CN113325460B - Method for adjusting radon extraction rate and effective decay constant of radon extraction rate standard device - Google Patents

Abstract

The device and the method for adjusting the radon exhalation rate and the effective decay constant of the standard device for the radon exhalation rate are characterized in that one end of a filter membrane in the device is connected with a measuring chamber of a measuring instrument through a pipeline, the other end of the filter membrane is connected with a drying pipe through a pipeline, the other end of the drying pipe is connected with a radon collection cover through a pipeline, one end of a pump is connected with the measuring chamber of the measuring instrument through a pipeline, the other end of the pump is connected with the radon collection cover through a pipeline, an air outlet connector and an air inlet connector are respectively installed on a compact material plate, the air outlet connector is connected with an adjustable micro pump through a pipeline, the other end of the adjustable micro pump is connected with a flow meter through a pipeline, the other end of the flow meter is connected with a flow type radon source through a pipeline, and the other end of the flow type radon source is connected with the air inlet connector through a pipeline. The measuring method comprises a conventional radon exhalation rate measuring process and a process of adjusting the radon exhalation rate and the effective decay constant of a radon exhalation rate standard device, and the radon exhalation rate and the effective decay constant can be adjusted by adjusting the flow rate of an adjustable micropump in the device.

Description

Method for adjusting radon extraction rate and effective decay constant of radon extraction rate standard device

technical field

The invention relates to a nuclear radiation detection technology, in particular to a method for adjusting the radon precipitation rate and effective decay constant of a radon precipitation rate standard device by using a gas-flow radon source.

Background technique

Radon in the air environment mainly comes from the precipitation on the surface of media such as soil. There are many methods and instruments for measuring the radon precipitation rate on the surface of the medium. Since the radon release rate on the surface of the medium such as soil varies greatly with the changes of the temperature, humidity and air pressure of the environment, the accuracy and reliability of the method and instrument for measuring the radon release rate on the medium surface need to be independent of the environment. Standard device for radon release rate for changes in temperature, humidity and air pressure. Some researchers have proposed to use the changes in the number and area of leaking holes to arbitrarily adjust the effective decay constant. However, in practice, due to the influence of dust accumulation in the small holes, the effective decay constant will deviate from the preset value, affecting the accuracy of the device. sex.

A conventional radon precipitation rate measuring device is shown in FIG. 2 , including a measuring instrument 1 , a filter membrane 2 , a drying tube 3 , a radon collecting cover 4 and a pump 5 .

One end of the filter membrane 2 is connected to the measuring chamber of the measuring instrument 1 through a pipeline, the other end of the filter membrane 2 is connected to the drying tube 3 through a pipeline, the other end of the drying tube 3 is connected to the radon collecting cover 4 through a pipeline, and one end of the pump 5 passes through The pipeline is connected with the measuring chamber of the measuring instrument 1, and the other end of the pump 5 is connected with the radon collecting cover 4 through the pipeline.

The process of measuring the radon release rate using a conventional radon release rate measuring device is as follows:

The radon collecting cover 4 with one side opening is buckled on the surface of the medium to be measured, because the radon atoms in the medium escape from the surface and enter the radon collecting cover 4 under the action of diffusion and seepage, resulting in the change of the radon concentration in the radon collecting cover 4, and the pump 5 The radon in the collection chamber of the radon collecting cover 4 is always pumped into the measuring chamber of the measuring instrument 1 through the drying tube 3 and the filter membrane 2 after filtering out the daughter body at a constant flow rate, and the flow rate is 0.5-15 liters/min, so that the measuring chamber of the measuring instrument 1 is The radon concentration of the radon is in equilibrium with the radon concentration in the radon collection cover 4 .

Since the flow rate of the pump 5 is relatively large, the radon concentration in the measuring chamber of the measuring instrument 1 is equal to the radon concentration in the radon collecting cover 4, and the radon concentration C(t) in the measuring chamber of the measuring instrument 1 is:

λ _e =λ+λ _b +λ _leak (2)

Among them: J is the radon precipitation rate on the surface of the measured medium; S is the bottom area of the radon collecting cover 4; V is the space volume of the _radon collecting cover 4; Leakage coefficient λ _leak and anti-diffusion coefficient λ _b of inner radon; t is the time for collecting radon.

The solution of formula (1) is:

C ₀ is the ambient radon concentration, which can be ignored. Equation (3) can be changed to:

The radon precipitation rate can be obtained by linear or nonlinear fitting according to the variation law of the radon concentration in the radon collecting cover 4 measured by multiple measurement cycles.

