Device and method for measuring radon exhalation rate and radon leakage amount on surface of medium in open-loop manner

Abstract

The invention discloses a device and method for measuring the radon exhalation rate and the radon leakage amount on the surface of a medium in an open-loop mode. The device comprises an RAD7 radon measuring instrument, a drying pipe, a ventilation chamber and a pipeline. The ventilation chamber comprises a cuboid cover, an air outlet large round pipe, an air outlet small round pipe, an air inlet large round pipe, an air inlet small round pipe and a removable sleeve; three air inlet large round pipes with removable sleeves are installed on one side face of the cuboid cover at equal intervals, an air inlet small round pipe is vertically installed on the air inlet large round pipe in the middle, the ventilation chamber is communicated with a drying pipe through a pipeline, the drying pipe is communicated with an RAD7 emanometer, and the RAD7 emanometer is communicated with the atmospheric environment. By measuring, calculating and comparing the open-loop radon exhalation rate and the closed-loop radon exhalation rate, the change of device parameters is controlled, the medium surface radon exhalation rate measured in an open-loop mode is obtained, and the radon leakage amount is calculated according to the Fick law. The device is simple in structure and convenient to calculate, pumping and leakage during open-loop measurement of the radon exhalation rate on the soil surface can be effectively reduced, and the measurement result is more accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear radiation detection, and particularly relates to a device and method for measuring the radon emanation rate and radon leakage of a medium surface in an open loop. BACKGROUND

[0002] Radon is a colorless and odorless radioactive gas naturally occurring, with a half-life of 3.82 days, and is the main source of radiation from natural radiation to humans. Radon produces alpha decay and releases alpha particles. Radon and its daughter are inhaled into the lungs and can damage the lungs, leading to lung cancer. Radon comes from the decay of uranium, which almost exists in all soils. Soil is one of the main sources of radon, and accurate measurement of soil radon concentration plays an important role in evaluating environmental radon level and prevention and treatment.

[0003] The measurement of soil surface radon exhalation rate mainly includes closed loop method and open loop method. The equipment for measuring soil surface radon exhalation rate by closed loop method mainly includes RAD7 radon detector, drying tube and accumulation chamber. For example, literature [1] Tan Y, Xiao D. A simple model for automatically measuring radon exhalation rate from medium surface[J]. Radiation measurements, 2014, 64: 44-47. discloses a method for measuring soil surface radon exhalation rate by closed loop method, which calculates through the radon concentration in the accumulation chamber, and performs nonlinear fitting on the measurement data to obtain the radon exhalation rate. The equipment for measuring soil surface radon exhalation rate by open loop method mainly includes RAD7 radon detector, drying tube and ventilation chamber. For example, literature [2] Tan Y, Yuan H, Xie Y, et al. No flow meter method for measuring radon exhalation from the medium surface with a ventilation chamber[J]. Applied Radiation and Isotopes, 2020, 166: 109328. discloses a method for measuring soil surface radon exhalation rate by open loop method; however, when the existing open loop method is used to measure soil surface radon exhalation rate, due to the pumping action of the pump built in the RAD7 radon detector, there is pumping action in the ventilation chamber during the measurement process, which causes the measured gas to include the gas pumped from the surrounding soil, that is, the external air is not completely introduced from the air inlet of the ventilation chamber, so that the measured radon concentration is too high, and finally the radon exhalation rate is also too high; at the same time, if the air inlet of the ventilation chamber is not reasonably designed, it will cause excessive radon leakage. Therefore, it is a challenging and meaningful work to design a ventilation chamber with reduced pumping action and a device for measuring radon leakage. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned deficiencies of the prior art and provide an open loop type device and method for measuring medium surface radon exhalation rate and radon leakage, which further improves the measurement result of radon exhalation rate by improving the ventilation chamber, and accurately measures the radon leakage during the operation of the device.

[0005] The technical solution of the present application is: an open loop type device for measuring medium surface radon exhalation rate and radon leakage, comprising a RAD7 radon detector, a drying tube, a ventilation chamber and a pipeline.

