Neutron poisoning monitoring device

Abstract

The present disclosure provides a neutron poisoning monitoring device. The neutron poisoning monitoring device comprises: a container for containing a liquid to be tested including neutron poisoning; a neutron source configured to emit neutrons to the liquid to be tested; a detector configured to detect the number of neutrons and / or photons in the liquid to be tested; a multi-channel calibrator configured to send the number of neutrons and / or photons detected by the detector to a neutron poisoning monitoring control device; the neutron poisoning monitoring control device is configured to control the neutron source to emit neutrons to the liquid to be tested, and within a time range after the neutron source is controlled to stop emitting neutrons to the liquid to be tested, control the detector to detect the number of neutrons or photons in the liquid to be tested to obtain multiple detection values, use the background value to correct each of the multiple detection values ​​to obtain multiple correction values, and use the multiple correction values ​​to determine the neutron poisoning concentration in the liquid to be tested; a shielding device configured to shield the liquid to be tested and the detector from external interference.

Description

Technical Field

[0001] The present disclosure relates to the field of detection, and particularly to a neutron poison monitoring device. Background Art

[0002] Traditional neutron poison concentration detection includes two implementation schemes, specifically titration method and on-line instrument detection method. Among them, the titration method requires manual sampling, so there is a risk of radioactive contamination to the staff, and there is a certain time lag in the detection result, which is not continuous, but the detection result is relatively accurate. The instrument method uses on-line measurement to continuously measure the boron concentration, and the measurement result has no lag. Summary of the Invention

[0003] The inventors noticed that in traditional neutron poison concentration detection technology, it is defaulted that the influence of the background on the detection result is stable or even negligible. This leads to a deterioration in the accuracy of the measurement result when the background influence changes. For example, in the field of spent fuel treatment, when monitoring the neutron poison concentration, since the background is not negligible and the background count changes over time, the existing solutions cannot obtain accurate monitoring results.

[0004] Accordingly, the present disclosure provides a neutron poison monitoring device, which can obtain accurate monitoring results by using background data to correct the detection values obtained by the detector.

[0005] In a first aspect of the present disclosure, there is provided a neutron poison monitoring device, including: a container for containing a liquid to be measured including neutron poison; a neutron source configured to emit neutrons to the liquid to be measured; a detector configured to detect the number of neutrons and / or photons in the liquid to be measured; a multi-channel scaler configured to send the number of neutrons and / or photons detected by the detector to the neutron poison monitoring control device; a neutron poison monitoring control device configured to control the neutron source to emit neutrons to the liquid to be measured, and within a specified time range after controlling the neutron source to stop emitting neutrons to the liquid to be measured, control the detector to detect the number of neutrons or photons in the liquid to be measured in each of a plurality of specified time periods to obtain a plurality of detection values, use the background value to correct each of the plurality of detection values to obtain a plurality of corrected values, and use the plurality of corrected values to determine the neutron poison concentration in the liquid to be measured; a shielding device configured to shield the external interference received by the liquid to be measured and the detector.

[0006] In some embodiments, the neutron poison monitoring control device is configured to control the detector to detect the number of neutrons and / or photons in the liquid to be measured when the liquid to be measured does not include neutrons emitted by the neutron source, so as to measure the background value by using the detection result.

[0007] In some embodiments, the neutron poison monitoring and control device is configured to control the detector to detect the number of neutrons and / or photons in the liquid to be measured multiple times within the background measurement time period, so as to obtain multiple background detection values, and calculate the average value of the multiple background detection values to obtain the background value.

[0008] In some embodiments, after the neutron poison monitoring and control device is configured to control the neutron source to emit neutron pulses to the liquid to be measured, a specified time delay is set. After the specified time delay and before controlling the neutron source to emit the next neutron pulse to the liquid to be measured, the detector is controlled to detect the number of neutrons and / or photons in the liquid to be measured multiple times, so as to obtain multiple background detection values, and calculate the average value of the multiple background detection values to obtain the background value.

[0009] In some embodiments, the specified time delay is a predetermined multiple of the neutron lifetime.

[0010] In some embodiments, the predetermined multiple is not less than 10.

[0011] In some embodiments, the neutron poison monitoring and control device is configured to calculate the logarithm of each correction value among the multiple correction values to obtain multiple logarithm values, perform linear fitting on the multiple logarithm values to obtain the slope of the fitting curve, and determine the neutron poison concentration according to the absolute value of the slope.