It is not enough to test the accuracy and reliability of the method and instrument for measuring the radon precipitation rate on the surface of the medium on a standard device. It is not sufficient to compare only under the condition of a specific effective decay constant. It is necessary to arbitrarily adjust the effective decay constant. method.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device by utilizing a gas flow radon source.

The technical scheme of the present invention is: the method for adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device, based on the device for adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device, the device comprises a measuring instrument, a filter membrane, a drying Tubes, radon hoods and pumps. One end of the filter membrane is connected to the measuring chamber of the measuring instrument through the pipeline, the other end of the filter membrane is connected to the drying tube through the pipeline, the other end of the drying tube is connected to the radon collecting cover through the pipeline, and one end of the pump is connected to the measuring chamber of the measuring instrument through the pipeline. Connection, the other end of the pump is connected to the radon collection cover through the pipeline.

The device for adjusting the radon precipitation rate standard device for radon precipitation rate and effective decay constant also includes a dense material plate, an outlet joint, an air inlet joint, a flow type radon source, an adjustable micro pump and a flow meter. The air outlet connector and the air inlet connector are respectively installed on the dense material board. The air outlet connector is connected to the adjustable micro pump through the pipeline, the other end of the adjustable micro pump is connected to the flow meter through the pipeline, and the other end of the flow meter is connected to the flow type radon through the pipeline. source connection, and the other end of the flow-type radon source is connected to the air inlet connector through a pipeline.

The flow meter is used to measure the flow rate of the adjustable micro pump;

The specific measurement process is as follows:

A. Buckle the radon collecting cover with an opening on the surface of the medium to be tested. Due to the diffusion and seepage of the radon atoms in the medium, the radon atoms escape from the surface and enter the radon collecting cover, resulting in the change of the radon concentration in the radon collecting cover. The radon in the collection chamber of the radon collecting hood is pumped into the measuring chamber of the measuring instrument at a constant flow rate through the drying tube and the filter membrane to filter out the daughters, and the flow rate is 0.5-15 liters/min, so that the radon concentration in the measuring chamber of the measuring instrument is the same as that of the radon collecting hood. The radon concentration within the equilibrium.

Due to the large flow rate of the pump, the radon concentration in the measuring chamber of the measuring instrument is equal to the radon concentration in the radon collecting hood, and the radon concentration C(t) in the measuring chamber of the measuring instrument is:

λ _e =λ+λ _b +λ _leak (2)

Among them: J is the radon precipitation rate on the surface of the measured medium; S is the bottom area of the radon collecting cover; V is the space volume of the _radon collecting cover; Leakage coefficient λ _leak and anti-diffusion coefficient λ _b ; t is the time for collecting radon.

The solution of formula (1) is:

C ₀ is the ambient radon concentration, which can be ignored. Equation (3) can be changed to:

B. Use the air-flow radon source to adjust the radon precipitation rate and effective decay constant of the radon precipitation rate standard device. When measuring, fasten the radon collection cover on the dense material plate, and cover the outlet and air inlet joints on the radon collection cover. Inside.

It can be seen from formula (4) that as long as the radon concentration in the radon collecting hood is controlled to change according to formula (4), it can be used as a standard device for radon precipitation rate.

Since the surface of the radon collecting cover and the dense material plate is well sealed, the leakage rate does not need to be considered, and the dense material plate does not need to consider the back diffusion.

Taking the derivative of both sides of Equation (4), we can get:

Suppose the flow rate of the adjustable micro-pump is L(t), and the activity of radon produced by the air-flow radon source per unit time is A. Since the void volume in the air-flow radon source is very small, it can be approximated that all the radon produced by the air-flow radon source is adjustable. When the micro pump is pumped out, under the action of the adjustable micro pump, the radon concentration in the radon collecting cover changes as follows:

Substitute equation (5) into equation (6):

Substitute equation (4) into equation (7):

By adjusting the flow rate of the adjustable micro pump according to formula (8), the radon precipitation rate and the effective decay constant can be adjusted.

Compared with the prior art, the present invention has the following characteristics:

The measuring device and the measuring method provided by the invention are simple, the radon precipitation rate and the effective decay constant can be adjusted arbitrarily, and can be used for checking the accuracy and reliability of the method and the instrument for measuring the radon precipitation rate on the surface of the medium.

