Raman spectrometry quantification method

Abstract

Method for quantification by Raman spectrometry This method comprises a step (242) of determining a partial pressure P(λ)c of a gaseous component, inside a containment enclosure of a nuclear reactor, corrected for a radio-induced attenuation using the following relation: P(λ)c = K*(A(λe1) / A(λ))*(r(λ) / r(λe1))*T, where: - K is a predetermined constant, - A(λe1) is a value of a radio-induced attenuation coefficient at the wavelength λe1, this value A(λe1) being equal to a ratio between raw values ​​representative of the amplitude of a Raman line produced by a standard in the presence and absence of radio-induced attenuation, - A(λ) is a value of the radio-induced attenuation coefficient at the wavelength λ, this value A(λ) being equal to a ratio between raw values ​​representative of the amplitude of a Raman line produced by the gaseous component in the presence and absence of radio-induced attenuation,and - T is the measured temperature of the gaseous component. Fig. 5,

Description

Title of the invention: Method of quantification by Raman spectrometry

[0001] The invention relates to a method and a device for quantifying, by Raman spectrometry, at least one gaseous component inside a containment enclosure of a nuclear reactor. The invention also relates to a probe for producing this quantification device.

[0002] For example, such a quantification device is used to measure the concentrations of gaseous components in a gaseous medium located inside the containment of a nuclear power plant. In this case, the containment is known as the "reactor building" (RB). Indeed, nuclear power plants used for the production of electrical energy comprise, inside a reactor building, a vessel containing the core of the nuclear reactor which can be cooled, inside the vessel, by pressurized or boiling light water or by heavy water. In the case of a nuclear accident resulting, for example, in a loss of the core cooling function, there is an increase in the temperature of the core components and in particular of the nuclear fuel. The increase in the core temperature can lead to a meltdown of the internal components of the nuclear reactor.

[0003] At high temperatures, metals become very reactive and oxidize on contact with the water vapor present in the reactor vessel containing the core. The cladding of the fuel assemblies, which are made of a zirconium alloy, are elements which are first subjected to these oxidation reactions. The zirconium is oxidized by the water vapor following the reaction Zr + 2H2O -> ZrO2 + 2H2. This results in a very rapid release of a significant quantity of hydrogen.

[0004] In the event of a rupture of the reactor vessel, the interaction between the corium (molten core) and the concrete base of the containment vessel leads to the production of hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2).

[0005] Thus, during a nuclear accident, the containment enclosure may contain flammable gases (H2 and CO) and oxygen which can lead to the formation of an explosive atmosphere (ATEX) and the risk of loss of the integrity of the containment enclosure. This risk is known as the "hydrogen risk" or "H2 risk".

[0006] Therefore, it is important to be able to measure the concentration of gaseous components present in the reactor building during a nuclear accident.

[0007] In particular, the presence of gaseous components such as hydrogen, oxygen and carbon monoxide can lead to explosive mixtures. The implementation of control means making it possible to know the nature and proportion of the main gaseous components which are present in the reactor building is therefore necessary. This makes it possible to assess the risk of explosion and to initiate the necessary preventive actions to mitigate this risk.

[0008] Application FR2733050A1 describes a device for quantifying, by Raman spectrometry, gaseous components present inside the reactor building of a nuclear power plant. This device comprises one or more probes located inside the reactor building and a processing unit located outside. The processing unit is connected to the probes by optical fibers and electrical cables. Thus, its implementation requires providing passages through the reactor building. This very little degrades the sealing of the reactor building with respect to radiation and radioactive materials. In this respect, this device is very advantageous compared to other known quantification devices which require extracting a sample of the gaseous medium to the outside of the reactor building for analysis. Indeed, in the latter case, it is necessary to use tubes which pass through the reactor building to connect the inside of the reactor building to the outside.Such tubes are problematic because they call into question the tightness of the reactor building.

[0009] The following article describes in detail a device for quantifying gaseous components present inside the reactor building of a nuclear power plant by Raman spectrometry: S. Magne et al: “In situ gas monitoring by fiber-coupled Raman spectrometry for H2-risk management in nuclear containment during a severe nuclear accident”, IEEE Trans. Nucl. Sci. 67 (4), 2020, pp. 617-624. Hereinafter, this article is referred to as “Magne2020”. This device comprises a probe located inside the reactor building and a processing unit located outside. The probe comprises optical components for exciting a sample of the gaseous medium and for collecting, in response, an optical signal scattered by the Raman effect. The processing unit is connected to the probes by optical fibers and electrical cables.

[0010] In the event of a nuclear accident, the probe and the portions of the optical fibers located inside the reactor building may be exposed to high doses of radiation. In response, the optical fibers and optical components darken and become more opaque to the transmission of light. As a result, the number of photons collected by the probe decreases and the measured signal is weaker. This phenomenon is referred to as radiation-induced attenuation or RIA. If nothing is done to compensate for it, radiation-induced attenuation distorts the measurements and leads to an underestimation of the quantity of each of the gaseous components present inside the reactor building. In addition, this radiation-induced attenuation is not generally not uniform over the spectral range of interest. The RIA is often higher for shorter wavelengths, which means that the Raman signal from the rotational Si line of H2 (~785 nm) may experience greater attenuation than that of H2O (~1035 nm) for example. To compensate for this RIA phenomenon, the Magne2020 article proposes to increase the integration time in the event of a nuclear accident, i.e. to increase the duration of the acquisition window during which the collected photons are counted. This leads to a slowdown in the frequency of establishing new measurements. In addition, the frequency of establishing new measurements cannot be slowed down as much as desired because guidelines, such as the Severe Accident Management Guidelines (SAMG), impose minimum frequencies for establishing new measurements.

[0011] Furthermore, the use of a standard to compensate for variations in the intensity of an excitation beam used to perform analyses by Raman spectrometry is described in the prior art, such as for example in application US20140268129A1. In application US20140268129A1, the standard is a transparent fiber made of sapphire or YAG (Y3A15 Oi2) placed in the head of the probe.

[0012] The invention aims to propose a method for quantifying, by Raman spectrometry, at least one gaseous component inside a containment enclosure of a nuclear reactor which simply corrects the effect of radiation-induced attenuation.

[0013] The subject of the invention is therefore a method for quantifying, by Raman spectrometry, at least one gaseous component inside a confinement enclosure of a nuclear reactor, this method comprising the following steps:

[0014] - excitation, by a probe placed inside the confinement enclosure and using a monochromatic excitation beam, a sample of the gaseous medium located inside the confinement enclosure and, simultaneously, a standard whose quantity is constant during the execution of the quantification process, and in parallel

[0015] - the collection, by the probe, of an optical signal diffused, by Raman effect, by the sample and the standard simultaneously excited so that the Raman spectrum of the collected optical signal comprises:

[0016] - a Raman line at a wavelength X corresponding to the gaseous component at quantify, and

[0017] - at least one Raman line at a wavelength Xei corresponding to the standard, this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification process,

[0018] - the measurement, by a reading unit, of the optical signal collected by the probe,

[0019] - the establishment, by an electronic calculator, from the measured optical signal, of raw values ​​including at least: a raw value r(X) representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified, and a raw value r(Xei) representative of the amplitude of the Raman line at wavelength Xei produced by the standard,

[0020] in which the method comprises:

[0021] - a step of measuring the temperature of the sample, and

[0022] - a step of determining the partial pressure of the gaseous component at quantify corrected for radiation-induced attenuation using the following relationship: P(X)C = K*(A(Xel) / A(X))*(r(X) / r(^ where:

[0023] - P(X)C is the partial pressure of the gaseous component to be quantified corrected by radiation-induced attenuation,

[0024] - K is a predetermined constant independent of the radiation-induced attenuation,

[0025] - A(Xei) is a value of a radiation-induced attenuation coefficient at the length wavelength Xeb this value A(Xei) being equal to the ratio r(Xei) / r(Xei)o, where r(Xei)o is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xei produced by the standard in the absence of radio-induced attenuation,

[0026] - A(X) is a value of the radiation-induced attenuation coefficient at the wavelength X, this value A(X) being equal to the ratio r(X) / r(X)c, where r(X)c is a raw value representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified in the absence of radio-induced attenuation, and

[0027] - T is the temperature measured during the temperature measurement step of the sample.

[0028] Embodiments of this quantification method may include one or more of the following features:

[0029] 1)

[0030] - when the standard is excited by the monochromatic excitation beam, the spectrum Raman of the optical signal collected by the probe comprises, in addition to the first Raman line at wavelength Xeb, a second Raman line at a wavelength Xe2 different from wavelength Xei and different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification method,

[0031] - the step of establishing raw values ​​also includes the establishment, by the cal electronic generator and from the measured optical signal, a raw value r(Xe2) representative of the amplitude of the Raman line at the wavelength Xe2 produced by the standard, and

[0032] - the method comprises estimating the value A(X) of the attenuation coefficient radiation-induced at wavelength X using the ratios r(Xei) / r(Xei)0 and r(Xe2) / r(Xe2)0, where r(Xe2)0 is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xe2 produced by the standard at an instant when the radiation-induced attenuation is zero.

[0033] 2) The estimation of the value A(X) involves the calculation of the value A(X) using the following relation: A(X) = A(Xei) - p*(X - Xei), where:

[0034] - A(Xei) is equal to the ratio r(Xei) / r(Xei)0,

[0035] - p is equal to (A(Xel) - A(Xe2)) / (Xe2 - Xel),

[0036] - A(Xe2) is equal to the ratio r(Xe2) / r(Xe2)0.

[0037] 3) During the step of determining the partial pressure, the ratio A(Xei) / A(X) is taken equal to one.

[0038] 4) The excitation of the standard comprises the excitation of a standard gas contained in a gas-tight, constant-volume enclosure.

[0039] 5)

[0040] - establishing multiple raw values ​​includes establishing a value raw r(X) for several different wavelengths / . of interest, each of these wavelengths of interest corresponds to a particular gaseous component to be quantified in the excited sample, the measurements at these different wavelengths of interest being carried out simultaneously, then

[0041] - the execution, for each of these wavelengths of interest, of the step of determining determination of a partial pressure of this gaseous component to be quantified corrected for the radiation-induced attenuation.

[0042] 6) The wavelengths of interest include wavelengths of interest cor corresponding to hydrogen, water vapor, oxygen and nitrogen.

[0043] 7) The wavelengths of interest include wavelengths of interest cor responding to carbon monoxide and carbon dioxide.

[0044] 8) The excitation beam is a continuous laser beam.

