CN113325461B - Method for adjusting radon exhalation rate and effective decay constant by using radon chamber - Google Patents
Method for adjusting radon exhalation rate and effective decay constant by using radon chamber Download PDFInfo
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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
Technical Field
The invention relates to a nuclear radiation detection technology, in particular to a method for adjusting radon exhalation rate and effective decay constant of a radon exhalation rate standard device by using a radon chamber.
Background
Radon in the air environment mainly comes from precipitation on the surface of media such as soil, and various methods and instruments are used for measuring the precipitation rate of radon on the surface of the media. Because the radon exhalation rate of the surface of a medium such as soil greatly changes with the temperature, the humidity and the air pressure of the environment, a radon exhalation rate standard device which is not influenced by the temperature, the humidity and the air pressure of the environment is needed for testing the accuracy and the reliability of the method and the instrument for measuring the radon exhalation rate of the surface of the medium. Researchers have proposed to arbitrarily adjust the effective decay constant by using the change of the number and area of the leak pores, but in practical practice, the effective decay constant deviates from the preset value due to the influence of dust accumulated in the pores, which affects the accuracy of the device.
The conventional radon exhalation rate measuring device is shown in the attached figure 2 and comprises a measuring instrument 1, a filter membrane 2, a drying tube 3, a radon collection cover 4 and a pump 5.
One end of the filter membrane 2 is connected with a measuring chamber of the measuring instrument 1 through a pipeline, the other end of the filter membrane 2 is connected with the drying tube 3 through a pipeline, the other end of the drying tube 3 is connected with the radon collecting cover 4 through a pipeline, one end of the pump 5 is connected with the measuring chamber of the measuring instrument 1 through a pipeline, and the other end of the pump 5 is connected with the radon collecting cover 4 through a pipeline.
The process of measuring the radon exhalation rate by adopting the conventional radon exhalation rate measuring device is as follows:
the radon collection cover 4 with an opening on one side is buckled on the surface of a medium to be measured, radon atoms in the medium escape from the surface and enter the radon collection cover 4 under the action of diffusion and seepage, so that the radon concentration in the radon collection cover 4 changes, the pump 5 pumps the radon in the radon collection cover 4 collection chamber into the measurement chamber of the measurement instrument 1 after filtering daughter by the drying tube 3 and the filter membrane 2 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 measurement instrument 1 is balanced with the radon concentration in the radon collection cover 4.
Because the flow rate of the pump 5 is 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 as follows:
λe＝λ+λb+λleak (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 4; v is the space volume of the radon collecting cover 4; lambda [ alpha ]eIs an effective decay constant including decay constant lambda of radon and leakage coefficient lambda of radon in radon collection cover 4leakAnd back diffusion coefficient lambdab(ii) a t is the radon collecting time.
The solution of formula (1) is:
C0being the ambient radon concentration, negligible, equation (3) can be varied as:
the radon exhalation rate can be obtained through linear or nonlinear fitting according to the change rule of the radon concentration in the radon collection cover 4 measured by a plurality of measurement periods.
The accuracy and reliability of the method and the instrument for detecting the radon exhalation rate on the surface of the measuring medium on a standard device are insufficient when comparison is carried out only under a certain specific effective decay constant condition, and a method capable of arbitrarily adjusting the effective decay constant is required.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for adjusting the radon exhalation rate and the effective decay constant of a radon exhalation rate standard device by using a radon chamber.
The technical scheme of the invention is as follows: the device comprises a measuring instrument, a filter membrane, a drying pipe, a radon collection cover and a pump, wherein one end of the filter membrane is connected with the measuring chamber of the measuring instrument through a pipeline, the other end of the filter membrane is connected with the drying pipe through a pipeline, the other end of the drying pipe 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 connector and the air inlet connector are respectively arranged on the dense material plate, the air outlet connector 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 connector through a pipeline.
The flowmeter is used for measuring the flow rate of the adjustable micro pump; the specific measurement process is as follows:
A. the radon collecting 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 collecting cover under the action of diffusion and seepage, the radon concentration in the radon collecting cover changes, the pump always pumps the radon in the radon collecting cover collecting chamber into a measuring 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 measuring chamber of the measuring instrument is balanced with the radon concentration in the radon collecting 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:
λe＝λ+λb+λleak (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 coverleakAnd back diffusion coefficient lambdab(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 collecting cover is well sealed with the surface of the compact material plate, the leakage rate is not considered, and the back diffusion is not considered for the compact material plate.
The derivation can be obtained for both sides of equation (4):
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).
Compared with the prior art, the invention has the following characteristics:
the measuring device and the measuring method provided by the invention are simple, the radon exhalation rate and the effective decay constant can be adjusted at will, and the measuring device and the measuring method can be used for testing the accuracy and reliability of the method and the instrument for measuring the radon exhalation rate on the surface of the medium.
The detailed structure of the present invention will be further described with reference to the accompanying drawings and the detailed description.
Drawings
FIG. 1 is a schematic diagram of the structure and measurement process of the device for adjusting the radon exhalation rate and the effective decay constant by using a radon chamber, provided by the invention;
fig. 2 is a schematic diagram of the structure and the measurement process of the conventional radon exhalation rate measurement device.