[0012] In some embodiments, the absolute value of the slope has a linear relationship with the neutron poison concentration.

[0013] In some embodiments, among the multiple specified time periods, the 0th time period is the time period when the neutron source stops emitting neutrons to the liquid to be measured, or the time period after the neutron source stops emitting neutrons to the liquid to be measured and after a specified time delay.

[0014] In some embodiments, the detector includes at least one of a neutron detector and a γ detector; alternatively, the detector is a detector that simultaneously detects neutrons and γ photons.

[0015] In some embodiments, the detector is a counting detector or an energy spectrum detector.

[0016] In some embodiments, the neutron source is an optical neutron source based on an electron linear accelerator or a pulsed neutron source based on a neutron tube.

[0017] Other features and advantages of the present disclosure will become clear through the following detailed description of the exemplary embodiments of the present disclosure with reference to the accompanying drawings. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 Structural schematic diagram of a neutron poison monitoring device according to an embodiment of the present disclosure;

[0020] Figure 2 Schematic diagram of the measurement period for measuring the background value according to an embodiment of the present disclosure;

[0021] Figure 3 Schematic diagram showing the change of the detection value over time according to an embodiment of the present disclosure;

[0022] Figure 4 Schematic diagram of the calibration curve of the neutron poison concentration according to an embodiment of the present disclosure;

[0023] Figure 5 Structural schematic diagram of a neutron poison monitoring device according to another embodiment of the present disclosure;

[0024] Figure 6 Structural schematic diagram of a neutron poison monitoring device according to yet another embodiment of the present disclosure;

[0025] Figure 7 Structural schematic diagram of a neutron poison monitoring device according to yet another embodiment of the present disclosure. Detailed implementation manners

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present disclosure.

[0027] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present disclosure.

[0028] At the same time, it should be understood that for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0029] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification.

[0030] In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0031] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

[0032] Figure 1 The structural schematic diagram of a neutron poison monitoring device according to an embodiment of the present disclosure is shown as follows. Figure 1 As shown, the neutron poison monitoring device includes a neutron poison monitoring control device 11, a container 13 for containing a liquid to be measured 12, a neutron source 14, a detector 15, a multi-channel scaler 16, and a shielding device 17. The liquid to be measured 12 contains neutron poisons.

[0033] The neutron source 14 is configured to emit neutrons to the liquid to be measured 12.

[0034] In some embodiments, the neutron source 14 is a photo-neutron source based on an electron linear accelerator, or a pulsed neutron source based on a neutron tube, or other forms of pulsed neutron sources.

[0035] For example, the width of the neutron pulse generated by the pulsed neutron source is between 0.5 and 4 μs, and the pulse frequency is in the range of 100 to 1000 Hz.

[0036] For example, the neutron poison is boron, cadmium, samarium, or other well-known neutron poison elements.

[0037] It should be noted here that since the present disclosure needs to detect the time spectrum of neutrons or γ particles, the neutron source needs to send neutrons intermittently, and in this case, an isotope neutron source that continuously sends neutrons cannot be used.

[0038] The detector 15 is configured to detect the number of neutrons or photons in the liquid to be measured 12.

[0039] In some embodiments, the detector 15 includes at least one of a neutron detector and a γ detector. Alternatively, the detector 15 is a detector that simultaneously detects neutrons and γ photons.

[0040] In some embodiments, the detector 15 is a counting-type detector or an energy spectrum-type detector.

[0041] The multi-channel scaler 16 is configured to send the number of neutrons or photons detected by the detector 15 to the neutron poison monitoring and control device 11.

[0042] The shielding device 17 is configured to shield the external interference received by the liquid under test 12 and the detector 15.

[0043] For example, the shielding device 17 includes a neutron shielding device and a photon shielding device.

[0044] The neutron poison monitoring and control device 11 is configured to control the neutron source 14 to emit neutrons to the liquid under test 12. Within a specified time range after controlling the neutron source 14 to stop emitting neutrons to the liquid under test 12, the detector 15 is controlled to detect the number of neutrons or photons in the liquid under test 12 in each of a plurality of specified time periods to obtain a plurality of detection values (i.e., time spectra), correct each of the plurality of detection values using the background value to obtain a plurality of corrected values, and determine the neutron poison concentration in the liquid under test 12 using the plurality of corrected values.

