Concentration detection method for equivalent replacement of gaseous radioactive sources in steam pipelines

Abstract

This invention belongs to the field of steam pipeline gamma contamination detection technology, and aims to solve the problem of the inability to obtain standards. 85 Kr、 133 The calibration of Xe gas radioactive sources makes it impossible to determine the accuracy of gamma pollution monitors in steam pipelines. This paper provides a concentration detection method using an equivalent replacement of a gas radioactive source within a steam pipeline, comprising the following steps: based on simulated parameter values ​​and the calculation formula for activity concentration within the pipeline, the gas source within the pipeline is determined as... 85 Kr or 133 The activity concentration in the pipe corresponding to Xe was obtained; a linear fitting relationship was established with the detector count rate to obtain the relationship between the activity concentration in the pipe and the detector count rate; the activity concentration in the pipe was obtained. 85 Kr and 133 The concentration ratio of Xe gas is revised to obtain the final activity concentration of the gas in the pipeline. This invention, through... 137 The Cs point source moves along the centerline of the pipe to simulate different activities. 137 The Cs point source, and then through different types of radioactive sources, generates the same counting principle on the equipment, which is then transformed into... 85 Kr、 133 The activity concentration of the Xe gas source.

Description

Technical Field

[0001] This invention belongs to the field of steam pipeline gamma pollution detection technology, specifically relating to a method for detecting the concentration of gas radioactive sources in steam pipelines through equivalent substitution. Background Technology

[0002] The PLM1000 steam pipeline gamma contamination monitor is mainly installed around nuclear heating steam pipelines to monitor gamma radioactive materials in the steam pipelines and determine whether a certain concentration exists in the steam inside the pipeline. 85 Kr、 133 Xe nuclide.

[0003] However, due to practical limitations, it is impossible to obtain a standard. 85 Kr、 133 The Xe gas radiation source was tested and calibrated, making it impossible to determine the accuracy of the steam pipeline gamma pollution monitor.

[0004] For steam pipeline gamma contamination monitors, the measurement results are calculated based on the pulses output by the detector. Under approximately identical test conditions and with the same detector, equipment structure, and back-end electronic circuitry, the impact of differences in "conversion efficiency" on the test can be ignored. Therefore, regardless of the radiation source inside the pipeline... 137 Cs point source or 85 Kr、 133 The Xe gas source will eventually be converted into an electronic pulse signal.

[0005] How to achieve a certain level of activity 137 Cs point source, equivalent to a concentration capable of generating the same pulse count rate on the device. 85 Kr、 133 The Xe gas source has become an urgent problem to be solved. Summary of the Invention

[0006] In order to solve at least one of the above-mentioned technical problems in the prior art, the present invention provides a method for detecting the concentration of equivalent replacement of gas radioactive sources in steam pipelines.

[0007] This invention employs the following technical solution: a method for detecting the concentration of equivalent replacement of a gas radioactive source in a steam pipeline, comprising the following steps:

[0008] Establish a gas source within the pipeline 85 Kr or 133 The formula relating detector counts to activity concentration in the pipe at time Xe;

[0009] Establish the pipeline inside 137 The detector count corresponding to the Cs point source and the inside of the pipe 137The relationship between the activity of the Cs point source;

[0010] Based on the principle that the detector counts are the same, the two aforementioned relationships are combined to obtain the formula for calculating the activity concentration inside the pipe; the formula for calculating the activity concentration inside the pipe is as follows:

[0011]

[0012]

[0013] In the formula, The detector is positioned directly above the gas volume inside the pipe. For different 137 The activity of Cs point source, and The quantity is known; The gas source in the pipeline is 85 Detection efficiency at Kr; The gas source in the pipeline is 133 Detection efficiency at Xe; for 137 Cs point source detection efficiency at different distances from the center of the pipeline; The gas source in the pipeline is 85 Activity concentration at Kr; The gas source in the pipeline is 133 The activity concentration of Xe;

[0014] Parameters were obtained through Geant4 simulation. , The value;

[0015] The parameters obtained based on simulation , The numerical value and the formula for calculating the activity concentration inside the pipeline are used to obtain the gas source inside the pipeline. 85 Kr or 133 The corresponding activity concentration in the pipe at Xe;

[0016] The gas source in the pipeline is 85 Kr or 133 A linear fitting relationship was established between the activity concentration in the pipe corresponding to Xe and the detector count rate, and the relationship between the activity concentration in the pipe and the detector count rate was obtained.

