Method and system for determining working parameters of nuclear reactor fission chamber detector

Abstract

The invention relates to a method and a system for determining working parameters of a nuclear reactor fission chamber detector. The method comprises the following steps: acquiring output current relation information of a detected detector; determining a working voltage test range of the detected detector according to the output current relation information; and sequentially setting the working gas pressure of the detected detector as a plurality of preset gas pressure values, and controlling the detected detector to work based on the working voltage test range after setting the working gas pressure each time. Obtaining and determining counting rate data corresponding to each predetermined air pressure value according to the output current when the neutron beam is injected into the detected detector; and determining ideal working parameters of the detected detector according to the counting rate data. The method can help a worker determine ideal working parameters of the fission chamber detector, and improves the working stability and reliability of the detector.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fission chamber detector, and particularly to a method and system for determining working parameters of a nuclear reactor fission chamber detector. BACKGROUND

[0002] The fission chamber detector is a primary instrument in the intermediate range of the nuclear instrument system, and is one of the important equipment for ensuring the safe operation of the reactor. Therefore, the performance of the fission chamber detector is very critical for maintaining the safe operation of the nuclear power plant. The working gas pressure of the fission chamber detector has a great influence on the performance of the detector, but the performance of the fission chamber detector is also affected by other factors such as ion drift speed and electric field strength. Since the industry lacks sufficient verification and analysis of the working condition influence, it is impossible to exclude the mutual influence of various factor combinations, resulting in that the staff lacks a systematic and reliable technical means to improve the performance of the detector by adjusting the working parameters. In order to improve the safety of the reactor, the nuclear power plant urgently needs a technical means for accurately determining the working parameters of the fission chamber detector. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a method and system for determining working parameters of a nuclear reactor fission chamber detector.

[0004] The technical solution adopted by the present application to solve the technical problem is: a method for determining working parameters of a nuclear reactor fission chamber detector is constructed, comprising:

[0005] obtaining output current relationship information of a measured detector;

[0006] determining a working voltage test range of the measured detector according to the output current relationship information;

[0007] sequentially setting a working gas pressure of the measured detector to a plurality of predetermined pressure values, and after each setting of the working gas pressure, controlling the measured detector to work based on the working voltage test range, and obtaining and determining count rate data corresponding to each of the predetermined pressure values according to the output current of the measured detector when a neutron beam is injected;

[0008] determining ideal working parameters of the measured detector according to the count rate data.

[0009] Preferably, the step of obtaining the output current relationship information of the measured detector comprises: constructing a simulation model equivalent to the circuit structure of the measured detector, and analyzing the simulation model to determine the output current relationship information.

[0010] Preferably, the step of constructing a simulation model equivalent to the circuit structure of the measured detector comprises:

[0011] constructing a circuit schematic equivalent to a circuit structure of the detector under test to obtain an initial circuit model;

[0012] simplifying a circuit structure of the initial circuit model to obtain a simulation model;

[0013] The simulation model comprises a power supply, an ionization chamber equivalent module, a fission chamber equivalent capacitor C1, a load equivalent resistor R0 and a load equivalent capacitor C2. A positive electrode of the power supply is connected to a first end of the ionization chamber equivalent module. A second end of the ionization chamber equivalent module is connected to a negative electrode of the power supply through the load equivalent resistor R0 in one path and connected to the negative electrode of the power supply through the load equivalent capacitor C2 in another path.

[0014] Preferably, the step of analyzing the simulation model to determine output current relationship information comprises:

[0015] determining an output current expression of the detector under test based on the law of conservation of energy and a circuit structure of the simulation model;

[0016] The output current expression is expressed as:

[0017]

[0018] wherein I(t) represents an output current of the detector under test, V0 represents a working voltage of the detector under test, V(t) represents a second end voltage of the ionization chamber equivalent module, represents an electric field strength of a position of a jth positive ion in the fission chamber at time t, represents a drift speed of the jth positive ion in the fission chamber at time t, represents an electric field strength of a position of a kth electron in the fission chamber at time t, represents a drift speed of the kth electron in the fission chamber at time t.

[0019] Preferably, the step of determining a working voltage test range of the detector under test according to the output current relationship information comprises:

[0020] The lower limit voltage of the working voltage test range is set to a voltage value greater than N·V(t), and N is a positive number.

[0021] Preferably, the setting range of the plurality of predetermined gas pressure values is 2.0 atm to 6.0 atm.

[0022] Preferably, the step of controlling the detector under test to work based on the working voltage test range, obtaining and determining count rate data corresponding to each of the predetermined gas pressure values according to the output current of the detector under test comprises:​​

[0023] determining a plurality of working voltage points according to the working voltage test range;

[0024] sequentially setting the working voltage of the measured detector as the plurality of working voltage points;

[0025] after each working voltage point is set, controlling the neutron source to inject a neutron beam to the measured detector, acquiring the output current of the measured detector within a set time for multiple times, and calculating the average count rate corresponding to the working voltage point according to the output current acquired for multiple times;

[0026] generating count rate data according to the average count rate of each working voltage point under various predetermined gas pressure values.

