(AC) METHOD AND SYSTEM FOR DETERMINING THE RELATIVE CONCENTRATION OF A SUBSTANCE IN A MIXTURE BY MEASURING DYNAMIC SENSITIVITY

Abstract

The present invention relates to a method for measuring the relative concentration of materials in a mixture, comprising the steps of: a / providing an emission coil (2) and at least one receiving coil (3.1, 3.2); b / providing a coil with different magnetic susceptibilities (χ1, χ2, ..χ n c / providing a mixture (P, E) containing n materials having a magnetic field P, E, c / introducing the mixture into a receiving coil, d / using a voltage generator to supply at least one non-zero excitation frequency to an emitting coil to generate an excitation field, e / measuring a signal of a voltage induced in the receiving coil, and f / determining the relative concentrations of the n materials based on a comparison of the overall magnetic susceptibility of the mixture obtained via the voltage measurement in step e / with the overall magnetic susceptibility of a reference mixture in which the relative concentrations of the n materials are known. The invention also relates to a related system.

Description

[Technical field]

[0001] The present invention relates to the field of measuring the concentration of materials in mixtures, especially binary mixtures.

[0002] The present invention primarily aims to optimize this type of measurement by proposing a compact, reliable, fast and non-destructive solution that allows integration in particularly restrictive environments in terms of available space and / or in continuous production lines.

[0003] Although described with reference to measuring the relative contents of plutonium (Pu) and uranium (U) and associated oxides in the form of MOX fuel powder or pellets, the invention applies to measuring the relative mass proportions of solid materials, each solid material having a given magnetic susceptibility of a binary mixture, or more generally to any measurement of any mixture of materials, possibly non-binary materials, each material having a given magnetic susceptibility.

[0004] As another example, the invention applies in the case of solid materials and / or mixtures containing impurities (of ferromagnetic or metallic type) whose magnetic susceptibility has a magnetic susceptibility signature that is much higher (at least an order of magnitude higher) than the magnetic susceptibility of the other components, despite their low concentration in the mixture. [Background technology]

[0005] The production of new MOX ("mixed oxide fuel") type nuclear fuel pellets involves a process that includes the successive steps of mixing, pressing, and sintering UO2 and Pu2 dioxide powders. The mixture can optionally be assisted by chamotte (pellet manufacturing scrap).

[0006] The resulting MOX fuel pellets can be irradiated, for example, in a light water reactor (or LWR) or a fast neutron reactor (or FNR).

[0007] The reproducibility of the plutonium or uranium composition of the pellets is one of the major manufacturing limitations, and it is therefore considered important that the composition for each production batch is systematically known.

[0008] More specifically, there is a need to know the relative mass concentrations, or in other words the relative mass fractions, of Pu and U oxides and related oxides, especially in the MOX pellets coming off the production line. This knowledge must be able to be provided from an analytical laboratory or from a small device installed in the nuclear glove box or on the continuous production line.

[0009] The currently implemented solutions for determining the relative concentrations are methods that require extensive chemical analysis of the pellets.

[0010] Chemical analyses, although precise and selective, are destructive, tedious, generally take hours / days to produce results, cannot be applied very systematically and require sampling from the production line, thereby limiting statistics on production batches.

[0011] Spectroscopic solutions have also been proposed, but these suffer from the same drawbacks as chemical analysis.

[0012] Another solution involving magnetic measurements (VSM (Vibrating Sample Magnetometry)) has also been proposed. This solution involves measuring the magnetic moment of a pellet sample under a static and variable high-value magnetic field, typically above 1 Tesla. This standard experimental technique requires the implementation of large electromagnets or superconducting magnets. As a result, it is practically impossible to introduce superconducting magnets inside a glove box or on a nuclear production line, making such a VSM measurement solution prohibitive.

[0013] Thus, there is a need to improve solutions for measuring the mass concentration of materials in mixtures, particularly binary mixtures, particularly with regard to space requirements so that objects such as MOX fuel pellets can be installed in restrictive environments, such as nuclear environments, and / or on continuous production lines. Summary of the Invention [Problem to be solved by the invention]

[0014] It is an object of the present invention to at least partially address this need. [Means for solving the problem]