[0045] The invention also relates to a device for quantifying, by Raman spectrometry, at least one gaseous component inside a confinement enclosure of a nuclear reactor, this device comprising:

[0046] - a laser source capable of emitting a monochromatic excitation beam,

[0047] - a probe, placed inside the containment enclosure, capable of:

[0048] - to be excited, using the monochromatic excitation beam emitted by the source laser, a sample of the gaseous medium located inside the containment enclosure and, simultaneously, a standard whose quantity is constant during the execution of the quantification process, and in parallel

[0049] - to collect an optical signal scattered, by Raman effect, by the sample and by the standard simultaneously excited so that the Raman spectrum of the collected optical signal includes:

[0050] - a Raman line at a wavelength X corresponding to the gaseous component at quantify, and

[0051] - at least one Raman line at a wavelength Xei corresponding to the standard, this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification process,

[0052] - a reading unit capable of measuring the optical signal collected by the probe, and

[0053] - an electronic calculator configured to establish, from the measured optical signal, raw values ​​including at least one raw value r(X) representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified, and one raw value r(Xei) representative of the amplitude of the Raman line at wavelength Xei produced by the standard,

[0054] in which:

[0055] - the probe comprises a temperature sensor capable of measuring the temperature of the sample, and

[0056] - the electronic calculator is also configured to determine the partial pressure of the gaseous component to be quantified corrected for radiation-induced attenuation using the following relation: P(X)C = K*(A(Xei) / A(X))*(r(X) / r(Xei))*T, where:

[0057] - P(X)C is the partial pressure of the gaseous component to be quantified corrected by radiation-induced attenuation,

[0058] - K is a predetermined constant independent of the radiation-induced attenuation,

[0059] - A(Xei) is a value of a radiation-induced attenuation coefficient at the length wavelength Xeb this value A(Xei) being equal to the ratio r(Xei) / r(Xei)0, where r(Xei)o is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xei produced by the standard in the absence of radio-induced attenuation,

[0060] - A(X) is a value of the radiation-induced attenuation coefficient at the wavelength X, this value A(X) being equal to the ratio r(X) / r(X)c, where r(X)c is a raw value representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified in the absence of radio-induced attenuation, and

[0061] - T is the temperature measured by the sample temperature sensor.

[0062] The invention also relates to a probe for producing the above quantification device, in which the probe is intended to be placed inside the confinement enclosure and capable of:

[0063] - to be excited, using a monochromatic excitation beam emitted by the source laser, a sample of the gaseous medium located inside the containment enclosure and, simultaneously, a standard whose quantity is constant during the execution of the quantification process, and in parallel

[0064] - to collect an optical signal scattered, by Raman effect, by the sample and by the standard simultaneously excited so that the Raman spectrum of the collected optical signal comprises:

[0065] - a Raman line at a wavelength X corresponding to the gaseous component at quantify, and

[0066] - at least one Raman line at a wavelength Xei corresponding to the standard, this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample,

[0067] in which:

[0068] - the probe comprises a temperature sensor capable of measuring the temperature of the sample, the standard and a case,

[0069] - the standard comprises a standard gas which, when excited by the excitation beam emitted by the laser source, produces the Raman line at wavelength Xei in the optical signal collected by the probe, and

[0070] - the housing contains the standard gas, this housing being sealed to this standard gas and of volume constant and this housing comprising a transparent window arranged to allow the excitation beam, which excited the standard gas, to exit the housing to excite the sample of the gaseous medium.

[0071] Embodiments of this probe may include one or more of the following features:

[0072] 1) The standard contained in the housing is suitable, when excited by the beam excitation emitted by the laser source, to produce, in addition to the first Raman line at wavelength Xeb, a second Raman line at a wavelength Xe2 different from wavelength Xei and different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample.

[0073] 2) The standard comprises ethane or a mixture of methane and nitric oxide.

[0074] 3) The housing comprises, inside the housing:

[0075] - the end of an incoming optical fiber through which the beam monochromatic excitation is introduced inside the housing,

[0076] - the end of an outgoing optical fiber through which the signal collected optical energy is emitted to the outside of the housing,

[0077] - all the optical components necessary to excite the sample and collect the optical signal scattered, by Raman effect, by the gaseous components to be quantified in this sample.

[0078] The invention will be better understood on reading the description which follows, given solely by way of non-limiting example and made with reference to the drawings in which:

[0079] - [Fig.l] is a schematic illustration of the architecture of a quantization device fication, by Raman spectrometry, of gaseous components inside a containment vessel of a nuclear reactor,

[0080] - [Fig.2] is an illustration of a Raman spectrum of the gaseous components at quantify,

[0081] - [Fig.3] is a schematic illustration of the architecture of a probe of the device of [Fig.l],

[0082] - [Fig.4] is an illustration of Raman spectra in the presence of radiation Cherenkov,

[0083] - [Fig.5] is a flowchart of a quantification method using the device of [Fig.l],

[0084] - [Fig.6] is a timing diagram of different operating periods of the device of [Fig.l],

[0085] - [Fig.7] is a flowchart of another embodiment of the quan method tification using the device in [Fig.l].

[0086] In this description, the terminology, conventions and definitions of the terms used in this text are introduced in a chapter I. Then, a detailed example of an embodiment is described in a chapter II with reference to the figures. In a chapter III, variants of this embodiment are presented. Finally, the advantages of the different embodiments are specified in a chapter IV.

[0087] Chapter I: Definitions, terminologies and conventions:

[0088] In the figures, the same references are used to designate the same elements.

[0089] In the remainder of this description, the characteristics and functions well known to those skilled in the art are not described in detail.

[0090] The symbol “*” denotes scalar multiplication.

[0091] A gaseous component is typically a gaseous molecule.

[0092] The terms “quantification” and “quantify” designate the operation of measuring the quantity of a gaseous component and, in particular, a concentration expressed in % or a partial pressure expressed in Pa.

[0093] The term "quantity", when used without further specification, refers to both an absolute quantity, such as a partial pressure, and a relative quantity, such as a concentration in %.

[0094] In this text, a relative quantity is a proportion, for example expressed in percent, of the gaseous component within the gaseous medium.

[0095] An absolute quantity is typically the partial pressure of the gas component.

[0096] A Raman spectrum is the power spectrum of the optical signal scattered by the Raman effect.

[0097] A "Raman line" is a line in the Raman spectrum whose integral, i.e. its surface, or amplitude varies as a function of the quantity of a gaseous component.

[0098] The “Raman spectral band” is the wavelength range which contains all the Raman lines useful for implementing the quantification method.

[0099] The term "nuclear accident" of loss of core cooling refers to any accident that leads to the partial or complete meltdown of the core of the nuclear reactor. In such an accident, hydrogen is produced. Eventually, other gaseous components are produced such as carbon monoxide and carbon dioxide. Such an accident often originates from a total or partial loss of cooling of the core of the nuclear reactor.

[0100] A beam is considered “monochromatic” when the half-width of its single line, in its power spectrum, is less than 1 nm and, preferably, less than 0.5 nm.

[0101] A raw value representative of the amplitude of a Raman line in the Raman spectrum is a value obtained before it is corrected to compensate for the effect of radiation-induced attenuation.

[0102] The value A(X) of a coefficient A of radio-induced attenuation at the wavelength X is equal to the ratio r(X) / r(X)„ where:

[0103] - r(X) is the amplitude of the Raman line at wavelength X measured in the presence of radiation-induced attenuation, and

[0104] - r(X)c is the amplitude that this same Raman line would have at wavelength X in absence of radiation-induced attenuation.

[0105] Chapter II: Examples of embodiments

[0106] [Fig.l] represents a device 2 for quantifying, by Raman spectrometry, at least one gaseous component inside a containment enclosure 4 of a nuclear reactor supported by a concrete base 7. Subsequently, the description of the device 2 is made in the particular case where the enclosure 4 is a reactor building of a nuclear power plant which produces electricity. To simplify [Fig.l], only the following elements contained inside the reactor building have been schematically represented:

[0107] - core 6 of the nuclear reactor,

[0108] - the tank 8 in which the heart 6 is baked, and

[0109] - the gaseous medium 10 in which the different elements located inside are bathed of enclosure 4.

[0110] The enclosure 4 is sealed, as far as possible, against radiation and radioactive materials in order to prevent them from escaping into the external environment, including, if possible, in the event of a nuclear accident. Typically, the enclosure 4 and the base 7 are essentially made of concrete.

[0111] The gaseous medium 10 is typically air, that is to say a gaseous mixture composed, at more than 98% by volume, of oxygen (O2) and nitrogen (N2) in known proportions.

[0112] In this example, the device 2 is designed to quantify the following gaseous components: hydrogen (H2), water vapor (H2O), oxygen (O2), nitrogen (N2), carbon monoxide (CO) and carbon dioxide (CO2). Indeed, the H2 risk is estimated on the basis of the quantities of hydrogen, air (O2, N2) and water vapor (H2O) represented on a Shapiro-Moffette ternary diagram. The measurement of the quantities of carbon monoxide and carbon dioxide makes it possible to monitor the corium-concrete interaction (Molten Core Concrete Interaction - MCCI). In this particular context, the term "gaseous components" therefore designates the gaseous components belonging to the group consisting of hydrogen (H2), water vapor (H2O), oxygen (O2), nitrogen (N2), carbon monoxide (CO) and carbon dioxide (CO2).

[0113] The device 2 comprises, fixed inside the enclosure 4:

[0114] - one or more probes 20 located at different locations to measure the concentrations of gaseous components at these different locations,

[0115] - a pressure sensor 22, and

[0116] - one or more temperature sensors 24.

[0117] Subsequently, the device 2 is described in the simplified case where the device 2 comprises a single probe 20 and a single temperature sensor 24. However, everything described in this simplified case also applies to the case where there are several probes 20 and several temperature sensors 24. Typically, the temperature sensor 24 is placed in the probe 20.

[0118] The device 2 also comprises, outside the enclosure 4, a processing unit 30 which processes the data transmitted by the probe 20 and the sensors 22 and 24 to quantify the presence of the gaseous components in the medium 10.

[0119] The processing unit 30 comprises for this purpose: a laser source 32, a reading unit 34, an electronic computer 36, a man-machine interface 38, and a power source 40.

[0120] The probe 20 is connected to the processing unit 30 by means of two optical fibers 42 and 44. The fiber 42 brings an excitation beam, generated by the laser source 32, inside the probe 20. For this purpose, its proximal end is connected to the laser source 32 and its distal end opens inside the probe 20. The fiber 44 brings the optical signal scattered by the Raman effect from the probe 20 to the reading unit 34. For this purpose, its proximal end is connected to the reading unit 34 and its distal end opens inside the probe 20. These fibers 42 and 44 pass through the enclosure 4, each taking its own passage. optical waterproof assembly better known by the acronym OPA (“Optical Penetration Assembly”).

[0121] The probe 20 is also connected to the unit 30 by means of several electrical cables collectively designated by the reference numeral 46. Each cable 46 passes through the enclosure 4 by using an electrical sealed crossing better known by the acronym EPA (“Electrical Penetration Assembly”). These cables 46 make it possible in particular to power the probe 20 and to convey control signals for the probe 20.

[0122] The sensors 22 and 24 are connected to the unit 30 by electrical cables, respectively, 48 and 49. These cables 48, 49 pass through the enclosure 4, each using a respective sealed electrical crossing.

[0123] To simplify [Fig.l], the oblique lines on each cable 46, 48 and 49 indicate that this cable is implemented, in practice, by several electric cables.