[0027] Preferably, the step of determining the ideal working parameter of the measured detector according to the count rate data comprises:

[0028] fitting a plurality of plateau characteristic curves corresponding to each predetermined gas pressure value according to the count rate data;

[0029] determining plateau characteristic data corresponding to each plateau characteristic curve;

[0030] determining the ideal plateau voltage range and the ideal working gas pressure range of the measured detector according to the plateau characteristic data.

[0031] Preferably, the plateau characteristic data comprises a plateau voltage, a plateau length and a plateau slope.

[0032] The step of determining the ideal plateau voltage range and the ideal working gas pressure range of the measured detector according to the plateau characteristic data comprises:

[0033] for each plateau length of each plateau characteristic curve, judging whether the plateau length of the plateau characteristic curve is greater than a set plateau length, and if yes, marking the plateau characteristic curve;

[0034] when there is at least one plateau characteristic curve being marked, for each marked plateau characteristic curve, judging whether the plateau slope of the plateau characteristic curve is less than a set plateau slope, and if yes, determining the plateau characteristic curve as a qualified curve;

[0035] determining the ideal working gas pressure range according to the predetermined gas pressure value of all the qualified curves;

[0036] determining the ideal plateau voltage range according to the plateau voltage of all the qualified curves.

[0037] In addition, the present application also constructs a nuclear reactor fission chamber detector working parameter determination system, comprising:

[0038] a gas supply device for providing working gas to the detector under test;

[0039] a neutron source for providing a neutron beam for testing the detector under test;

[0040] a testing device comprising an acquisition unit, a range determination unit, a voltage control unit, a gas supply control unit, a counting unit and a parameter determination unit;

[0041] the acquisition unit is configured to acquire output current relationship information of the detector under test;

[0042] the range determination unit is configured to determine a working voltage test range of the detector under test;

[0043] the voltage control unit is configured to control operation of the detector under test based on the working voltage test range;

[0044] the gas supply control unit is configured to control the gas supply device to sequentially provide working gas pressures of a plurality of predetermined pressure values to the detector under test;

[0045] the counting unit is configured to acquire output currents of the detector under test when the detector under test is injected with a neutron beam and operates based on the working voltage test range at each of the predetermined pressure values, and determine count rate data corresponding to each of the predetermined pressure values based on the output currents;

[0046] the parameter determination unit is configured to determine ideal working parameters of the detector under test based on the count rate data.

[0047] Preferably, the gas supply control unit comprises:

[0048] a gas supply pipeline mechanically connected between the detector under test and the gas supply device;

[0049] a valve arranged on the gas supply pipeline and configured to adjust a flow rate of the working gas input to the detector under test;

[0050] a pressure gauge configured to measure a working gas pressure of the detector under test.

[0051] Preferably, the counting unit comprises:

[0052] an amplifier configured to amplify the output current of the detector under test;

[0053] a single-channel analyzer configured to discriminate single-channel pulses meeting a set condition from the amplified output current;

[0054] a scaler configured to count the single-channel pulses meeting the set condition and output count information;

[0055] a counter for determining a counting rate data corresponding to each of the predetermined gas pressure value according to the counting information.

[0056] Preferably, the nuclear reactor fission chamber detector working parameter determination system further comprises:

[0057] a gas extraction device for extracting air in the measured detector and keeping the gas pressure of the measured detector not more than a set pressure value before providing working gas to the measured detector;

[0058] a temperature maintaining device for keeping the measured detector in a set temperature range during the gas extraction.

[0059] The technical scheme of the present application can help the staff to determine the ideal working parameters of the fission chamber detector, increase the probability of ionization of fission fragments in the fission chamber detector, make the fragment energy fully deposited in the sensitive region, thus increase the amplitude of the output current, improve the signal-to-noise ratio of the detector, help to improve the sensitivity and detection efficiency of the detector, make the detection ability of the detector stronger, and have great significance for improving the working stability and reliability of the detector. BRIEF DESCRIPTION OF DRAWINGS

[0060] The present application will be further described below in conjunction with the drawings and examples, wherein:

[0061] Figure 1 is a program flow chart of the nuclear reactor fission chamber detector working parameter determination method in some embodiments of the present application;

[0062] Figure 2 is a circuit principle diagram of the initial circuit model in some embodiments of the present application;

[0063] Figure 3 is a circuit principle diagram of the simulation model in some embodiments of the present application;

[0064] Figure 4 is Figure 3 is a further simplified circuit principle diagram;

[0065] Figure 5 is a program flow chart of step S30 in some embodiments of the present application;

[0066] Figure 6 is a program flow chart of step S40 in some embodiments of the present application;

[0067] Figure 7 is a plateau characteristic curve when the predetermined gas pressure value is 2.0atm to 6.0atm in some embodiments of the present application;

[0068] Figure 8is a structural schematic diagram of a nuclear reactor fission chamber detector working parameter determination system in some embodiments of the present application.