[0017] Get inside the pipe 85 Kr and 133 The concentration ratio of Xe gas is used as a weighting factor for the pipeline. 5 Kr and 133 The Xe activity concentration was revised to obtain the final activity concentration of the gas inside the pipeline. .

[0018] Preferably, the inside of the pipe is 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship for the activity of the Cs point source is expressed as:

[0019] ;

[0020] The gas source inside the pipeline is 85 Kr or 133 The relationship between the detector count and the activity concentration in the pipe at Xe is expressed as follows:

[0021]

[0022]

[0023] In the formula, Count the detectors.

[0024] Preferably, the inside of the pipe is 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship for the activity of the Cs point source is expressed as:

[0025]

[0026] In the formula, Count the detectors; For different 137 The activity of the Cs point source; for 137 Cs point source detection efficiency at different distances from the center of the device.

[0027] Preferably, the parameters are obtained based on Geant4 simulation. The steps include:

[0028] Define the detector's geometry and materials using G4Box and G4LogicalVolume;

[0029] Define the geometry and material of the pipe using G4Tubs and G4LogicalVolume;

[0030] Gas sources are defined using G4ParticleGun and G4PrimaryVertex. 85 Kr or gas source 133 Xe;

[0031] The gas source 85 Kr or gas source 133 Xe is placed in the center of the pipe;

[0032] The gas source inside the pipeline was obtained using the CalculateDetectionEfficiency method. 85 Detection efficiency at Kr Or the gas source in the pipeline is 133 Detection efficiency at Xe .

[0033] Preferably, the parameters are obtained based on Geant4 simulation. The steps include:

[0034] Define the detector's geometry and materials using G4Box and G4LogicalVolume;

[0035] Define the geometry and material of the pipe using G4Tubs and G4LogicalVolume;

[0036] Defined by G4ParticleGun and G4PrimaryVertex 137 Cs point source;

[0037] The 137 The Cs point source is placed in the center of the pipe;

[0038] Obtained through the CalculateDetectionEfficiency method 137 The detection efficiency when the Cs point source is at the center of the pipe. ;

[0039] Will 137 The Cs point source moves along the pipe centerline to different distances to simulate different activities at the pipe center. 137 Cs point source;

[0040] Obtained through the CalculateDetectionEfficiency method 137 Detection efficiency of Cs point source at different distances from the center of the pipe .

[0041] Preferably, the relationship between the activity concentration in the pipe and the detector count rate is as follows:

[0042]

[0043]

[0044] In the formula, All are linear fitting coefficients. The detector count rate;

[0045] Get inside the pipe 85 Kr and 133The concentration ratio of Xe gas is used as a weighting factor for the pipeline. 5 Kr and 133 The Xe activity concentration was revised to obtain the final activity concentration of the gas inside the pipeline. The final expression for the activity concentration of the gas inside the pipe is:

[0046]

[0047] In the formula, , For inside the pipe 85 Kr and 133 The concentration ratio of Xe gas.

[0048] Preferably, the detector has dimensions of 1250mm×400mm×50mm, is made of plastic scintillator, and is surrounded by a 2mm thick sheet metal; the pipe has a diameter of 1016mm and a thickness of 16mm, and is made of iron.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] This invention will... 137 The Cs point source moves along the centerline of the pipe to simulate different activities. 137 The Cs point source, and then through different types of radioactive sources, generates the same counting principle on the equipment, which is then transformed into... 85 Kr、 133 The activity concentration of the Xe gas source. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 In this invention 137 A schematic diagram of radiation from a Cs point source placed in a pipe;

[0053] Figure 2 In this invention 85 Kr、 133 A schematic diagram of Xe gas source placed in a pipeline for radiation;

[0054] Figure 3 This is a flowchart of the present invention. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should fall within the scope of the technical content disclosed in the present invention. It should be noted that in this specification, relational terms such as "first" and "second" are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0057] This invention provides an embodiment:

[0058] like Figures 1 to 3 As shown, a method for detecting the concentration of equivalent replacement of a gas radioactive source in a steam pipeline includes the following steps:

[0059] Establish a gas source within the pipeline 85 Kr or 133 The relationship between the detector count and the activity concentration in the pipeline at Xe; the gas source in the pipeline is... 85 Kr or 133 The relationship between the detector count and the activity concentration in the pipe at Xe is expressed as follows:

[0060]

[0061]

[0062] In the formula, Count the detectors; The gas source in the pipeline is 85 Activity concentration at Kr; The gas source in the pipeline is 133 The activity concentration of Xe; The detector is positioned directly above the volume of gas inside the pipe; The gas source in the pipeline is 85 Detection efficiency at Kr; The gas source in the pipeline is 133 Detection efficiency at Xe.

[0063] Establish the pipeline inside 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship between the activity of the Cs point source and the content of the pipe is as follows: 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship for the activity of the Cs point source is expressed as:

[0064]

[0065] In the formula, Count the detectors; For different 137 The activity of the Cs point source; for 137 Cs point source detection efficiency at different distances from the center of the device.

[0066] Based on the principle that the detector counts are the same, the two aforementioned relationships are combined to obtain the formula for calculating the activity concentration inside the pipe; the formula for calculating the activity concentration inside the pipe is as follows:

[0067]

[0068]

[0069] In the formula, The detector is positioned directly above the gas volume inside the pipe. For different 137 The activity of Cs point source, 137 Cs point sources are radioactive sources with known activity. Their purpose is to simulate unknown sources, or in other words, uncalibrated radioactive gas sources, using known sources. and The quantity is known; The gas source in the pipeline is 85 Detection efficiency at Kr; The gas source in the pipeline is 133 Detection efficiency at Xe; for 137 Cs point source detection efficiency at different distances from the center of the pipeline; The gas source in the pipeline is 85 Activity concentration at Kr; The gas source in the pipeline is 133 The activity concentration of Xe;

[0070] Parameters were obtained through Geant4 simulation. , The value;

[0071] The simulation process of Geant4 is as follows:

[0072] 1.1 Define the detector and measurement environment

[0073] Create a new class `DetectorConstruction` that inherits from `G4VUserDetectorConstruction`. `G4VUserDetectorConstruction` is the core base class in the Geant4 framework used to construct detector geometry. `DetectorConstruction` is a user-defined concrete implementation class that inherits from this base class, responsible for defining all material structures and geometric layouts in the simulation. In this class, `G4Box` and `G4LogicalVolume` are used to define the detector's geometry. `G4Box` is the base class for defining cuboid-shaped geometry, and `G4LogicalVolume` is used to define the volume attributes and behavioral logic within the detector's geometry. The detector material is a plastic scintillator, and the detector dimensions are 1250mm × 400mm × 50mm, with a 2mm thick sheet metal covering its outer perimeter. Create another new class `PipeGeometry` that inherits from `G4VUserDetectorConstruction`. In this class, `G4Tubs` and `G4LogicalVolume` are used to define the pipe geometry. `G4Tubs` is the core class for defining cylindrical or tubular solid geometry. The pipe has a diameter of 1016mm and a thickness of 16mm, and is made of iron.

[0074] 1.2 Simulated Radioactive Source

[0075] Create a new class, PrimaryGeneratorAction, that inherits from G4VUserPrimaryGeneratorAction. G4VUserPrimaryGeneratorAction is also a base class, used to define the abstract interface for particle source generation. It is one of the core base classes that Geant4 mandates users to implement, and PrimaryGeneratorAction inherits from G4VUserPrimaryGeneratorAction. In this class, G4ParticleGun and G4PrimaryVertex are defined... 137 Cs point source ( 85 Kr、 133Xe can also be set), G4ParticleGun is the core class used to define and emit primary particles, and G4PrimaryVertex is a method to simulate the particle generation process. The point source is placed in the center of the pipe, and its energy is 662 keV. Create a new class RunAction that inherits from G4UserRunAction. G4UserRunAction is the core base class that manages the simulation run (Run) phase, while the user-defined RunAction class inherits and implements its interface to control the initialization, data collection, and result output of the Run. In this class, the run operation is defined using G4RunManager. Implement the CalculateDetectionEfficiency method in the RunAction class. CalculateDetectionEfficiency is a method used to calculate the detector's detection efficiency. This method will automatically simulate and calculate the detection efficiency based on the energy deposition in the detector, thereby obtaining the gas source in the pipe. 85 Detection efficiency at Kr Or the gas source in the pipeline is 133 Detection efficiency at Xe as well as 137 The detection efficiency when the Cs point source is at the center of the pipe. .