[0045] It should be noted here that the concentration of neutron poison can be obtained by using the change in neutron count over time obtained by a neutron detector, or by using the change in γ photon count over time measured by a photon detector. According to neutron nuclear reaction theory, the number of γ photons generated by the reaction of neutrons with matter is proportional to the neutron flux, that is, the count of γ photons is proportional to the count of neutrons. Therefore, analyzing using the γ photon count can also obtain the neutron poison concentration value.

[0046] In some embodiments, among the plurality of specified time periods, the 0 time period is the time period when the neutron source stops emitting neutrons to the liquid under test, or the time period after the neutron source stops emitting neutrons to the liquid under test and delays for a specified duration, N 0 is the number of neutrons and / or photons detected in the 0 time period, N(t) is the number of neutrons and / or photons detected in the t time period, 1 ≤ t ≤ T, and T is the maximum time period. For example, in the case of a pulsed neutron source, T can be a certain time period before the next neutron pulse is about to be emitted, or a certain moment before the next neutron pulse is about to be emitted.

[0047] It should be noted here that within a period of time after controlling the neutron source to stop emitting neutrons to the liquid under test, for example, within a period of time after the pulse ends, the change in neutron and γ photon counts over time satisfies the law of negative exponential decay. The fast neutrons generated by the neutron source mainly go through two processes when entering the liquid under test and being absorbed.

[0048] 1) Energy loss processes through inelastic scattering or elastic scattering: The fast neutrons (e.g., in the MeV energy range) generated by the neutron source, after entering the liquid to be measured, will undergo inelastic scattering or elastic scattering with the nuclides therein, rapidly losing energy, and thus leaving the fast neutron region and entering the slow neutron region.

[0049] 2) Neutron diffusion and absorption processes: After the neutrons enter the slow neutron region, the motion of the neutrons in the medium can be regarded as a diffusion process. At the end of the neutron diffusion process, the neutrons are absorbed by the various nuclides in the liquid. The absorption cross-section σ of the neutrons is inversely proportional to the velocity v of the neutrons, so it is called the 1 / v region.

[0050] In the 1 / v region, the absorption probability of neutrons within any time segment is constant, which enables the survival probability of neutrons in this process to be expressed using the exponential decay law:

[0051]

[0052] In formula (1), N 0 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 lifetime of the neutrons therein.

[0053] Since the time of process 1) is very short, only from ns (nanoseconds) to dozens of nanoseconds, while the time of process 2) is often on the order of 10 microseconds. Therefore, relative to the entire process, the time occupied by process 1) can be ignored, and the lifetime of the neutrons in the liquid to be measured, that is, their survival time, is mainly determined by process 2). In process 2), the lifetime τ of the neutrons is determined by the following formula:

[0054]

[0055] where t 0 represents the time when the neutrons enter the liquid to be measured, t c represents the time when the neutrons are absorbed, represents the average value of the time difference between these two times measured through experiments, which is equal to the lifetime τ of the neutrons. n represents the number of nuclide types in the liquid, n ！ represents the number density (1 / cm 3 ) of nuclide i, σ 0,！ represents the neutron absorption cross-section of this nuclide at an energy of 25.3 meV, v 0 is the velocity of the 25.3 meV neutrons, which is 2.2×10 5 cm / s. Since neutron poison elements have a huge cross-section, their proportion in the denominator on the right side of formula (2) is significant. Therefore, changes in the concentration of neutron poison elements in the liquid will significantly affect the magnitude of τ, and the measurement of the concentration of neutron poison elements can be achieved through the analysis of τ.

[0056] Taking the reciprocal of both sides of equation (8), we get:

[0057]

[0058] Using a similar analysis as before, ∑ 0,a (The macroscopic absorption cross-section of thermal neutrons) can be considered to come from neutron poisons and other elements. The macroscopic absorption cross-section of thermal neutrons for the part of other elements is almost constant. Therefore The value is linearly related to the concentration of neutron poisons.

[0059] Taking the logarithm of both sides of formula (1), we get:

[0060]

[0061] From formula (4), it can be seen that on a semi-logarithmic graph, the number of neutrons and time are linearly related, and the absolute value of the linear slope is the reciprocal of the neutron lifetime. Therefore, by measuring the curve of neutron count versus time (time spectrum curve), taking the logarithm and then performing linear fitting to obtain the slope, the absolute value of this slope is linearly related to the value of neutron poison concentration.

[0062] Considering that the neutron poison monitoring device may operate in a situation where the background influence is large and the background value changes slowly, the neutron poison monitoring device must consider the background count N bkg The influence on the measurement, that is, by measuring the background value and subtracting the background value from the detection value obtained by the detector.