[0015] To this end, the present invention relates to a method for measuring the relative concentrations of ingredients of a mixture, comprising, according to one of its aspects, a / providing an emission coil and at least one receiving coil; b / Different magnetic susceptibilities (χ1, χ2, ..χ n providing a mixture comprising n materials, c / introducing the mixture into a receiving coil; d / using a voltage generator to supply at least one non-zero excitation frequency to an emission coil so as to generate an excitation magnetic field; e / measuring the signal of the voltage induced in at least one receiving coil; f) determining the relative concentrations of the n ingredients based on a comparison of the overall magnetic susceptibility of the mixture obtained by the voltage measurement according to step e) with the overall magnetic susceptibility of a reference mixture in which the relative concentrations of the n ingredients are known; The present invention relates to a method comprising the steps of:

[0016] According to an advantageous embodiment, when n=2, the method comprises in step f) determining the magnetic susceptibility of the mixture provided, based on the mass of the mixture m(mix)=ml+m2, using the following relationship:

[0017]

number

[0018] Recognizing the various magnetic susceptibilities (χ1, χ2), the following relationship is obtained:

[0019]

number

[0020] and

[0021]

number

[0022] and determining the mass concentration of each of the materials using the method.

[0023] According to an advantageous alternative embodiment, the method further comprises, in step e / , either an in-phase and / or a phase quadrature measurement of the signal of the voltage induced in the at least one receiving coil so as to obtain an absolute value of the signal.

[0024] Advantageously, the receive coil is tuned so that its resonant frequency is substantially equal to at least one excitation frequency.

[0025] The mixture provided according to step b / may be a binary mixture of materials having two different magnetic susceptibilities (χ1, χ2).

[0026] According to an advantageous embodiment, the method comprises, after step b), a step b1 / of weighing the mixture so as to obtain the relative mass concentrations of said mixture in step f).

[0027] The mixture provided according to step b / may be a mixture comprising three or more materials, one of which has a magnetic susceptibility much higher than that of the other materials. The other materials may be ferromagnetic or metallic impurities, etc. The invention thus makes it possible to measure the magnetic susceptibility of a component, provided that this component has a magnetic susceptibility much higher than that of the other materials, for example 100 times higher, despite being in a low concentration compared to the other components of the mixture.

[0028] Indeed, in this case the magnetic susceptibility of the mixture is given by the following equation, which has the masses and magnetic susceptibilities of each of the n materials of the mixture:

[0029]

number

[0030] If one of the materials (in this case mass m1 and magnetic susceptibility χ1) has a magnetic susceptibility much higher than that of the other material, this simplifies to:

[0031]

number

[0032] According to a preferred application, the mixture provided according to step b / may be in the form of a solid compound. The term "solid compound" is understood herein to mean, within the scope of the present invention, equally small pellets and powders or any other solid structure.

[0033] According to an advantageous alternative embodiment, step d / comprises applying a given voltage by varying the excitation frequency.

[0034] Preferably, the excitation frequency is higher than 10 kHz, preferably higher than 100 kHz, preferably in the range 100 kHz to 250 kHz.

[0035] According to a first configuration, step a / includes providing a single receiving coil, and the method further includes, before step c / , performing steps e / and f / to obtain a basic signal representative of an empty single receiving coil.

[0036] Alternatively, step a / comprises providing two, preferably identical, receiving coils and the method comprises repeating steps c / to e / with each of the two receiving coils and an additional step e1 / of subtracting the signals induced by the two coils between the two measurements, before step f / .

[0037] According to this alternative embodiment, the method advantageously comprises electrically connecting two receive coils in series, preferably assembled with counter-windings, and tuning the receive frequency of each of the receive coils, which makes it possible to improve the output signal-to-noise ratio and to increase the output signal, the measurement being centered around the resonant frequency of the receive coil.

[0038] Preferably, step e / is performed using synchronous detection for each excitation frequency.

[0039] More preferably, step e / consists of several measurements, each measurement being performed at a receiving frequency centered on the resonant frequency of one or more detection coils. Advantageously, step d / is performed to generate an excitation magnetic field having a value lower than 50 mT, preferably in the range of 1 mT to 20 mT. This low magnetic field brings the advantage that no large coils need to be generated, whereby the acquisition part of the system is compact and therefore fits into limited space requirements.

[0040] According to an advantageous embodiment, when the mixture comprises a ferromagnetic material, the method comprises, before step c / , an additional step b2 / which comprises exposing the mixture to a constant magnetic field.

[0041] A further object of the invention is a system for measuring the relative concentrations of ingredients of a mixture, intended to implement the method described above, comprising: a voltage generator for providing at least one frequency, referred to as the excitation frequency; an emission coil connected to the generator; at least one receiving coil whose shape is adapted to receive a mixture containing at least two materials having different magnetic susceptibilities and whose receiving frequency is tuned to at least one excitation frequency; a voltage measuring means connected to one or more receiving coils; The system includes:

[0042] Preferably, the generator is a variable frequency low frequency generator (LFG). Preferably, the generator is configured such that the excitation frequency is higher than 10 kHz, preferably higher than 100 kHz, preferably in the range 100 kHz to 250 kHz.