The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Description of drawings

Accompanying drawing 1 is the device structure and measuring process schematic diagram of regulating radon precipitation rate standard device radon precipitation rate and effective decay constant provided by the present invention;

2 is a schematic diagram of the structure and measurement process of the existing radon precipitation rate measuring device.

Detailed ways

Embodiment 1. The device for adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device, including a measuring instrument 1, a filter membrane 2, a drying tube 3, a radon collecting cover 4, a pump 5, a dense material plate 6, a gas outlet joint 7, Air inlet connector 8 , air flow type radon source 9 , adjustable micro pump 10 and flow meter 11 .

One end of the filter membrane 2 is connected to the measuring chamber of the measuring instrument 1 through a pipeline, the other end of the filter membrane 2 is connected to the drying tube 3 through a pipeline, the other end of the drying tube 3 is connected to the radon collecting cover 4 through a pipeline, and one end of the pump 5 passes through The pipeline is connected to the measuring chamber of the measuring instrument 1, the other end of the pump 5 is connected to the radon collecting cover 4 through the pipeline, the gas outlet joint 7 and the gas inlet joint 8 are respectively installed on the dense material plate 6, and the gas outlet joint 7 is connected to the adjustable trace through the pipeline. The pump 10 is connected, the other end of the adjustable micro pump 10 is connected with the flow meter 11 through the pipeline, the other end of the flow meter 11 is connected with the flow type radon source 9 through the pipeline, and the other end of the flow type radon source 9 is connected with the air inlet connector 8 through the pipeline connect.

The flow meter 11 is used to measure the flow rate of the adjustable micro pump 10 .

Embodiment 2, adopt the apparatus for adjusting radon precipitation rate standard device radon precipitation rate and effective decay constant as described in Example 1 to adjust the method for radon precipitation rate standard device radon precipitation rate and effective decay constant, including conventional radon precipitation rate The measurement process and the process of adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device by using the air-flow radon source, the specific measurement process is as follows:

A. Conventional radon precipitation rate measurement process

The conventional radon precipitation rate measurement process is shown in Figure 2. The radon collecting cover 4 with an opening on one side is buckled on the surface of the medium to be measured. Because the radon atoms in the medium are under the action of diffusion and seepage, the surface escapes and enters the radon collecting cover. 4. The radon concentration in the radon collection cover 4 is changed, and the pump 5 pumps the radon in the collection chamber of the radon collection cover 4 through the drying pipe 3 and the filter membrane 2 at a constant flow rate after filtering the daughter body into the measuring room of the measuring instrument 1. 0.5-15 liters/min, so that the radon concentration in the measuring chamber of the measuring instrument 1 is balanced with the radon concentration in the radon collecting hood 4 .

Since the flow rate of the pump 5 is relatively large, the radon concentration in the measuring chamber of the measuring instrument 1 is equal to the radon concentration in the radon collecting cover 4, and the radon concentration C(t) in the measuring chamber of the measuring instrument 1 is:

λ _e =λ+λ _b +λ _leak (2)

Among them: J is the radon precipitation rate on the surface of the measured medium; S is the bottom area of the radon collecting cover 4; V is the space volume of the _radon collecting cover 4; Leakage coefficient λ _leak and anti-diffusion coefficient λ _b of inner radon; t is the time for collecting radon.

The solution of formula (1) is:

C ₀ is the ambient radon concentration, which can be ignored. Equation (3) can be changed to:

The radon precipitation rate can be obtained by linear or nonlinear fitting according to the variation law of the radon concentration in the radon collecting cover 4 measured by multiple measurement cycles.

It is not enough to test the accuracy and reliability of the method and instrument for measuring the radon precipitation rate on the surface of the medium on a standard device. It is not sufficient to compare the effective decay constant only under a certain condition. It is necessary to be able to adjust the effective decay constant arbitrarily.

B. The process of adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device by using a flowing radon source

The process of adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device by using the air-flow radon source is shown in Figure 1. During the measurement, the radon collecting cover 4 is buckled on the dense material plate 6, and the air outlet joint 7 And the air inlet joint 8 is covered in the radon collecting cover 4.

It can be seen from the formula (4) that as long as the radon concentration in the radon collecting cover 4 is controlled to change according to the formula (4), it can be used as a standard device for the radon precipitation rate.

Since the surface of the radon collecting cover 4 and the dense material plate 6 is well sealed, the leakage rate does not need to be considered, and the dense material plate 6 does not need to consider back diffusion.