[0124] The laser source 32 emits an excitation beam. This beam is a monochromatic beam at a wavelength Xp. The wavelength Xi is preferably between 730 nm and 750 nm. Indeed, the use of a wavelength Xi between 730 nm and 750 nm makes it possible to obtain Raman lines located in the spectral range [785 nm - 1030 nm], where the radiation-induced attenuation is the lowest in silica optical fibers. For example, here, the wavelength Xi is equal to 750 nm.

[0125] The power of the optical signal generated by the Raman effect is in particular proportional to the power of the excitation beam. Here, to improve the sensitivity and precision of the device 2, the power of the excitation beam is greater than 500 mW and, preferably, greater than or equal to 1 W. In this example, the power of the excitation beam is chosen so that its power inside the gas mixture is greater than or equal to 180 mW. To generate such an excitation beam with a small footprint, the laser source 32 is a continuous laser source with a power equal to or greater than one Watt.

[0126] The reading unit 34 makes it possible to record the power of the optical signal at the different wavelengths of interest. Here, the wavelengths of interest are equal to the wavelengths at which lines, characteristic of the presence of the gaseous components to be quantified, appear in the power spectrum of the optical signal scattered by the Raman effect by the medium 10. Subsequently, the wavelengths of interest of hydrogen, carbon dioxide, oxygen, carbon monoxide, nitrogen and water vapor are noted, respectively, XH2, XCo2, X02, XCo, XN2 and XH2o-These wavelengths of interest are known and represented on the Raman spectrum of [Fig.2],

[0127] The spectrum of [Fig.2] is reconstructed from experimental Raman shift values. The amplitudes of the lines are normalized to that of nitrogen (N2) at the value unit for a partial pressure of 1 atm and room temperature. The amplitudes of the lines are proportional to the quantity of each gaseous component in the medium 10. In practice, the measured Raman lines do not have a zero width. For example, in this embodiment, the full width at half maximum or FWHM (Full Width at Half Maximum) of each line is typically 6 nm. Under these conditions, the (integral) surface of the line is representative of its amplitude and therefore proportional to the quantity of the corresponding gaseous component. Thus, subsequently the terms "Raman line amplitude" and "Raman line surface" are used interchangeably.

[0128] In the particular case of hydrogen, several rotational lines So to S3 correspond to the presence of hydrogen. Among the four lines So to S3 of hydrogen, the line Si is the most intense of all. Moreover, in practice, the line So is not observed because it is contained in the rejection band of the filter 96 ([Fig.3]). Here, the wavelength X h2 is taken equal to the wavelength at which the line Si of hydrogen appears. In this case, the value of the optical signal scattered by the Raman effect by the hydrogen is taken equal to the surface of the line Si.

[0129] The two carbon dioxide lines overlap but can still be distinguished. The value of the optical signal for carbon dioxide is equal to the area of ​​these two lines.

[0130] The spectrum of [Fig.2] also represents two standard lines produced, by Raman effect, by a standard when it is excited with the same excitation beam as that used to excite the gaseous components to be quantified. These standard lines are located, respectively, at wavelengths Xei and Xe2. These wavelengths Xei and Xe2 are different from the wavelengths where Raman lines corresponding to the gaseous components to be quantified appear. In particular, these wavelengths Xei and Xe2 are different from the wavelengths where Raman lines corresponding to gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification method. In addition, these wavelengths Xei and Xe2 are preferably spaced from each other by at least 50 nm or 100 nm.In this first embodiment, the standard is a mixture of two standard gases, namely methane (CH4) and nitrogen monoxide (NO). In this case, the wavelength Xei corresponding to methane is equal to 960 nm and the wavelength Xe2 corresponding to nitrogen monoxide is equal to 873 nm when the wavelength Xi of the excitation beam is equal to 750 nm. The interest of these standard lines is explained later.

[0131] In addition to the wavelengths of interest and the wavelengths Xei and Xe2, between the lines So and Si of hydrogen, there is located a first reference wavelength Xrefi. Between the lines Si and S2 of hydrogen, there is located a second wavelength of Xref2 reference. As explained later, the Xref2 and Xref2 wavelengths allow the extraction of the value of the optical signal scattered by the Raman effect by hydrogen using the baseline subtraction (BSL) method.

[0132] To obtain measurements for each of the wavelengths of interest and for the lengths Xeb Xe2, Xrefi and Xref2, the unit 34 comprises a circuit 51 for demultiplexing these different wavelengths and for each of the demultiplexed wavelengths, only one acquisition chain.

[0133] The proximal end of the fiber 44 is connected to an input of the circuit 51. The circuit 51 has as many outputs as there are wavelengths to be processed. On each of these outputs, the circuit 51 delivers the optical signal corresponding to the wavelength to be processed. A respective acquisition chain is connected to each of these outputs. Here, these acquisition chains are structurally identical to each other and only one acquisition chain 50 for a wavelength X is described and shown in [Fig.l]. The demultiplexing circuit 51 is for example produced as described in application US7385692.

[0134] The chain 50 successively comprises a band-pass filter 52, a photodetector 54, an amplification-discrimination module 56 and a counter 58.

[0135] The transfer function of the bandpass filter 52 has the form of a Gaussian centered on the wavelength X. The width of this transfer function at mid-height is comprised:

[0136] - between 10 nm and 12 nm for the wavelengths Xeb Xe2, X02, XCo, XN2 and XH20,

[0137] - between 5 nm and 6 nm for the wavelengths XH2, Xrefi and Xref2, and

[0138] - between 15 nm and 18 nm for the XCo2 wavelength in order to take into account the fact that carbon dioxide corresponds to two overlapping lines.

[0139] The photodetector 54 generates a voltage pulse for each photon received in the optical signal filtered by the bandpass filter 52. Preferably, the photodetector 54 is a photomultiplier. For example, the photomultiplier is equipped with a photocathode extended in the visible red and near infrared range made of GaAs-Cs or InGaAs-Cs. This photomultiplier operates at a temperature of -20°C, by Peltier effect cooling for example. For this, a thermoelectric cooling module known by the acronym TEC (“Thermoelectric Cooler”) can be used.

[0140] The amplification-discrimination module 56 first amplifies the voltage pulses at the output of the photodetector 54. Then, the amplification-discrimination module 56 eliminates most of the pulses coming from the masking signal. For this, typically, the amplification-discrimination module 56 eliminates the pulses whose amplitude is lower than a predetermined threshold.

[0141] Counter 58 is incremented by each pulse delivered at the output of the module amplification-discrimination 56. The counter 58 therefore counts the number of pulses received during an interval of a predetermined duration Te. At the end of the interval, the value of the counter 58 is reset to zero and the counter starts counting the pulses received during the following interval again. For example, the duration Te is typically of the order of 10 ms, i.e. an acquisition frequency fe of 100 Hz.

[0142] At the end of each interval, a measurement of the number of counts received during this interval is therefore delivered. This measurement is expressed in cps (counts per second).

[0143] The computer 36 typically comprises a programmable microprocessor 60 and a memory 62 containing the data and instructions necessary for executing the method of [Fig. 5]. The computer 36 is in particular capable of controlling the laser source 32, the probe 20 and the human-machine interface 38. The computer 36 also acquires the measurements delivered by the unit 34 and the sensors 22 and 24. The computer 36 integrates all the measurements delivered during a predetermined acquisition window to obtain a value S(X) measured during this acquisition time window and expressed in number of counts.

[0144] The human-machine interface 38 typically comprises a screen 66.

[0145] Here, the power source 40 is a backed-up power source capable of powering all of the components of the processing unit 30, the probe 20 and the sensors 22 and 24 even in the event of a power supply network outage.

[0146] [Fig. 3] shows the probe 20 in more detail. The probe 20 comprises a housing 80 inside which are housed the various optical components necessary to produce and collect the optical signal scattered, by the Raman effect, by the gaseous components to be quantified. The distal ends of the fibers 42 and 44 are located inside the housing 80.

[0147] This housing 80 is waterproof and dustproof to protect the optical components. For example, the housing 80 has a protection rating equal to IP69. The interior of the housing 80 is filled with a gaseous medium in which the optical components are immersed.

[0148] The housing 80 also includes an etalon 81 which produces the etalon lines when it is excited by an excitation beam. In this first embodiment, the etalon 81 is in a gaseous medium. Thus, subsequently, the same reference numeral 81 is also used to designate this gaseous medium. In this embodiment, the etalon 81 is the gaseous medium in which the optical components are immersed. Thus, the housing 80 is used both to protect the optical components and as a container for the gaseous medium 81. For this purpose, the housing 80 is sealed against the gaseous medium 81 and its volume is constant. The pressure of the gaseous medium 81 inside the housing 80 at ambient temperature To is typically close to atmospheric pressure. For example, here, for a temperature To of 25°C (298 K), the pressure of the gaseous medium 81 is equal to 1 atm (101.32 kPa). For this purpose, the housing 80 is provided with a valve connection 83. When this is closed, it ensures the sealing of the housing. When it is open, it is connected to a junction of two parallel ways. The first way is connected to a quarter-turn valve followed by a vacuum pump (which can be a primary vane pump, preferably oil-free) and the second way, to one or more gas cylinders equipped with a pressure regulator and pressure gauge. A vacuum is first created in the housing by activating the pump and opening the quarter-turn valve. Once a vacuum has been created in the body of the housing, the quarter-turn valve is closed and the cylinder is opened to fill the housing with the gaseous medium 81 to the desired pressure (typically atmospheric pressure). This operation is carried out at the known temperature To (typically room temperature).

[0149] In this first example, the standard 81 is a mixture consisting, in known proportions, of methane and nitrogen monoxide. Here, the volume fractions of methane and nitrogen monoxide are chosen so that the amplitude of the Raman lines of methane and nitrogen monoxide have similar amplitudes. For example, the volume fractions of methane and nitrogen monoxide are equal, respectively, to 5% and 95%. The partial pressures P(Xei)o and P(Xe2)o, respectively of methane and nitrogen monoxide, at temperature To are therefore also known.

[0150] Internal walls of the housing 80 are covered with a textured material that traps light and minimizes reflections of the laser beam on these internal walls.

[0151] Inside the housing 80, the probe 20 comprises the following components arranged one after the other along the path of the excitation beam and the collected optical signal from the fiber 42 to the fiber 44: a collimator 82, a polarizer 84, a filter 86, a beam splitter 88, a parabolic mirror 90, a window 92, an analysis chamber 94, a filter 96, a polarizer 98, a rotator 100 and a parabolic mirror 102. In [Fig. 3], the path of the excitation beam and the collected optical signal is represented by oriented arrows.

[0152] Here, inside the housing 80 the excitation beam and the collected optical signal move parallel to a predetermined PI plane fixed relative to the housing 80. For example, the PI plane is parallel to a base on which the different components of the probe 20 are fixed.

[0153] The collimator 82 makes it possible to obtain a collimated beam, directed towards the polarizer 84, from the excitation beam emitted by the distal end of the fiber 42. For this purpose, for example, the collimator 82 is a parabolic mirror.