[0043] Generally, 1 / 10 to 10 millimu.mol -1 For a mixture of oxides with a magnetic susceptibility of about 100 kHz, the frequency range can be in the range of 100 to 250 kHz.

[0044] It should be noted that the frequency is selected according to the coil design, independent of the value of the magnetic susceptibility, and therefore the system according to the invention does not need to be tuned to the type of material, but rather to the dimensions of the sample being analyzed.

[0045] According to an alternative configuration, the system comprises two receiving coils electrically connected in series, the receiving frequencies of each of the receiving coils being adjusted.

[0046] According to an alternative configuration, the receiving coil or coils are arranged inside the excitation coil, so that the acquisition part of the system (the associated emission coil and receiving coil in electrical connection) is compact.

[0047] According to an advantageous embodiment, the system comprises: A housing for electromagnetic protection; a first connector mounted within the housing and connected to the emission coil by a first power supply wire inside the housing, the first connector intended to be remotely connected to the generator by a first power supply cable; and a second connector mounted in the housing and connected to the at least one receiving coil by a second power supply wiring inside the housing, the second connector intended to be remotely connected to the measurement means by a second power supply cable. Such an arrangement facilitates the integration of the system in restrictive environments, in particular nuclear environments such as glove boxes, in particular by limiting the interface cables between the housing containing the measurement acquisition (coils) and the measurement electronics part, without the need for the measurement electronics part and the power supply generator to be located in the nuclear environment.

[0048] Furthermore, this allows the measurement electronics and power generator to be remotely located outside the radiation emitting environment by means of an interface cable in the housing, so that the measurement acquisition part (coil) is not affected by radiation.

[0049] According to an advantageous alternative embodiment, the measuring means comprise a synchronous detection amplifier.

[0050] According to an advantageous configuration, the one or more receiving coils are arranged coaxially inside the discharging coil by defining in the receiving coil a passage for a portion of a conveyor adapted to move the mixture in the form of a solid product such as pellets. The conveyor may be manual or motorized.

[0051] Preferably, the system comprises two, preferably identical, receiving coils spaced one behind the other and positioned relative to the emitting coil so as to carry out three successive measurements when the solid product moved by the conveyor is located outside the receiving coils, when it is located within one of the receiving coils, and then when it is located within the other of the receiving coils.

[0052] Advantageously, the part of the conveyor passing through the receiving coil is a motorized conveyor band or belt. Thus, easy integration in production lines is possible, in particular for solid objects containing binary mixtures of materials with different magnetic susceptibilities. This can be intended for a line for producing MOX nuclear fuel pellets.

[0053] Finally, an object of the invention is the application of the method or system described above for measuring the relative mass concentrations of plutonium (Pu) and uranium (U) and associated oxides in MOX type nuclear fuel pellets. The invention also applies in the field of nuclear fuel cycles of UOX pellets (for impurities). The invention is also applicable to the detection of metal type impurities in MOX.

[0054] Thus, the invention basically involves measuring the relative concentration, either in percentage or mass units, of any complex mixture of two or more paramagnetic materials by weighing the mixture with a system having an emitting (magnetic excitation) coil and a receiving coil to measure the overall magnetic susceptibility (χmix) of the mixture and comparing it with a calibrated mixture of the same materials with known weight and mass concentrations.

[0055] Thus, according to the invention, the quantity measured is the magnetic susceptibility of the mixture with a fixed or variable frequency measurement and a magnetic field with a roughly fixed amplitude, typically a low amplitude of a few mT. This weak magnetic field is generated by a coil system that is simple to implement and compact.

[0056] An additional measurement of the weight of the mixture may be performed.

[0057] Thus, if the magnetic susceptibilities of the two materials in a binary mixture are χ1 and χ2 respectively, and the mass of the mixture m(mix) = m1 + m2, the magnetic susceptibility of the mixture is given by the following relation:

[0058]

number

[0059] This means that once χ1 and χ2 are known, based on tables or measurements of the pure compounds,

[0060]

number

[0061] and

[0062]

number

[0063] This means that it is possible to estimate

[0064] Therefore, based on these non-invasive measurements and comparison to known standards, the composition of the mixture can be known.

[0065] For a known standard, a weight and a reference signal are pre-established.

