Method, system and equipment for precisely measuring concentration of tritium in air

Abstract

The invention relates to the technical field of ionization concentration measurement, in particular to a method, a system and equipment for precisely measuring the concentration of tritium in air. The method comprises the following steps: acquiring an ionization chamber current and an energy spectrum diagram; according to the current extreme value distribution and the time interval, whether ionization chamber voltage correction is carried out is determined, and when correction is determined, a voltage correction value is obtained through analysis; determining interference nuclides according to the peak energy range analysis of the nuclides to be detected in the energy spectrograms of the two adjacent voltage corrections; determining the current contribution proportion of the interference nuclide according to the energy distribution of the interference nuclide in the peak energy range in the energy spectrum diagram; and determining a correction current by combining the ionization current, the tritium and the current contribution proportion of all interference nuclides, and calculating the tritium concentration in the air based on the correction current. According to the invention, the voltage of the ionization chamber is corrected, so that ion pairs can be captured more comprehensively. And the interference of interference nuclides on the ionization chamber method is removed, so that the accuracy of the calculated tritium concentration content in the air is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of ionization concentration measurement, and particularly relates to a precise measurement method, system and equipment for tritium concentration in air. Background Art

[0002] The ionization method is a common method for measuring tritium concentration in air. Its principle is based on the β decay characteristic of tritium. When tritium decays, the released β particles can ionize air molecules. In the core device of the ionization chamber, which is filled with air and equipped with electrodes. When tritium-containing air enters the ionization chamber, β particles collide with air molecules to generate ion pairs. At this time, by applying an electric field between the electrodes, the ion pairs are collected to form a current. The magnitude of this current is related to the number of β particles generated by tritium decay, that is, related to the tritium concentration. During measurement, first, a tritium standard source with a known activity is used to calibrate the ionization chamber to establish a calibration curve of current versus tritium activity. Then, the tritium-containing air sample to be measured is injected, the current is measured, and the tritium activity is calculated based on the calibration curve, and then the tritium concentration is calculated in combination with the air volume.

[0003] In the related art, the ionization method is analyzed based on a fixed voltage, and other nuclides that undergo β decay in the air will interfere with the measurement of tritium concentration in the ionization method, resulting in a low accuracy of the measured result of tritium concentration in the air. Summary of the Invention

[0004] In order to solve the technical problem that the analysis is based on a fixed voltage and other nuclides will interfere with the measurement of tritium concentration in the ionization method, resulting in a low accuracy of the measured result of tritium concentration in the air, the present invention provides a precise measurement method, system and equipment for tritium concentration in air. The specific technical solutions adopted are as follows:

[0005] The present invention proposes a precise measurement method for tritium concentration in air, and the method includes:

[0006] Obtain the ionization chamber current and the energy spectrum diagram of the semiconductor detector at different times;

[0007] According to the extreme value distribution of the ionization chamber current and the time interval at different times, determine the modification deviation index of the ionization chamber voltage at the current time; according to the modification deviation index, determine whether to correct the ionization chamber voltage at the current time. When it is determined to correct, according to the current and voltage of the previous correction, the current at the current time and the modification deviation index, correct the voltage at the current time to obtain a voltage correction value, and use the voltage correction value as the ionization chamber voltage at the current time;

[0008] In the energy spectrum diagrams of two adjacent voltage correction processes, according to the analysis of the peak energy range of the nuclide to be measured, determine the interfering nuclides that cause interference; according to the energy distribution of each interfering nuclide in the peak energy range corresponding to the energy spectrum diagram, determine the current contribution ratio of each interfering nuclide during voltage correction.

[0009] Combine the ionization current at the current moment, the current contribution ratio of tritium, and the current contribution ratios of all interfering nuclides to determine the corrected current at the current moment, and calculate the tritium concentration in the air based on the corrected current.

[0010] Furthermore, according to the extreme value distribution of the ionization chamber current and the time interval at different moments, determine the modification bias index of the ionization chamber voltage at the current moment, including:

[0011] Perform curve fitting on the ionization chamber currents at different moments based on the least squares method to obtain a current curve;

[0012] According to the current at each moment in the current curve and the extreme value change and time interval of the closest distance, determine the modification bias index of the ionization chamber voltage at the current moment.

[0013] Furthermore, according to the current at each moment in the current curve and the extreme value change and time interval of the closest distance, determine the modification bias index of the ionization chamber voltage at the current moment, including:

[0014] Determine the time interval and current difference between the data point at the current moment in the current curve and the closest extreme value point;

[0015] Take the ratio of the current difference to the time interval between the corresponding two moments as the fitting slope of the data point at the current moment;

[0016] Calculate the ratio of the absolute value of the fitting slope of the data point at the current moment to the maximum value of the absolute values of the fitting slopes corresponding to all moments to obtain the current change index at the current moment;

[0017] Calculate the product value of the current change index and the time interval, and perform normalization processing as the modification bias index of the ionization chamber voltage at the current moment.

[0018] Furthermore, determine whether to correct the ionization chamber voltage at the current moment according to the modification bias index, including:

[0019] When the modification bias index is greater than the preset modification index threshold, determine that the ionization chamber voltage is corrected; otherwise, do not correct it.