[0069] Figure 9 is a structural schematic diagram of a gas supply control unit in some embodiments of the present application. DETAILED DESCRIPTION

[0070] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0071] It should be noted that the flowchart shown in the accompanying drawings is only illustrative, and does not necessarily include all the contents and operations / steps, nor does it necessarily execute in the order described. For example, some operations / steps can be further decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0072] The block diagram shown in the accompanying drawings is only a functional entity, and does not necessarily correspond to a physically independent entity. That is, these functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0073] Figure 1 is a program flowchart of a nuclear reactor fission chamber detector working parameter determination method in some embodiments of the present application. The method is used to determine the ideal working parameters of the fission chamber detector, to ensure that the fission chamber detector can meet the requirements of sensitivity and detection efficiency, and has great significance for improving the working stability and reliability of the detector. In addition, the working parameters of the fission chamber detector include the working gas pressure and the working voltage of the fission chamber detector.

[0074] It should be noted that in the present application, the fission chamber detector being tested is referred to as the measured detector.

[0075] Please refer to Figure 1 The nuclear reactor fission chamber detector working parameter determination method can include steps S10, S20, S30 and S40.

[0076] Step S10 includes obtaining the output current relationship information of the measured detector. In the present embodiment, the current relationship information includes the relationship between the output current of the measured detector and the working parameters of the measured detector and the electronic device parameters, and the electronic device includes the ionization chamber, the fission chamber capacitor, the load resistor, the mixed capacitor of the fission chamber connecting cable and other devices, and the amplifier and other devices.

[0077] In some embodiments, the output current relationship information of the detector under test may be determined by constructing a simulation model equivalent to the circuit structure of the detector under test, and analyzing the simulation model to determine the output current relationship information.

[0078] In some embodiments, the simulation model can be constructed by: constructing a circuit schematic diagram equivalent to the circuit structure of the detector under test to obtain an initial circuit model; simplifying the circuit structure of the initial circuit model to obtain a simulation model.

[0079] In some embodiments, see Figure 2 The initial circuit model may include a power supply 100, an ionization chamber equivalent module 200, a fission chamber equivalent capacitor C1, a load resistor R1, a hybrid capacitor C' of a fission chamber connecting cable and other devices, and an amplifier 300, wherein the amplifier 300 includes an amplifier equivalent resistor R i and the amplifier equivalent capacitance C i Accordingly, the step of simplifying the circuit structure of the initial circuit model may include: equating all capacitors connected in parallel in the simulation model to a load equivalent capacitor, and equating all resistors connected in parallel in the simulation model to a load equivalent resistor, thereby obtaining the simulation model. Figure 3 The simulation model may include a power supply 100, an ionization chamber equivalent module 200, a fission chamber equivalent capacitor C1, a load equivalent resistor R0, and a load equivalent capacitor C2. The positive electrode of the power supply 100 is connected to the first terminal of the ionization chamber equivalent module 200, the second terminal of the ionization chamber equivalent module 200 is connected to the negative terminal of the power supply 100 via the load equivalent resistor R0, and the second terminal of the ionization chamber equivalent module 200 is connected to the negative terminal of the power supply 100 via the load equivalent capacitor C2.

[0080] In some embodiments, the output current relationship information may be clarified in the following manner: an output current expression of the detector under test is determined based on the law of conservation of energy and the circuit structure of the simulation model.

[0081] Specifically, analyze Figure 3 It can be seen that the output power of the power supply 100 can be expressed as: W(t)=I s (t)·V0, due to This formula is recorded as formula (1). Further deduction can be obtained: This formula is recorded as formula (2). W(t) represents the output power of the power supply 100, I s (t) represents the output current of the power supply 100, V0 represents the output voltage of the power supply 100 (i.e., the working voltage of the detector under test), Represents the current flowing through the load equivalent resistance R0, Represents the current flowing through the load equivalent capacitance C2.

[0082] The total power of resistor R0 and capacitor C2 can be expressed as: This equation is expressed as equation (3), where W1(t) represents the total power of the resistor R0 and the capacitor C2, and V(t) represents the voltage at the second end of the ionization chamber equivalent module.

[0083] The power of the fission chamber equivalent capacitor C1 can be expressed as: This equation is expressed as equation (4). W2(t) represents the power of the fission chamber equivalent capacitor C1, and C1 represents the capacitance of the fission chamber equivalent capacitor C1.

[0084] The power consumed by the drift of positive ions and electrons ionized by the ionization chamber equivalent module 200 under the action of the electric field can be expressed as: This formula is recorded as formula (4). W3(t) represents the power consumed by the drift of positive ions and electrons. It means that the jth positive ion is located in the fission chamber at time t. The electric field strength, represents the drift velocity of the jth positive ion in the fission chamber at time t, It means that the kth electron is located in the fission chamber at time t The electric field strength, It represents the drift velocity of the kth electron in the fission chamber at time t.

[0085] Based on the law of conservation of energy, we can obtain formula (5): W(t) = W1(t) + W2(t) + W3(t). By converting formula (2) to formula (5), we can obtain: This formula is recorded as formula (6). This equation is recorded as equation (7). It should be noted that V(t) is related to the resistance and capacitance in the circuit of the detector under test.

