Concentration detection device, method, storage medium and program product

Abstract

The present application relates to a concentration detection device, method, storage medium and program product. The concentration detection device includes a pulsed neutron source, a measuring tank, an attenuator, a detector and a processing device. The measuring tank contains a first solution and a neutron poison element; the pulsed neutron source is used to generate neutrons that are incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; the attenuator is used to attenuate the first gamma signal and the second gamma signal, and output the attenuated first gamma signal and the attenuated second gamma signal to the detector; the detector is used to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device; the processing device is used to detect the concentration of the neutron poison element based on the attenuated first gamma signal and the attenuated second gamma signal, so that the concentration of the neutron poison element is more accurate.

Description

Technical Field

[0001] The present application relates to the field of nuclear technology, and in particular to a concentration detection device, method, storage medium and program product. Background Art

[0002] During the nuclear fuel processing process, solutions containing uranium, plutonium, and transuranic elements are produced. Because uranium, plutonium, and transuranic elements can undergo neutron-induced fission reactions, leading to subcriticality and posing safety concerns, appropriate amounts of neutron poison elements, such as gadolinium, cadmium, and boron, are often added to the solution to inhibit these reactions and ensure process safety. Therefore, the concentration of these neutron poison elements in the solution is crucial. For example, the concentration of gadolinium ranges from 0.1g / L to 1.0g / L. Accurate analysis of the gadolinium content in the liquid is essential for accurate control of the nuclear fuel processing process. Summary of the Invention

[0003] Based on this, it is necessary to provide a concentration detection device, method, storage medium and program product that can improve measurement accuracy in response to the above technical problems.

[0004] In a first aspect, the present application provides a concentration detection device, comprising a pulsed neutron source, a measuring tank, an attenuator, a detector, and a processing device, wherein the measuring tank contains a first solution and a neutron poison element;

[0005] The pulsed neutron source is used to generate neutrons incident on the measuring cell; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal;

[0006] The attenuator is configured to attenuate the first gamma signal and the second gamma signal, and output the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0007] The detector is configured to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device;

[0008] A processing device is used to detect the concentration of the neutron poison element according to the attenuated first gamma signal and the attenuated second gamma signal.

[0009] In one embodiment, the attenuator comprises a collimator;

[0010] The collimator is used to change the quantity of the first gamma signal and the second gamma signal incident on the detector.

[0011] In one embodiment, the attenuator further comprises a hardened body;

[0012] The hardened body is used to change the intensity of the first gamma signal and the second gamma signal incident to the detector.

[0013] In one embodiment, the concentration detection device further includes a neutron absorption layer, a neutron moderator and a gamma shield, the neutron absorption layer wraps the measuring slot, and the distance between the neutron moderator and the measuring slot is less than a preset distance, the neutron moderator wraps the neutron absorption layer, and the gamma shield wraps the neutron moderator.

[0014] In one embodiment, the concentration detection device further includes a neutron attenuation detector;

[0015] The neutron attenuation detector is used to measure the number of neutrons that have penetrated the measuring slot.

[0016] In one embodiment, the pulsed neutron source includes an electron accelerator and a neutron conversion target;

[0017] The electron accelerator is used to generate radiation, so that the radiation generates neutrons on the neutron conversion target and is incident on the measurement slot.

[0018] In one embodiment, the concentration detection device further includes a neutron monitoring detector, which is used to monitor the radiation generated by the electron accelerator.

[0019] In one embodiment, the concentration detection device further comprises a calibration tank containing a second solution, wherein the second solution comprises the first solution and a preset weight of a neutron poison element;

[0020] The calibration tank is used to determine the relationship between the concentration of the neutron poison element in the second solution and the neutron capture lifetime corresponding to the concentration.

[0021] In a second aspect, the present application provides a concentration detection method, which is applied to a concentration detection device, wherein the concentration detection device includes a pulsed neutron source, a measuring tank, an attenuator, a detector, and a processing device, wherein the measuring tank contains a first solution and a neutron poison element;

[0022] generating neutrons incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal;

[0023] attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0024] detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to the processing device;

[0025] The concentration of the neutron poison element is detected according to the attenuated first gamma signal and the attenuated second gamma signal.

[0026] In a third aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0027] generating neutrons incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal;

[0028] attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0029] detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to the processing device;

[0030] The concentration of the neutron poison element is detected according to the attenuated first gamma signal and the attenuated second gamma signal.

[0031] In a fourth aspect, the present application further provides a computer program product, comprising a computer program, which, when executed by a processor, implements the following steps:

[0032] generating neutrons incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal;

[0033] attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0034] detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to the processing device;

[0035] The concentration of the neutron poison element is detected according to the attenuated first gamma signal and the attenuated second gamma signal.