[0020] Furthermore, according to the current and voltage of the previous correction, the current at the current moment, and the modification bias index, correct the voltage at the current moment to obtain a voltage correction value. The corresponding calculation formula is:

[0021] V j =V j-1 ×(1+sig{(I j -I j-1 )×Q i}); where, V j-1is the voltage value after the (j - 1)-th voltage correction; I j and I j-1 are the magnitudes of the current at the j-th and (j - 1)-th corrections respectively; Q i is the modification bias index of the current moment i in the j-th voltage correction; sig{} represents the sigmoid function.

[0022] Furthermore, according to the analysis of the peak energy range of the nuclide to be measured, the interfering nuclides with interference are determined, including:

[0023] Obtain the peak energy range of different nuclides to be measured when they decay in the energy spectrum diagram;

[0024] Perform S-G smoothing processing on the energy spectrum diagram at the current moment, and obtain the maximum value points in the smoothed energy spectrum diagram based on the method of taking derivatives;

[0025] Compare the energy position where the maximum value point is located with the peak energy ranges corresponding to all nuclides to be measured to determine the interfering nuclides.

[0026] Furthermore, according to the energy distribution of the peak energy ranges corresponding to different interfering nuclides in the energy spectrum diagram, determine the ionization current contribution ratio of each interfering nuclide during voltage correction, including:

[0027] According to the energy value at the maximum count rate within the corresponding peak energy range of the interfering nuclide, and the total sum of all count rates within the corresponding peak energy range of the interfering nuclide, determine the existence ratio value of each interfering nuclide;

[0028] According to the existence ratio values of all interfering nuclides, and the energy value where the maximum count rate is located within the peak energy range of the interfering nuclide, determine the ionization current contribution ratio of each interfering nuclide during voltage correction;

[0029] Among them, the method for determining the existence ratio value of each interfering nuclide includes:

[0030] Take the energy value at the maximum count rate within the corresponding peak energy range of the interfering nuclide as the analysis energy value of the interfering nuclide;

[0031] Take the difference between the analysis energy value of any interfering nuclide and the minimum value of the analysis energy values of all interfering nuclides as the peak difference;

[0032] Calculate the negative value of the peak difference for normalization processing to obtain the count rate weight;

[0033] Take the product of the total sum of all count rates within the corresponding peak energy range of the interfering nuclide and the count rate weight as the existence ratio value of the interfering nuclide;

[0034] Among them, the method for determining the ionization current contribution ratio of each interfering nuclide during voltage correction includes:

[0035] The ratio of the analysis energy value of any interfering nuclide to the maximum value of the analysis energy values of all interfering nuclides is taken as the energy proportion.

[0036] The product of the presence proportion value of the interfering nuclide and the energy proportion is taken as the additional contribution coefficient; the sum value of the additional contribution coefficient and the presence proportion value is calculated and normalized as the current contribution proportion.

[0037] Furthermore, in combination with the ionization current at the current moment, the current contribution proportion of tritium, and the current contribution proportions of all interfering nuclides, the corrected current at the current moment is determined, including:

[0038] Calculate the sum of the current contribution proportion of tritium and the current contribution proportions of all interfering nuclides, and take the ratio of the sum to the current contribution proportion of tritium as the current adjustment coefficient;

[0039] The product value of the current adjustment coefficient and the ionization current at the current moment is taken as the corrected current.

[0040] In a second aspect, the present invention also provides a precise determination system for tritium concentration in air. The system includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of a precise determination method for tritium concentration in air as described in any one of the foregoing items are implemented.

[0041] In a third aspect, the present invention also provides a precise determination device for tritium concentration in air, including:

[0042] An acquisition module for acquiring the ionization chamber current and the energy spectrum diagram of the semiconductor detector at different moments;

[0043] A voltage correction module for determining the modification bias index of the ionization chamber voltage at the current moment according to the extreme value distribution of the ionization chamber current and the time interval at different moments; determining whether to correct the ionization chamber voltage at the current moment according to the modification bias index, and when it is determined to correct, correcting the voltage at the current moment according to the current and voltage of the previous correction, the current at the current moment, and the modification bias index to obtain a voltage correction value, and taking the voltage correction value as the ionization chamber voltage at the current moment;

[0044] A current contribution analysis module for analyzing in the energy spectrum diagrams during two adjacent voltage correction processes to determine the interfering nuclides with interference according to the peak energy range of the nuclide to be measured; determining the current contribution proportion of each interfering nuclide during voltage correction according to the energy distribution in the peak energy range corresponding to different interfering nuclides in the energy spectrum diagram;

[0045] A concentration measurement module is used to determine the corrected current at the current moment by combining the ionization current at the current moment, the current contribution ratio of tritium, and the current contribution ratios of all interfering nuclides, and calculate the tritium concentration in the air based on the corrected current.