[0086] Comparing equation (1) with equation (6), we can see that I(t) is larger than Is(t), and the difference is This is the current value when V(t) is added to the equivalent capacitance C1 of the fission chamber. Therefore, I(t) is the sum of the currents flowing through the resistor R0, the capacitor C2, and the self-capacitor C1. Therefore, I(t) can be used as the total current signal output by the fission chamber when the load resistance R1≠0, that is, the output current when the voltage value applied to the fission chamber C1 remains constant at V0, that is, the current value of the fission chamber output circuit when R1=0. Furthermore, if V0>>V(t), then Equation (7) can also be written as: This equation is recorded as equation (8). If V0>>V(t), comparing equations (7) and (8), we can see that in the two cases of R1=0 and R1≠0, the current value output by the fission chamber is basically the same, that is, I(t) in equation (8) can represent the output current of the detector under test.

[0087] Further, it can be seen from formula (8) that the output current of the measured detector is irrelevant to the resistance and capacitance in the circuit of the measured detector, so the ionization chamber can be equivalent to a current source, and based on this, the formula (2-9) can be simplified to the circuit diagram shown in formula (2-10). Figure 3 Figure 4 In formula (2-10), C0=C1+C2, and it can be seen from formula (2-10) that the potential difference between the two plates of the fission chamber (or ionization chamber) is unchanged, and the output current I0(t) is only contributed by the drift of all positive ions and electrons in the sensitive volume, and is irrelevant to the external loop parameters R0 and C0. Figure 4

[0088] The working gas in the fission chamber detector absorbs the energy carried by the fission fragments after nuclear reaction, and ionizes positive ions and electrons, so in general, the working gas in the fission chamber detector is selected to be an easily ionized gas (such as Ar). It can be seen from the above analysis of the fission chamber detector that the output pulse signal amplitude of the fission chamber detector is contributed by the drift of all positive ions and electrons in the sensitive volume, which is actually related to the ionization probability generated in the drift rate and drift path, and the ion drift speed is proportional to the electric field strength and inversely proportional to the gas pressure, that is, u + =μ + ξ / P, which is denoted as formula (9), u + represents the ion drift speed, μ + represents the correlation coefficient, ξ represents the electric field strength, and P represents the working gas pressure. That is, when V0>>V(t), as the working gas pressure increases, the probability of ionization of the fission fragments in the working area will increase, and the fragment energy will be fully deposited in the sensitive area, and the output pulse amplitude of the fission chamber will become larger. It can be seen from formula (9) that when the working gas pressure increases, the ion drift speed in the working area becomes smaller, so the plate voltage needs to be increased (equivalent to increasing the electric field strength) to compensate for the increase of the working gas pressure.

[0089] It should be noted that the role of the analysis simulation model is to clarify the relationship between the output current of the measured detector and some influencing factors, to reduce the number of output current influencing factors as much as possible, so that the staff can adjust the performance of the fission chamber detector by setting a smaller number of working parameters, simplify the working parameter setting process, and play a positive role in improving work efficiency.

[0090] Step S20 includes determining a working voltage test range of the measured detector according to the output current relationship information.

[0091] ​​From the analysis of formula (7) to formula (8) above, when V0 is set to a value much larger than V(t), the influence of the hardware circuit of the fission chamber detector can be eliminated, and the performance of the detector can be adjusted by setting the working gas pressure and the working voltage of the fission chamber detector. Therefore, in some embodiments, the working voltage test range of the detector under test can be determined in the following manner: the lower limit voltage of the working voltage test range is set to a voltage value greater than N·V(t), so as to eliminate or ignore the influence of the electronic devices of the detector under test on the output current. Wherein, N is a positive number.

[0092] It should be noted that the second end voltage V(t) of the ionization chamber equivalent module is determined by the actual circuit structure of the detector under test, and can be obtained from the manufacturer or measured by using the prior art. N can be a positive number not less than 5, so as to ensure that the influence of V(t) can be ignored.

[0093] Since the V(t) of some existing fission chamber detectors is small, in some embodiments, the working voltage test range can be set to 100V to 900V.

[0094] Step S30 comprises: sequentially setting the working gas pressure of the detector under test to a plurality of predetermined gas pressure values, and after setting the working gas pressure each time, controlling the detector under test to work based on the working voltage test range, and obtaining and determining the count rate data corresponding to each predetermined gas pressure value according to the output current of the detector under test when it is injected with a neutron beam.

[0095] In some embodiments, the count rate data corresponding to each predetermined gas pressure value can be determined by performing steps S301 to S304 shown in the following table. Figure 5

[0096] Step S301 comprises: determining a plurality of working voltage points according to the working voltage test range. Specifically, a plurality of working voltage points can be extracted in the working voltage test range based on the set voltage width, and the plurality of working voltage points can be represented as: Vmin, Vmin+VK, Vmin+2·VK, …, Vmin+m·VK, Vmax. Vmin represents the lower limit voltage of the working voltage test range, VK represents the set voltage width, m is a natural number, and Vmax represents the upper limit voltage.

