52. The fluorescence 46 is detected as previously, for example by a bundle of optical fibers 53, indicated by OPT on the Figure 6, placed near the measurement segment. The light is converted into current in a photomultiplier 54, indicated by MULTI in FIG. 6, then in voltage in a current-voltage converter 55, indicated by IN. A synchronous detection on the voltage signal is carried out on the wavelength of the first source, for example in a first frequency filter 56, indicated by FREQ1, and likewise a synchronous detection on the voltage signal is carried out on the wavelength of the second source, for example in a second frequency filter 57, indicated by FREQ2. Synchronous detection makes it possible to detect a signal even when its intensity is very low, while minimizing the influence of noise, which manifests itself as erratic signals. A quotient of the signals resulting from the two synchronous detections is realized in a signal processing system 58, indicated by SIG, and also makes it possible to obtain a signal that is characteristic of the presence or absence of a tracer without implying the need for an internal reference. or a reference sample, facilitating continuous analysis. The excitation at two wavelengths of the fluorescence of the tracer-probe complex, then the measurement of the ratio of the fluorescence intensities relative to these two excitations, make it possible to directly obtain the tracer flow rate in the water, free from the need for a prior calibration of the measuring system. In particular, by using a first exciting el complex wavelength and a second wavelength exciting the probe, the ratiometric measurement makes it possible to overcome the influence of the concentration of the probe on the result. This so-called ratiometric measurement is therefore of great interest.

Alternatively, a fluorescent standard may be injected into the microfluidic circuit. The standard is for example a molecule different from the probe and which does not react with the tracer. In this case, the second source 49 emits at a wavelength corresponding to an excitation wavelength of the standard. The rest of the synchronous detection steps remain unchanged. Indeed, it is possible that the spectral difference as well in absorption as in fluorescence between the probe and the complex is very weak, or even non-existent. In such a case, the excitation by means of two wavelengths of the probe and the complex does not make it possible to overcome the influence of the concentration of the probe. The addition of the fluorescent standard then makes it possible to establish an internal reference for the ratiometric measurement. Such a fluorescent standard may for example be a dye such as fluorescein or rhodamine. The detection device 11 thus formed makes it possible to implement continuous monitoring of a conduit 101, and in particular of the conduit 101 of a withdrawal circuit 10, for example on the secondary circuit 3 of a nuclear power station 1. water withdrawal means in the conduit 101 allow for a continuous circulation of water from the sampling point 15 to the analysis system 16. The measurement is faster and more reliable The device 11 being easily transportable and can be bulky, it can be placed in various strategic points along the circuit 10 to monitor. The device 11 requires little staff to implement it, reducing maintenance costs.

The use of microfluidic technology in the analysis system 16 is particularly well suited to the continuous detection of liquid in the withdrawal pipe 101 of the withdrawal circuit 10, since it allows the implementation of analytical techniques in accordance with the present invention. continued. It also makes it possible to reduce the size, facilitating the implantation of the device on the industrial site of the plant 1.

Claims (20)