[0066] The reference signal is either known from tables, literature etc. or from a conventional calibration measurement with the measurement system according to the invention. Thus, in general, for MOX pellets, a calibration with pure PuO2 and UO2 pellets can be carried out beforehand to obtain the reference signal.

[0067] The inventors have carefully considered using the difference in magnetic susceptibility values ​​of the paramagnetic materials in a mixture to estimate the relative mass proportions of the paramagnetic materials using dynamic magnetic susceptibility measurements.

[0068] Dynamic susceptibility measurements, often referred to as AC susceptibility, are less developed but have already been described in several papers.

[0069] Therefore, publication [1] proposes a system for measuring AC susceptibility covering a wide temperature range. In this regard, reference [2] proposes a two-coil susceptometer operating from 100 Hz to 100 kHz.

[0070] A dynamic (AC) magnetic susceptibility measurement system is commercially available from Quantum Design.

[0071] These various systems operate over a wide frequency band, making it possible to obtain susceptibility values ​​in typical times of one minute for a given frequency.

[0072] Generally, known systems are interested in measuring the change in magnetic susceptibility as a function of an external parameter, such as temperature or pressure, in order to feed back information, such as the phase transitions, of a given material.

[0073] Surprisingly, however, it has never been considered to use dynamic (AC) susceptibility measurements to measure the ratio of mass concentrations of a mixture containing two or more materials with different magnetic susceptibilities.

[0074] According to a preferred application, the measurements are carried out to know the relative mass concentrations in the MOX fuel pellets, and the two oxides of interest have different magnetic susceptibility values, and according to the literature [3], the value χ for UO2 is 3.0.10 -3 emu.mol -1 while the value of PuO2 is 0.4.10 -3 emu.mol -1 is equal to.

[0075] Finally, the present invention provides a number of advantages, including: Much faster measurements than prior art measurement, chemical, or spectroscopic solutions. In general, for AC susceptibility measurements according to the present invention, measurement times per MOX fuel pellet can be on the order of a few seconds. Measurements are no longer carried out by taking a few samples from a production batch as in the prior art, but can be carried out systematically on each mixture produced, and in particular on each nuclear fuel pellet during production. Due to the small dimensions of the equipment and the measurement acquisition part (the housing and the coils contained therein), the measurement system according to the invention can be more easily adapted to the nuclear environment compared to prior art solutions, in particular magnetic measurement systems (VSM). A measuring system that can be easily integrated into continuous production lines for products containing mixtures of materials, e.g. pellet production / / conveying lines. The measurement method and system can be used for any complex mixture of at least two different paramagnetic or ferromagnetic materials. Unlike prior art solutions, the homogeneity of the mixture can be known based on the analysis of the shape of the measurement signal.

[0076] Further advantages and features of the invention will become more apparent upon reading the detailed description of embodiments thereof, given by way of non-limiting example with reference to the following figures: [Brief description of the drawings]

[0077] [Figure 1] FIG. 1 is a schematic perspective view of a system for measuring the relative mass concentrations of two ingredients of a binary mixture in the form of solid pellets according to the present invention. [Diagram 2] 1 is a photographic view of an example of a system according to the present invention in which a portion of a connector is implemented according to the present invention. [Figure 3A] FIG. 13 shows, by means of curves, in-phase measurements for various paramagnetic components in a system according to the invention in which the receive coil frequency is tuned to the excitation frequency. [Figure 3B] Similar to FIG. 3A, this figure illustrates, using curves, orthogonal measurements for various paramagnetic components. [Figure 4]FIG. 2 shows, by means of curves, examples of measurements of samples with variable concentrations of a binary mixture in the form of solid pellets, the measurements being obtained according to the invention. [Diagram 5] FIG. 1 is a perspective view of a measurement system according to one embodiment of the present invention an integral part of a motorized conveyor system. [Figure 6] FIG. 6 is a cross-sectional view of the system according to FIG. [Figure 7A] FIG. 2 is a schematic diagram showing the conventional steps of magnetizing a ferromagnetic product according to an alternative embodiment of the measurement method according to the invention; [Figure 7B] FIG. 7B is a schematic diagram illustrating the steps of introducing the magnetized product according to FIG. 7A into a receiving coil for carrying out a measurement method according to the invention; [Figure 8] 1 shows graphically the measurements of the maximum absolute value of magnetic susceptibility for a sample comprising carbon nanotubes in a non-ferromagnetic matrix, obtained by the method according to the invention as a function of the magnetic moment of said sample measured using VSM. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Throughout this application, the terms "lower", "upper", "bottom", "top", "lower" and "above" are understood with reference to the housing.