[0006] The ventilation chamber comprises a cuboid cover with an open lower end, a large-diameter gas outlet pipe, a small-diameter gas outlet pipe, a large-diameter gas inlet pipe, a small-diameter gas inlet pipe and removable sleeves; one large-diameter gas outlet pipe is installed on one side of the cuboid cover, a small-diameter gas outlet pipe is vertically installed on the large-diameter gas outlet pipe, and the large-diameter gas outlet pipe and the small-diameter gas outlet pipe are in communication; three large-diameter gas inlet pipes are installed at equal intervals on the other side of the cuboid cover, each of the other ends of the three large-diameter gas inlet pipes is provided with a corresponding removable sleeve, and a small-diameter gas inlet pipe is vertically installed on the middle large-diameter gas inlet pipe, and the middle large-diameter gas inlet pipe and the small-diameter gas inlet pipe are in communication.

[0007] The large-diameter gas inlet pipe of the ventilation chamber is in communication with the outside atmosphere through the small-diameter gas inlet pipe thereon, the large-diameter gas outlet pipe is in communication with the gas inlet of the drying tube through a pipeline, the gas outlet of the drying tube is in communication with the gas inlet of the RAD7 radon detector, and the gas outlet of the RAD7 radon detector is in communication with the atmospheric environment; during use, the open lower end of the ventilation chamber is pressed into the soil, the surrounding of the ventilation chamber is sealed with soil, the sleeves on the large-diameter gas inlet pipes are removed, the pump built in the RAD7 radon detector sucks gas from the ventilation chamber through the pipeline, the gas is dried by the drying tube and then reaches the internal measuring cavity of the RAD7 radon detector, and finally the gas is discharged to the atmosphere through the pipeline from the gas outlet of the RAD7 radon detector.

[0008] A further technical solution of the present application is that the length and width of the bottom surface of the cuboid cover are a meters and b meters, the cross-sectional circular area of the large-diameter gas inlet pipe is S, and the length is h meters, and the length of the open lower end of the ventilation chamber pressed into the soil is two to six centimeters.

[0009] Another technical solution of the present application is a method applied to a device for measuring the radon exhalation rate and the radon leakage of a medium in an open loop, comprising radon exhalation rate measurement and calculation and radon leakage measurement and calculation. A, radon exhalation rate measurement and calculation A-1, start the RAD7 radon detector, remove the sleeves on the three large-diameter gas inlet pipes, the pump built in the RAD7 radon detector sucks gas from the ventilation chamber through the pipeline, the gas in the environment enters the RAD7 radon detector through the ventilation chamber and the drying tube, the RAD7 radon detector records the radon concentration, and the average value of the radon concentration data in the environment is recorded by multiple measurements C 0 (t) .

[0010] A-2, press the lower end opening of the ventilation chamber into the position of two to six centimeters from the surface of the medium soil to be measured, seal the soil around the ventilation chamber, remove the sleeves on the three large circular tubes of the air inlet, start the RAD7 radon detector, the pump built-in the RAD7 radon detector sucks the gas from the ventilation chamber through the pipeline, the gas is dried through the drying tube and then reaches the internal measurement cavity of the RAD7 radon detector, finally the gas is discharged to the atmosphere through the air outlet of the RAD7 radon detector through the pipeline, and the radon in the medium soil to be measured is separated into the ventilation chamber along with the flow of the gas; the measurement period of the RAD7 radon detector is set to 30 minutes, and the measurement times are 16 times, because the radon concentration in the ventilation chamber does not reach equilibrium at the beginning of measurement, in order to ensure the accuracy of measurement, the first 4 groups of data are discarded, and the measurement data of the last 6 hours are calculated, and the average value of the radon concentration measured in the medium soil to be measured in the open loop is recorded as C ν1 (t) .

[0011] A-3, all the sleeves on the three large circular tubes of the air inlet of the ventilation chamber are sleeved, and the air outlet of the RAD7 radon detector is connected in communication with the small circular tube of the air inlet on the middle air inlet large circular tube through the pipeline; start the RAD7 radon detector, the pump built-in the RAD7 radon detector sucks the gas from the ventilation chamber through the pipeline, the gas is dried through the drying tube and then reaches the internal measurement cavity of the RAD7 radon detector, finally the gas is discharged to the atmosphere through the air outlet of the RAD7 radon detector through the pipeline, and the radon in the medium soil to be measured is separated into the ventilation chamber along with the flow of the gas; the measurement period of the RAD7 radon detector is set to 10 minutes, and the measurement times are 12 times, because the radon concentration in the ventilation chamber does not reach equilibrium at the beginning of measurement, in order to ensure the accuracy of measurement, the first 4 groups of data are discarded, and the measurement data of the last 8 groups are calculated, and the average value of the radon concentration measured in the closed loop is recorded as C ν2 (t) .