[0097] In some embodiments, the set voltage width is preferably 100V, and accordingly, when the working voltage test range is 100V to 900V, the plurality of working voltage points include 100V, 200V, 300V, 400V, 500V, 600V, 700V, 800V, and 900V.

[0098] Step S302 comprises: sequentially setting the working voltage of the detector under test to a plurality of working voltage points. ​

[0099] Step S303 comprises: after each working voltage point is set, controlling the neutron source to inject a neutron beam to the measured detector, and acquiring the output current of the measured detector within a set time for multiple times; and calculating the average count rate corresponding to the working voltage point according to the output current acquired for multiple times.

[0100] Specifically, after the working voltage of the measured detector is set to a certain working voltage point each time, the measured detector is injected with a neutron beam with stable fluence rate, so that the measured detector senses the neutron beam. Then, the output current of the measured detector within a set time is acquired repeatedly for multiple times, and each acquired output current can represent the number of neutrons detected by the measured detector within the set time at the working voltage point, that is, a plurality of neutron numbers are obtained, and the average count rate of the working voltage point at the corresponding predetermined pressure value is calculated by calculating the ratio of the average of the plurality of neutron numbers to the set time.

[0101] In some embodiments, the number of times of acquiring the output current of the measured detector within the set time can be 3, and the set time can be 20 seconds. In addition, the present step can inject the measured detector with a neutron beam with stable fluence rate by using an existing neutron source.

[0102] Step S304 comprises: generating count rate data according to the average count rates of various predetermined pressure values at multiple working voltage points. Specifically, the count rate data contains the average count rates of each predetermined pressure value at multiple working voltage points, respectively.

[0103] In some embodiments, the setting range of the plurality of predetermined pressure values can be 2.0 atm to 6.0 atm. Further, the plurality of predetermined pressure values can specifically include 2.0 atm, 3.0 atm, 4.0 atm, 5.0 atm, and 6.0 atm.

[0104] Step S40 comprises: determining the ideal working parameters of the measured detector according to each count rate data.

[0105] In some embodiments, the ideal working parameters can be determined by performing steps S401 to S403 as shown in the figure. Figure 6 The ideal working parameters include an ideal plateau voltage range and an ideal working gas pressure range.

[0106] Step S401 comprises: fitting a plurality of plateau characteristic curves corresponding to each predetermined pressure value according to the count rate data. In this step, the abscissa of the plateau characteristic curve can be the working voltage, and the ordinate can be the average count rate, which facilitates the analysis of the trend change of the plateau characteristic curve.

[0107] The step S402 comprises determining the plateau characteristic data corresponding to each plateau characteristic curve. The plateau characteristic data can comprise plateau voltage, plateau length and plateau slope.

[0108] The step S403 comprises determining the ideal plateau voltage range and the ideal working gas pressure range of the detector under test according to the plateau characteristic data.

[0109] Further, the ideal plateau voltage range and the ideal working gas pressure range of the detector under test can be determined by performing the following steps: for each plateau length of each plateau characteristic curve, judging whether the plateau length of the plateau characteristic curve is greater than a set plateau length, and if yes, marking the plateau characteristic curve; when there is at least one plateau characteristic curve being marked, for each marked plateau characteristic curve, judging whether the plateau slope of the plateau characteristic curve is less than a set plateau slope, and if yes, defining the plateau characteristic curve as a qualified curve; determining the ideal working gas pressure range according to the predetermined gas pressure values of all the qualified curves; and determining the ideal plateau voltage range according to the plateau voltages of all the qualified curves.

[0110] In some embodiments, the set plateau length can be 300 VDC, and the set plateau slope can be 3% / 100 VDC. It should be noted that the calculation of the plateau voltage, the plateau length and the plateau slope can refer to the prior art, which will not be described here.

[0111] For the convenience of understanding, the detailed process of the steps S30 and S40 will be described below through a specific embodiment. In the specific embodiment, the plurality of working voltage points comprise 100 V, 200 V, 300 V, 400 V, 500 V, 600 V, 700 V, 800 V and 900 V, the plurality of predetermined gas pressure values comprise 2.0 atm, 3.0 atm, 4.0 atm, 5.0 atm and 6.0 atm, and the set time is 20 seconds, and the number of times of obtaining the output current of the detector under test within the set time is 3.

[0112] Table 1 is the count rate data when the predetermined gas pressure value is 2.0 atm, and the count rate data of other predetermined gas pressure values is similar to Table 1, which will not be described one by one here.

[0113]

[0114] Table 1

[0115] Figure 7 Fig. 1 is the plateau characteristic curves when the predetermined gas pressure values are 2.0 atm to 6.0 atm in some embodiments of the present application, wherein curve (a) is the plateau characteristic curve when the predetermined gas pressure value is 2.0 atm, curve (b) is the plateau characteristic curve when the predetermined gas pressure value is 3.0 atm, curve (c) is the plateau characteristic curve when the predetermined gas pressure value is 4.0 atm, curve (d) is the plateau characteristic curve when the predetermined gas pressure value is 5.0 atm, and curve (e) is the plateau characteristic curve when the predetermined gas pressure value is 6.0 atm.