[0154] The polarizer 84 eliminates the polarization component perpendicular to the PI plane, to retain only the polarization component parallel to this PI plane. Thus, at the output of the polarizer 84, the polarization of the excitation beam is linear and parallel to the PI plane. Preferably, the polarizer 84 is a polarizer cube or PBS (“Polarization BeamSplitter cube”) which simultaneously exhibits good laser beam resistance but also low reported fluorescence.

[0155] The filter 86 eliminates or reduces the fluorescence generated by the polarizer 84 and the fiber 42 as well as the components of the polarized beam greater than the wavelength Xb. More precisely, the filter 86 eliminates or greatly reduces all the components of the polarized beam likely to interfere with the optical signal scattered by the Raman effect. For this, the filter 86 allows the polarized excitation beam to pass while eliminating the wavelengths greater than the wavelength Xi of the excitation beam. For this purpose, the filter 86 is a low-pass or band-pass filter whose cut-off wavelength at -70 dB is, preferably, between Xi + 15 nm and Xi + 25 nm at normal incidence. For example, the filter 86 is a SWP filter (“Short Wave Pass filter”) mounted on an adjustable mount which makes it possible to adjust the angle of incidence of the laser beam relative to the normal to the surface of the filter 86.This angle of incidence is adjusted to obtain the desired rejection performance on the Raman spectrum.

[0156] The splitter plate 88 folds the excitation beam onto the parabolic mirror 90. For the optical signal reflected by the mirror 90 and which passes through the splitter plate 88, the splitter plate 88 also behaves as a high-pass filter which eliminates or reduces the components of the optical signal which pass through it whose wavelengths are equal to or less than the wavelength Xb. For this purpose, typically, the plate 88 has a cut-off wavelength at -70 dB, preferably between Xi + 5 nm and Xi + 22 nm. For this purpose, here, the plate 88 is also mounted on an orientable mount which makes it possible to adjust the angle of incidence of the incident optical signal relative to the normal to the surface of the plate 88. This angle of incidence is adjusted to obtain the desired rejection performance on the Raman spectrum.

[0157] The parabolic mirror 90 focuses the polarized beam at a point R located inside the analysis chamber 94.

[0158] The chamber 94 contains the sample of the medium 10 to be analyzed. The chamber 94 isolates the sample from the light which may be present inside the enclosure 4. In addition, the chamber 94 is also designed to protect the sample from possible water splashes as well as from pollution by aerosols.

[0159] Here, the chamber 94 is crossed by a gas flow of the medium 10 so that the sample of the medium 10 is constantly renewed. This gas flow of the medium 10 occurs, for example, by natural convection. For this, the chamber 94 has vents for the entry and exit of the medium 10. The internal volume of the chamber 94 is for example 200 cm3 or 500 cm3.

[0160] The chamber 94 is fluidically isolated from the interior of the housing 80. For this purpose, the housing 80 comprises the window 92 which is transparent to the excitation beam and to the optical signal scattered, by Raman effect, by the gaseous components to be quantified. Here, the window 92 is configured to transmit the polarized excitation beam in full without reflecting part of it. For this purpose, the window is here a Brewster window, that is to say a window inclined at the Brewster angle relative to the optical axis of the incident excitation beam so as not to reflect the incident beam.

[0161] At least the inner wall of the chamber 94, located opposite the window 92 and on the other side of the point R, is covered with a textured material which traps the light and minimizes the reflection of the excitation beam on this inner wall. Preferably, this inner wall of the chamber 94 is placed far enough away to limit the scattered spectral background. For example, the distance between the window 92 and this inner wall of the chamber 94 is greater than or equal to 5 cm.

[0162] In this embodiment, the power of the polarized excitation beam at point R is approximately 180 mW for a power emitted by the laser source 32 of approximately 1 Watt.

[0163] The temperature sensor 24 is housed inside the chamber 94 near the point R. In addition, preferably, the chamber 94 also includes an anti-condensation module 95 which makes it possible to prevent water vapor from condensing on the window 92. This anti-condensation module 95 is powered via the cables 46. However, to simplify [Fig.2], the connection of this anti-condensation module 95 to the cables 46 is not shown.

[0164] The optical signal diffused, by Raman effect, by the interaction, at point R, of the excitation beam with the gaseous components present, is returned to the interior of the housing 80 and collected by the mirror 90. The mirror 90 then returns the optical signal to the separating plate 88 which transmits it to the filter 96.

[0165] The filter 96 is a high-pass filter or LWP filter (“Long-Wave Pass”) which also has a cut-off wavelength at -70 dB preferably, between Xi + 5 nm and Xi + 22 nm. For this purpose, here, the filter 96 is also mounted on an adjustable mount which makes it possible to adjust the angle of incidence of the incident optical signal relative to the normal to the surface of the filter 96. This angle of incidence is adjusted to obtain the desired rejection performance on the Raman spectrum.

[0166] The optical signal filtered by filter 96 is then polarized by polarizer 98. For example, polarizer 98 is a PBS (“Polarizing Beam Splitter”) polarizer similar to polarizer 84.

[0167] The monostable electromagnetic rotator 100 makes it possible to rotate the polarizer 98 by 90° in response to a control signal received via the cables 46. For example, the rotator 100 comprises a shaft on which a set 97 of gears is mounted. This set 97 of gears comprises, for example, a first wheel toothed wheel which rotates a second toothed wheel on which the polarizer 98 is mounted. The rotator 100 is powered via the cables 46. When this rotator 100 is powered, this triggers a rotation of its shaft which rotates the polarizer 98 by 90° around its optical axis. When the power is cut off, the rotator 100 returns to its initial position under the action of a mechanical spring. Here, in the absence of power, the passing axis of the polarizer 98 is parallel to the PI plane so that the power of the optical signal passing through it is maximum. Conversely, when the rotator 100 is powered, the passing axis of the polarizer 98 is perpendicular to the PI plane and the power of the optical signal passing through the polarizer 98 is minimum. Subsequently, when the passing axis of the polarizer 98 is parallel to the PI plane, it is said that the optical signal is measured with “parallel polarization”.Conversely, when the passing axis of the polarizer 98 is perpendicular to the plane PI, we say that the optical signal is measured with a “perpendicular polarization”. The electronics which make it possible to power the rotator 100 and, alternately, to cut off its power supply is located in the processing unit 30 and has not been shown to simplify [Fig. 1].

[0168] To rotate its shaft, the rotator 100 comprises an electromagnetic actuator comprising coils and magnets. To ensure that it is capable of operating correctly even in the event of a nuclear accident, typically, the electrical wires of the coils are coated with silicone. Similarly, the permanent magnets are made of magnetic materials that have a Curie temperature greater than 300°C or 450°C. For this purpose, for example, magnets made of Sm-Co (samarium-cobalt) or Al-Ni-Co (Aluminium-Nickel-Cobalt) are recommended.

[0169] The parabolic mirror 102 focuses the optical signal which has passed through the polarizer 98 onto the distal end of the fiber 44. The optical signal scattered by the Raman effect is therefore guided by the fiber 44 to the reading unit 34.

[0170] [Fig.4] represents four Raman spectra 120, 122, 124 and 126 of air measured using a device almost identical to device 2 in which:

[0171] - the reading unit 34 is replaced by a spectrometer which makes it possible to measure the amplitude, in cps (counts per second), of the optical signal collected for a large number of wavelengths, for example a few dozen wavelengths corresponding to Raman lines, distributed between 750 nm and 1050 nm, and

[0172] - the gaseous medium 81 is replaced by a neutral gas, such as argon, which does not produces no Raman lines in the spectral band of interest.

[0173] In [Fig.4], a solid line curve corresponds to the Raman spectrum of an optical signal measured with parallel polarization. A dotted line curve corresponds to the Raman spectrum of an optical signal measured with perpendicular polarization. The spectra 120 and 122 were recorded by exposing a 10 m length of the fiber 44 to photon radiation with an energy equal to 1.25 MeV and a flow rate of dose equal to 250 Gy / h. Both spectra 124 and 126 were recorded under the same conditions except that the dose rate was equal to 1016 Gy / h.

[0174] In this [Fig.4], the lines, produced by the Raman effect, corresponding to oxygen and nitrogen are identified by the symbols, respectively, “02” and “N2”.

[0175] First of all, it can be observed that the "O2" and "N2" lines are discernible only in the optical signals measured with parallel polarization. This comes from the fact that the Raman effect which produces these lines has a very low depolarization ratio p for oxygen and nitrogen. The depolarization ratio p is the ratio between the amplitude of the signal measured with perpendicular polarization on the amplitude of the signal measured with parallel polarization. Thus, for oxygen and nitrogen, the Raman effect is only visible on the optical signal whose polarization direction is identical to the polarization direction of the excitation beam. This is also true for carbon dioxide, carbon monoxide, water vapor and the gaseous medium 81. On the other hand, this is false for the Si line of hydrogen.In the case of hydrogen, the Si line exists in the Raman spectra of optical signals measured with parallel polarization and with perpendicular polarization. However, the amplitude of the Si line in the Raman spectrum of the optical signal measured with parallel polarization is about 25% larger than the amplitude of the same Si line in the Raman spectrum of the optical signal measured with perpendicular polarization. In other words, the depolarization ratio p of the Si line of hydrogen is about 75%.

[0176] Cherenkov radiation is radiation that appears in optical fibers and optical components when they are exposed to high-energy photon or electron radiation. In silica, the threshold for the appearance of this radiation is located at 180 keV. Cherenkov radiation can increase substantially in the event of a nuclear accident compared to the nominal operating situation of the reactor. As illustrated by spectrum 120, for a fiber length of 10 meters exposed under a dose rate equal to 250 Gy / h, the amplitude of the Cherenkov radiation exceeds the amplitude of the "O2" line by a factor greater than 50 and the amplitude of the "N2" line by a factor greater than 20. In the case of spectrum 124, the amplitude of the Cherenkov radiation exceeds the amplitude of the "O2" line by a factor greater than 180 and the amplitude of the "N2" line by a factor greater than 60.This shows that during operation of the device 2, the optical Raman scattering signal is drowned in a masking signal corresponding, to a significant extent, to the Cherenkov radiation which appears mainly in the silica and therefore in the fiber 44 as well as, to a lesser extent, in the optical components of the probe 20.

[0177] Another part of this masking signal originates from:

[0178] - the electronic noise of the acquisition chain 50 known by the English term of "dark noise", and

[0179] - a fluorescence signal from optical components.

[0180] The fluorescence signal of the optical components is typically caused by the fluorescence of these optical components of the device 2 when they are illuminated by the excitation beam.

[0181] The operation of the device 2 will now be described with reference to the method of [Fig.5].

[0182] The method begins with a calibration phase 198 during which all of the parameters necessary for determining the quantities of the gaseous components are determined and recorded in the memory 62.