[0079] 1 and 2 show an example of a device 1 forming the acquisition part of a system for measuring the mass concentration of Pu and U oxides in MOX fuel pellets by magnetic susceptibility.

[0080] The device 1 firstly comprises a housing 10, preferably for electromagnetic protection, which accommodates an emission coil (excitation) 2 and two receiving coils 3.1, 3.2, which are preferably identical and mounted electrically in series. The excitation coil 2 and the receiving coils 3.1, 3.2 in this case are arranged in the same plane. The coils are preferably counter-wound so that the emission field provides as weak a signal as possible in the receiving coils.

[0081] In the illustrated example, the emission coil 2 is in the form of a frame housing the receiving coils 3.1, 3.2, each of which is in the form of a hollow cylinder. The diameter and height of the cylinders are typically selected to accommodate pellets P of MOX fuel within the cylinders. In general, the lateral dimensions of the housing 10 may typically be on the order of 5 to 10 times the diameter of the pellets P. The housing 10 may therefore be lightweight and quite compact, thereby enabling it to be easily transported and positioned in quite restrictive environments such as a glove box.

[0082] Since the desired excitation magnetic field may be on the order of a few mT, typically 1-20 mT, the dimensions of the excitation coil 2 may be reduced.

[0083] A first connector 4 is attached to the housing 10 and is connected inside the housing to the emitting coil 2 by a first power supply wire 40. This first connector 4 is remotely connected to a low frequency generator 6 by a first power supply cable 41.

[0084] A second connector 5 is mounted on the housing 10 and is connected inside the housing to the receive coils 3.1, 3.2 by a second power supply wire 50. This second connector 5 is remotely connected to the synchronous detection amplifier 7 by a second power supply cable 51.

[0085] The housing 10 is therefore compact and contains the entire measurement acquisition part of the system (coils 2, 3.1, 3.2) and associated connectors, the low frequency generator 6 and the amplifier 7 are remote with respect to the environment in which the housing is placed, so that if the environment is irradiated, the signal generation and signal processing parts are not affected, i.e. are protected from the radiation.

[0086] We now describe a method for measuring the relative mass concentrations of ingredients of a binary mixture in the form of solid pellets, implemented in accordance with the invention, in particular by the system described above.

[0087] Step a / : The device 1 according to figures 1 and 2 is installed by connecting the electrical connections respectively to a low frequency generator 6 and to a synchronous detection amplifier.

[0088] The two receiving coils 3.1, 3.2 are placed in parallel with a capacitor whose value is chosen so that the resonance of this LC circuit is between 50 kHz and 200 kHz. For small pellets, frequencies up to a few MHz can be chosen.

[0089] Step b / : A sample of MOX fuel solid pellets P is provided for assessing the respective mass concentrations of PuOx and UOx.

[0090] Step b1 / : The pellets P are weighed. This step can usually be carried out using a conventional weighing scale.

[0091] Step c / : As shown in FIG. 1, a pellet P is introduced into the first receiving coil 3.1 and then into the second receiving coil 3.2.

[0092] Step d / : The emission coil 2 is powered by a low frequency generator 6 with a variable non-zero excitation frequency so as to generate an excitation magnetic field in the coil 2. The power supply can be interrupted when the pellet P transitions from the first receiving coil to the second receiving coil.

[0093] The excitation of the excitation coil 2 is therefore performed by applying a given voltage, typically a few volts, and varying the frequency, typically up to a few hundreds of Khz or even several MHz.

[0094] Step e / : The signal of the voltage induced in the receiving coil 3.1 and the signal of the voltage in the receiving coil 3.2 are measured in phase and in quadrature at each excitation frequency.

[0095] The voltages measured at the terminals of the two coils 3.1, 3.2 are advantageously subtracted and then amplified by a synchronous detection amplifier 7.

[0096] In the absence of the pellet P, the signal obtained at the output of the two coils 3.1, 3.2 to which the excitation field is applied is zero or balanced to be close to zero. The value of the signal can be known to be equal to V0.

[0097] Making the measurement by the difference between the signals emitted by the two receiving coils means that it is possible to eliminate any offset added to the value V0, and therefore the traditional no-load measurement becomes unnecessary.

[0098] When the pellet P is present in the first receiving coil 3.1, the received signal takes the value V1=V0+dV, and when the pellet P is in the second coil 3.2, the value of the signal is V2=V0-dV.

[0099] Therefore, the difference is V1-V2=2dV, where dV is proportional to the complex susceptibility of the pellet P.