[0063] In some embodiments, the neutron poison monitoring and control device is configured to control the detector to detect the number of neutrons and / or photons in the liquid to be measured in the case where the liquid to be measured does not include neutrons emitted by a neutron source, so as to measure the background value using the detection result. For example, the following Example 1 and Example 2 can be used to measure the background value.

[0064] Example 1

[0065] During the background measurement time period, the neutron poison monitoring and control device controls the detector to detect the number of neutrons in the liquid to be measured multiple times to obtain multiple background detection values. It should be noted that during the background measurement time period, the liquid to be measured does not include neutrons emitted by a neutron source. Next, calculate the average value of the multiple background detection values to obtain the background value.

[0066] For example, a measurement period is divided into a background measurement time period and a beam-on measurement time period. The background value is measured during the background measurement time period. During the beam-on measurement time period, by controlling the neutron source to emit neutrons to the liquid to be measured, within a specified time range after the neutron source stops emitting neutrons to the liquid to be measured, the detector is controlled to detect the number of neutrons in the liquid to be measured in each of a plurality of specified time periods, so as to obtain a plurality of detection values. Next, each detection value is corrected by using the obtained background value to obtain a plurality of corrected values.

[0067] Embodiment 2

[0068] As Figure 2 shown, after the neutron poison monitoring and control device controls the neutron source to emit a neutron pulse to the liquid to be measured, a specified delay duration T1 is set. The specified delay duration T1 is a predetermined multiple of the neutron lifetime, and the predetermined multiple is not less than 10.

[0069] For example, when the neutron lifetime does not exceed τ 0 , the specified delay duration T1 is 10τ 0 . By this specified delay duration, it can be ensured that the neutrons emitted by the neutron source are not included in the liquid to be measured.

[0070] After the specified delay duration T1 and before the neutron poison monitoring and control device controls the neutron source to emit the next neutron pulse to the liquid to be measured, within the duration T2 as Figure 2 shown, the neutron poison monitoring and control device controls the detector to detect the number of neutrons in the liquid to be measured multiple times to obtain a plurality of background detection values. By calculating the average value of the plurality of background detection values, the background value is obtained.

[0071] It should be noted here that since the background count caused by the background radioactivity is a white noise spectrum in the time distribution, the background count can be the average value obtained for the time channels (the channels in MCS (multichannel scaling), which represent a time interval).

[0072] In some embodiments, the neutron poison monitoring and control device is configured to calculate the logarithm of each of the plurality of corrected values to obtain a plurality of logarithm values. For example, the above logarithm value is a natural logarithm value. Next, a linear fit is performed on the plurality of logarithm values to obtain the slope of the fit curve, and then the neutron poison concentration is determined according to the absolute value of the slope.

[0073] It should be noted here that since the absolute value of the slope has a linear relationship with the neutron poison concentration, the neutron poison concentration can be determined according to the absolute value of the slope.

[0074] For example, for different neutron poison concentrations, first, the obtained background value is used to correct each detected value to obtain multiple corrected values. Next, according to formula (4), the natural logarithm value of each corrected value among the multiple corrected values is calculated. In this case, the schematic diagram of the detected value changing with time is as Figure 3 shown. Next, linear fitting is performed on the multiple natural logarithm values to obtain the slope of the fitting curve, and then the neutron poison concentration is determined according to the absolute value of the slope, as Figure 4 shown.

[0075] As can be seen from Figure 4 , by adopting the above embodiments of the present disclosure, the concentration of neutron poison can be accurately measured.

[0076] In addition, it should be noted that since the quantity statistically analyzed in the time spectrum is and therefore, the statistical quantity is essentially a differential signal. This differential characteristic reduces the requirement for the stability of the neutron source, and the actual detection device does not need to detect the intensity fluctuation of the neutron source either.

[0077] Figure 5 FIG. is a schematic structural diagram of a neutron poison monitoring device according to another embodiment of the present disclosure. Figure 5 Different from Figure 1 is that in the embodiment shown in Figure 5 , the detector 15 only includes a photon detector 151, and the shielding device 17 includes a neutron shielding device 171 and a photon shielding device 172.

[0078] Figure 6 FIG. is a schematic structural diagram of a neutron poison monitoring device according to still another embodiment of the present disclosure. Figure 6 Different from Figure 5 is that in the embodiment shown in Figure 6 , the detector 15 only includes a neutron detector 152.