[0183] Then, during an operating phase 220, for the gaseous components other than hydrogen, the computer 36 determines a raw value of the quantity of this gaseous component using the following relation (1): r(X) = [S3(X) / t3 - S1(X) / tl] -k(X)*[S4(X) / t4 - S2(X) / t2], where:

[0184] - X is the wavelength at which the Raman line produced by this appears gaseous component,

[0185] - r(X) is a raw value representative of the amplitude of the Raman line, centered on the wavelength X, generated by the sample contained inside chamber 94, expressed in counts per second,

[0186] - S1(X) and S2(X) are the values, for wavelength X, respectively, of optical signals S1 and S2 measured when the laser source 32 is switched off,

[0187] - S3(X) and S4(X) are the values, for wavelength X, respectively, of optical signals S3 and S4 measured when the laser source 32 is switched on,

[0188] - k(X) is the value, for the wavelength X, of a scale coefficient k pre determined, and

[0189] - tl, t2, t3 and t4 are the durations of the time windows during which the signals SI, S2, S3 and S4 are measured.

[0190] The values ​​S1(X), S2(X), S3(X) and S4(X) are expressed in number of moves.

[0191] The signals SI and S3 are measured with parallel polarization during the durations, respectively, tl and t3. The signals S2 and S4 are measured with perpendicular polarization for the durations, respectively, t2 and t4. The ratios Sl(X) / tl, S2(X) / t2, S3(X) / t3 and S4(X) / t4 are therefore measurements, in counts per second, of the optical signal collected, by the probe 20, at the wavelength X.

[0192] Since the signals S1 and S2 are measured while the laser source 32 is switched off, these signals represent measurements of the Cherenkov radiation, respectively, with parallel polarization and with perpendicular polarization. Under these conditions, the first difference S3(X) / t3 - Sl(X) / tl makes it possible to obtain a signal optical signal corrected for Cherenkov radiation. However, this first difference is not corrected for the fluorescence signal of the optical components. Indeed, this fluorescence signal is absent from the SI signal because the SI signal is measured when the laser source 32 is off. Here, this fluorescence signal is estimated from the second difference S4(X) / t4 - S2(X) / t2. More precisely, this second difference estimates the amplitude of the fluorescence signal when the optical signals are measured with perpendicular polarization. However, the fluorescence signal is generally weakly polarized so that its amplitudes, when measured with parallel polarization and with perpendicular polarization, are close. In this embodiment, the fluorescence signal present in the S3 signal measured with parallel polarization is assumed to be proportional to the fluorescence signal present in the S4 signal.Thus, the fluorescence signal present in the signal S3 is estimated by the term k(X)*[S4(X) / t4 - S2(X) / t2] of the relation (1).

[0193] The value of the coefficient k for all wavelengths of interest must first be determined before relation (1) can be used. Thus, the calibration phase 198 comprises a step 200 of determining the various required values ​​of the coefficient k. Here, step 200 is executed while the probe 20 is fixed inside the enclosure 4. In this case, preferably, step 200 is executed at a time when the nuclear reactor is shut down so that the Cherenkov radiation is of very low magnitude, or even unmeasurable. For example, step 200 is executed on the occasion of a ten-year shutdown of the nuclear reactor.

[0194] During step 200, a reference sample, the composition of which is known, is located inside the chamber 94. Here, the reference sample is air.

[0195] Finally, during step 200, the processing unit 30 is replaced by a processing unit which makes it possible to measure the amplitude of the optical signal both at the wavelengths of interest and at other wavelengths. For example, for this purpose the reading unit 34 is replaced by a spectrometer identical to that used to measure the Raman spectra of [Fig.4].

[0196] Here, the variation of the coefficient k as a function of the wavelength X is assumed to be linear over the entire spectral band of interest, i.e. here between 750 nm and 1050 nm. Under these conditions, the values ​​of the coefficients of the line which approximates the evolution of the value k(X) as a function of the wavelength X, are obtained from measurements carried out for wavelengths X; located outside the lines of oxygen, nitrogen and the gaseous medium 81 and therefore far from the wavelengths X02, XN2, Xei and Xe2. The index i is an identifier of the wavelength.

[0197] Therefore, during an operation 202, for each wavelength X;:

[0198] - a Spara(Xi) value of an optical signal Spara is measured with a polarization parallel, and

[0199] - a Sperp(X;) value of an optical signal Sperp is measured with a polarization perpendicular.

[0200] The Spara and Sperp signals are measured while the laser source 32 is switched on and therefore when the sample present inside the chamber 94 is excited by the excitation beam.

[0201] Furthermore, in this embodiment, during an operation 204, the electronic noise of each acquisition chain 50 of the reading unit 34 is measured. Here, this electronic noise is assumed to be identical for each acquisition chain 50. Furthermore, it is assumed that this electronic noise does not vary as a function of the wavelength X within the spectral band of interest. Finally, it is also assumed that this electronic noise is independent of the polarization of the measured optical signal. For example, the amplitude DN of this electronic noise is measured by occluding the distal end of the fiber 44 then averaging the amplitudes measured by each acquisition chain 50.

[0202] During an operation 206, for each wavelength Xi5 a value k(X;) is calculated using the following relation: k(X;) = [Spara(Xi) - DN] / [Sperp(X;) - DN].

[0203] Then, during an operation 208, the values ​​k(Xei), k(Xe2), k(XC02), k(XO2), k(XCo), k(X N2) and k(XH2o) are calculated, by interpolation, from the values ​​k(Xi). For this purpose, the function which associates with each wavelength X, the corresponding value k(X) of the coefficient k, is obtained by mathematical adjustment. For example, here, the interpolation used is a linear interpolation. For this purpose, the coefficients a and b of the straight line which minimizes the deviations with the different values ​​k(X;), are calculated. Then, using the equation of this straight line, the values ​​k(Xei), k(Xe2), IdXcmk k(XO2), k(XCo), k(XN2) and k(X H20) are calculated then recorded in the memory 62.

[0204] Then, during a step 210, raw values ​​r(Xei)0 and r(Xe2)0 of the amplitudes of the standard lines in the absence of radiation-induced attenuation are measured using the device 2. Here, these raw values ​​r(Xei)0 and r(Xe2)0 are measured, for example, by the same method as that described later for measuring a raw value r(Xei) during the operating phase 220. These raw values ​​r(Xei)0 and r(Xe2)0 are also recorded in the memory 62.

[0205] Furthermore, as justified by relation (5) of the article Magne2020, in the absence of induced radio attenuation, the amplitude r(X) of the Raman line (in cps) of a gaseous component to be quantified is linked to the partial pressure P(X) of this gaseous component by the following relation (2): r(X)*T = Ii*0>*P(X), where:

[0206] - T is the temperature of the gaseous component,

[0207] - h is the intensity of the excitation beam expressed in W / cm2, and

[0208] - Ox is a constant coefficient whose value depends in particular on the section(s) differential Raman interaction(s) of the gaseous component(s) and of different ca geometric characteristics of the probe and the tank containing the gaseous component.

[0209] The Raman interaction section is defined in the article Magne2020 and corresponds to the term called “Raman differential cross section”. The coefficient o, depends on the wavelength X. On the other hand, it is independent, in particular, of the temperature T, the intensity Ii of the excitation beam and the partial pressure P(X).

[0210] Relation (2) is also valid for methane and nitrogen monoxide of the gaseous medium 81. However, in the case of methane and nitrogen monoxide, since the volume of the housing 80 is constant, the ratio P(X) / T is constant. Thus, for methane and nitrogen monoxide, relation (2) can also be written in the form of the following relations (3):

[0211] - for methane, r(Xei)= where K / ei is a constant equal to Oxei*P(Xei) / Tei, and

[0212] - for nitrogen monoxide, r(Xe2)= Ii*Kxe2, where is a constant equal to e2) / Re2,

[0213] Since methane and nitrogen monoxide are contained in the same housing 80 and mixed, the temperatures Tei and Te2 of these two gases are equal.

[0214] During a step 212, for each gaseous component to be quantified and for the methane and the nitrogen monoxide of the gaseous medium 81, the value of the corresponding coefficient o^ is determined then recorded in the memory 62. The value of each coefficient o^ is determined experimentally in the absence of induced radio attenuation. Typically, for this, the probe 20 is used to measure the value r(X) under experimental conditions where the temperature T, the intensity h of the excitation beam and the partial pressure P(X) are known.

[0215] Finally, during phase 198, the temperature To and the partial pressures P(Xel)0 and P(Xe2 )0 at this temperature To of the methane and the nitrogen monoxide of the gaseous medium 81 are also recorded in the memory 62. Thus, the constants K / ei and KAe2 are known since they are equal, respectively, to Oxei*P(Xei)o / To and 0xe2*P(Xe2)o / To.

[0216] The calibration phase 200 is then completed and the phase 220 of operation of the device 2 begins. Phase 220 is typically executed during a nuclear accident. However, it can also be executed while the nuclear reactor is operating normally, i.e. in an operational situation.

[0217] Phase 220 comprises a measurement cycle repeated throughout the duration of phase 220. In [Fig.6], the different measurement cycles are identified by the symbol Q, where the index j is the order number of the cycle since the start of phase 220. To simplify [Fig.6], only cycles Ci and C2 are fully represented.

[0218] Each cycle Q comprises a period TOff and a period T0N which, preferably, are immediately consecutive. During the period TOff, the computer 36 controls the laser source 32 so that it is switched off for the entire duration AOff of this T0FF period.

[0219] The period T0FF comprises two time windows designated in Figure 6, respectively, by the symbols C / / and C ± . Preferably, these two windows C / / and C ± follow each other immediately. Here, the sum of the durations t1 and t2 of the windows, respectively C / / and C ± , is equal to the duration A0FF.

[0220] Throughout the duration tl of the window C / / , the computer 36 maintains the passing axis of the polarizer 98 parallel to the plane PI. For this, the computer 36 does not supply the rotator 100. At the same time, the computer acquires the values ​​S l(XeX), S l(Xe2), SK / , cod. S1(XO2), Sl(Xco), S1(XN2) and S1(W-

[0221] Throughout the duration t2 of the window C ± I, the computer 36 maintains the passing axis of the polarizer 98 perpendicular to the plane PI. For this, the computer 36 supplies the rotator 100 via the cables 46. At the same time, the computer 36 acquires the values ​​S2(Xei), S2(Xe2), S2(XCO2), S2(XO2), S2(XC0), S2(XN2) and S2(XH2O).

[0222] During the period T0N, the computer 36 controls the laser source 32 so that it generates the excitation beam for the entire duration A0N of this period T0N. The period T0N comprises two time windows designated in FIG. 6, respectively, by the symbols R / / and R -L . Preferably, these two windows R / / and R -L follow each other immediately. Here, the sum of the durations t3 and t4 of the windows, respectively R / / and R -L , is equal to the duration A0N of the period T0N.

[0223] Preferably, the ratio t3 / t4 is equal to the ratio tl / t2. In addition, to simplify relation (1), here, the durations t3 and t4 are chosen to additionally verify the following condition: tl+t2 = t3+t4, i.e. the durations A0FF and A0N are equal. For this, here, all the durations tl, t2, t3 and t4 are equal. Under these conditions, relation (1) is written in the following simplified form: R(X) = S3(X) - S1(X) - k(X)*(S4(X) - S2(k)), where R(X) is the amplitude of the Raman line at wavelength X, expressed in number of counts.