[0036] The above-mentioned concentration detection device, method, storage medium and program product include a pulsed neutron source, a measuring tank, an attenuator, a detector and a processing device. The measuring tank contains a first solution and a neutron poison element. The pulsed neutron source is used to generate neutrons that are incident on the measuring tank. The neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal and react with the neutron poison element to generate a second gamma signal. The attenuator is used to attenuate the first gamma signal and the second gamma signal and output the attenuated first gamma signal and the attenuated second gamma signal to the detector. The detector is used to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device. The processing device is used to detect the concentration of the neutron poison element based on the attenuated first gamma signal and the attenuated second gamma signal. In this application, the attenuator is used to attenuate the first gamma signal and the second gamma signal to improve the signal-to-value ratio and the throughput rate of the concentration detection device, so that the concentration of the neutron poison element determined based on the energy spectrum analysis of the attenuated first gamma signal and the attenuated second gamma signal is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the structure and liquid composition of a measuring tank to be analyzed in one embodiment;

[0038] Figure 2 Schematic diagram of a neutron cross section of two main elements to be analyzed in a measuring cell in one embodiment;

[0039] Figure 3 is a first structural schematic diagram of a concentration detection device in one embodiment;

[0040] Figure 4 Schematic diagram of the three-dimensional structure of a concentration detection device in one embodiment;

[0041] Figure 5 Schematic diagram of neutron absorption cross section of each element in one embodiment;

[0042] Figure 6 Schematic diagram of the relationship between the captured neutron lifetime and the concentration of the Gd element in one embodiment;

[0043] Figure 7 A schematic diagram of the relationship between neutron survival time and neutron number in one embodiment;

[0044] Figure 8 FIG1 is a schematic diagram showing the relationship between the captured neutron lifetime and the concentration of the Gd element in another embodiment;

[0045] Figure 9 is a schematic diagram of the principle of an attenuator in one embodiment;

[0046] Figure 10FIG1 is a schematic diagram of a gamma signal after cascade decay of fission fragments in one embodiment;

[0047] Figure 11 is a second structural schematic diagram of a concentration detection device in one embodiment;

[0048] Figure 12 is a third structural schematic diagram of a concentration detection device in one embodiment;

[0049] Figure 13 is a fourth structural schematic diagram of a concentration detection device in one embodiment;

[0050] Figure 14 Schematic diagram of the detection accuracy of neutron poison elements under different intensities of pulsed neutron sources and different measurement times in one embodiment.

[0051] Description of reference numerals:

[0052] 100. Concentration detection device; 10. Pulsed neutron source; 11. Measuring cell;

[0053] 12. Attenuator; 13. Detector; 14. Processing equipment;

[0054] 121. Collimator; 122. Hardened body;

[0055] 15. Neutron absorption layer; 16. Neutron moderator; 17. Gamma shield;

[0056] 18. Neutron attenuation detector; 101. Electron accelerator; 102. Neutron conversion target;

[0057] 19. Neutron monitoring detector; 20. Calibration tank; 21. Base. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0060] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0061] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0062] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0063] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0064] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0065] When used herein, the singular forms "a", "an", and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0066] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0067] During the nuclear fuel processing process, a solution containing uranium, plutonium, and transuranic elements is produced. Since uranium, plutonium, and transuranic elements can all undergo neutron-induced fission reactions, causing subcriticality and posing safety issues, an appropriate amount of neutron poison elements are usually added to the solution to inhibit the neutron-induced fission reactions of uranium, plutonium, and transuranic elements, ensuring the safety of the production process. Among them, neutron poison elements refer to elements with particularly large neutron absorption cross-sections, such as gadolinium, cadmium, boron, etc. 157 The cross section of Gd is 255,000 barn@25.3 meV.

[0068] During processing, the gadolinium concentration range is a critical parameter, typically ranging from 0.1 g / L to 1.0 g / L. Accurate analysis of the gadolinium content in the liquid is essential for accurate control of the nuclear fuel processing process. Table 1 provides typical measurement cell volumes, gadolinium concentration ranges, analytical accuracy, and the specific activity (activity per unit volume) of other radionuclides in the measured liquid.

[0069] Table 1

[0070]

[0071] like Figure 1 As shown, the liquid in the measurement tank contains not only uranium (U), plutonium (Pu), and transuranic elements, but also large amounts of highly radioactive fission fragment nuclides (Cs, Y, and Ba). These levels are unstable and vary with the progress of the production process. (Under typical operating conditions, the maximum total activity in the liquid tank can reach 3.6×1011 Bq, a significant amount.) Therefore, the radioactivity level in the liquid can vary over a wide range, posing a significant challenge to accurately measuring gadolinium concentration.

[0072] In the related art, the problem of measuring the concentration of gadolinium in liquid can generally be considered from two aspects. The first aspect is to obtain the neutron poison element content in the liquid by analyzing the transmittance of the radiation.

[0073] Analyzing the transmittance of rays includes “analyzing the concentration of neutron poison elements by analyzing photon transmittance” and “analyzing the concentration of neutron poison elements by neutron transmittance”.

[0074] Taking gadolinium as an example, due to the presence of varying amounts of uranium and plutonium in liquids, which have higher atomic numbers and potentially much higher number densities (1 / cm³) within the liquid, gadolinium's photon attenuation is relatively minor. Therefore, measuring gadolinium concentration via photon transmittance is not feasible.