[0012] A-4, the average value of the radon concentration measured in the open loop is C ν1 (t) The open loop radon exhalation rate J is calculated V ±J N , J N is the standard deviation of the open loop exhalation rate; the average value of the radon concentration measured in the closed loop is C ν2 (t) The closed loop radon exhalation rate J is calculated ±J M , J M is the standard deviation of the closed loop exhalation rate, and the size of the open loop radon exhalation rate and the closed loop radon exhalation rate is compared, if the open loop radon exhalation rate J VIf the open-loop radon emission rate J is greater than the closed-loop radon emission rate J, then the size of the inlet section circle S is increased, and the length of the inlet pipe h is reduced. If the open-loop radon emission rate J is less than the closed-loop radon emission rate J, then the removable sleeve on the large inlet pipe is removed one by one until the open-loop radon emission rate J is obtained. V If the open-loop radon emission rate J is greater than the closed-loop radon emission rate J, then the size of the inlet section circle S is increased, and the length of the inlet pipe h is reduced. If the open-loop radon emission rate J is less than the closed-loop radon emission rate J, then the removable sleeve on the large inlet pipe is removed one by one until the open-loop radon emission rate J is obtained. V If the open-loop radon emission rate J is greater than the closed-loop radon emission rate J, then the size of the inlet section circle S is increased, and the length of the inlet pipe h is reduced. If the open-loop radon emission rate J is less than the closed-loop radon emission rate J, then the removable sleeve on the large inlet pipe is removed one by one until the open-loop radon emission rate J is obtained. C ν1 (t) The corresponding radon emission rate is J ν , which is the medium surface radon emission rate measured by the open-loop measurement.

[0013] B. Measurement and calculation of radon leakage B-1. When the open-loop radon emission rate and the closed-loop radon emission rate are within one standard deviation, record the radon concentration at the end of the large inlet pipe close to the ventilation chamber during the measurement in A-4. C(h), The value of this radon concentration is the average radon concentration in the ventilation chamber; record the radon concentration at the end of the large inlet pipe close to the external environment. C(0) ， The value of this radon concentration is the radon concentration in the external environment; at the same time, the radon concentration at the position of the large inlet pipe with a length of x from the ventilation chamber is recorded as C(x) . B-2. Since the diameter of the small inlet pipe is much smaller than that of the large inlet pipe, most of the radon is leaked out of the large inlet pipe. In order to facilitate the calculation of radon leakage, the pumping action of the built-in pump of the RAD7 radon detector and the leakage at the connection of the small inlet pipe are ignored. The diffusion of radon in the air in the large inlet pipe satisfies Fick's law, and the formula is: (1) Where D is the diffusion coefficient of radon in air, with a unit of m 2 / s, and the value is 9.98*10 -6 . x is the length of the large inlet pipe from the ventilation chamber, with a unit of m; C(x) is the radon concentration at the position of the large inlet pipe with a length of x from the ventilation chamber, with a unit of Bqm -3 . λ Rn is the decay constant of Rn-222, with a unit of s -1 , and the value is 2.1*10 -6 . When x = 0 , the radon concentration is the average radon concentration in the ventilation chamber, and the value of C(h) measured is also the measurement value of the RAD7 radon detector Cν (t) When x = h , the radon concentration is the average radon concentration in the external environment, that is, the measured value of C(0) , and the average value of the radon concentration data in the environment is C 0 (t) ; solve the above formula (1), and substitute the measured values of x = 0 and x = h into the solution of formula (1) to obtain the general term solution, so that the solution of formula (1) is as follows: C(x) = (2) Wherein, A is the value of C(h) ; B is the value of C(0) ; Then the leakage rate of the large circular pipe of the air inlet can be calculated by the following formula: (3) Wherein, T 1 The leakage rate of the large circular pipe of the air inlet is Bqm -2 s -1 , and the leakage rate of the large circular pipe of the air inlet is calculated by substituting C(0) into formula (3) T 1 ; Further, the leakage amount of the large circular pipe of the air inlet is calculated by the following formula: T L = T 1 *S (4) Wherein, T L The leakage amount of the large circular pipe of the air inlet is Bqs -1 ; S is the cross-sectional circular area of the large circular pipe of the air inlet, and the unit is m 2 .