[0046] The present invention has the following beneficial effects:

[0047] In the present invention, by obtaining the ionization chamber current and the energy spectrum diagram of the semiconductor detector, and then, based on the extreme value distribution of the ionization chamber current and the time interval, voltage modification bias analysis is carried out to achieve voltage correction. Since the magnitude of the voltage can directly affect the magnitude of the generated current, and further affect the tritium concentration detection, therefore, in this application, voltage self-adaptive adjustment is carried out through voltage correction, and in the subsequent energy spectrum diagram obtained at the voltage correction interval, the proportion of different nuclides is used to adjust the current obtained by the ionization chamber to obtain the most accurate tritium concentration. Specifically, by analyzing the interfering nuclides that cause interference, and according to the peak energy distribution corresponding to the interfering nuclides and the energy fluctuation in the actually measured energy spectrum diagram, current contribution ratio analysis is carried out. By analyzing the numerical distribution of the current contribution ratios of tritium and different interfering nuclides, the corrected current affected by the tritium concentration at the current moment is determined, and the tritium concentration in the air is calculated based on the corrected current. In this application, the ionization chamber voltage is corrected by the feedback change of the ionization chamber current, making the capture of ion pairs more comprehensive. The current obtained by the ionization chamber is adjusted according to the proportion of different nuclides in the energy spectrum diagram obtained at the voltage correction interval to remove the interference of interfering nuclides on the ionization chamber method, making the calculated tritium concentration content in the air more accurate. Description of the Drawings

[0048] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0049] Figure 1 It is a flowchart of a method for precisely measuring the tritium concentration in the air provided by an embodiment of the present invention;

[0050] Figure 2 It is a schematic diagram of an ionization chamber model provided by an embodiment of the present invention;

[0051] Figure 3 It is a schematic diagram of the structure of a semiconductor detector provided by an embodiment of the present invention. Detailed Embodiments

[0052] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific implementation manner, structure, features and effects of a precise measurement method, system and device for tritium concentration in air proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0054] The following specifically describes the specific solution of a precise measurement method for tritium concentration in air provided by the present invention in combination with the accompanying drawings.

[0055] Please refer to Figure 1 , which shows a flowchart of a precise measurement method for tritium concentration in air provided by an embodiment of the present invention. The method includes:

[0056] S101: Obtain the ionization chamber current and the energy spectrum diagram of the semiconductor detector at different times.

[0057] The ionization method is a common method for measuring tritium concentration in air. Its principle is based on the β decay characteristics of tritium. When tritium decays, the released β particles can ionize air molecules. In the core device of the ionization chamber, which is filled with air and equipped with electrodes. When tritium-containing air enters the ionization chamber, β particles collide with air molecules, generating ion pairs. At this time, by applying an electric field between the electrodes, the ion pairs are collected to form a current. The magnitude of this current is related to the number of β particles generated by tritium decay, that is, related to the tritium concentration.

[0058] During measurement, first, a tritium standard source with a known activity is used to calibrate the ionization chamber to establish a calibration curve of current versus tritium concentration. Then, the tritium-containing air sample to be measured is injected, the current is measured, and the tritium activity is calculated based on the calibration curve. Finally, the tritium concentration is calculated in combination with the air volume. The present invention judges the actual tritium concentration in air by adjusting the ionization voltage and combining the ionization method with the energy spectrum diagram.

[0059] Connect the two electrodes of the ionization chamber to a sensitive current measurement circuit. Control the temperature of the ionization chamber at 20 ± 5 °C, and at the same time monitor the air pressure to keep it in a stable state close to the standard atmospheric pressure.

[0060] Put the air to be detected into the ionization chamber, apply a voltage to the ionization chamber, monitor the real-time current through a current measuring instrument, and obtain the ionization chamber current at different times. It should be noted that the time in the embodiments of the present invention specifically refers to the periodic sampling time, that is, the current value at the sampling time can be set at fixed intervals, such as 0.01 seconds, which is not limited herein. For the sake of simplicity of description, it will be hereinafter referred to as "time".

[0061] See Figure 2 , which is a schematic diagram of the ionization chamber model provided by an embodiment of the present invention. The ionization chamber includes a sealed cavity. One side of the sealed cavity is an air inlet end and an air outlet end to realize vacuum pumping of the sealed cavity and injection of the gas to be measured. The other side of the ionization chamber is provided with a lead end connected to the controller. Inside the ionization chamber, near the lead end, there is a fixing frame. An electrode connected to the lead end is provided on the fixing frame. The motor electrolyzes the gas in the sealed cavity through power transmission by an external high-voltage device, and detects the electrolyzed charges through an electrometer provided in the ionization chamber and connected to the lead end, and feeds back to the controller.

[0062] To ensure the stability of the motor and the influence of possible arcs at the connection terminals on the charge detection, the fixing frame includes a fixing disk and a supporting part. The electrode is installed on the fixing disk. A shielding cover capable of covering the electrode connection terminal is provided on the fixing disk. The electrometer is arranged at a position close to the end of the electrode to ensure the accuracy of detection. To ensure the safety outside the ionization chamber, an insulating layer is provided between the supporting part and the inner wall of the sealed cavity.