[0079] Figure 7 FIG. is a schematic structural diagram of a neutron poison monitoring device according to still another embodiment of the present disclosure. Figure 7 Different from Figure 6 is that in the embodiment shown in Figure 7 , the detector 15 includes a photon detector 151 and a neutron detector 152.

[0080] By implementing the above embodiments of the present disclosure, the concentration of neutron poison can be accurately measured online in an environment with a relatively high background value, providing an effective measurement solution for the online monitoring of the neutron poison concentration in a nuclear device.

[0081] The device provided by the present disclosure effectively addresses the need to measure the concentration of neutron poisons in nuclear devices, which is of great significance for ensuring the critical safety of nuclear devices.

[0082] In some embodiments, the functional units described above can be implemented as a general-purpose processor, a programmable logic controller (PLC), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or any suitable combination thereof for performing the functions described in the present disclosure.

[0083] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above embodiments can be completed by hardware or by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium. The storage medium mentioned above can be a read-only memory, a magnetic disk, an optical disc, or the like.

[0084] The description of the present disclosure is provided for purposes of illustration and description, and is not intended to be exhaustive or to limit the present disclosure to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are chosen and described in order to best explain the principles of the present disclosure and its practical applications, and to enable those of ordinary skill in the art to understand the present disclosure and design various embodiments with various modifications suitable for specific purposes.

Claims

1. A neutron poisoning monitoring device, comprising: A container for containing a liquid to be tested including a neutron poison; A neutron source, configured to emit neutrons toward the liquid to be tested; A detector configured to detect the number of neutrons and / or photons in the liquid to be tested; a multi-channel calibrator configured to send the number of neutrons and / or photons detected by the detector to the neutron poisoning monitoring and control device; A neutron poisoning monitoring and control device, configured to control a neutron source to emit neutrons to the liquid to be tested, control the detector to detect the number of neutrons or photons in the liquid to be tested in each of a plurality of specified time periods within a specified time range after the neutron source is controlled to stop emitting neutrons to the liquid to be tested, so as to obtain a plurality of detection values, correct each of the plurality of detection values ​​using a background value to obtain a plurality of correction values, and determine the neutron poisoning concentration in the liquid to be tested using the plurality of correction values, and further configured to control the detector to detect the number of neutrons and / or photons in the liquid to be tested when the liquid to be tested does not include neutrons emitted by the neutron source, so as to measure the background value using the detection result; The shielding device is configured to shield the liquid to be tested and the detector from external interference.

2. The device according to claim 1, wherein: The neutron poisoning monitoring and control device is configured to control the detector to detect the number of neutrons and / or photons in the liquid to be tested multiple times within the background measurement time period to obtain multiple background detection values, and calculate the average value of the multiple background detection values ​​to obtain the background value.

3. The device according to claim 1, wherein: The neutron poisoning monitoring and control device is configured to control the neutron source to delay for a specified time after emitting a neutron pulse to the liquid to be tested, and after the delay for the specified time and before controlling the neutron source to emit the next neutron pulse to the liquid to be tested, control the detector to detect the number of neutrons and / or photons in the liquid to be tested multiple times to obtain multiple background detection values, and calculate the average value of the multiple background detection values ​​to obtain the background value.

4. The device according to claim 3, wherein: The specified time duration is a predetermined multiple of the neutron lifetime.

5. The device according to claim 4, wherein: The predetermined multiple is not less than 10.

6. The device according to claim 1, wherein: The neutron poisoning monitoring and control device is configured to calculate the logarithmic value of each of the multiple correction values ​​to obtain multiple logarithmic values, perform linear fitting on the multiple logarithmic values ​​to obtain the slope of the fitting curve, and determine the neutron poisoning concentration according to the absolute value of the slope.

7. The device according to claim 6, wherein: The absolute value of the slope is linearly related to the neutron poison concentration.

8. The device according to claim 1, wherein: In the multiple specified time periods, time period 0 is a time period when the neutron source stops emitting neutrons to the liquid to be tested, or is a time period delayed for a specified time after the neutron source stops emitting neutrons to the liquid to be tested.

9. The device according to any one of claims 1 to 8, wherein: The detector comprises at least one of a neutron detector and a gamma detector; or The detector is a detector for detecting neutrons and gamma photons simultaneously.

10. The device according to claim 9, wherein: The detector is a counting detector or an energy spectrum detector.

11. The device according to any one of claims 1 to 8, wherein: The neutron source is a photoneutron source based on an electron linear accelerator, or a pulsed neutron source based on a neutron tube.

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