[0075] Figure 2 Schematic diagrams of the neutron cross-sections for the two main elements in the measurement cell are shown. It can be seen that while Gd has a significantly larger cross-section in the thermal neutron region, the cross-section curve rapidly decreases as it transitions from the thermal to the epithermal neutron region, becoming smaller than the cross-section for H. Therefore, to ensure sensitive analysis of gadolinium, the thermal neutron region should be selected. However, since H is the dominant element in the liquid, its contribution to the macroscopic neutron attenuation cross-section is large. The mean free path of thermal neutrons in the liquid is only approximately 0.19 cm, while the liquid thickness required for neutron penetration is at least 8 cm (see Table 1 above). The efficiency of direct neutron penetration without scattering is close to zero. Therefore, the probability of neutrons penetrating the liquid is very low, making it difficult to use for practical measurement and analysis.

[0076] The second aspect is to induce the neutron poison element in the liquid to produce characteristic radiation by injecting external radiation into the liquid, and then analyze the concentration of the neutron poison element. Since the liquid to be tested contains a high background of gamma rays from fission fragments, the maximum activity of the solution must be 3.6×10 11Under the background of Bq, how to achieve an acceptable system signal-to-noise ratio and meet the detection system's throughput rate, even when applying external radiation to the liquid, will face great challenges. Therefore, this application proposes a concentration detection device, method, storage medium, and program product that can improve the accuracy of neutron poison element detection.

[0077] Figure 3 FIG. 1 is a first structural diagram of a concentration detection device in one embodiment, as shown in FIG. Figure 3 As shown, the concentration detection device 100 includes a pulsed neutron source 10, a measuring tank 11, an attenuator 12, a detector 13 and a processing device 14. The measuring tank 11 contains a first solution and a neutron poison element; the pulsed neutron source 10 is used to generate neutrons that are incident on the measuring tank 11; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; the attenuator 12 is used to attenuate the first gamma signal and the second gamma signal, and output the attenuated first gamma signal and the attenuated second gamma signal to the detector 13; the detector 13 is used to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device 14; the processing device 14 is used to detect the concentration of the neutron poison element according to the attenuated first gamma signal and the attenuated second gamma signal.

[0078] In the embodiments of this application, Figure 3 As shown, the concentration detection device 100 includes a pulsed neutron source 10, a measuring slot 11, an attenuator 12, a detector 13 and a processing device 14. The neutrons generated by the pulsed neutron source 10 are injected into the measuring slot 11, where they are slowed down and captured to generate a first gamma signal and a second gamma signal. The first gamma signal and the second gamma signal are measured by the detector 13 after passing through the attenuator 12. The detector 13 detects and outputs the attenuated first gamma signal and the second gamma signal. The processing device 14 performs attenuation characteristic analysis on the attenuated first gamma signal and the second gamma signal to obtain the concentration of the neutron poison element.

[0079] Optionally, the three-dimensional structure diagram of the concentration detection device is as follows Figure 4 As shown, Figure 4 The left side shows the positional relationship of the concentration detection device 100 in the installed measurement room, and the right side is a schematic overview of the structure of the concentration detection device 100.

[0080] Among them, the pulsed neutron source 10 needs to consider issues such as source strength and working life. Optionally, it can be a neutron source or a neutron generator, for example, it can be a pulsed neutron source 10 composed of an electron accelerator and a neutron conversion target. It can also be a pulsed neutron source 10 composed of a hadron accelerator (accelerated protons, deuterons, etc.) and a neutron conversion target. The hadron accelerator can generate 10 10～13n / s ray.

[0081] Optionally, the detector 13 may use a scintillator, the luminescence time of which is no more than 100 ns.

[0082] Optionally, the concentration detection device 100 may further include a base, which is used to support the entire concentration detection device 100 , and the detector 13 and the attenuator 12 may also move in parallel through the bottom device.

[0083] The pulsed neutron source 10 generally produces fast neutrons with MeV energy. The fast neutrons enter the measuring tank 11 and react with the nuclides and neutron poison elements in the first solution of the measuring tank 11 and are absorbed by them. For example, gadolinium reacts with neutrons, and the absorption capacity of Gd for neutrons is mainly determined by 155 Gd (61000 barn@25.3 meV, abundance 14.8%) and 157 Gd (255,000 barn @ 25.3 meV, abundance 15.7%) contributes to the (n, γ) reaction with neutrons, which emits a second gamma signal of several MeV. This is the most promising reaction for measuring Gd concentration. This can be expressed by the following formula:

[0084] n+ 155 Gd→ 156 Gd * → 156 Gd+γ s +ICe -

[0085] n+ 157 Gd→ 158 Gd * → 158 Gd+γ s +ICe -

[0086] Among them, n is neutron, γ s is the second gamma signal generated after the reaction, ICe - is the internal conversion electron, 156 Gd* and 158 Gd* is a composite nucleus and both have very high excitation energies, 8.536MeV and 7.937MeV respectively.