[0076] Will 137 The Cs point source moves along the pipe centerline to different distances to simulate different activities at the pipe center. 137 Cs point source; in actual execution, the existing 5 points are used. 137 The Cs point source was placed in the center of the pipe, and different activity concentrations were simulated using the Monte Carlo method. 85 Kr、 133 Xe gas source. However, in practice, it is impossible to find a continuous activity level. 137 Cs point source, therefore, moving a point source along the pipe centerline to different distances simulates different activities located at the pipe center. 137 Cs point source.

[0077] The geometric position of the radiation source is set by adjusting the parameters in the SetParticlePosition() method, thereby obtaining... 137 Detection efficiency of Cs point source at different distances from the center of the pipe SetParticlePosition is a member function of the G4ParticleGun class, used to set the initial emission position of primary particles. As shown in the text, it is used to adjust the position of the emission source, and different positions produce different efficiencies.

[0078] The parameters obtained based on simulation , The numerical value and the formula for calculating the activity concentration inside the pipeline are used to obtain the gas source inside the pipeline. 85 Kr or 133 The corresponding activity concentration in the pipe at Xe;

[0079] The table obtained through simulation calculations is as follows:

[0080] Table 1 Different activities 137 Cs point source is equivalent to 85 Kr / 133 Xe gas source activity-concentration relationship table

[0081]

[0082] Referring to Table 1, when a specified radioactive source is placed at a specified location, detector counts and the corresponding activity concentrations of the gas sources in the table can be obtained. Taking the first column as an example, numbers 7, 8, 10, 12, and 25 are respectively... 137 The Cs point source is placed at 0m (i.e., the center of the pipe), corresponding to... 85 Kr activity concentration (Bq / m³) 3 The values ​​are 3.78 × 10⁻⁶. 6 Bq / m 3 2.98×10 6 Bq / m 3 9.84×10 5 Bq / m 3 1.87×10 8 Bq / m 3 8.07×10 9 Bq / m 3 The detector counts obtained were c1, c2, c3, c4, and c5, respectively.

[0083] The horizontal axis represents the detector count, and the vertical axis represents... 85 The conversion relationship between the activity concentration of the Kr gas source and the curve is obtained by curve fitting. Furthermore, the more types and denser the locations of the radioactive sources, the more accurate the fitted curve and the more accurate the measurement results.

[0084] The gas source in the pipeline is 85 Kr or 133 A linear fit was established between the activity concentration in the pipe corresponding to Xe and the detector count rate, yielding the following relationship:

[0085]

[0086]

[0087] In the formula, All are linear fitting coefficients. The detector count rate;

[0088] Get inside the pipe 85 Kr and 133 The concentration ratio of Xe gas is used as a weighting factor for the pipeline. 5 Kr and 133 The Xe activity concentration was revised to obtain the final activity concentration of the gas inside the pipeline. The final expression for the activity concentration of the gas inside the pipe is:

[0089]

[0090] In the formula, , For inside the pipe 85 Kr and 133 The concentration ratio of Xe gas.