[0014] Compared with the prior art, the present application has the following characteristics: The device provided by the present application has simple structure and is convenient to use, which can effectively reduce the pumping effect when measuring the soil surface radon release rate in an open loop, so that the measurement result is more accurate.

[0015] The number of air inlets of the ventilation chamber provided by the present application can be selected by removing the sleeve, so that the air inlet area can be flexibly adjusted under different measurement conditions, the pumping effect in the measurement process is reduced, and the application scenarios of the device and method are widened.

[0016] This invention utilizes the sleeve at the side end of the large circular pipe at the air inlet of the ventilation chamber to accurately measure the amount of radon leakage during the measurement process, providing a basis for further processing.

[0017] The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0018] Appendix Figure 1 A schematic diagram of an open-loop device for measuring the radon exudation rate on the surface of a medium; Appendix Figure 2 This is a schematic diagram of the ventilation chamber. Detailed Implementation

[0019] Example 1, as shown in the appendix Figures 1-2 As shown, the open-loop device for measuring the radon exudation rate and radon leakage on the surface of a medium includes a RAD7 radon meter 1, a drying tube 2, a ventilation chamber 3, and pipes.

[0020] The ventilation chamber 3 includes a cuboid cover 3-1 with an opening at the lower end, a large round pipe 3-2 for the air outlet, a small round pipe 3-3 for the air outlet, a large round pipe 3-4 for the air inlet, a small round pipe 3-5 for the air inlet, and a removable sleeve 3-6. The length and width of the bottom surface of the cuboid cover 3-1 are a meters and b meters respectively. A large air outlet pipe 3-2 is installed on one side of the cuboid cover 3-1. A small air outlet pipe 3-3 is vertically installed on the large air outlet pipe 3-2. The large air outlet pipe 3-2 and the small air outlet pipe 3-3 are connected. On the other side of the cuboid cover 3-1, three large air inlet pipes 3-4 are installed at equal intervals. Each of the three large air inlet pipes 3-4 has a corresponding removable sleeve 3-6 at its other end. A small air inlet pipe 3-5 is vertically installed on the middle large air inlet pipe 3-4. The middle large air inlet pipe 3-4 and the small air inlet pipe 3-5 are connected.

[0021] The cross-sectional circular area of the air inlet large circular pipe 3-4 is S square meters, and the length is h meters. The existing measuring device ventilation chamber air inlet is mostly directly connected with the external environment. Because there is a concentration difference between the radon concentration in the ventilation chamber and the radon concentration in the external environment, the radon in the ventilation chamber will diffuse from the air inlet to the external environment, causing radon leakage and reducing the accuracy of the measurement results. In the embodiment, the device is connected with the ventilation chamber 3 through the air inlet large circular pipe 3-4 with a length of h meters. By reasonably setting the values of the cross-sectional circular area S and the length h of the air inlet large circular pipe 3-4, the diffusion of radon in the ventilation chamber to the external environment is reduced, the leakage of radon is reduced, and the accuracy of the measurement is improved. This is because if the cross-sectional circular area S of the air inlet large circular pipe 3-4 of the ventilation chamber 3 is too small, the pump of the RAD7 will have a suction effect on the deep soil in the ventilation chamber 3, resulting in an excessively high measured radon release rate. If the cross-sectional circular area S of the air inlet large circular pipe 3-4 is too large, too much radon will leak from the air inlet large circular pipe 3-4, resulting in an excessively low measured radon release rate.

[0022] During the measurement process, the air inlet large circular pipe 3-4 of the ventilation chamber 3 is connected with the external atmosphere through the air inlet small circular pipe 3-5 thereon. In the air inlet process, the air inlet small circular pipe 3-5 faces the problem of wind resistance, because there is a significant wind resistance effect near the external end of the air inlet large circular pipe 3-4. In addition, the air inlet small circular pipe 3-5 of the ventilation chamber 3 has a relatively small diameter compared to the air inlet large circular pipe 3-4 and the pipe extends relatively long, further exacerbating the wind resistance, resulting in a significant drop in air pressure for the external gas entering the ventilation chamber 3. Therefore, the gas flow rate near the end of the air inlet large circular pipe 3-4 of the ventilation chamber 3 is lower than the flow rate of the built-in pump of the RAD7 radon measurement instrument 1. Under the driving of the built-in pump, the ventilation chamber 3 produces a certain suction effect on the covered soil surface.