[0100] At each measurement frequency point, the output signal measured by the amplifier 7 provides access to the in-phase and quadrature signals relative to the excitation signal at the measured frequency.

[0101] Typically, measurements may be performed at 1 to 20 frequency points centered around the resonant frequency of detection.

[0102] The in-phase and quadrature signals provide information about the complex susceptibility of the pellet at the measurement frequency (real X and Y imaginary components: χ=X+iY). When the method of the invention measures only the in-phase signal, the measurement obtained is proportional to the real part of the susceptibility, when the method of the invention measures the in-phase and quadrature signals, the measurement obtained allows access to the real and imaginary components and therefore to the absolute value.

[0103] Examples of in-phase and quadrature measurements on various paramagnetic materials in a system 1 according to the invention, with the receiving frequency tuned around 180 kHz, are shown in FIGS. 3A and 3B.

[0104] The various materials tested are dysprosium oxide, which has the chemical formula Dy2O3, neodymium oxide, which has the chemical formula Nd2O3, and yttrium oxide, which has the chemical formula Y2O3.

[0105] Step f / :

[0106] Based on a frequency scan over a possible range of excitation frequencies, it is possible to extract the absolute value M and the integral I from these measurements over said frequency range according to the following formulas:

[0107]

number

[0108]

number

[0109] These absolute and integral values ​​then make it possible to quantitatively compare the sample (pellet) considered against a reference sample in which the relative mass concentrations of the two materials are known.

[0110] Comparing the mass between the measured sample and a reference sample ultimately determines the mass concentrations of the two materials in the sample.

[0111] Generally, for MOX pellets P, a comparison is established on a mass basis to pure pellets of PuO2 and UO2.

[0112] Figure 4 shows the measurements of samples with variable concentrations of a mixture of two materials with different magnetic susceptibilities, obtained according to the method described above. It should be noted that in Figure 4 the abscissa represents the concentration in % and the ordinate represents the integral (in arbitrary units) of the signal detected by amplifier 7.

[0113] 5 and 6 show an alternative device to that shown in FIGS.

[0114] In this device, the receiving coils 3.1, 3.2 are arranged coaxially inside the discharging coil 2 by defining in the receiving coils 3.1, 3.2 a passage 30 for a portion of a conveyor 8 having a band 80, the band 80 being adapted to move the mixture in the form of a solid product such as pellets.

[0115] More specifically, the conveyor 8 comprises a frame 81 supporting an electromagnetically shielded housing 10 formed by an outer cylinder and an inner cylinder 82 separated by a spacer 83 and defining on the inside a passage 30 for the pellets to be measured.

[0116] The excitation coil 2 is arranged between a spacer 83 and an outer cylinder 10 in the form of a coaxial cylinder.

[0117] Two receiving coils 3.1, 3.2, each in the form of a coaxial cylinder, are arranged at a distance from one another between a spacer 83 and an inner cylinder 82.

[0118] This device makes it possible to automatically transport the sample to be measured from a first receiving coil 3.1 to a next receiving coil 3.2.

[0119] The sample is transported along the excitation cylinder 2 from the first coil to the second coil by moving a conveyor band or belt 80, either manually or by a motorized system.

[0120] Transporting the sample makes it possible to reach three measurement positions, namely an empty position where the sample is not in any receiving coil, a position where the sample is in the first receiving coil 3.1 and then a position where the sample is in the second receiving coil 3.2.

[0121] For the measurement, the sample preferably moves at a constant speed through each of the two receiving coils 3.1, 3.2, which has the advantage that the speed of the production line is not slowed down much, if at all.

[0122] To increase the measurement speed, measurements can be performed at several discontinuous frequencies, typically three measurements can be performed simultaneously. To make measurements much faster than this, a single frequency is used and the signal is measured at only one of the receiving coils 3.1, 3.2.

[0123] In fact, it is easy to send a single frequency and measure the response of the sample at this frequency by synchronous detection. For example, it is also possible to send three frequencies simultaneously using a random frequency generator and measure at these three frequencies by detection using three synchronous modulators. This allows, by adjustment, to reconstruct the frequency response of the system into a single measurement instead of performing measurements at different frequencies one after the other.

[0124] Of course, it is also possible to increase or decrease the number of frequencies simultaneously, for example by two or four or more.

[0125] When the sample is centered on the cylinder of the receiving coil, ie, the central plane of the sample substantially coincides with the central plane of the coil, the received signal is maximized and depends on the concentration ratio of the materials in the sample.

[0126] If the sample path is continuous, repeated measurements can be performed to determine the signal when the sample is in the center of the receive coil and corresponds to a maximum in the received signal.