[0116] It should be noted that the plateau voltage refers to a voltage range in which the average count rate of the fission chamber detector remains substantially unchanged or the plateau slope is less than a certain value. Therefore, by analyzing curves (a) to (e), Table 2 can be obtained:

[0117] predetermined air pressure value plateau V plateau length V plateau slope % / 100 V 2.0 atm 200-900 700 0.93 3.0 atm 200-900 700 0.90 4.0 atm 300-900 600 0.71 5.0 atm 500-900 400 1.73 6.0 atm 500-900 400 3.52

[0118] If the set plateau length is 300 VDC and the set plateau slope is 3% / 100 VDC, it can be determined that the predetermined gas pressure values of 2.0 atm to 5.0 atm can meet the above requirements. It should be noted that the shorter the plateau slope, the better the quality of the detector. Therefore, in some embodiments, when the number of predetermined gas pressure values that meet the requirements of the set plateau length and the set plateau slope is greater than 2, the two predetermined gas pressure values with the smallest plateau slope among all the predetermined gas pressure values that meet the above requirements are taken as the ideal working gas pressure range, i.e., the ideal working gas pressure range of the present embodiment is 3.0 atm to 4.0 atm. Further, it can be known from the analysis of the plateau region column that the plateau regions corresponding to different predetermined gas pressure values are different, and the intersection of the plateau regions corresponding to 3.0 atm to 4.0 atm is 300 V to 900 V. Accordingly, the ideal plateau voltage range can be determined as 300 V to 900 V.

[0119] Referring to Figure 8 The present application also provides a nuclear reactor fission chamber detector working parameter determination system, which can include a gas supply device 1, a neutron source 2, and a test device 3.

[0120] The gas supply device 1 is used to provide working gas for the detector under test. Specifically, the gas supply device 1 can be an existing gas supply device capable of providing working gas (such as Ar) for the detector.

[0121] The neutron source 2 is used to provide a test neutron beam for the detector under test. The neutron source 2 can be an existing neutron source device capable of providing a neutron beam with improved fluence rate stability.

[0122] Referring to Figure 8 The test device 3 includes an acquisition unit 31, a range determination unit 32, a voltage control unit 33, a gas supply control unit 34, a counting unit 35, and a parameter determination unit 36.

[0123] The acquisition unit 31 is used to acquire and display the output current relationship information of the detector under test. The output current relationship information can include an output current expression, and the determination method of the output current expression is described above and will not be repeated here. Further, the acquisition unit 31 can include a display.

[0124] The range determination unit 32 is used to determine the operating voltage test range of the detector under test based on the operation. Specifically, after obtaining the output current relationship information through the acquisition unit 31, the operator can operate the range determination unit 32 to set the operating voltage test range. Furthermore, the range determination unit 32 may include a mouse and a keyboard.

[0125] The voltage control unit 33 is used to control the operation of the detector under test based on the working voltage test range. The voltage control unit 33 can be an existing adjustable voltage source that can output a voltage of 0V to 1000V according to the control instruction.

[0126] The gas supply control unit 34 is used to control the gas supply device 1 to sequentially provide the detector under test with working gas pressures of multiple predetermined pressure values.

[0127] In some embodiments, as Figure 9 As shown, the air supply control unit 34 may include an air supply pipeline 341 , a valve 342 and a pressure gauge 343 .

[0128] The air supply pipe 341 is used for mechanical connection between the detector under test and the air supply device 1 .

[0129] The valve 342 is provided on the gas supply pipeline and is used to adjust the flow of the working gas input to the detector under test. The valve 342 can be an existing ball valve.

[0130] The pressure gauge 343 is provided on the pipeline between the detector under test and the valve 342 , and is used to measure the working gas pressure of the detector under test.

[0131] The counting unit 35 is used to obtain the output current of the detector under test when the neutron beam is injected and the detector operates at each predetermined pressure value based on the working voltage test range, and determine the counting rate data corresponding to each predetermined pressure value according to the output current.

[0132] In some embodiments, the counting unit 35 may include an amplifier, a single-channel analyzer, a scaler, and a counter.

[0133] The amplifier is used to amplify the output current of the detector under test to improve the accuracy of the single-channel analyzer in identifying single-channel pulses, which helps to improve the counting accuracy.

[0134] The single-channel analyzer is used to identify single-channel pulses within the amplified output current that meet the specified criteria. It should be noted that the output current of the detector under test is a pulsed current, which is superimposed with some noise. The single-channel analyzer's function is to identify single-channel pulses within a specific amplitude range (i.e., meeting the specified criteria). The number of these single-channel pulses that meet the specified criteria can be used to represent the neutron count.

[0135] The scaler is configured to count the single-channel pulses meeting the set condition and output the counting information. The counting information can represent the number of neutrons detected by the detector under test.

[0136] The counter is configured to determine the count rate data corresponding to each predetermined pressure value according to the counting information. Specifically, the counter is configured to repeatedly determine the number of neutrons detected by the detector under test within a set time according to the counting information to obtain a plurality of numbers of neutrons. The method for determining the count rate data is described above and will not be repeated here.