[0063] Arrange a semiconductor detector beside the ionization chamber and turn on the signal acquisition system for measurement. During the measurement process, the multi-channel pulse amplitude analyzer automatically records the counting rates of different energy signals. After the measurement is completed, these data are exported from the multi-channel pulse amplitude analyzer through computer software. With energy as the abscissa and counting rate as the ordinate, an energy spectrum diagram is plotted. The semiconductor detector has two electrodes with a certain bias voltage applied. When an incident particle enters the sensitive area of the semiconductor detector, electron-hole pairs are generated. After applying a voltage between the two electrodes, the charge carriers drift towards the two electrodes, and charges will be induced on the collecting electrodes, thereby forming a signal pulse in the external circuit. See Figure 3 , Figure 3 is a schematic diagram of the structure of the semiconductor detector provided by an embodiment of the present invention.

[0064] S102: Determine the modification bias index of the ionization chamber voltage according to the extreme value distribution and time interval of the ionization chamber current at different times; determine whether to correct the ionization chamber voltage at the current time according to the modification bias index, and when it is determined to correct, correct the voltage at the current time according to the current and voltage of the previous correction, the current at the current time and the modification bias index to obtain a voltage correction value, and use the voltage correction value as the ionization chamber voltage at the current time.

[0065] The basic working principle of the ionization chamber is based on the ionization of gas by radiation. When tritium undergoes β decay and releases β particles, the β particles collide with gas molecules in the ionization chamber, causing the gas molecules to ionize and generate ion pairs (positive ions and negative ions). A voltage is applied between the two electrodes of the ionization chamber, and the ion pairs move towards the two electrodes under the action of the electric field, thus forming an ionization current.

[0066] The magnitude of the voltage will affect the collection efficiency of the ion pairs. At a lower voltage, the moving speed of the ion pairs under the action of the electric field is slower, and some ion pairs may recombine during the movement, resulting in fewer collected ion pairs than the actually generated ion pairs, thus making the measured ionization current smaller. If the voltage is too large and exceeds the saturation region, the electric field strength in the ionization chamber becomes very high, which will cause gas amplification. In this case, the ions will gain enough energy during the movement towards the electrodes, collide with other gas molecules and ionize them, generating more ion pairs, so that the ionization current is no longer proportional to the tritium concentration. At this time, the measured ionization current will increase abnormally due to the gas amplification effect, resulting in a higher measurement result of the tritium concentration and unable to accurately reflect the actual situation. Therefore, to ensure that the ionization chamber can more accurately reflect the tritium concentration, the voltage should be corrected according to the real-time current situation.

[0067] Furthermore, in some embodiments of the present invention, according to the extreme value distribution and time interval of the ionization chamber current at different times, a modification bias index of the ionization chamber voltage at the current time is determined, including: performing curve fitting on the ionization chamber current at different times based on the least squares method to obtain a current curve; and determining the modification bias index of the ionization chamber voltage at the current time according to the current at each time in the current curve and the change in the extreme value and time interval closest to it.

[0068] In the embodiments of the present invention, the least squares method is an algorithm well-known in the art, and curve fitting can be performed based on the least squares method, which will not be further limited and described herein. It should be noted that in some other embodiments of the present invention, the currently obtained current curve can be smoothed using the S-G smoothing algorithm to facilitate subsequent data analysis based on the current curve. Among them, for signals with certain smoothness and continuity, such as spectral data, chromatographic data, etc., the S-G smoothing algorithm usually can achieve better smoothing effects.

[0069] After determining the current curve, analysis can be performed based on the extreme values in the current curve. By taking the derivative, the extreme value points of the smoothed curve can be obtained, that is, the greater the change in the extreme value, the more modification is required to achieve a stable effect.

[0070] Therefore, in some other embodiments of the present invention, according to the current at each moment in the current curve, the change and time interval from the nearest extreme value, a modification bias index of the ionization chamber voltage at the current moment is determined, including: determining the time interval and current difference between the data point at the current moment in the current curve and the nearest extreme value point; taking the ratio of the current difference to the time interval between the corresponding two moments as the fitting slope of the data point at the current moment; calculating the ratio of the absolute value of the fitting slope of the data point at the current moment to the maximum value of the absolute values of the fitting slopes corresponding to all moments to obtain the current change index at the current moment; calculating the product value of the current change index and the time interval, and performing normalization processing as the modification bias index of the ionization chamber voltage at the current moment.

[0071] Among them, the current difference can specifically be the difference between the current value at the current moment and the current value at the extreme value point. The modification bias index represents the modification bias situation, that is, the larger the value of the modification bias index, the more voltage correction is required at the current moment. In the embodiments of the present invention, the current difference analysis can be realized through the slope change, and the corresponding calculation formula can be specifically, for example:

[0072]

[0073] Among them, max{|k|} is the maximum value of the absolute values of the fitting slopes obtained at all moments, |k i | represents the absolute value of the fitting slope at the current moment i, t i represents the time interval between the data point at the current moment i and the nearest extreme value point, norm represents linear normalization, and Q i represents the modification bias index of the ionization chamber voltage at the current moment i.