Taking the derivative of both sides of Equation (4), we can get:

Assuming that the flow rate of the adjustable micro pump 10 is L(t), the activity of radon produced by the air-flow radon source 9 per unit time is A. Since the void volume in the air-flow radon source 9 is very small, it can be approximated that the radon generated by the air-flow radon source 9 is very small. All are pumped out by the adjustable micro pump 10, then under the action of the adjustable micro pump 10, the radon concentration in the radon collecting cover 4 changes as follows:

Substitute equation (5) into equation (6):

Substitute equation (4) into equation (7):

By adjusting the flow rate of the adjustable micro pump 10 according to the formula (8), the radon precipitation rate and the effective decay constant can be adjusted.

Claims (1)

1. adopt the device that regulates radon precipitation rate standard device radon precipitation rate and effective decay constant to adjust the method for radon precipitation rate standard device radon precipitation rate and effective decay constant, described regulating radon precipitation rate standard device radon precipitation rate and effective decay constant The device includes a measuring instrument, a filter membrane, a drying tube, a radon collecting cover, and a pump; one end of the filter membrane is connected to the measuring chamber of the measuring instrument through a pipeline, the other end of the filter membrane is connected to the drying tube through a pipeline, and the other end of the drying tube is connected It is connected with the radon collecting cover through the pipeline, one end of the pump is connected with the measuring chamber of the measuring instrument through the pipeline, and the other end of the pump is connected with the radon collecting cover through the pipeline; it also includes a dense material plate, an air outlet joint, an air inlet joint, and a flow-type radon source. , Adjustable micro-pump and flowmeter; the outlet joint and the inlet joint are respectively installed on the dense material plate, the outlet joint is connected to the adjustable micro-pump through a pipeline, and the other end of the adjustable micro-pump is connected to the flowmeter through a pipeline, and the flowmeter The other end of the air flow type radon source is connected to the air flow type radon source through a pipeline, and the other end of the air flow type radon source is connected to the air inlet joint through a pipeline; the flow meter is used to measure the flow rate of the adjustable micro pump; Its characteristics are: its specific measurement process is as follows: A. Buckle the radon collecting cover with an opening on the surface of the medium to be tested. Due to the diffusion and seepage of the radon atoms in the medium, the radon atoms escape from the surface and enter the radon collecting cover, resulting in the change of the radon concentration in the radon collecting cover. The radon in the collection chamber of the radon collecting hood is pumped into the measuring chamber of the measuring instrument at a constant flow rate through the drying tube and the filter membrane to filter out the daughters, and the flow rate is 0.5-15 liters/min, so that the radon concentration in the measuring chamber of the measuring instrument is the same as that of the radon collecting hood. radon concentration balance within; Due to the large flow rate of the pump, the radon concentration in the measuring chamber of the measuring instrument is equal to the radon concentration in the radon collecting hood, and the radon concentration C(t) in the measuring chamber of the measuring instrument is:

λ _e =λ+λ _b +λ _leak (2) Among them: J is the radon precipitation rate on the surface of the measured medium; S is the bottom area of the radon collecting cover; V is the space volume of the _radon collecting cover; Leakage coefficient λ _leak and anti-diffusion coefficient λ _b ; t is the time for collecting radon; The solution of formula (1) is:

C ₀ is the ambient radon concentration, which can be ignored. Equation (3) can be changed to:

B. Use the air-flow radon source to adjust the radon precipitation rate and effective decay constant of the radon precipitation rate standard device. When measuring, fasten the radon collection cover on the dense material plate, and cover the outlet and air inlet joints on the radon collection cover. Inside; It can be seen from formula (4) that as long as the radon concentration in the radon collecting hood is controlled to change according to formula (4), it can be used as a standard device for radon precipitation rate; Since the surface of the radon collecting cover and the dense material plate is well sealed, the leakage rate does not need to be considered, and the dense material plate does not need to consider the back diffusion; Taking the derivative of both sides of Equation (4), we can get:

Suppose the flow rate of the adjustable micro-pump is L(t), and the activity of radon produced by the air-flow radon source per unit time is A. Since the void volume in the air-flow radon source is very small, it can be approximated that all the radon produced by the air-flow radon source is adjustable. When the micro pump is pumped out, under the action of the adjustable micro pump, the radon concentration in the radon collecting cover changes as follows:

Substitute equation (5) into equation (6):

Substitute equation (4) into equation (7):

By adjusting the flow rate of the adjustable micro pump according to formula (8), the radon precipitation rate and the effective decay constant can be adjusted.

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