[0137] The parameter determination unit 36 is configured to determine the ideal working parameter of the detector under test according to the count rate data. The method for determining the ideal working parameter is described above and will not be repeated here.

[0138] In order to improve the concentration of the working gas filled in the detector under test, in some embodiments, the nuclear reactor fission chamber detector working parameter determination system can further comprise a gas extraction device and a heat preservation device.

[0139] The gas extraction device is configured to extract the air in the detector under test before providing the working gas to the detector under test, and to make the pressure of the detector under test not greater than the set pressure value. Optionally, the set pressure value is not greater than 10 Pa. In an ideal state, the pressure of the detector under test after extraction should be maintained within 10 Pa to 3 Pa.

[0140] The heat preservation device is configured to keep the detector under test within a set temperature range during the extraction. Optionally, the set temperature range is 118℃ to 122℃, and the ideal state is to keep it around 120℃ as much as possible. It is easy to understand that heating the detector under test helps to reduce the pressure as much as possible before the working gas is injected into the gas extraction device.

[0141] In some embodiments, in order to simplify the determination process, the working gas pressure can be charged to the maximum predetermined pressure value when the detector under test is filled with the working gas by the gas supply device 1. In this way, in the subsequent process, the working staff can only adjust the valve to make the working gas pressure decrease to the remaining predetermined pressure values in turn to carry out the corresponding test.

[0142] In some embodiments, the nuclear reactor fission chamber detector working parameter determination system can further comprise a wave recorder configured to record the output current waveform of the detector under test, so as to facilitate the working staff to check and observe the process parameters.

[0143] Understandably, the technical scheme of the present application can help the staff to determine the ideal working parameters of the fission chamber detector, increase the probability of ionization of fission fragments in the fission chamber detector, so that the fragment energy can be fully deposited in the sensitive region, thereby increasing the amplitude of the output current, improving the signal-to-noise ratio of the detector, and helping to improve the sensitivity and detection efficiency of the detector, so that the detection ability of the detector for fission fragments is stronger, and it has great significance for improving the working stability and reliability of the detector.

[0144] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0145] The skilled person can further realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be realized by electronic hardware, computer software or a combination of the two. In order to clearly show the interchangeability of hardware and software, the components and steps of the examples have been described in the above description. Whether the functions are realized by hardware or software depends on the specific application and design constraints of the technical scheme. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0146] The steps of the method or algorithm described in combination with the embodiments disclosed herein can be directly implemented by hardware, software modules executed by a processor, or a combination of the two. The software modules can be placed in random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art.

[0147] It can be understood that the above embodiments only express the preferred embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application; It should be noted that for ordinary skilled persons in the art, the above technical features can be freely combined without departing from the concept of the present application, and some modifications and improvements can be made, which are within the scope of protection of the present application; Therefore, any equivalent transformation and modification within the scope of the claims of the present application shall be covered by the claims of the present application.

Claims

1. A method for determining working parameters of a nuclear reactor fission chamber detector, characterized in that: include: Obtain output current relationship information of the detector under test; Determine the operating voltage test range of the detector under test according to the output current relationship information; sequentially setting the working gas pressure of the detector under test to a plurality of predetermined gas pressure values, and after each setting of the working gas pressure, controlling the detector under test to operate based on the working voltage test range, and obtaining and determining count rate data corresponding to each predetermined gas pressure value based on the output current of the detector under test when a neutron beam is injected; The ideal operating parameters of the detector under test are determined based on the count rate data.

2. The method for determining the working parameters of a nuclear reactor fission chamber detector according to claim 1, characterized in that: The step of obtaining the output current relationship information of the detector under test includes: constructing a simulation model equivalent to the circuit structure of the detector under test, and analyzing the simulation model to determine the output current relationship information.

3. The method for determining the working parameters of a nuclear reactor fission chamber detector according to claim 2, characterized in that: The step of constructing a simulation model equivalent to the circuit structure of the detector under test includes: Constructing a circuit schematic diagram equivalent to the circuit structure of the detector under test to obtain an initial circuit model; Simplifying the circuit structure of the initial circuit model to obtain a simulation model; The simulation model includes a power supply, an ionization chamber equivalent module, a fission chamber equivalent capacitor C1, a load equivalent resistor R0 and a load equivalent capacitor C2; the positive pole of the power supply is connected to the first end of the ionization chamber equivalent module, and the second end of the ionization chamber equivalent module is connected to the negative pole of the power supply through the load equivalent resistor R0 in one path and to the negative pole of the power supply through the load equivalent capacitor C2 in another path.

4. The method for determining the working parameters of a nuclear reactor fission chamber detector according to claim 3, characterized in that: The step of analyzing the simulation model to determine output current relationship information includes: Determining an output current expression of the detector under test based on the law of conservation of energy and the circuit structure of the simulation model; Wherein, the output current expression is expressed as: Wherein, I(t) represents the output current of the detector under test, V0 represents the operating voltage of the detector under test, and V(t) represents the second terminal voltage of the ionization chamber equivalent module. It means that the jth positive ion is located in the fission chamber at time t. The electric field strength, represents the drift velocity of the jth positive ion in the fission chamber at time t, It means that the kth electron is located in the fission chamber at time t The electric field strength, represents the drift velocity of the kth electron in the fission chamber at time t.