[0087] However, the deexcitation of a compound nucleus in a high-energy excited state has the following characteristics: (1) It is usually impossible to deexcite directly to the ground state, but loses the excitation energy through cascade deexcitation. The deexcitation process will produce 2 to 3 γ photons, and the deexcitation path is not single; (2) Since the energy states at high energy levels are dense, although the energy of each γ transition is certain, on average, since there are too many energy levels corresponding to γ photons, the γ energy spectrum will appear as a continuously distributed peakless structure. Therefore, it is impossible to obtain a clear full-energy peak through the γ energy spectrum measured by the detector 40, and it is difficult to directly identify the information of the Gd element based on this. (3) As a high-Z nucleus, the compound nucleus 156 Gd * and 158 Gd * When de-excited to a low energy state, an isobaric state will appear, which makes it possible for internal conversion electrons and subsequent emission of characteristic X-rays and Auger electrons. The corresponding rays of characteristic X-rays and Auger electrons have insufficient penetrating power and are of no value for measurement.

[0088] Based on the above analysis, it is clear that the concentration of the neutron poison element cannot be determined by directly performing energy spectrum analysis on the first and second gamma signals after the reaction. Therefore, the first and second gamma signals are attenuated by attenuator 12 to obtain the attenuated first and second gamma signals. The processing device 14 receives the attenuated first and second gamma signals, analyzes the attenuation characteristics of the attenuated first and second gamma signals, and detects the concentration of the neutron poison element.

[0089] Optionally, attenuating the first gamma signal and the second gamma signal includes attenuating the number of the first gamma signal and the second gamma signal; and attenuating the intensity of the first gamma signal and the second gamma signal, wherein the attenuator attenuates the first gamma signal and the second gamma signal, thereby improving the pass rate and signal-to-source ratio of the detector 13. The signal-to-source ratio is the ratio of the intensity of the second gamma signal to the intensity of the first gamma signal, or the ratio of the number of photons in the second gamma signal to the number of photons in the first gamma signal.

[0090] After entering the measuring tank 11, the neutrons are absorbed by the first solution in the measuring tank 11 and undergo two main processes:

[0091] The first process is an energy loss process through inelastic scattering or elastic scattering, in which the fast neutrons (for example, in the MeV energy range) generated by the pulsed neutron source 10, after entering the measurement slot 11, will undergo inelastic scattering or elastic scattering with the nuclides therein, rapidly lose energy, and leave the fast neutron zone and enter the slow neutron zone.

[0092] The second process is the absorption process after entering the 1 / v region. That is, after entering the slow neutron region, the neutron may be absorbed by various nuclides and neutron poison elements in the first solution. The absorption cross section σ is inversely proportional to the neutron velocity v, that is, σ∝1 / v. In the 1 / v region, the probability of a neutron being absorbed in any time segment is constant, so the exponential decay law can be used to describe the neutron's survival probability in this process:

[0093]

[0094] Where N0 is the number of neutrons in the liquid at time 0, N(t) is the number of neutrons at time t, and τ is the neutron capture lifetime. Since the first process is very short, on the scale of nanoseconds to tens of nanoseconds, it is negligible compared to the second process. Therefore, the neutron capture lifetime, or how long it survives, is primarily determined by the second process. In the second process, the neutron capture lifetime τ is determined by the following formula:

[0095]

[0096] Among them, t0 represents the time when the neutron enters the liquid, t c represents the time it takes for the neutron to be absorbed, represents the average value obtained by measuring the two time differences, namely the neutron capture lifetime τ, k represents the number of nuclides in the liquid, and n i represents the number density of nuclide i (1 / cm 3 ), σ 0,i Represents the neutron absorption cross section (cm2) of the nuclide at a certain energy. 2 ), v0 corresponds to the velocity of the neutron at that energy. For example, the velocity of the neutron at an energy of 25.3 meV is 2.2×10 5 cm / s.

[0097] Figure 5 Schematic diagram of neutron absorption cross section of each element in one embodiment, as shown in FIG. Figure 5 As shown, since the neutron absorption cross section of the neutron poison element Gd is large, its proportion in the denominator on the right side of the above formula is significant. Therefore, the change in the concentration of the Gd element in the first solution will significantly affect the size of the neutron capture lifetime τ, and the measurement of the Gd concentration can be achieved by analyzing the neutron capture lifetime τ.

[0098] Among them, Table 2 shows the relative contribution of each element including H and Gd in the first solution to the neutron absorption capacity. It can be seen that H and Gd are the main contributors to the neutron absorption process. Moreover, when the concentration of Gd changes within the specified range of [0.1 g / L, 1 g / L], its relative contribution to neutron absorption increases from 40.5% to 87.1%, a change of 46.7%. This shows that the effect of Gd concentration on the neutron capture lifetime τ is significant. Therefore, in turn, the neutron capture lifetime τ can be used to analyze the concentration of the neutron poison element Gd. The analysis results are shown in FIG. Figure 6 As shown, it can be obtained that the captured neutron lifetime changes with the Gd concentration. The higher the Gd concentration, the shorter the neutron capture lifetime and the stronger the neutron absorption ability; the lower the Gd concentration, the longer the neutron capture lifetime and the weaker the neutron absorption ability.

[0099] Table 2

[0100]

[0101] In a possible implementation, the processing device 14 performs gamma spectrum analysis on the attenuated first gamma signal and the second gamma signal to obtain the following: Figure 7 The diagram below shows the relationship between the neutron survival time (neutron capture lifetime) and the number of surviving neutrons. For example, for a neutron emitted at time t0, if the detector detects a second gamma signal at time t1, the corresponding neutron capture lifetime is t1-t0. The processing device 14 performs segmented statistics on the neutron capture lifetimes corresponding to all first and second gamma signals detected by the detector 13. The neutrons in each interval are those that survived from time t0 onwards.