[0023] By removing the sleeve 3-6 at the side end of the air inlet large circular pipe 3-4, the gas entry path in the ventilation chamber 3 is optimized, and the air inlet small circular pipe 3-5 and the air inlet large circular pipe 3-4 with the removed sleeve 3-6 jointly bear the function of gas introduction, which effectively reduces the wind resistance of the air inlet large circular pipe 3-4 near the ventilation chamber 3, and further makes the air pressure inside the ventilation chamber 3 consistent with the external environment air pressure, and the pumping action of the built-in pump of the RAD7 radon measurement instrument 1 is weakened.

[0024] The gas outlet large pipe 3-2 of the ventilation chamber 3 is communicated with the gas inlet of the drying pipe 2 through a pipe, the gas outlet of the drying pipe 2 is communicated with the gas inlet of the RAD7 radon detector 1, and the gas outlet of the RAD7 radon detector 1 is communicated with the atmosphere. When in use, the lower end opening of the ventilation chamber 3 is pressed into the soil by two to six centimeters, the ventilation chamber 3 is sealed with soil around, the sleeve 3-6 on the gas inlet large pipe 3-4 is removed, the pump built in the RAD7 radon detector 1 sucks the gas from the ventilation chamber 3 through a pipe, the gas reaches the internal measuring cavity of the RAD7 radon detector 1 after being dried by the drying pipe 2, and finally the gas is discharged to the atmosphere through a pipe from the gas outlet of the RAD7 radon detector 1.

[0025] In the embodiment, the length a of the bottom surface of the ventilation chamber 3 is 30 cm, the width b is 22 cm, the height is 8 cm, and the thickness is 0.5 cm. The diameter of the gas inlet large pipe 3-4 of the ventilation chamber 3 is 3 cm, the thickness is 0.2 cm, and the length h is 6 cm. The diameter of the gas inlet small pipe 3-5 is 1 cm, the thickness is 0.2 cm, and the length is 3.5 cm. The gas outlet large pipe 3-2 and the gas outlet small pipe 3-3 are respectively the same size as the gas inlet large pipe 3-4 and the gas inlet small pipe 3-5, and the removable sleeve is made of rubber sleeve material to realize its sealing property.

[0026] In the embodiment, the length a of the bottom surface of the ventilation chamber 3 is 30 cm, the width b is 22 cm, the height is 8 cm, and the thickness is 0.5 cm. The diameter of the gas inlet large pipe 3-4 of the ventilation chamber 3 is 3 cm, the thickness is 0.2 cm, and the length h is 6 cm. The diameter of the gas inlet small pipe 3-5 is 1 cm, the thickness is 0.2 cm, and the length is 3.5 cm. The gas outlet large pipe 3-2 and the gas outlet small pipe 3-3 are respectively the same size as the gas inlet large pipe 3-4 and the gas inlet small pipe 3-5, and the removable sleeve is made of rubber sleeve material to realize its sealing property.

[0027] A, measurement and calculation of radon exhalation rate A-1, start the RAD7 radon detector 1, remove the sleeve 3-6 on the three gas inlet large pipes 3-4, the pump built in the RAD7 radon detector 1 sucks the gas from the ventilation chamber 3 through a pipe, the gas in the environment enters the RAD7 radon detector 1 through the ventilation chamber 3 and the drying pipe 2, the RAD7 radon detector 1 records the radon concentration, and the average value of the radon concentration data in the environment is recorded C 0 (t) .