5. The method for determining working parameters of a nuclear reactor fission chamber detector according to claim 4, characterized in that: The step of determining the operating voltage test range of the detector under test according to the output current relationship information includes: The lower limit voltage of the working voltage test range is set to a voltage value greater than N·V(t), where N is a positive number.

6. The method for determining working parameters of a nuclear reactor fission chamber detector according to claim 1, wherein: The setting range of the plurality of predetermined air pressure values ​​is 2.0 atm to 6.0 atm.

7. The method for determining the working parameters of a nuclear reactor fission chamber detector according to any one of claims 1 to 6, characterized in that: The step of controlling the operation of the detector under test based on the operating voltage test range, and obtaining and determining the count rate data corresponding to each predetermined air pressure value according to the output current of the detector under test includes: Determining a plurality of operating voltage points according to the operating voltage test range; Setting the operating voltage of the detector under test to the multiple operating voltage points in sequence; After each operating voltage point is set, the following steps are performed: controlling a neutron source to inject a neutron beam into the detector under test, and obtaining an output current of the detector under test within a set time multiple times; and calculating an average count rate corresponding to the operating voltage point based on the output currents obtained multiple times. Count rate data is generated according to the average count rates at the various predetermined gas pressure values ​​at the various operating voltage points.

8. The method for determining working parameters of a nuclear reactor fission chamber detector according to claim 7, characterized in that: The step of determining the ideal operating parameters of the detector under test according to each of the count rate data comprises: fitting a plurality of plateau characteristic curves corresponding to the predetermined air pressure values ​​according to the count rate data; Determine the plateau characteristic data corresponding to each of the plateau characteristic curves; An ideal plateau voltage range and an ideal working gas pressure range of the detector under test are determined according to the plateau characteristic data.

9. The method for determining working parameters of a nuclear reactor fission chamber detector according to claim 8, characterized in that: The plateau characteristic data include plateau voltage, plateau length and plateau slope; The step of determining the ideal plateau voltage range and the ideal working gas pressure range of the detector under test according to the plateau characteristic data comprises: For each of the plateau characteristic curves, the plateau length is determined as follows: whether the plateau length of the plateau characteristic curve is greater than a set plateau length, and if so, the plateau characteristic curve is marked; When at least one of the plateau characteristic curves is marked, for each of the marked plateau characteristic curves, the following steps are performed: determining whether the plateau slope of the plateau characteristic curve is less than a set plateau slope; if so, determining the plateau characteristic curve as a qualified curve; Determining an ideal working gas pressure range based on predetermined gas pressure values ​​of all the qualified curves; The ideal plateau voltage range is determined based on the plateau voltages of all the qualified curves.

10. A system for determining working parameters of a nuclear reactor fission chamber detector, characterized in that: include: A gas supply device, used to provide working gas to the detector under test; a neutron source, used to provide a neutron beam for testing to the detector under test; A testing device comprising an acquisition unit, a range determination unit, a voltage control unit, a gas supply control unit, a counting unit, and a parameter determination unit; The acquisition unit is used to obtain output current relationship information of the detector under test; The range determination unit is used to determine the working voltage test range of the detector under test; The voltage control unit is used to control the operation of the detector under test based on the operating voltage test range; The gas supply control unit is used to control the gas supply device to sequentially provide the detector with a plurality of working gas pressures of predetermined pressure values; The counting unit is used to obtain the output current of the detector under test when the neutron beam is injected and the detector operates based on the operating voltage test range at each predetermined gas pressure value, and determine the counting rate data corresponding to each predetermined gas pressure value according to the output current; The parameter determination unit is used to determine the ideal operating parameters of the detector under test according to each of the count rate data.

11. The nuclear reactor fission chamber detector working parameter determination system according to claim 10, characterized in that: The air supply control unit comprises: an air supply pipe, used for mechanical connection between the detector under test and the air supply device; a valve, provided on the gas supply pipeline, for regulating the flow of the working gas input to the detector under test; The pressure gauge is used to measure the working gas pressure of the detector under test.

12. The nuclear reactor fission chamber detector working parameter determination system according to claim 10, characterized in that: The counting unit comprises: an amplifier, for amplifying the output current of the detector under test; A single-channel analyzer, used to identify single-channel pulses that meet set conditions in the amplified output current; a scaler, configured to count the single-channel pulses meeting the set conditions and output counting information; A counter is used to determine the counting rate data corresponding to each of the predetermined air pressure values ​​according to the counting information.

13. The nuclear reactor fission chamber detector working parameter determination system according to any one of claims 10 to 12, characterized in that: The nuclear reactor fission chamber detector working parameter determination system also includes: An air extraction device, used to extract the air in the detector under test before supplying working gas to the detector under test, and to ensure that the air pressure of the detector under test is not greater than a set pressure value; The heat preservation device is used to keep the detector under test within a set temperature range during the air extraction period.

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