[0074] In the formula, The larger it is, the greater the current change, which means that the number of ion pairs generated by the β decay of the gas in the ionization chamber increases or decreases significantly. The larger t i is, the longer the trend of the detected gas current increasing or decreasing lasts. To ensure that the voltage of the ionization chamber is suitable for capturing the current generated by the current β decay, the voltage of the ionization chamber should be corrected in time. Therefore, the larger the value of the modification bias index, the normalization is performed through norm, so as to have the same dimension and facilitate subsequent analysis.

[0075] Determining whether to correct the ionization chamber voltage at the current moment according to the modification bias index includes:

[0076] When the modification bias index is greater than the preset modification index threshold, it is determined that the ionization chamber voltage is corrected; otherwise, no correction is performed.

[0077] Among them, a preset modification index threshold is the threshold value of the modification bias index. Optionally, it can specifically be 0.7. That is to say, when the modification bias index is greater than 0.7, it is determined that the ionization chamber voltage needs to be corrected. When the modification bias index is less than or equal to 0.7, it is determined that the ionization chamber voltage does not need to be corrected.

[0078] Among them, when the ionization chamber voltage does not need to be corrected, the original voltage is directly used for detection. When correction is required, the voltage data after correction needs to be re-analyzed.

[0079] Furthermore, in some embodiments of the present invention, according to the current and voltage of the previous correction, the current at the current moment, and the modification bias index, the voltage at the current moment is corrected to obtain a voltage correction value. The corresponding calculation formula is:

[0080] V j = V j-1 ×(1 + sig{(I j - I j-1 ) × Q i ) ;

[0081] Among them, V j-1 is the voltage value after the (j - 1)-th voltage correction; I j , I j-1 are the magnitudes of the current at the j-th and (j - 1)-th corrections respectively; Q i is the modification bias index of the current moment i in the j-th voltage correction; sig{} represents the sigmoid function.

[0082] In the formula, the larger the values of (I j - I j-1 ) and Q i , the greater the degree of current increase. To avoid the slow movement speed of ion pairs under the action of the electric field due to the relatively small voltage, and the recombination of some ions during movement, resulting in fewer ion pairs collected than the actual number of ion pairs generated, thus making the measured ionization current smaller, the voltage should be increased. The smaller the value of (I j - I j-1 ) and the larger Q i , the greater the degree of current decrease. To avoid the occurrence of gas amplification phenomenon, resulting in more ion pairs and affecting the judgment of tritium concentration, the voltage should be decreased.

[0083] Thus, in the embodiments of the present invention, a voltage correction link is determined to adaptively adjust voltage data according to state changes, obtain a voltage correction value, and use the voltage correction value as the ionization chamber voltage at the current moment.

[0084] S103: In the energy spectrum diagrams during two adjacent voltage correction processes, analyze according to the peak energy range of the nuclide to be measured to determine the interfering nuclides that cause interference; according to the energy distribution of the corresponding peak energy ranges of different interfering nuclides in the energy spectrum diagram, determine the current contribution ratio of each interfering nuclide during voltage correction.

[0085] It can be understood that voltage correction is not required at every moment. Therefore, for the data information during two adjacent voltage correction processes, its specific parameters are relatively reliable and the influence of interference changes less. Therefore, two adjacent voltage correction processes are used as the statistical period for analyzing interfering nuclides to reduce the influence of statistical fluctuations.

[0086] In the embodiments of the present invention, the peak energy range of the known nuclide to be measured can be compared with the energy range in the energy spectrum diagram to determine the radioactive interfering nuclides that may be contained in the air at the current moment.

[0087] Further, in some embodiments of the present invention, analyzing according to the peak energy range of the nuclide to be measured to determine the interfering nuclides that cause interference includes: obtaining the peak energy ranges of different nuclides to be measured when they decay in the energy spectrum diagram; performing S-G smoothing processing on the energy spectrum diagram at the current moment, and obtaining the maximum points in the smoothed energy spectrum diagram based on the method of taking derivatives; comparing the energy positions where the maximum points are located with the peak energy ranges corresponding to all nuclides to be measured to determine the interfering nuclides.

[0088] It can be understood that when detecting tritium concentration, the nuclides that may cause interference can be specifically, for example, cesium-137, strontium-90, iodine-131, etc. These nuclides are all known nuclides, and the types of nuclides that may cause interference are also relatively common. Therefore, all types of nuclides that may cause interference can be directly obtained as the nuclides to be measured, and the peak energy ranges corresponding to each type of nuclide to be measured can be determined. This is a specific well-known technology and will not be elaborated here.

[0089] Among them, the obtaining of the maximum points is well-known to those skilled in the relevant art. By comparing the energy positions where the maximum points are located with the peak energy ranges corresponding to all nuclides to be measured, this comparison process can be specifically, for example, an overlapping comparison. That is, if the peak energy range corresponding to a certain nuclide to be measured exactly coincides with the energy position corresponding to the maximum point in the energy spectrum diagram, then it can be determined that this nuclide to be measured is an interfering nuclide.

[0090] If the energy position corresponding to a certain nuclide to be measured does not coincide with the energy position corresponding to the maximum point in the energy spectrum diagram, for example, the energy position corresponding to the maximum point in the energy spectrum diagram is 2 MeV, while the peak energy range of cesium-137 is 1.173 to 1.332 MeV (known), then at this time, cesium-137 does not belong to the interfering nuclide.