Detailed Description
The device for adjusting the radon exhalation rate and the effective decay constant by using the radon chamber comprises a measuring instrument 1, a filter membrane 2, a drying pipe 3, a radon collection cover 4, a pump 5, a dense material plate 6, an air outlet joint 7, an air inlet joint 8, a radon chamber 9, an adjustable micropump 10 and a flowmeter 11.
One end of the filter membrane 2 is connected with a measuring chamber of the measuring instrument 1 through a pipeline, the other end of the filter membrane 2 is connected with the drying tube 3 through a pipeline, the other end of the drying tube 3 is connected with the radon collecting cover 4 through a pipeline, one end of the pump 5 is connected with the measuring chamber of the measuring instrument 1 through a pipeline, the other end of the pump 5 is connected with the radon collecting cover 4 through a pipeline, the air outlet connector 7 and the air inlet connector 8 are respectively installed on the dense material plate 6, the air outlet connector 7 is connected with the adjustable micropump 10 through a pipeline, the other end of the adjustable micropump 10 is connected with the flowmeter 11 through a pipeline, the other end of the flowmeter 11 is connected with the radon chamber 9 through a pipeline, and the other end of the radon chamber 9 is connected with the air inlet connector 8 through a pipeline.
The flow meter 11 is used to measure the flow rate of the adjustable micropump 10.
The second embodiment adopts the method for adjusting the radon exhalation rate and the effective decay constant of the radon exhalation rate standard device by using the device for adjusting the radon exhalation rate and the effective decay constant by using the radon chamber as described in the first embodiment, and comprises a conventional radon exhalation rate measuring process and a process for adjusting the radon exhalation rate and the effective decay constant of the radon exhalation rate standard device by using the radon chamber, wherein the specific measuring process comprises the following steps:
A. routine radon exhalation rate measurement process
The conventional radon exhalation rate measuring process is shown in the attached figure 2, a radon collection cover 4 with an opening on one surface is buckled on the surface of a medium to be measured, radon atoms in the medium escape from the surface and enter the radon collection cover 4 under the action of diffusion and seepage, so that the radon concentration in the radon collection cover 4 is changed, a pump 5 pumps radon in a collection chamber of the radon collection cover 4 into a measuring chamber of a measuring instrument 1 at a constant flow rate after filtering out daughter bodies through a drying pipe 3 and a filter membrane 2, and the flow rate is 0.5-15 liters/minute, so that the radon concentration in the measuring chamber of the measuring instrument 1 is balanced with the radon concentration in the radon collection cover 4.
Because the flow rate of the pump 5 is 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 as follows:
λe＝λ+λb+λleak (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 4; v is the space volume of the radon collecting cover 4; lambda [ alpha ]eIs effective decay constant including decay constant lambda of radon and leakage coefficient lambda of radon in radon collecting cover 4leakAnd back diffusion coefficient lambdab(ii) a t is the radon collecting time.
The solution of formula (1) is:
C0being the ambient radon concentration, negligible, equation (3) can be varied as:
the radon exhalation rate can be obtained through linear or nonlinear fitting according to the change rule of the radon concentration in the radon collection cover 4 measured by a plurality of measurement periods.
The accuracy and reliability of the method and the instrument for detecting the radon exhalation rate on the surface of the measuring medium on a standard device are insufficient only by comparing under a certain specific effective decay constant condition, and the effective decay constant needs to be adjusted at will.
B. Process for adjusting radon exhalation rate and effective decay constant of radon exhalation rate standard device by using radon chamber
The process of adjusting the radon exhalation rate and the effective decay constant of the radon exhalation rate standard device is shown in the attached drawing 1, and during measurement, the radon collection cover 4 is buckled on the dense material plate 6, and the air outlet connector 7 and the air inlet connector 8 are covered in the radon collection cover 4.
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 4 is controlled to change according to the formula (4).
Because the surfaces of the radon collection cover 4 and the dense material plate 6 are well sealed, the leakage rate is not considered, and the dense material plate 6 is not considered to be back-diffused.
The two-sided derivation of equation (4) can be obtained:
if the flow rate of the adjustable micropump 10 is set to be L (t), the radon concentration in the radon collection cover 4 is changed into:
where C is the radon concentration of the radon chamber 9.
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 10 to change according to the formula (8).
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:
λe＝λ+λb+λleak (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 coverleakAnd back diffusion coefficient lambdab(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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| CN103499672B (en) * | 2013-10-16 | 2015-04-29 | 衡阳师范学院 | Method and device for optionally adjusting radon exhalation rate and effective decay constants |
| CN105929443B (en) * | 2016-04-29 | 2019-10-29 | 衡阳师范学院 | Actively any method for adjusting precipitation rate of radon and Effective Decay Constant |
| CN107831524B (en) * | 2017-12-18 | 2023-05-12 | 成都理工大学 | Radon exhalation rate continuous measurement device and measurement method |
| CN109655870B (en) * | 2018-12-28 | 2023-03-21 | 衡阳师范学院 | Device and method for arbitrarily adjusting radon exhalation rate and effective decay constant by using gas flow type radon source |
| CN109521462A (en) * | 2018-12-29 | 2019-03-26 | 衡阳师范学院 | Adjust the precipitation rate of radon standard set-up and method of precipitation rate of radon |
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