REVENDICATIONS1. Device for detecting (11) liquid water in a conduit (101) in which water circulates, the device (11) comprising: water sampling means (14) at a sampling point (15) of the conduit (101), an analysis system (16) of water taken from the conduit (101), for detecting a presence of liquid water, characterized in that the sampling means (14) comprise tapping means (17). ) continuous water conduit from the sampling point (15) to the analysis system (16). 2. Device (11) according to claim 1, further comprising an injector (13) of a tracer of liquid water at an injection point (12) of the duct (101), the analysis system (16) being able to detect a presence of the tracer of liquid water. 3. Device (11) according to one of claims 1 and 2, wherein the analysis system (16) comprises a microfluidic circuit (18). 4. Device (11) according to claim 3, wherein the stitching means (17) comprise a stitching capillary (21) connecting a sampling pipe (20), connected to the sampling point (15), to the system of analyzing (16) for injecting at least a portion of the water taken from the analysis system (16). 5. Device (11) according to claim 4, wherein the sampling pipe (20) comprises a so-called high point (29) on which a vent (30) is placed, the quilting capillary (21) being placed on the pipe sampling device (20) at a determined distance (h) from the high point (29) so as to form a hydraulic guard (24). 6. Device (11) according to any one of the preceding claims, comprising a flow regulator (22, 23) of water injected into the analysis system (16). 25 30 7. Device (11) according to any one of the preceding claims, comprising between the sampling point (15) and the analysis system (16) at least one heat exchanger (31, 32) adapted to cool a portion to less water taken before injection into the analysis system (16). 8. Device (11) according to any one of claims 2 to 7, wherein the liquid water tracer comprises a chemical tracer. 9. Device (11) according to any one of the preceding claims, further comprising: injection means (33) in the analysis system (16), a probe of a liquid water tracer present at the sampling point, means for mixing sampled water and the probe in the analysis system (16), means for analyzing (39) the mixture comprising sampled water and the probe. 10. Device (11) according to claim 9, comprising a regulator of the flow (23 ') of the probe injected into the analysis system (16). 11. Device (11) according to claim 9 or claim 10, wherein the probe comprises a fluorescent probe reactive with the tracer, the analysis means (39) of the mixture comprising a device for optical analysis of the fluorescence of the mixture. . 12. Device (11) according to claim 11, wherein the liquid water tracer comprises cesium, the fluorescent probe being selected from the components of the calixarene family. 13. Water withdrawal circuit (10) from a turbine body (7) of an electricity generation plant, comprising a conduit (101) for withdrawing hot water to heat food water of the plant, which circuit (10) comprises a device for the continuous detection (11) of liquid water according to one of claims 1 to 12. 14. Circuit (10) according to claim 13, wherein the bleed pipe (101) has a predetermined diameter (D), and the device (11) comprises an injector (13) of a tracer of liquid water and water sampling means (14) to be analyzed, the injector (13) and the sampling means (14) being separated by a distance function of a multiple of said predetermined diameter. A method for the continuous detection of liquid water in circulating water vapor in a conduit (101), the method comprising the following steps: / 1 / continuous sampling of water at a sampling point (12) of the conduit (101), / 2 / the continuous injection of at least a portion of the withdrawn water, into an analysis system (16), / 3 / the continuous detection of liquid water . 16. The method of claim 15, further comprising a step of continuous injection, at a point of injection (12) of the conduit (101), a tracer of liquid water, the continuous detection of water liquid comprising a continuous detection of said tracer of liquid water. 17. Method according to one of claims 15 and 16, wherein the step of continuous detection of liquid water comprises a continuous injection operation of a probe in the analysis system (16), simultaneously with the step of injecting the part of water taken. The method of claim 17, wherein the probe flow rate and the flow rate of water injected into the analysis system (16) are regulated against each other to obtain a mixture comprising water. taken and the probe in proportions determined according to a desired sensitivity. 19. The method of claim 17, wherein the probe injected into the analysis system (16) forms with the liquid water tracer a fluorescent complex, the step of continuous detection of liquid water comprising the following operations: excitation of the complex by a beam at a first wavelength and, simultaneously, excitation of the complex or probe in the analysis system (16) by a beam at a second wavelength different from the first wavelength; detecting the fluorescence of the excited complex as a voltage signal; synchronous detection on the voltage signal for the first wavelength; synchronous detection on the voltage signal for the second wavelength; the ratiometric measurement of the two signals resulting from the synchronous detections; the ratiometric measurement being defined as the quotient between the two signals resulting from the two synchronous detections. 20. The method of claim 17, wherein the probe injected into the analysis system (16) forms with the liquid water tracer a fluorescent complex, the step of continuous detection of liquid water comprising the following operations: injecting a fluorescent standard distinct from the probe into the analysis system (16), exciting the complex in the analysis system (16) with a beam at a first wavelength and, simultaneously, exciting the etalon in the analysis system (16) with a beam at a second wavelength different from the first wavelength; detecting the fluorescence of the excited complex and the fluorescence of the standard in the form of a voltage signal; synchronous detection on the voltage signal for the first wavelength; synchronous detection on the signal in voltage for the second wavelength: the ratiometric measurement on the two signals resulting from the synchronous detections; the ratiometric measurement being defined as the quotient between the two signals resulting from the two synchronous detections.