[0224] Advantageously, the durations A0FF and A0N are less than 10 s or 5 s. Thus, over the duration of a cycle, even in the event of a nuclear accident, the radiation-induced attenuation does not substantially modify the attenuation of the optical signal in the fibers and optical components. In addition, to obtain good precision, the durations A0FF and A0N are chosen to be greater than 0.01 s and, generally, greater than 1 s.

[0225] Throughout the duration t3 of the window R / / , the computer 36 maintains the passing axis of the polarizer 98 parallel to the plane PI. For this, the computer 36 does not supply the rotator 100. At the same time, the computer 36 acquires the values ​​S3(Xei), S3(Xe2), S3(Xrefl), S3(Xref2), S3(XH2), S3(XCO2), S3(âO2), S3(Xco), S3(Xn2) and S3(XH2O).

[0226] Throughout the duration t4 of the R -L window, the computer 36 maintains the passing axis of the polarizer 98 perpendicular to the PI plane. For this, the computer 36 supplies the rotator 100 via the cables 46. At the same time, the computer 36 acquires the values ​​S4(Xei), S4(Xe2), S4(XCo2), S4(XO2), S4(XCo), S4(XN2) and S4(XH2o)-

[0227] Then, during a step 230, the computer 36 establishes the raw values ​​r(Xei), r(Xe2), r(XH2), r(XCo2), r(XO2), r(XCo), r(XN2) and r(XH20). More precisely, during step 230, the computer 36 calculates the values ​​r(Xei), r(Xe2), r(XCo2), r(XO2), r(XCo), r(XN2) and r(XH20) using the relation (1) and the values ​​of the signals S1, S2, S3 and S4 acquired during the previous measurement cycle.

[0228] The value r(XH2) is, for its part, determined according to the baseline subtraction method or SLB method. Thus, the quantity of hydrogen is determined from the values ​​S3(XH2), S3(Xrefi) and S3(Xref2) of the signal S3. More precisely, the SLB method consists of defining a spectral function f representing the spectral background on which the Raman peaks appear. This can be linear or polynomial, for example, of order two. Here, by way of illustration, this function f is defined by one of the following relations: f(X) = a + b*(X - Xcte)2 and f(X) = a + b*(X - Xcte), where a, b and Xcte are calibration parameters. The last parameter Xcte is an optimization parameter, chosen a priori in the spectral band of interest. The parameters a and b are deduced from the values ​​S3(Xrefi) and S3(Xref2) by solving the following system of equations: f(Xrefi) = S3(X refi) and f(Xref2) = S3(Xref2).The value r(XH2) is then deduced by subtraction of the spectral function, i.e. using the following relation: r(XH2) = [S3(XH2) - f(XH2 )] / t3. .

[0229] The raw values ​​r(Xei), r(Xe2), r(XH2), r(XC02), r(XO2), r(Xco), r(XN2) and r(XH20) are expressed in counts per second (cps). These raw values ​​r(Xei), r(Xe2), r(XH2), r(XCo2), r(XO2), r(XCo), r(XN2) and r(XH20) are proportional to the amounts, respectively, of methane and nitrogen monoxide in the gaseous medium 81, of hydrogen, carbon dioxide, oxygen, carbon monoxide, nitrogen and water vapor.

[0230] Then, during a step 232, the calculator 36 constructs quantities of hydrogen, carbon dioxide, oxygen, carbon monoxide, nitrogen and water vapor corrected for the radiation-induced attenuation from the raw values ​​established during step 230.

[0231] In the presence of radiation-induced attenuation, the raw value r(X) is lower than that which would be established in the absence of radiation-induced attenuation. Thus, in the presence of radiation-induced attenuation, the preceding relations (2) and (3) become the following relations (4) and (5):

[0232] - relation (4): r(X)*T = Ii*O;*A(X)*P(X)c, where P(X)C is the partial pressure of the gaseous component corrected for radiation-induced attenuation, and

[0233] - relations (5): r(Xel)= Ii*K,el*A(Xel) and r(Xe2)=

[0234] The coefficient A is defined by the following relation, for any wavelength X: A(X) = r(X) / r(X)c, where:

[0235] - r(X) is the raw value of the amplitude of the Raman line at wavelength X established during step 230 and therefore measured in the presence of radiation-induced attenuation, And

[0236] - r(X)is a raw value of the amplitude of the same Raman line at the same length X-wave produced by the same quantity of the gaseous component to be quantified in the absence of radiation-induced attenuation.

[0237] The value A(X) is therefore between 0 and 1. The value 0 corresponds to the extreme case where the attenuation of the optical signal generated by the Raman effect is total, that is to say that, whatever the quantity of the gaseous component, the value r(X) is zero. The value 1 corresponds to the case where there is no radio-induced attenuation.

[0238] The values ​​A(Xei) and A(Xe2) are the values ​​of the coefficient A for the wavelengths, respectively, Xei and Xe2. Thus, A(Xei) = r(Xei) / r(Xei)c = r(Xei) / r(Xei)0 and A(Xe2) = r(Xe2) / r(Xe2)c = r(Xe2) / r(Xe2)0. Unlike the value A(X), the values ​​A(Xei) and A(Xe2) are known as soon as the raw values ​​r(Xei) and r(Xe2) are established.

[0239] In this embodiment, during an operation 234, the computer 36 estimates the value A(X) from the ratios r(Xei) / r(Xei)o and r(Xe2) / r(Xe2)o, where r(Xei)0 and r(Xe2)o are the raw values ​​pre-recorded in the memory 62 and representative of the amplitude of the Raman lines at wavelengths Xei and Xe2 produced by the gaseous medium 81 at an instant when the radiation-induced attenuation is zero. In this first embodiment, it is assumed that the radiation-induced attenuation coefficient A varies linearly as a function of the wavelength X over the spectral band of interest. In this case, the computer 36 estimates the value A(X) using the following relationship: A(X) = A(Xei) - p*(X - Xei), where:

[0240] - A(Xei) is equal to the ratio r(Xei) / r(Xei)0,

[0241] - p is equal to (A(Xel) - A(Xe2)) / (Xe2 - Xel),

[0242] - A(Xe2) is equal to the ratio r(Xe2) / r(Xe2)0.

[0243] In parallel with step 234, during an operation 240, the sensor 22 measures the temperature T of the sample and the computer 36 acquires this measurement.

[0244] During an operation 242, the computer 36 determines the partial pressure P(X)C of each of the gaseous components in the sample of the medium 10 using the following relation (6): P(X)C = K*(A(Xei) / A(X))*(r(X) / r(Xei))*T, where:

[0245] - K is a constant equal, in this mode of relation, to (K^i / oJ, and

[0246] - T is the temperature measured by the sensor 24 and acquired by the computer 36.

[0247] During a step 250, the computer 36 can also establish the proportion, as a percentage, of each of these gaseous components in the sample of the medium 10. For example, by assuming that the sum of the partial pressures of all the components quantified here (O2, N2, H2O, H2, CO and CO2) is equal to the total pressure PT in the enclosure 4, then the proportion of the gaseous component which corresponds to the Raman line at the wavelength X is taken equal to the ratio P(X)C / PT, where PT is the total pressure inside the enclosure 4 measured by the sensor 22.

[0248] Thus, at the end of each cycle Q, a new quantification of the gaseous components is available. For example, during a step 260, the computer 36 controls the human-machine interface 38 to display these quantifications on the screen 66.

[0249] The method of [Fig.7] is identical to the method of [Fig.5] except that the standard 81 is a gaseous medium which produces a single standard line in the spectral band of interest at the wavelength Xeb. For this purpose, the gaseous medium 81 here consists only of methane for which the wavelength Xei is equal to 960 nm when the methane is excited by a monochromatic excitation beam whose wavelength is equal to 750 nm.

[0250] The calibration phase 198 and the exploitation phase 220 are identical to what has been described with reference to [Fig.5] except that all the operations carried out for the wavelength Xe2 are omitted. In addition, step 232 is replaced by a step 282 of constructing the quantities of hydrogen, carbon dioxide, oxygen, carbon monoxide, nitrogen and water vapor corrected for the radio-induced attenuation from the raw values ​​established during step 230. Step 282 comprises the operation 240 of measuring the temperature T followed by an operation 292 of determining the partial pressure of each of the gaseous components.

[0251] Furthermore, in this second embodiment, it is assumed that the radiation-induced attenuation coefficient A does not vary as a function of the wavelength X. In this case, for all wavelengths of interest, the value A(X) is simply taken equal to the ratio r(Xei) / r(Xei)0. Under these conditions, relation (6) is simplified and is simply written in the following form: P(X)C = K*(r(X) / r(Xei))*T, since the ratio A(Xei) / A(X) is equal to one.

[0252] Under these conditions, during operation 292, for each wavelength of interest X, the partial pressure P(X)C corrected for the radiation-induced attenuation is directly determined using the following relation: P(X)C = K*(r(X) / r(Xei))*T, where K is the same constant as that of relation (6).

[0253] Thus, in this particular case, it is possible to determine the partial pressure P(X)C without going through an explicit estimation of the value A(X).

[0254] Chapter III: Variants:

[0255] Probe variants:

[0256] Alternatively, the probe comprises an outer housing which contains all of the optical components and an inner housing. The inner housing is located on the path of the excitation beam between the beam splitter 88 and the mirror 90. Only the inner housing contains the gaseous medium 81. This inner housing comprises an inlet porthole and an outlet porthole, arranged in a similar manner to the window 92 (oriented according to the Brewster incidence). In this case, all of the optical components or at least some of the optical components of the probe are located outside the inner housing. which contains the gaseous medium 81. For example, only the end of the fiber 42 is received inside the inner housing. This inner housing also includes a transparent window through which the excitation beam emerges after passing through the gaseous medium 81 contained in this inner housing. This excitation beam which emerges from the inner housing is then used to excite the sample contained in the chamber 94 of the probe.

[0257] Other standard gases are possible. For example, the mixture of methane and nitric oxide can be replaced by ethane (C2H6) which exhibits Raman lines at 810.5 nm (CC bond) and 958.5 nm (CH bond) when excited by an excitation beam whose wavelength is equal to 750 nm. In the embodiment of [Fig.7], methane can be replaced by nitric oxide.

[0258] Alternatively, the gaseous medium 81 further comprises a neutral gas which does not produce any Raman line in the spectral band of interest when it is excited by the excitation beam. For example, the neutral gas is argon.