[0091] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting the concentration of equivalent replacement of a gaseous radioactive source in a steam pipeline, characterized in that, Includes the following steps: Establish a gas source within the pipeline 85 Kr or 133 The formula relating detector counts to activity concentration in the pipe at time Xe; Establish the pipeline inside 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship between the activity of the Cs point source; Based on the principle that the detector counts are the same, the two aforementioned relationships are combined to obtain the formula for calculating the activity concentration inside the pipe; the formula for calculating the activity concentration inside the pipe is as follows: In the formula, The detector is positioned directly above the gas volume inside the pipe. For different 137 The activity of Cs point source, and The quantity is known; The gas source in the pipeline is 85 Detection efficiency at Kr; The gas source in the pipeline is 133 Detection efficiency at Xe; for 137 Cs point source detection efficiency at different distances from the center of the pipeline; The gas source in the pipeline is 85 Activity concentration at Kr; The gas source in the pipeline is 133 The activity concentration of Xe; Parameters were obtained through Geant4 simulation. , The value; The parameters obtained based on simulation , The numerical value and the formula for calculating the activity concentration inside the pipeline are used to obtain the gas source inside the pipeline. 85 Kr or 133 The corresponding activity concentration in the pipe at Xe; The gas source in the pipeline is 85 Kr or 133 A linear fitting relationship was established between the activity concentration in the pipe corresponding to Xe and the detector count rate, and the relationship between the activity concentration in the pipe and the detector count rate was obtained. Get inside the pipe 85 Kr and 133 The concentration ratio of Xe gas is used as a weighting factor for the pipeline. 5 Kr and 133 The Xe activity concentration was revised to obtain the final activity concentration of the gas inside the pipeline. .

2. The concentration detection method for equivalent replacement of gas radioactive sources in steam pipelines according to claim 1, characterized in that: The inside of the pipe is 137 The detector count corresponding to the Cs point source and the inside of the pipe 137 The relationship for the activity of the Cs point source is expressed as: ； The gas source inside the pipeline is 85 Kr or 133 The relationship between the detector count and the activity concentration in the pipe at Xe is expressed as follows: In the formula, Count the detectors.

3. The concentration detection method for equivalent replacement of gas radioactive sources in steam pipelines according to claim 2, characterized in that: Parameters were obtained through the Geant4 simulation. and The steps include: Define the detector's geometry and materials using G4Box and G4LogicalVolume; Define the geometry and material of the pipe using G4Tubs and G4LogicalVolume; Gas sources are defined using G4ParticleGun and G4PrimaryVertex. 85 Kr or gas source 133 Xe; The gas source 85 Kr or gas source 133 Xe is placed in the center of the pipe; The gas source inside the pipeline was obtained using the CalculateDetectionEfficiency method. 85 Detection efficiency at Kr Or the gas source in the pipeline is 133 Detection efficiency at Xe .

4. The concentration detection method for equivalent replacement of gas radioactive sources in steam pipelines according to claim 3, characterized in that: Parameters obtained based on the Geant4 simulation The steps include: Define the detector's geometry and materials using G4Box and G4LogicalVolume; Define the geometry and material of the pipe using G4Tubs and G4LogicalVolume; Defined by G4ParticleGun and G4PrimaryVertex 137 Cs point source; The 137 The Cs point source is placed in the center of the pipe; Obtained through the CalculateDetectionEfficiency method 137 The detection efficiency when the Cs point source is at the center of the pipe. ; Will 137 The Cs point source moves along the pipe centerline to different distances to simulate different activities at the pipe center. 137 Cs point source; Obtained through the CalculateDetectionEfficiency method 137 Detection efficiency of Cs point source at different distances from the center of the pipe .

5. The concentration detection method for equivalent replacement of gas radioactive sources in steam pipelines according to claim 1, characterized in that: The relationship between the activity concentration inside the pipe and the detector count rate is as follows: In the formula, All are linear fitting coefficients. The detector count rate; Get inside the pipe 85 Kr and 133 The concentration ratio of Xe gas is used as a weighting factor for the pipeline. 5 Kr and 133 The Xe activity concentration was revised to obtain the final activity concentration of the gas inside the pipeline. The final expression for the activity concentration of the gas inside the pipe is: In the formula, , For inside the pipe 85 Kr and 133 The concentration ratio of Xe gas.

6. The method for detecting the concentration of equivalent replacement of gas radioactive sources in steam pipelines according to claim 4, characterized in that: The detector measures 1250mm × 400mm × 50mm and is made of plastic scintillator. It is also surrounded by a 2mm thick sheet metal. The pipe measures 1016mm in diameter and 16mm in thickness and is made of iron.

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