[0091] After determining the interfering nuclides, the current contribution ratio can be analyzed. Among them, different interfering nuclides will all generate corresponding current interferences, that is, the obtained current value is affected by these interfering nuclides. Therefore, based on the counting rate exhibited by the energy within the peak energy range corresponding to the interfering nuclides, the current contribution analysis is carried out.

[0092] Further, in some embodiments of the present invention, according to the energy distribution of different interfering nuclides within the peak energy range corresponding in the energy spectrum diagram, the current contribution ratio ionized by each interfering nuclide during voltage correction is determined. Specifically, it can be referred to the steps shown in S201 - S202:

[0093] S201: Determine the presence ratio value of each interfering nuclide according to the energy value at the maximum counting rate within the corresponding peak energy range of the interfering nuclide and the total sum of all counting rates within the corresponding peak energy range of the interfering nuclide.

[0094] Among them, the method for determining the presence ratio value of each interfering nuclide includes: taking the energy value at the maximum counting rate within the corresponding peak energy range of the interfering nuclide as the analysis energy value of the interfering nuclide; taking the difference between the analysis energy value of any interfering nuclide and the minimum value of the analysis energy values of all interfering nuclides as the peak difference; calculating the opposite number of the peak difference for normalization processing to obtain the counting rate weight; taking the product of the total sum of all counting rates within the corresponding peak energy range of the interfering nuclide and the counting rate weight as the presence ratio value of the interfering nuclide.

[0095] It can be understood that the larger the total sum of the counting rates exhibited by the radioactive nuclide within the corresponding peak energy range, the larger the content of the radioactive nuclide in the air. However, due to the different detection efficiencies of the detector for rays with different energies, the detection efficiency for rays with smaller energies is smaller. To better represent the proportion of different radioactive nuclides in the air, the total sum of the counting rates within the peak energy range of different nuclides should be weighted by the energy value at the maximum counting rate within the peak energy range of different radioactive nuclides, that is, taking the energy value at the maximum counting rate within the corresponding peak energy range of the interfering nuclide as the analysis energy value of the interfering nuclide.

[0096] Then, the counting rate weight is determined through the peak difference. The smaller the value of the peak difference, the smaller the detection efficiency of the interfering nuclide corresponding to this energy, the larger the actual counting rate, and the larger the proportion of the radioactive nuclide in the air (that is, the presence ratio value). Therefore, calculate the opposite number of the peak difference for normalization processing to obtain the counting rate weight; take the product of the total sum of all counting rates within the corresponding peak energy range of the interfering nuclide and the counting rate weight as the presence ratio value of the interfering nuclide.

[0097] S202: Determine the ionization current contribution ratio of each interfering nuclide during voltage correction according to the presence ratio values of all interfering nuclides and the energy value at which the maximum count rate of the interfering nuclide lies within the peak energy range.

[0098] Among them, the method for determining the ionization current contribution ratio of each interfering nuclide during voltage correction includes: taking the ratio of the analysis energy value of any interfering nuclide to the maximum value of the analysis energy values of all interfering nuclides as the energy proportion; taking the product of the presence ratio value of the interfering nuclide and the energy proportion as the additional contribution coefficient; calculating the sum value of the additional contribution coefficient and the presence ratio value, and normalizing it as the current contribution ratio.

[0099] The greater the energy of the interfering nuclide during decay, the more gas in the ionization chamber will be ionized, generating more ion pairs and contributing more to the ionization current. Therefore, when correcting the current in the ionization chamber with the presence ratio values of each interfering nuclide for calculating the tritium concentration, the contribution of the energy generated by different interfering nuclides during decay to the ionization current should also be considered.

[0100] Thus, in the embodiments of the present invention, by calculating the energy proportion and performing energy analysis, taking the product of the presence ratio value of the interfering nuclide and the energy proportion as the additional contribution coefficient; calculating the sum value of the additional contribution coefficient and the presence ratio value, and normalizing it as the current contribution ratio.

[0101] This current contribution ratio can accurately represent the ratio value of the influence of the interfering nuclide on the current. It should be noted that this part of the calculation process can not only calculate different interfering nuclides, but also calculate the current contribution ratio of tritium itself, so as to facilitate subsequent tritium concentration analysis based on the calculation results.

[0102] S104: Combine the ionization current at the current moment, the current contribution ratio of tritium, and the current contribution ratios of all interfering nuclides to determine the corrected current at the current moment, and calculate the tritium concentration in the air based on the corrected current.

[0103] After determining the current contribution ratios of all interfering nuclides and tritium, the corrected current at the current moment can be determined by combining the ionization current at the current moment.

[0104] Further, combining the ionization current at the current moment, the current contribution ratio of tritium, and the current contribution ratios of all interfering nuclides to determine the corrected current at the current moment includes: calculating the sum of the current contribution ratio of tritium and the current contribution ratios of all interfering nuclides, and taking the ratio of the sum to the current contribution ratio of tritium as the current adjustment coefficient; taking the product value of the current adjustment coefficient and the ionization current at the current moment as the corrected current.