[0259] The standard 81 can also be a solid material. For example, the solid standard is a silicone ring crossed, in its center, by the excitation beam. This standard is located inside the housing 80, between the separating plate 88 and the mirror 90. The interaction between the silicone ring and the excitation beam takes place on the edge of the excitation beam. It is therefore much less effective than at the center of the excitation beam, which makes it possible to superimpose in the same Raman spectrum a standard line, at the wavelength Xeb coming from the solid standard with all the other Raman lines produced by the gaseous components to be quantified. In the case of a silicone standard, the Raman line produced by this standard is located at a wavelength very close to that of methane (CH4).Furthermore, in the case of a solid standard as in the case of a gaseous standard, the value r(Xei)0 is related, in the absence of radiation-induced attenuation, to the intensity h of the excitation beam by the following relation: r(Xei)0 = Kei*Ii, where Kei is a constant that can be determined experimentally during the calibration phase. Relation (5) also remains valid in the case of a solid standard. Under these conditions, the partial pressure P(X)C can be established using relation (6): P(X)C = K*(A(Xei) / A(X))*(r(X) / r(Xei))*X where K is the constant equal to Kei / Ov Thus, for a solid standard or for a gaseous standard, the partial pressure P(X)C is always proportional to the term (r(X) / r(Xei))*T.

[0260] In the case where the standard produces two standard lines, the standard may be formed by the combination of a standard gas that produces the standard line at wavelength Xei and a solid standard that produces the standard line at wavelength Xe2. For example, the standard gas is methane and the solid standard is a silicon ring.

[0261] The optical signal scattered by the Raman effect by the sample can be collected via a window other than window 92. For this, the housing 80 comprises a second transparent window distinct from the window 92. This second window is arranged near the point R to be crossed by the optical signal scattered by the Raman effect. The optical signal scattered by the Raman effect which passes through this second window is then directed towards the filter 96 and the polarizer 98. In such an embodiment, it is not necessary to collect the optical signal scattered by the Raman effect and which passes through the window 92.

[0262] Other solutions are possible for focusing the laser beam on the point R. For example, instead of using the parabolic mirror 90 for this, it is possible to use an achromatic doublet of converging lenses arranged so that the different wavelengths are focused on the same point R.

[0263] Alternatively, the filter 96 is omitted. In this case, the filtering function is provided solely by the blade 88.

[0264] Other embodiments of the polarizer 84 or 98 are possible. For example, the polarizer 84 or 98 is a glass polarizer (sodium-silicate) doped with ellipsoidal nanoparticles having a strong polarizing effect.

[0265] Alternatively, the polarizer 98 is replaced by a polarization splitter cube. This splitter cube separates the parallel and perpendicular polarization directions. Thus, the splitter cube simultaneously generates the signals S1 and S2 and then simultaneously the signals S3 and S4. In this case, the fiber 44 is replaced by a first and a second optical fiber. The first and second fibers guide the measured signals with, respectively, the parallel and perpendicular polarizations, to the reading unit. The reading unit 34 is then modified to be able to measure, simultaneously, the signals S1 and S2 and the signals S3 and S4.

[0266] In a simplified embodiment, the textured material is omitted.

[0267] Processing unit variants:

[0268] In another embodiment, the source 32 is optically connected to the probe 20 via an optical switch which directs the excitation beam towards the probe 20 and, alternately, towards another probe. In this case, the source 32 continuously emits the excitation beam and, during the period T0N, the switch directs the excitation beam towards the probe 20. During the period T0FF of the probe 20, the switch directs the excitation beam towards the other probe and no longer towards the probe 20.

[0269] Alternatively, a CCD (“Charge Coupled Device”) sensor is used in conjunction with an imaging spectrometer that disperses the received optical signal as a function of the wavelengths in the plane where the CCD sensor is located. Typically, such a CCD sensor is capable of measuring the optical signal at more than 300 or 1000 or 2048 different wavelengths regularly distributed within the spectral band of interest. Such a CCD sensor therefore measures both the optical signal received at each wavelength X of interest and also at other wavelengths of no interest.

[0270] The photomultiplier 54 can be replaced by a photodiode such as an avalanche photodiode or a SiPM (“Silicon-PhotoMultiplier”) detector.

[0271] Depending on the context of use, the processing unit may be configured to measure the quantity of one or more additional gaseous components other than those from the group consisting of water vapor, oxygen, nitrogen, carbon monoxide, carbon dioxide and hydrogen. In this case, the processing unit is configured to use an additional wavelength of interest corresponding to each additional gaseous component to be quantified. Conversely, the processing unit may also be configured to measure the quantity of only one or only part of the gaseous components from the group consisting of water vapor, oxygen, nitrogen, carbon monoxide, carbon dioxide and hydrogen. In this case, typically, the number of acquisition chains 50 is reduced.For example, alternatively, the partial pressure P(XH20) of water vapor is taken equal to the difference between the total pressure PT minus the sum of the partial pressures of hydrogen, carbon dioxide, oxygen, carbon monoxide and nitrogen. In this case, the acquisition chain 50 used to process the optical signal at the wavelength XH2o can be omitted.

[0272] Variants of the calibration phase:

[0273] Other approximations of the evolution of the value of the coefficient k as a function of the wavelength X are possible. For example, as a variant, the evolution of the value of the coefficient k as a function of the wavelength X is approximated using a polynomial of order greater than one.

[0274] In another embodiment, the value of the coefficient k also varies as a function of the measured radiation dose. In this case, the quantification device is also capable of measuring the radiation dose received by the sample of the gaseous medium. For example, this radiation dose is estimated from the intensity of the Cherenkov radiation measured in the absence of the excitation beam.

[0275] In a simplified variant, the electronic noise of the acquisition chain is neglected. In this case, each value k(X0 is simply taken equal to the ratio Spara(X; ) / Sperp(Xi).

[0276] In a very simplified variant, the value of the coefficient k is assumed to be constant regardless of the wavelength X.

[0277] In a degraded embodiment, the calibration step 198 is executed when the nuclear reactor is operating. In this case, the calibration phase is triggered during nominal operation of the nuclear reactor and the reference sample is identical to the sample of the gaseous medium 10.

[0278] In another variant, the calibration phase of the coefficient k is carried out during the manufacture of the device 2, that is to say at a time when the probe 20 is not installed at inside the enclosure.

[0279] Variants of the correction of radiation-induced attenuation:

[0280] Alternatively, an etalon producing more than two etalon lines in the spectral band of interest may be used. In this case, the relationship that relates the value A(X) of the radiation-induced attenuation to the wavelength X may be approximated by a more complex relationship than a linear relationship. For example, this more complex relationship is a second-order polynomial.

[0281] Variants of the quantification method

[0282] In another embodiment, the wavelength of the excitation beam is reduced so that the vibrational line of hydrogen is also measurable using the reading unit 34. This vibrational line is then present in the Raman spectrum of the signal S3 and almost absent from the Raman spectrum of the signal S4 given its low depolarization ratio. In this case, one of the wavelengths of interest used is the wavelength of this vibrational line of hydrogen and the quantity of hydrogen is then measured using relation (1). In another variant, although the use of relation (1) leads to using only approximately 25% of the signal S3(XH2), the quantity of hydrogen is still quantified using relation (1). In these last two cases, the reading unit 34 does not need to carry out measurements at wavelengths Xref1 and Xref2.

[0283] Alternatively, the ratios tl / t2 and t3 / t4 are different from one. The ratios tl / t2 and t3 / t4 are also not necessarily equal.

[0284] The ratio A0ff / A0n is also not necessarily equal to one. For example, the duration Aoff is greater than the duration A0N or vice versa.

[0285] What has been described so far also works if the durations A0FF and A0N are greater than 10 s. However, preferably, particularly in the presence of a nuclear accident, these durations A0FF and A0N are less than 10 s.

[0286] In another embodiment, the values ​​r(Xei), r(Xe2), r(XH2), ri / .cmk r(X02), r(XCo ), r(XN2) and r(XH2o) are also established using the SLB method. In this case, relation (1) is not used. Furthermore, in this case, the period T0FF and the window R -L can be omitted. On the other hand, during the window R / / , values ​​of the signal S3 located on either side of each Raman line must then be measured.

[0287] Other relationships than relationship (1) are possible. For example, as a variant, the noise caused by Cherenkov radiation is eliminated by implementing a synchronous demodulation method. For this, throughout the duration of the R / / and R -L windows, the method additionally comprises the modulation, typically at a predetermined frequency, of the amplitude of the excitation beam so that the sample is excited with an amplitude-modulated monochromatic excitation beam. Under these conditions, the optical signal collected by the probe 20 has the same amplitude modulation. Throughout the duration of the first window R / / , the computer acquires, at each end of a sampling period Te, values ​​S3(X)e, S3(Xei)e and S3(Xe2)e representative of the number of photons collected by the probe during this sampling period Te at the wavelengths, respectively, X, Xei and Xe2. Thus, at the end of the first window R / / , the computer 36 has acquired time sequences of values ​​S3(X)e, S3(Xei)e and S3(Xe2)e. Throughout the duration of the window A* ± The computer 36 acquires, at each end of the sampling period Te, values ​​S4(X)e, S4(Xei)e and S4(Xe2)e representative of the number of photons collected by the probe during this sampling period Te at the wavelengths, respectively, X, Xei and Xe2. Thus, at the end of the R -h window, the calculator 36 has acquired a time sequence of values ​​S4(X)e, S4(Xei)e and S4(Xe2)e.Then, the calculator 36 extracts the values ​​S3(X), S3(Xei), S3(Xe2), S4(X), S4(Xei) and S4(Xe2) from the time sequences of values, respectively, S3(X)e, S3(Xei)e, S3(Xe2)e, S4(X)e, S4(Xei)e and S4(Xe2)e acquired and by exploiting the predetermined amplitude modulation. For example, for this, the calculator carries out a synchronous demodulation. Each raw value r(X) is then calculated from the difference [(S3(X) / t3 - k(X)*S4(X) / t4]. .

[0288] Alternatively, it is also possible to determine the partial pressure P(XH2o)c of water vapor by calculating the difference between the total pressure in the enclosure 4, measured by the sensor 22, and the sum of all the partial pressures P(XH2)C, P(XCo2) c, P(X02)c, P(XCo)c and P(XN2)C determined during operation 242 or 292. It is then possible to deduce the relative humidity rate by the following calculation RH% = 100xP(X H2o)c / PSat, where Psat is the saturated vapor pressure which depends only on the temperature of the mixture at the measurement point R considered. The saturated vapor pressure can be estimated by an Antoine law, as described in relation (9) of the article Magne2020.

[0289] Other variants:

[0290] The continuous laser source can be replaced by a pulsed laser source.

[0291] In practice, the gaseous medium contained inside the containment vessel of a nuclear reactor does not always have a homogeneous composition. Thus, it is often necessary to quantify the gaseous components at several different locations inside the vessel 4. For this, a probe 20 is installed at each of these locations. In this case, the processing unit 30 is connected to all of these probes 20 in order to be able to quantify the gaseous components present at each of these locations. In the case where several probes 20 are installed inside the vessel 4, then, advantageously, the teaching of application FR2315145 filed on December 22, 2023 is implemented to limit the number of crossings of the vessel 4.

[0292] The teaching given here applies to any containment enclosure within which houses a nuclear reactor and not only in the case where the enclosure is that formed by a reactor building of a nuclear power plant which produces electricity.

[0293] The embodiments of Figures 5 and 7 can be implemented independently of each other.