[0102] It should be noted that Figure 7 The provided schematic diagram shows the relationship curves between the neutron capture lifetime and the number of neutron survival at multiple Gd concentrations. In the actual measurement process, the relationship curve between the neutron capture lifetime and the number of neutron survival corresponding to the first solution is obtained. The slope of the relationship between the neutron capture lifetime and the number of neutron survival is further determined based on the relationship curve between the neutron capture lifetime and the number of neutron survival corresponding to the first solution. The Gd concentration corresponding to the first solution is determined based on the calculated slope and the preset relationship between the neutron capture lifetime and the Gd concentration. The preset relationship between the neutron capture lifetime and the Gd concentration is as follows: Figure 8 shown.

[0103] The above-mentioned concentration detection device includes a pulsed neutron source, a measuring tank, an attenuator, a detector, and a processing device. The measuring tank contains a first solution and a neutron poison element; the pulsed neutron source is used to generate neutrons that are incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; the attenuator is used to attenuate the first gamma signal and the second gamma signal, and output the attenuated first gamma signal and the attenuated second gamma signal to the detector; the detector is used to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device; the processing device is used to detect the concentration of the neutron poison element based on the attenuated first gamma signal and the attenuated second gamma signal. In the present application, the attenuator is used to attenuate the first gamma signal and the second gamma signal, thereby improving the signal-to-value ratio and the pass rate of the concentration detection device, so that the concentration of the neutron poison element determined based on the energy spectrum analysis of the attenuated first gamma signal and the attenuated second gamma signal is more accurate.

[0104] Figure 9 FIG. 1 is a schematic diagram of the principle of an attenuator in one embodiment, as shown in FIG. Figure 9 As shown, the attenuator includes a collimator 121 and a hardener 122 ; the collimator 121 is used to change the amount of the first gamma signal and the second gamma signal incident to the detector 13 ; the hardener 122 is used to change the intensity of the first gamma signal and the second gamma signal incident to the detector 13 .

[0105] In the embodiment of this application, Figure 9 As shown, the attenuator includes a collimator 121 and a hardened body 122 . The parameters of the collimator 121 include a diameter D and a length L, and the parameters of the hardened body 122 include a thickness T. The hardened body 122 is located in the middle of the collimator 121 . Therefore, the height of the hardened body 122 is equal to the diameter D of the collimator 121 .

[0106] On the one hand, the resolution time of the detector 13 determines its pass rate (the number of ray signals that can be processed per unit time). The resolution time of the detector 13 is determined by the collection time of the carriers in the sensitive volume of the detector 13 and the formation time of the subsequent circuit. For the detector 13 in the pulse working mode, its typical value is at the level of ns to 10μs. If gamma energy spectrum analysis is to be carried out, it is necessary to take into account both detection efficiency and energy resolution. It is best to use inorganic scintillators or semiconductor detectors. Then this value will be above 100ns, so the pass rate corresponding to 10% counting loss will not be greater than 10 6 / s. If the maximum activity of the first solution reaches 3.6×10 11 Bq, means that the first solution has the potential to emit 10 11 / s (the specific value depends on the nuclide composition of the solution, which is a dynamic quantity related to the production process) of the first gamma signal, which is much greater than 10 6 / s, resulting in serious accumulation and making measurement impossible.

[0107] Therefore, when both the second gamma signal and the first gamma signal enter the detector 13, the passing rate of the detector 13 is limited. Even if the signal is relatively good, if the intensity (1 / s) of the first gamma signal and the first gamma signal is too large, the detector 13 still cannot work in the pulse mode, and thus cannot analyze the first gamma signal and the first gamma signal energy spectrum. Figure 9 The diameter D and length L of the middle collimator 121 can effectively change the number of first and second gamma signals entering the detector 13, allowing the detector 13 to operate in pulse mode. For example, by increasing the length L, the number of first and second gamma signals entering the detector 13 can be reduced.

[0108] On the other hand, since neutron poison elements are stable and non-radioactive, they need to be excited by an external radiation source in order to generate characteristic signals. Taking gadolinium as an example, gadolinium is placed in a 9L first solution, and the measuring tank has a stainless steel shell. Therefore, it is impossible to excite and measure the characteristic X-rays of gadolinium (maximum energy is K O23 =50.2keV, the penetration is too weak) to analyze gadolinium. It is necessary to use neutrons to induce gadolinium to produce a second gamma signal with MeV energy for measurement. Since after each (n, γ) reaction 155,157 Gd emits an average of 2 to 3 gamma photons. In order to make the second gamma signal count of gadolinium equal to the first gamma signal count (background) of other nuclides in the first solution, that is, the signal-to-background ratio is 1, it is required that the number of neutrons injected into the measuring cell and causing (n, gamma) reaction per second is 10 11 n / s level. Taking into account the injection efficiency of the neutron source and the reaction probability in the liquid, the neutron yield of the pulsed neutron source is estimated to be around 10 11 ~10 12 Between n / s, it puts too much pressure on protection and is not practical.