[0127] Based on the independent mass measurement performed in addition to the measurement of the maximum acquired signal, the ratio of mass concentrations of materials in the sample is determined, as explained above.

[0128] The methods and systems described above may be implemented on ferromagnetic samples.

[0129] In this case, an additional step b2 / is performed which involves exposing the sample to a constant magnetic field.

[0130] This is shown in FIG. 7A, where a sample E is pre-magnetized by a permanent magnet and then introduced into the first receiving coil 3.1 as in FIG.

[0131] The above mentioned measurement steps d / and e / are then carried out.

[0132] The inventors carried out absolute measurements of the complex magnetic susceptibility M of various samples, each containing a variable amount of carbon nanotubes. Carbon nanotubes are known for the ferromagnetic signature of the iron used in their synthesis in a non-ferromagnetic matrix. The inventors compared the results obtained with the magnetic moment measured using VSM.

[0133] The comparison result is shown in FIG. 8, where the maximum absolute value (on the ordinate) measured by the method according to the invention is a function of the magnetic moment measured using the VSM (on the abscissa), and the maximum absolute value (M max / norm) and magnetic moment (Moment norm.) are normalized by the respective mass of the samples. In this Figure 8, squares represent samples with carbon nanotube concentrations close to 0.5% by mass, diamonds represent samples with carbon nanotube concentrations close to 1.0% by mass, and triangles represent samples with carbon nanotube concentrations close to 2.0% by mass.

[0134] As can be seen in Figure 8, there is indeed a linear relationship between the maximum absolute value and the magnetic moment. Thus, the absolute value, or sometimes the integral, measurement of the magnetic susceptibility is actually proportional to the amount of ferromagnetic material.

[0135] The invention is not limited to the examples described above, but in particular it is possible to combine features of the examples shown in alternative embodiments not shown.

[0136] Other alternatives and modifications may be envisaged without departing from the scope of the invention.

[0137] Several configurations and arrangements of coils other than those shown in the various figures may be envisioned, particularly for less restrictive environments with respect to space requirements and / or non-nuclear power.

[0138] The method according to the invention operates with a single receiving coil, in which case a conventional unloaded measurement can be performed to obtain a basic signal corresponding to a deviation less than V0.

[0139] Instead of using a synchronous detection amplifier, it is possible to consider measuring the signal of each of the receiving coils with sufficient accuracy and to distinguish the signals of the receiving coils only in digital form.

[0140] (References) [1]:Review of Scientific Instruments 60, 113(1989); https: / / doi.org / 10.1063 / 1.1140593. [2]:Review of Scientific Instruments 84, 125105(2013); https: / / doi.org / 10.1063 / 1.4842255. [3]:”MAGNETIC SUSCEPTIBILITY OF THE ELEMENTS AND INORGANIC COMPOUNDS”; http: / www.fizika.si / magnetism / MagSusceptibilities.pdf. [Explanation of symbols]

[0141] 1 Devices, Systems 2 Emission coil, excitation coil 3.1, 3.2 Receiving coil 4 First Connector 5 Second Connector 6. Low Frequency Generator 7 Synchronous Detector Amplifier 8 Conveyor 10. Housing 30 Passage 40 First power supply wiring 41 First power cable 50 Second power supply wiring 51 Second power cable 80 Bands, Belts 81 Frames 82 Inner Cylinder 83 Spacer χ1, χ2 Magnetic susceptibility

Claims

1. 1. A method for measuring the relative concentrations of ingredients of a mixture, comprising: a / providing an emission coil (2) and at least one receiving coil (3.1, 3.2); b / Different magnetic susceptibilities (χ1, χ2, ..χ ｎ providing a mixture (P, E) containing n materials having a matrix of n, c / introducing said mixture into said at least one receiving coil; d / using a voltage generator to supply at least one non-zero excitation frequency to the emission coil so as to generate an excitation magnetic field, the step including applying a given voltage by varying the at least one excitation frequency; e / measuring the signal of the voltage induced in the at least one receiving coil; f) determining the relative concentrations of the n materials based on a comparison of the overall magnetic susceptibility of the mixture obtained by the voltage measurement according to step e) with the overall magnetic susceptibility of a reference mixture in which the relative concentrations of the n materials are known; A method comprising:

2. 2. The method of claim 1, wherein the mixture provided according to step b / is a binary mixture of materials having two different magnetic susceptibilities (χ1, χ2).

3. 2. The method of claim 1, wherein the mixture provided according to step b / is a mixture comprising three or more materials, one of the materials having a magnetic susceptibility 100 times higher than the magnetic susceptibility of the other materials.

