CN113325461B - The method of adjusting radon precipitation rate and effective decay constant by using radon chamber - Google Patents

Abstract

The device and the method for adjusting the radon exhalation rate and the effective decay constant by using the radon chamber 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 flowmeter through a pipeline, the other end of the flowmeter is connected with the radon chamber through a pipeline, and the other end of the radon chamber 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 by using a radon chamber, 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

The method of adjusting radon precipitation rate and effective decay constant by using radon chamber

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 radon chamber.

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, but 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 is connected through a pipeline. 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 radon chamber.

The technical scheme of the present invention is: a method for adjusting the radon precipitation rate and effective decay constant by using a radon chamber, and a device for adjusting the radon precipitation rate and effective decay constant by using a radon chamber, the device includes a measuring instrument, a filter membrane, a drying tube, a radon collector Cover, pump, 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 measurement chamber through the pipeline. The measuring chamber of the instrument is connected, and the other end of the pump is connected to the radon collecting cover through the pipeline; it also includes the dense material plate, the gas outlet joint, the gas inlet joint, the radon chamber, the adjustable micro pump and the flow meter; the gas outlet joint and the gas inlet joint are installed separately On the dense material board, the outlet joint is connected to the adjustable micro pump through a pipeline, the other end of the adjustable micro pump is connected to the flowmeter through a pipeline, the other end of the flowmeter is connected to the radon chamber through a pipeline, and the other end of the radon chamber is connected to the radon chamber through a pipeline. Intake connector connection.

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 radon chamber to adjust the radon precipitation rate and effective decay constant of the radon precipitation rate standard device. When measuring, fasten the radon collecting cover on the dense material plate, and cover the outlet joint and the air inlet joint in the radon collecting cover;

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:

Assuming that the flow rate of the adjustable micro-pump is L(t), then under the action of the adjustable micro-pump, the radon concentration in the radon collecting cover changes as:

where C is the radon concentration in the radon chamber;

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 utilizing radon chamber to adjust 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. A device for adjusting the radon precipitation rate and effective decay constant by using a radon chamber, including a measuring instrument 1, a filter membrane 2, a drying tube 3, a radon collection cover 4, a pump 5, a dense material plate 6, an air outlet connector 7, an air intake Joint 8, radon chamber 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 is connected through a pipeline. 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 to the flowmeter 11 through a pipeline, the other end of the flowmeter 11 is connected to the radon chamber 9 through a pipeline, and the other end of the radon chamber 9 is connected to the air inlet connector 8 through a pipeline.

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

Embodiment 2, adopt the device that utilizes radon chamber to adjust radon precipitation rate and effective decay constant as described in embodiment 1 to adjust radon precipitation rate standard device radon precipitation rate and the method for effective decay constant, including conventional radon precipitation rate measurement process And utilize the radon chamber to regulate the process of the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device, and its concrete 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 room of the radon collection cover 4 at a constant flow rate through the drying pipe 3 and the filter membrane 2 after filtering out the daughter body, and the flow rate is pumped 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 only under the condition of a specific effective decay constant. It is necessary to be able to adjust the effective decay constant arbitrarily.

B. The process of using the radon chamber to adjust the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device

The process of adjusting the radon precipitation rate and the effective decay constant of the radon precipitation rate standard device is as shown in accompanying drawing 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 are covered. Inside the radon hood 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 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), then under the action of the adjustable micro pump 10, the radon concentration in the radon collecting cover 4 changes as follows:

where C is the radon concentration in the radon chamber 9 .

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. The method for adjusting the radon exhalation rate and the effective decay constant of the standard radon exhalation rate device by using a radon chamber is adopted, the device for adjusting the radon exhalation rate and the effective decay constant by using the radon chamber comprises a measuring instrument, a filter membrane, a drying tube, a radon collection cover and a pump, one end of the filter membrane is connected with a measuring chamber of the measuring instrument through a pipeline, the other end of the filter membrane is connected with the drying tube through a pipeline, the other end of the drying tube is connected with the radon collection cover through a pipeline, one end of the pump is connected with the measuring chamber of the measuring instrument through a pipeline, and the other end of the pump is connected with the radon collection cover through a pipeline;

the device also comprises a compact material plate, an air outlet joint, an air inlet joint, a radon chamber, an adjustable micropump and a flowmeter; the air outlet joint and the air inlet joint are respectively arranged on the compact material plate, the air outlet joint is connected with the adjustable micropump through a pipeline, the other end of the adjustable micropump is connected with the flowmeter through a pipeline, the other end of the flowmeter is connected with the radon chamber through a pipeline, and the other end of the radon chamber is connected with the air inlet joint through a pipeline; the flowmeter is used for measuring the flow rate of the adjustable micro pump;

the method is characterized in that: the specific measurement process is as follows:

A. the radon collection cover with an opening on one surface is buckled on the surface of a medium to be measured, because radon atoms in the medium escape from the surface and enter the radon collection cover under the action of diffusion and seepage, the radon concentration in the radon collection cover changes, the pump always pumps the radon in the radon collection cover collection chamber into a measurement chamber of a measuring instrument through a drying pipe and a filter membrane to filter daughter at a constant flow rate, and the flow rate is 0.5-15L/min, so that the radon concentration in the measurement chamber of the measuring instrument is balanced with the radon concentration in the radon collection cover;

because the flow rate of the pump is large, the radon concentration in the measuring chamber of the measuring instrument is equal to the radon concentration in the radon collecting cover, and the radon concentration C (t) in the measuring chamber of the measuring instrument is as follows:

λ_e＝λ+λ_b+λ_leak (2)

wherein: j is the radon exhalation rate on the surface of the medium to be detected; s is the bottom area of the radon collection cover; v is the space volume of the radon collecting cover; lambda [ alpha ]_eIs effective decay constant including decay constant lambda of radon and leakage coefficient lambda of radon in radon collecting cover_leakAnd back diffusion coefficient lambda_b(ii) a t is radon collecting time;

the solution of formula (1) is:

C₀being the ambient radon concentration, negligible, equation (3) can be varied as:

B. adjusting the radon exhalation rate and the effective decay constant of the radon exhalation rate standard device by using a radon chamber, buckling a radon collection cover on a compact material plate during measurement, and covering an air outlet connector and an air inlet connector in the radon collection cover;

as can be seen from the formula (4), the radon exhalation rate standard device can be used as long as the radon concentration in the radon collection cover is controlled to change according to the formula (4);

because the radon collection cover and the surface of the compact material plate are well sealed, the leakage rate is not required to be considered, and the back diffusion is not required to be considered for the compact material plate;

the two-sided derivation of equation (4) can be obtained:

and setting the flow rate of the adjustable micropump as L (t), and changing the radon concentration in the radon collection cover into:

wherein C is the radon concentration of the radon chamber;

substituting formula (5) for formula (6):

substituting formula (4) for formula (7):

the radon exhalation rate and the effective decay constant can be adjusted by adjusting the flow rate of the adjustable micropump according to the formula (8).

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