[0109] The second gamma signal is an interference term. Although theoretically it can be deducted as background when measuring the neutron capture lifetime, its impact on statistics cannot be eliminated. It will inevitably reduce the measurement accuracy under the same time or increase the measurement time under the same accuracy requirement. Therefore, by adding the hardened body 122, the signal-to-value ratio is further increased. Figure 10As shown, since the first gamma signal in the first solution is mainly gamma rays after the β-γ cascade decay of fission fragments, its energy is mostly several hundred keV and generally difficult to exceed 2MeV. The second gamma signal is always several MeV or higher due to its binding energy with neutrons. Therefore, when lead is used as the hardener 122, the second gamma signal has better penetration and the first gamma signal will be more attenuated. Figure 9 When the thickness of the hardened body 122 is T, although the intensity of the second gamma signal also decreases, the intensity of the first gamma signal decreases more relatively. Therefore, the signal-to-noise ratio of the concentration detection device increases with the increase of the thickness of the hardened body.

[0110] Optionally, the hardened body 122 may be made of a high-Z material, not limited to the lead provided in this embodiment.

[0111] After considering the hardening effect, the neutron yield of the pulsed neutron source can be reduced accordingly. The calculation results show that the demand for neutron yield can be reduced to 2×10 8 n / s, improving the practicality of the concentration detection device.

[0112] Figure 11 FIG. 1 is a second structural diagram of a concentration detection device in one embodiment, as shown in FIG. Figure 11 As shown, the concentration detection device 100 further includes a neutron absorption layer 15, a neutron moderator 16 and a gamma shield 17. The neutron absorption layer 15 wraps the measuring tank 11, and the distance between the neutron absorption layer 15 and the measuring tank 11 is less than a preset distance. The neutron moderator 16 wraps the neutron absorption layer 15, and the gamma shield 17 wraps the neutron moderator 16.

[0113] In the embodiment of this application, Figure 11 As shown, the neutron absorption layer surrounds the measuring cell 11, the neutron moderator 16 surrounds the neutron absorption layer 15, and the gamma shield 18 surrounds the neutron moderator 16. By providing a neutron absorption layer 15 with strong absorption capability, the nuclides and neutron poison elements in the first solution can be absorbed by neutrons as quickly as possible. Since neutrons include fast neutrons and slow neutrons, and slow neutrons are rapidly absorbed, the neutron moderator 16 is wrapped around the neutron absorption layer 15 to moderate the fast neutrons to produce slow neutrons, thereby improving neutron absorption capability. Furthermore, the gamma shield 17 is wrapped around the neutron moderator 16 to provide isolation, reducing the amount of neutrons and the first and second gamma signals generated by the concentration detection process, thereby ensuring environmental safety and improving detection accuracy.

[0114] It should be noted that, in order to ensure the equipment safety of the concentration detection device 100 , a certain gap needs to be left between the neutron absorption layer 15 and the measuring tank 11 .

[0115] As mentioned above Figure 11As shown, the concentration detection device further includes a neutron attenuation detector 18 ; the neutron attenuation detector 18 is used to measure the number of neutrons after penetrating the measuring slot 11 .

[0116] In this embodiment of the present application, the concentration detection device 100 further includes a neutron attenuation detector 18. This detector is positioned behind the measurement cell 11 and is used to measure the number of neutrons that have passed through the measurement cell 11. This detector can reflect changes in the concentration of the neutron poison element based on the number of neutrons that have passed through the measurement cell 11. For example, a greater number of neutrons that have passed through the measurement cell 11 indicates a lower concentration of the neutron poison element involved in the reaction, and a lower concentration of the neutron poison element.

[0117] On the other hand, the change in the total amount of neutron poison elements in the first solution can be reflected according to the number of neutrons that penetrate the measuring tank 11. For example, the fewer the number of neutrons that penetrate the measuring tank 11, the greater the total amount of neutron poison elements in the first solution.

[0118] Figure 12 FIG. 3 is a third structural diagram of a concentration detection device in one embodiment, as shown in FIG. Figure 12 As shown, the pulsed neutron source includes an electron accelerator 101 and a neutron conversion target 102 ; the electron accelerator 101 is used to generate radiation, so that the radiation generates neutrons on the neutron conversion target 102 that are incident on the measurement slot 11 .

[0119] In the embodiment of the present application, the neutron yield of the pulsed neutron source based on the neutron generator is generally only about 10 8 n / s, some can achieve 10 10 n / s neutron yield, but it is difficult to take into account the service life at the same time. 8 At a neutron yield of n / s, the guaranteed service life is generally over a thousand hours. When operating in high-yield mode, the service life is even shorter. Although its structure is compact, it is difficult to meet the needs of actual working conditions.

[0120] Pulsed neutron sources based on hadron accelerators can produce 10 10～13 The neutron conversion target 102 can produce neutrons at a rate of n / s, but it occupies a large area, cannot be used on site, and is very expensive. In addition, the long-term reliability of the neutron conversion target 102 has not been fully verified.

[0121] Therefore, a pulsed neutron source based on an electron accelerator can take into account lifespan, yield, and volume at the same time. For example, the maximum annual operating time of an electron accelerator used for irradiation is ∼6,000 hours.