[0294] Several of the variants described above can be combined in the same embodiment.

[0295] Chapter IV: Advantages of the embodiments described:

[0296] Determining the partial pressure P(X)C using the relation P(X)C = KAAL. ei) / A(X))*(r(X) / r(Xei))*T makes it possible to determine a partial pressure corrected for radiation-induced attenuation and therefore to improve the accuracy of the quantification method when it is implemented during a nuclear accident.

[0297] Using the ratios r(Xei) / r(Xei)0 and r(Xe2) / r(Xe2)0 to estimate the value A(X) also allows us to take into account the fact that the radiation-induced attenuation coefficient varies as a function of the wavelength X.

[0298] Taking the ratio A(Xei) / A(X) equal to one makes it possible to use a single standard line and therefore to simplify the production of the quantification device.

[0299] Using a standard that includes a standard gas makes the probe less sensitive to the relative position of the standard to the excitation beam.

[0300] Carrying out the measurements at different wavelengths of interest makes it possible to measure the quantity of several different gaseous components simultaneously.

[0301] Simultaneously measuring the quantities of water vapor, oxygen and nitrogen makes it possible to assess the risk of an explosion occurring inside the enclosure.

[0302] Measuring the quantities of carbon monoxide and carbon dioxide makes it possible to trace the corium-concrete interaction (Molten Core Concrete Interaction -MCCI) which occurs after the vessel is breached in the event of a nuclear reactor core meltdown.

[0303] Using a continuous laser beam makes it possible, for the same size, to have a laser beam whose average power is much greater than if a pulsed laser beam were used. However, the greater the average power of the laser beam, the greater the precision of the measurement of the quantity of the gaseous component.

[0304] Housing the standard gas in the sealed housing of the probe makes it possible to establish the r(X)c value corrected for the effect of radiation-induced attenuation and, in addition, to establish the partial pressure of the gaseous component without having to use a pressure sensor.

[0305] Using a standard that produces two Raman lines at wavelengths Xei and Xe2 makes it possible to use the relation A(X) = A(Xei) - p*(X - Xei) to estimate more precisely the radiation-induced attenuation and therefore to make more precise measurements in the case nuclear accident.

[0306] Housing all the components of the probe inside the same housing as that which contains the standard gas also makes it possible to protect these components from attacks from the external environment and, in particular, from exposure to aerosols and water vapor.

Claims

Claims

1. Method for quantifying, by Raman spectrometry, at least one gaseous component inside a containment enclosure of a nuclear reactor, this method comprising the following steps: - the excitation (R / / , R -L ), by a probe placed inside the containment enclosure and using a monochromatic excitation beam, of a sample of the gaseous medium located inside the containment enclosure and, simultaneously, of a standard whose quantity is constant during the execution of the quantification method, and in parallel - the collection (R / / , R -L), by the probe, of an optical signal scattered, by Raman effect, by the sample and by the standard simultaneously excited so that the Raman spectrum of the collected optical signal comprises: - a Raman line at a wavelength X corresponding to the gaseous component to be quantified, and - at least one Raman line at a wavelength Xei corresponding to the standard, this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification method, - the measurement (R / / , R -L ), by a reading unit, of the optical signal collected by the probe, - the establishment (230), by an electronic calculator, from the measured optical signal, of raw values ​​including at least: - a raw value r(X) representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified, and - a raw value r(Xei) representative of the amplitude of the Raman line at wavelength Xei produced by the standard, characterized in that the method comprises: - a step (240) of measuring the temperature of the sample, and - a step (242; 292) of determining the partial pressure of the gaseous component to be quantified corrected for the radiation-induced attenuation using the following relation: P(X)C = K*(A(Xei) / A(X))*(r(X) / r(Xei))*T, where: - P(X)C is the partial pressure of the gaseous component to be quantified corrected for the radiation-induced attenuation, - K is a predetermined constant independent of radio attenuation- induced, - A(Xei) is a value of a radio-induced attenuation coefficient at wavelength Xeb this value A(Xei) being equal to the ratio r(Xei) / r(Xei)0, where r(Xei)o is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xei produced by the standard in the absence of radio-induced attenuation, - A(X) is a value of the radio-induced attenuation coefficient at wavelength X, this value A(X) being equal to the ratio r(X) / r(X)c, where r(X)c is a raw value representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified in the absence of radio-induced attenuation, and - T is the temperature measured during the sample temperature measurement step.

2. Method according to claim 1, in which: - when the standard is excited by the monochromatic excitation beam, the Raman spectrum of the optical signal collected by the probe comprises, in addition to the first Raman line at wavelength Xeb, a second Raman line at a wavelength Xe2 different from wavelength Xei and different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification method, - the step (230) of establishing raw values ​​also comprises the establishment, by the electronic computer and from the measured optical signal, of a raw value r(Xe2) representative of the amplitude of the Raman line at wavelength Xe2 produced by the standard,and - the method comprises estimating (234) the value A(X) of the radiation-induced attenuation coefficient at wavelength X using the ratios r(X ei) / r(Xei)0 and r(Xe2) / r(Xe2)0, where r(Xe2)0 is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xe2 produced by the standard at an instant when the radiation-induced attenuation is zero.,

3. The method of claim 2, wherein estimating the value A(X) comprises calculating the value A(X) using the following relationship: A(X) = A(Xei) - p*(X - Xei), where: - A(Xei) is equal to the ratio r(Xei) / r(Xei)o, - p is equal to (A(Xei) - A(Xe2)) / (Xe2 - Xei), - A(Xe2) is equal to the ratio r(Xe2) / r(Xe2)0.

4. The method of claim 1, wherein in the step of determining- mination (292) of the partial pressure, the ratio A(Xei) / A(X) is taken equal to a

5. 1111. Method according to any one of the preceding claims, in which the excitation (R / / , R -L ) of the standard comprises the excitation of a standard gas contained in a housing sealed to the standard gas and of constant volume.

6. Method according to any one of the preceding claims, in which: - the establishment (230) of several raw values ​​comprises the establishment of a raw value r(X) for several different wavelengths X of interest, each of these wavelengths of interest corresponds to a particular gaseous component to be quantified in the excited sample, the measurements at these different wavelengths of interest being carried out simultaneously, then - the execution, for each of these wavelengths of interest, of the step (242; 292) of determining a partial pressure of this gaseous component to be quantified corrected for the radiation-induced attenuation.

7. The method of claim 6, wherein the wavelengths of interest include wavelengths of interest corresponding to hydrogen, water vapor, oxygen, and nitrogen.

8. A method according to claim 6 or 7, wherein the wavelengths of interest comprise wavelengths of interest corresponding to carbon monoxide and carbon dioxide.

9. A method according to any preceding claim, wherein the excitation beam is a continuous laser beam.

10. Device for quantifying, by Raman spectrometry, at least one gaseous component inside a containment enclosure of a nuclear reactor, this device comprising: - a laser source (32) capable of emitting a monochromatic excitation beam, - a probe (20), placed inside the containment enclosure, capable: - of exciting, using the monochromatic excitation beam emitted by the laser source, a sample of the gaseous medium located inside the containment enclosure and, simultaneously, a standard whose quantity is constant during the execution of the quantification method, and in parallel - of collecting an optical signal scattered, by Raman effect, by the sample and by the standard simultaneously excited so that the Raman spectrum of the collected optical signal includes: - a Raman line at a wavelength X corresponding to the gaseous component to be quantified, and - at least one Raman line at a wavelength Xei corresponding to the standard, this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample and the quantities of which are likely to vary during the execution of the quantification method, - a reading unit (34) capable of measuring the optical signal collected by the probe, and - an electronic calculator (36) configured to establish, from the measured optical signal, raw values ​​including at least: - a raw value r(X) representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified, and - a raw value r(Xei) representative of the amplitude of the Raman line at wavelength Xei produced by the standard, characterized in that: - the probe comprises a temperature sensor (22) capable of measuring the temperature of the sample, and - the electronic calculator (6) is also configured to determine the partial pressure of the gaseous component to be quantified corrected for the radiation-induced attenuation using the following relation: P(X)C = K*(A(Xel) / A(X))*(r(X) / r(^ where: - P(X)C is the partial pressure of the gaseous component to be quantified corrected for the radiation-induced attenuation, - K is a predetermined constant independent of the radiation-induced attenuation, - A(Xei) is a value of a radio-induced attenuation coefficient at wavelength Xeb, this value A(Xei) being equal to the ratio r(Xei) / r(Xei)0, where r(Xei)o is a pre-recorded raw value representative of the amplitude of the Raman line at wavelength Xei produced by the standard in the absence of radio-induced attenuation, - A(X) is a value of the radiation-induced attenuation coefficient at wavelength X, this value A(X) being equal to the ratio r(X) / r(X)c, where r(X)c is a raw value representative of the amplitude of the Raman line at wavelength X produced by the component to be quantified in the absence of radiation-induced attenuation, and - T is the temperature measured by the temperature sensor of the sample.

11. Probe (20) for producing a quantification device according to claim 10, wherein the probe is intended to be placed inside the confinement enclosure and capable of: - exciting, using a monochromatic excitation beam emitted by the laser source, a sample of the gaseous medium located inside the confinement enclosure and, simultaneously, a standard whose quantity is constant during the execution of the quantification method, and in parallel - collecting an optical signal scattered, by Raman effect, by the sample and by the standard simultaneously excited so that the Raman spectrum of the collected optical signal comprises: - a Raman line at a wavelength X corresponding to the gaseous component to be quantified, and - at least one Raman line at a wavelength Xei corresponding to the standard,this wavelength Xei being different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample, characterized in that: - the probe comprises a temperature sensor (22) capable of measuring the temperature of the sample, the standard (81) and a housing (80), - the standard (81) comprises a standard gas which, when excited by the excitation beam emitted by the laser source, produces the Raman line at the wavelength Xei in the optical signal collected by the probe, and - the housing (80) contains the standard gas, this housing being sealed to this standard gas and of constant volume and this housing comprising a transparent window (92) arranged to allow the excitation beam, which excited the standard gas, to exit the housing to excite the sample of the gaseous medium.,

12. Probe according to claim 11, in which the standard (81) contained in the housing is capable, when excited by the excitation beam emitted by the laser source, of producing, in addition to the first Raman line at the wavelength Xeb, a second Raman line at a wavelength X e2 different from the wavelength Xei and different from the wavelengths where Raman lines appear corresponding to the gaseous components present in the excited sample.

13. A probe according to claim 12, wherein the standard (81) comprises ethane or a mixture of methane and nitric oxide.

14. A probe according to any one of claims 11 to 13, wherein the housing (80) comprises, inside the housing: - the end of an incoming optical fiber (42) through which the monochromatic excitation beam is introduced inside the housing, - the end of an outgoing optical fiber (44) through which the collected optical signal is emitted towards the outside of the housing, - all of the optical components (82, 84, 86, 88, 90, 96, 98, 102) necessary to excite the sample and collect the optical signal scattered, by Raman effect, by the gaseous components to be quantified in this sample.

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