[0105] Through proportional analysis, determine the current adjustment coefficient that contributes to the tritium-generated current, and then use the product value of the current adjustment coefficient and the ionization current at the current moment as the corrected current. This corrected current represents the current generated by tritium radiation. Thus, tritium concentration analysis can be achieved through the corrected current.

[0106] In the controller, substitute the measured corrected current value into the corresponding relationship between the ionization current and the tritium concentration obtained during ionization chamber calibration (i.e., the calibration curve of current and tritium concentration) to calculate the tritium concentration in the air.

[0107] In the present invention, by obtaining the ionization chamber current and the energy spectrum diagram of the semiconductor detector, and then based on the extreme value distribution and time interval of the ionization chamber current for voltage modification bias analysis, voltage correction is achieved. Since the magnitude of the voltage can directly affect the magnitude of the generated current, and thus affect the tritium concentration detection, therefore, in this application, voltage self-adaptive adjustment is performed through voltage correction, and in the subsequent energy spectrum diagram obtained at the voltage correction interval, the proportion of different nuclides is used to adjust the current obtained by the ionization chamber to obtain the most accurate tritium concentration. Specifically, by analyzing the interfering nuclides that cause interference, and according to the peak energy distribution corresponding to the interfering nuclides and the energy fluctuations in the actually measured energy spectrum diagram, current contribution ratio analysis is carried out. Through the analysis of the numerical distribution of the current contribution ratios of tritium and different interfering nuclides, determine the corrected current affected by the tritium concentration at the current moment, and calculate the tritium concentration in the air based on the corrected current. In this application, the ionization chamber voltage is corrected through the feedback change of the ionization chamber current, making its capture of ion pairs more comprehensive. The current obtained by the ionization chamber is adjusted according to the proportion of different nuclides in the energy spectrum diagram obtained at the voltage correction interval to remove the interference of interfering nuclides on the ionization chamber method, making the accuracy of the calculated tritium concentration content in the air higher.

[0108] In a second aspect, the present invention also provides a precise tritium concentration determination system in air. The system includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of a precise tritium concentration determination method in air as described in any one of the foregoing items.

[0109] In a third aspect, the present invention also provides a precise tritium concentration determination device in air, including:

[0110] An acquisition module for acquiring the ionization chamber current and the energy spectrum diagram of a semiconductor detector at different times; a voltage correction module for determining a modification bias index of the ionization chamber voltage at the current time according to the extreme value distribution of the ionization chamber current and the time interval at different times; determining whether to correct the ionization chamber voltage at the current time according to the modification bias index, and when it is determined to correct, correcting the voltage at the current time according to the current and voltage of the previous correction, the current at the current time and the modification bias index to obtain a voltage correction value, and using the voltage correction value as the ionization chamber voltage at the current time; a current contribution analysis module for analyzing the energy spectrum diagrams during two adjacent voltage correction processes to determine interfering nuclides with interference according to the peak energy range of the nuclide to be measured; determining the current contribution ratio of each interfering nuclide during voltage correction according to the energy distribution of the corresponding peak energy range of different interfering nuclides in the energy spectrum diagram; a concentration measurement module for combining the ionization current at the current time, the current contribution ratio of tritium and the current contribution ratios of all interfering nuclides to determine the corrected current at the current time, and calculating the tritium concentration in the air based on the corrected current.

[0111] Among them, a precise tritium concentration measurement device for air provided is used to implement the steps of any one of the foregoing precise tritium concentration measurement methods for air.

[0112] It should be noted that the above sequence of the embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0113] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

Claims

1. A method for accurately measuring tritium concentration in air, characterized in that: Methods include: Obtain the ionization chamber current and the energy spectrum of the semiconductor detector at different times; Determine the modification bias index of the ionization chamber voltage at the current moment according to the distribution of the extreme values ​​of the ionization chamber current at different moments and the time intervals; determine whether to perform ionization chamber voltage correction at the current moment according to the modification bias index, and when determining the correction, correct the voltage at the current moment according to the current and voltage corrected last time, the current moment and the modification bias index to obtain a voltage correction value, and use the voltage correction value as the ionization chamber voltage at the current moment; In the energy spectra of two adjacent voltage correction processes, the interfering nuclides are determined according to the peak energy range of the nuclides to be measured; According to the energy distribution of different interfering nuclides in the corresponding peak energy range in the energy spectrum, the current contribution ratio of each interfering nuclide during voltage correction is determined; The corrected current at the current moment is determined by combining the ionization current at the current moment, the current contribution ratio of tritium and the current contribution ratios of all interfering nuclides, and the tritium concentration in the air is calculated based on the corrected current.

2. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: According to the distribution of the extreme values ​​of the ionization chamber current and the time interval at different times, the modification bias index of the ionization chamber voltage at the current time is determined, including: Based on the least square method, the ionization chamber current at different times is curve-fitted to obtain the current curve; According to the current at each moment in the current curve and the change in the nearest extreme value and the time interval, the modification bias index of the ionization chamber voltage at the current moment is determined.