[0122] The electron accelerator 101 generates X-rays e - , using X-ray e - Target bombardment of tungsten target W produces high energy photons γ, which pass through 9 Be or2 H to produce neutrons n. The reactions involved are as follows:

[0123] e - +W→W+e - '+γ

[0124]

[0125] Optionally, the tungsten target used in the neutron conversion target 102 in the above formula generates high-energy photons γ. 9 Be or 2 H to produce neutrons n, and other types of neutron conversion targets 102 can also be used to produce high-energy photons γ, which are then passed through low (γ, n) threshold nuclides to cause neutron reactions to produce pulsed fast neutrons with sufficiently high intensity.

[0126] In the embodiment of the present application, since the electron accelerator has a high target electron current intensity, it can produce a sufficiently high neutron yield; in addition, the electron accelerator has a compact structure and reliable operation, which can fully meet the needs of this work.

[0127] Furthermore, as mentioned above Figure 12 As shown, the concentration detection device 100 further includes a neutron monitoring detector 19 , which is used to monitor the radiation generated by the electron accelerator 101 .

[0128] In the embodiment of the present application, the concentration detection device 100 further includes a neutron monitoring detector 19, which is used to monitor the radiation generated by the electron accelerator 101. Because the electron accelerator 101 outputs a fixed number of pulses each time, i.e., a fixed number of radiation, the neutron monitoring detector 19 can be used to monitor the radiation generated by the electron accelerator 101, thereby ensuring the stability of the electron accelerator's operation and thus improving the reliability of the concentration detection device.

[0129] As mentioned above Figure 12 As shown, the concentration detection device 100 also includes a calibration tank 20, which contains a second solution, and the second solution includes the first solution and a preset weight of a neutron poison element; the calibration tank 20 is used to determine the relationship between the concentration of the neutron poison element in the second solution and the neutron capture lifetime corresponding to the concentration.

[0130] In the embodiment of this application, Figure 12 and Figure 13As shown, the calibration slot 20 can be arranged in front of the measuring slot 11, that is, the neutron incident path is to first pass through the calibration slot 20 and then enter the measuring slot 11. The neutron absorption layer 15 is wrapped around the periphery of the measuring slot 11 and the calibration slot 20, the neutron moderator 16 is wrapped around the periphery of the neutron absorption layer 15, and the gamma shield 17 is wrapped around the periphery of the neutron moderator 16, with a certain gap left between the neutron absorption layer 15 and the measuring slot 11 and the calibration slot 20.

[0131] The calibration tank 20 contains a second solution comprising the first solution and a predetermined weight of a neutron poison element. During calibration, the attenuator and detector 13 are aligned with the calibration tank 20 using the base 21 for calibration measurement. Specifically, X-rays generated by the electron accelerator 101 generate neutrons on the neutron conversion target 102. These neutrons enter the calibration tank 20 and react with the second solution in the calibration tank 20, generating gamma signals. The gamma signals pass through the collimator 121 and the hardened body 122 before entering the detector 13. This allows the neutron capture lifetime of the neutron poison element at different concentrations to be determined, as described above. Figure 8 During calibration, a neutron attenuation detector 18 can also be used to monitor the neutrons penetrating the calibration slot 20 .

[0132] During the actual measurement process, the second solution in the calibration tank 20 can be drained, and the attenuator and the detector 13 can be aligned with the measurement tank using the base 21 to detect the concentration of the neutron poison element.

[0133] In one embodiment, a concentration detection method is provided, which is applied to Figure 3 The concentration detection device in is described as an example, comprising the following steps: generating neutrons incident on the measuring tank; using the neutrons to react with the nuclides generated by the first solution to generate a first gamma signal, and reacting with the neutron poison element to generate a second gamma signal; attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector; detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to the processing equipment; and detecting the concentration of the neutron poison element according to the attenuated first gamma signal and the attenuated second gamma signal.

[0134] In the present embodiment, concentration detection was performed using the concentration detection method provided in this embodiment, based on the aforementioned concentration detection device. Table 3 shows the physical quantities that affect measurement accuracy and their typical values. During actual measurement, the activity of the first solution in the measuring tank and the Gd content are variables. Therefore, the values of the various parameters in Table 3 are within a certain range rather than fixed values.

[0135] Table 3

[0136]

[0137] The analysis accuracy calculation formula provided in Table 3 can be used to calculate the analysis accuracy under different measurement time lengths. Figure 14 Figure 1 is a schematic diagram of the detection accuracy of neutron poison elements under different intensities of pulsed neutron sources and different measurement times in one embodiment. It can be seen that when the output of the pulsed neutron source increases from 5×10 7 n / s to 5×10 8 When n / s changes, the analysis accuracy under different measurement time lengths is better when the intensity of the pulse neutron source is greater and the measurement time is longer.

[0138] It can be seen that as long as the intensity of the pulsed neutron source is slightly greater than 10 8 n / s, it is possible to achieve a measurement accuracy of 20% in about 5 minutes and a measurement accuracy of less than 10% in 30 minutes.