4. 4. The method according to claim 1, further comprising, after step b), a step b1 / , in step f), weighing the mixture so as to obtain the relative mass concentration of the mixture.

5. In step f), based on the mass m(mix)=m1+m2 of the mixture obtained according to step b1 / , determining the magnetic susceptibility of the mixture provided using the following relationship: [0010] Recognizing the various magnetic susceptibilities (χ1, χ2), the following relationship is obtained: [0025] and [0030] and determining the mass concentration of each of the materials using a method according to claim 2 in combination with claim 4.

6. 6. The method according to claim 1, further comprising in-phase and / or phase quadrature measurements of the signal of the voltage induced in the at least one receiving coil so as to obtain an absolute value of the signal.

7. 7. The method of claim 1, wherein the receiving coil is tuned such that its resonant frequency is substantially equal to at least one excitation frequency.

8. 8. The method according to claim 1, wherein the mixture provided according to step b / is in the form of a solid compound.

9. 9. The measurement method according to claim 1, wherein step a / comprises providing a single receiving coil, and the method further comprises, before step c / , performing steps d / and e / to obtain a basic signal representative of the empty single receiving coil.

10. 9. A method according to any one of claims 1 to 8, wherein step a / comprises providing two, preferably identical, receiving coils, the method comprising repeating steps c / to e / with each of the two receiving coils and an additional step e1 / of subtracting the signals induced by the two coils between the two measurements, before step f / .

11. The measurement method according to claim 10, further comprising: electrically connecting the two receiving coils in series; and adjusting a receiving frequency of each of the receiving coils.

12. 12. A measuring method according to claim 1, wherein step e / is performed using synchronous detection for each excitation frequency.

13. 13. The measurement method according to claim 1, wherein step e / consists of several measurements, each measurement being performed at a reception frequency centred on the resonant frequency of the detection coil or coils.

14. A method according to any one of the preceding claims, wherein step d / is performed to generate an excitation magnetic field having a value lower than 50 mT, preferably in the range of 1 mT to 20 mT.

15. 15. The method of claim 1, wherein if the mixture comprises a ferromagnetic material, the method comprises, before step c / , an additional step b2 / comprising exposing the mixture to a constant magnetic field.

16. A system (1) for measuring the relative concentrations of n ingredients of a mixture, intended to implement the method according to any one of claims 1 to 15, comprising: a voltage generator (6) for generating at least one frequency, called the excitation frequency, the voltage generator (6) being a variable frequency low frequency generator (LFG); an emission coil (2) connected to the generator; at least one receiving coil (3.1, 3.2) whose shape is adapted to receive a mixture containing n materials with different magnetic susceptibilities, said receiving frequency being tuned to at least one excitation frequency; voltage measuring means (7) connected to said one or more receiving coils; A system comprising:

17. 17. The system of claim 16, comprising two receive coils electrically connected in series, the receive frequency of each of the receive coils being tuned.

18. 18. The system of claim 16, wherein the one or more receive coils are disposed inside the excitation coil.

19. a housing (10), preferably for electromagnetic protection; a first connector (4) mounted within the housing and connected to the emission coil by a first power supply wire (40) inside the housing, the first connector (4) intended to be remotely connected to the generator by a first power supply cable (41); 19. The system (1) according to any one of claims 16 to 18, further comprising a second connector (5) mounted in the housing and connected to at least one receiving coil by a second power supply wiring (50) inside the housing, the second connector (5) intended to be remotely connected to the measuring means by a second power supply cable (51).

20. 20. A system according to any one of claims 16 to 19, wherein the measuring means comprises a synchronous detection amplifier.

21. 21. The system of claim 16, wherein the one or more receiving coils are arranged coaxially inside the discharging coil by defining a passage in the receiving coil for a portion of a conveyor adapted to move the mixture in the form of a solid product such as pellets.

22. 22. The system of claim 21, comprising two, preferably identical, receiving coils spaced one behind the other and positioned relative to the emitting coil so as to perform three successive measurements when the solid product moved by the conveyor is located outside the receiving coils, when it is located within one of the receiving coils, and then when it is located within the other of the receiving coils.

23. 23. The system of claim 21 or 22, wherein the portion of the conveyor that passes the receiving coil is a band or belt of a motorized conveyor.

24. Application of the method according to any one of claims 1 to 15 and the system according to any one of claims 16 to 23 for measuring the relative mass concentrations of plutonium (Pu) and uranium (U) and associated oxides in MOX type nuclear fuel pellets.

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