3. A method for accurately measuring tritium concentration in air as claimed in claim 2, characterized in that: According to the current at each moment in the current curve and the change in the nearest extreme value and the time interval, the modification bias index of the ionization chamber voltage at the current moment is determined, including: Determine the time interval and current difference between the current data point at the current moment and the nearest extreme point in the current curve; The ratio of the current difference to the time interval between the two corresponding moments is taken as the fitting slope of the data point at the current moment; Calculate the ratio of the absolute value of the fitting slope of the data point at the current moment to the maximum absolute value of the fitting slope corresponding to all the moments to obtain the current change index at the current moment; The product value of the current change index and the time interval is calculated and normalized to be used as the modification bias index of the ionization chamber voltage at the current moment.

4. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: Determine whether to perform ionization chamber voltage correction at the current moment according to the modified deflection index, including: When the modification bias index is greater than a preset modification index threshold, it is determined that the ionization chamber voltage is modified; otherwise, no modification is performed.

5. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: According to the last corrected current and voltage, the current current and the modified bias index, the voltage at the current moment is corrected to obtain the voltage correction value. The corresponding calculation formula is: V j =V j-1 ×(1+sig{(I j -I j-1 )×Q i }); Among them, V j-1 is the voltage value after the j-1th voltage correction; I j ,I j-1 are the current magnitudes at the jth and j-1th corrections respectively; Q i is the modification bias index at the current time i in the j-th voltage correction; sig{} represents the sigmoid function.

6. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: According to the peak energy range analysis of the nuclide to be tested, the interfering nuclides are determined, including: Obtain the peak energy range in the energy spectrum when different nuclides to be measured decay; Perform SG smoothing on the energy spectrum at the current moment, and obtain the maximum point in the smoothed energy spectrum based on the derivation method; The interfering nuclide is determined by comparing the energy position of the maximum point with the peak energy range corresponding to all the nuclides to be tested.

7. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: According to the energy distribution of different interfering nuclides in the corresponding peak energy range in the energy spectrum, determine the current contribution ratio of each interfering nuclide during voltage correction, including: Determine the existence ratio value of each interfering nuclide according to the energy value of the interfering nuclide at the maximum counting rate within the corresponding peak energy range and the sum of all counting rates of the interfering nuclide within the corresponding peak energy range; According to the existence ratio values ​​of all interfering nuclides and the energy value at which the interfering nuclides have the maximum counting rate in the peak energy range, the current contribution ratio of each interfering nuclide ionized during voltage correction is determined; The method for determining the existence ratio value of each interfering nuclide includes: The energy value of the interfering nuclide at the maximum counting rate within the corresponding peak energy range is taken as the analytical energy value of the interfering nuclide; The difference between the analysis energy value of any interfering nuclide and the minimum analysis energy value of all interfering nuclides is taken as the peak difference; The inverse of the peak difference is calculated for normalization to obtain the count rate weight; The product of the sum of all the counting rates of the interfering nuclide in the corresponding peak energy range and the counting rate weight is taken as the existence ratio value of the interfering nuclide; The method for determining the current contribution ratio of each interfering nuclide ionized during voltage correction includes: The ratio of the analytical energy value of any interfering nuclide to the maximum analytical energy value of all interfering nuclides is taken as the energy ratio; The product of the existence ratio value of the interfering nuclide and the energy proportion is taken as the additional contribution coefficient; the sum of the additional contribution coefficient and the existence ratio value is calculated and normalized as the current contribution ratio.

8. A method for accurately measuring tritium concentration in air as claimed in claim 1, characterized in that: Combine the current ionization current, the current contribution ratio of tritium and the current contribution ratio of all interfering nuclides to determine the current correction current, including: Calculate the sum of the current contribution ratio of tritium and the current contribution ratios of all interfering nuclides, and use the ratio of the sum to the current contribution ratio of tritium as the current adjustment coefficient; The product of the current adjustment coefficient and the current ionization current is used as the correction current.

9. A system for accurately measuring tritium concentration in air, the system comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of any one of the methods of claims 1 to 8 are implemented.

10. A device for accurately measuring tritium concentration in air, characterized in that: include: An acquisition module, used for acquiring the ionization chamber current and the energy spectrum of the semiconductor detector at different times; The voltage correction module is used to determine the modification bias index of the ionization chamber voltage at the current moment according to the distribution of the ionization chamber current extreme values ​​and the time intervals at different moments; determine whether to perform ionization chamber voltage correction at the current moment according to the modification bias index, and when determining the correction, correct the voltage at the current moment according to the current and voltage of the previous correction, the current moment current and the modification bias index, obtain a voltage correction value, and use the voltage correction value as the ionization chamber voltage at the current moment; The current contribution analysis module is used to determine the interfering nuclides in the energy spectrum of two adjacent voltage correction processes according to the peak energy range of the nuclides to be measured; According to the energy distribution of different interfering nuclides in the corresponding peak energy range in the energy spectrum, the current contribution ratio of each interfering nuclide during voltage correction is determined; The concentration determination module is used to determine the corrected current at the current moment by combining the ionization current at the current moment, the current contribution ratio of tritium and the current contribution ratio of all interfering nuclides, and calculate the tritium concentration in the air based on the corrected current.

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