[0139] The pulsed neutron source used in the embodiment of the present application can easily achieve 2×10 8 The neutron yield of n / s is based on the above Figure 14 It can be seen that the requirements can be met within a measurement time of 300 seconds, and the accuracy is about 10%.

[0140] Table 4 shows the measurement accuracy at different measurement times. It can be seen that when the output of the pulsed neutron source is 2×10 8 When the measurement speed is 1000 nm / s, the measurement accuracy within 5 to 30 minutes required by the technical specifications is between 19.66% and 8.03%, which fully meets the accuracy requirement of ±20%. Therefore, this application can provide greater convenience to users, allowing them to determine the analysis speed according to their needs.

[0141] Table 4

[0142] Measurement duration (s) 300 600 1200 1800 Measurement accuracy (%) 19.66 13.9 9.83 8.03

[0143] In the above-mentioned concentration detection method, neutrons incident on the measuring tank react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; the first gamma signal and the second gamma signal are attenuated, and the attenuated first gamma signal and the attenuated second gamma signal are output to the detector; the attenuated first gamma signal and the attenuated second gamma signal are detected and output to the processing equipment. The processing equipment detects the concentration of the neutron poison element based on the attenuated first gamma signal and the attenuated second gamma signal. In the present application, the first gamma signal and the second gamma signal are attenuated to improve the signal-to-noise ratio and the pass rate of the concentration detection device, so that the concentration of the neutron poison element determined based on the energy spectrum analysis of the attenuated first gamma signal and the second gamma signal is more accurate.

[0144] It should be understood that, although the steps in the flowcharts of the above embodiments are shown in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in the flowcharts of the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily to be performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0145] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0146] Generating neutrons incident on the measuring cell; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and to react with the neutron poison element to generate a second gamma signal;

[0147] attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0148] detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to a processing device;

[0149] The concentration of the neutron poison element is detected based on the attenuated first gamma signal and the attenuated second gamma signal.

[0150] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0151] Generating neutrons incident on the measuring cell; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and to react with the neutron poison element to generate a second gamma signal;

[0152] attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector;

[0153] detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to a processing device;

[0154] The concentration of the neutron poison element is detected according to the attenuated first gamma signal and the attenuated second gamma signal.

[0155] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0156] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0157] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A concentration detection device, characterized in that: The concentration detection device includes a pulsed neutron source, a measuring tank, an attenuator, a detector and a processing device, wherein the measuring tank contains a first solution and a neutron poison element; The pulsed neutron source is used to generate neutrons incident on the measuring cell; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; The attenuator is configured to attenuate the first gamma signal and the second gamma signal, and output the attenuated first gamma signal and the attenuated second gamma signal to the detector; The detector is configured to detect and output the attenuated first gamma signal and the attenuated second gamma signal to the processing device; The processing device is used to detect the concentration of the neutron poison element according to the attenuated first gamma signal and the attenuated second gamma signal.

2. The device according to claim 1, characterized in that The attenuator includes a collimator; The collimator is used to change the quantity of the first gamma signal and the second gamma signal incident on the detector.

3. The device according to claim 1, characterized in that The attenuator further includes a hardened body; The hardened body is used to change the intensity of the first gamma signal and the second gamma signal incident to the detector.

4. The device according to claim 1, characterized in that The concentration detection device also includes a neutron absorption layer, a neutron moderator and a gamma shield. The neutron absorption layer wraps the measuring slot and the distance between the neutron absorption layer and the measuring slot is less than a preset distance. The neutron moderator wraps the neutron absorption layer, and the gamma shield wraps the neutron moderator.

5. The device according to claim 1, characterized in that The concentration detection device also includes a neutron attenuation detector; The neutron attenuation detector is used to measure the number of neutrons that have penetrated the measuring slot.

6. The device according to claim 1, characterized in that The pulsed neutron source includes an electron accelerator and a neutron conversion target; The electron accelerator is used to generate radiation, so that the radiation generates neutrons on the neutron conversion target and is incident on the measurement slot.

7. The device according to claim 6, characterized in that The concentration detection device further includes a neutron monitoring detector, which is used to monitor the radiation generated by the electron accelerator.

8. The device according to claim 1, characterized in that The concentration detection device further comprises a calibration tank containing a second solution, wherein the second solution comprises the first solution and a preset weight of a neutron poison element; The calibration tank is used to determine the relationship between the concentration of the neutron poison element in the second solution and the neutron capture lifetime corresponding to the concentration.

9. A concentration detection method, characterized in that: The concentration detection method is applied to a concentration detection device, which includes a pulsed neutron source, a measuring tank, an attenuator, a detector, and a processing device. The measuring tank contains a first solution and a neutron poison element. generating neutrons incident on the measuring tank; the neutrons are used to react with the nuclides generated by the first solution to generate a first gamma signal, and react with the neutron poison element to generate a second gamma signal; attenuating the first gamma signal and the second gamma signal, and outputting the attenuated first gamma signal and the attenuated second gamma signal to the detector; detecting and outputting the attenuated first gamma signal and the attenuated second gamma signal to the processing device; The concentration of the neutron poison element is detected according to the attenuated first gamma signal and the attenuated second gamma signal.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to claim 9 are implemented.

11. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to claim 9 are implemented.

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