[0028] A-2, press the lower end opening of the ventilation chamber 3 into the position of two to six centimeters from the surface of the medium soil to be measured, seal the ventilation chamber 3 with soil, remove the sleeve 3-6 on the three large air inlet pipes 3-4; start the RAD7 radon detector 1, the pump built-in in the RAD7 radon detector 1 sucks the gas from the ventilation chamber 3 through the pipeline, the gas is dried by the drying tube 2 and then reaches the internal measuring cavity of the RAD7 radon detector 1, finally the gas is discharged to the atmosphere through the outlet of the RAD7 radon detector 1, and the radon in the medium soil to be measured is separated into the ventilation chamber 3 along with the flow of the gas. The measurement period of the RAD7 radon detector 1 is set to 30 minutes, and the measurement times are 16 times. Since the radon concentration in the ventilation chamber 3 does not reach equilibrium at the beginning of the measurement, in order to ensure the accuracy of the measurement, the first 4 groups of data are discarded, and the measurement data of the last 6 hours are calculated to record the average value of the radon concentration in the medium soil to be measured in the open loop as C ν1 (t) 。

[0029] A-3, cover the sleeve 3-6 on the three large air inlet pipes 3-4 of the ventilation chamber 3, and connect the outlet of the RAD7 radon detector 1 and the small air inlet pipe 3-5 on the middle air inlet pipe 3-3 through the pipeline; start the RAD7 radon detector 1, the pump built-in in the RAD7 radon detector 1 sucks the gas from the ventilation chamber 3 through the pipeline, the gas is dried by the drying tube 2 and then reaches the internal measuring cavity of the RAD7 radon detector 1, finally the gas is re-entered into the ventilation chamber 3 through the outlet of the RAD7 radon detector 1 through the pipeline, and the radon in the medium soil to be measured is separated into the ventilation chamber 3 along with the flow of the gas. The measurement period of the RAD7 radon detector 1 is set to 10 minutes, and the measurement times are 12 times. Since the radon concentration in the ventilation chamber 3 does not reach equilibrium at the beginning of the measurement, in order to ensure the accuracy of the measurement, the first 4 groups of data are discarded, and the measurement data of the last 8 groups are calculated to record the average value of the radon concentration measured in the closed loop as C ν2 (t) 。

[0030] A-4, the average value of the radon concentration measured in the open loop is C ν1 (t) According to the formula in document 2, the open loop radon exhalation rate J is calculated V ±J N , J N is the standard deviation of the open loop exhalation rate; the average value of the radon concentration measured in the closed loop is C ν2 (t) According to the formula in document 1, the closed loop radon exhalation rate J is calculated ±J M , J M is the standard deviation of the closed loop exhalation rate. Compare the open loop radon exhalation rate with the closed loop radon exhalation rate, if the open loop radon exhalation rate JV greater than the closed-loop radon exhalation rate J, then the size of the inlet section circle S is increased, and the length of the inlet pipe h is reduced, if the open-loop radon exhalation rate J V less than the closed-loop radon exhalation rate J, then the removable sleeve 3-6 on the large inlet pipe 3-4 is put on one by one until the open-loop radon exhalation rate J V is within one standard deviation of the closed-loop radon exhalation rate J, that is, the open-loop exhalation rate J V +J N or J V -J N is within the range of J±J M , that is, within one standard deviation. At this time, the average value of the radon concentration measured by the open-loop measurement is recorded as C ν1 (t) The corresponding radon exhalation rate is J ν , that is, the open-loop measurement of the medium surface radon exhalation rate.

[0031] In actual measurement, if the inlet of the ventilation chamber 3 is too small, the pump built-in the RAD7 radon measurement instrument 1 will have a suction effect on the deep soil in the ventilation chamber 3, resulting in an overestimation of the radon exhalation rate. In addition, if the inlet is too large, too much radon will leak from the inlet, resulting in an underestimation of the radon exhalation rate. Therefore, after the measurement device is set up in A-4, the amount of radon leakage needs to be calculated to determine whether the open-loop radon exhalation rate measured is consistent with the actual value, so as to reduce the influence of pump suction on the measurement of radon exhalation rate.

[0032] B, Measurement and calculation of radon leakage B-1, When the open-loop radon exhalation rate and the closed-loop radon exhalation rate are within one standard deviation during the measurement of A-4, the radon inside the large inlet pipe 3-3 will diffuse from the end close to the ventilation chamber 3 to the end close to the external environment, causing radon leakage due to the difference in radon concentration at the two ends of the length of the large inlet pipe 3-3. Record the radon concentration at the end of the large inlet pipe 3-4 close to the ventilation chamber 3 as C(h), The value of this radon concentration is the average radon concentration in the ventilation chamber 3; record the radon concentration at the end of the large inlet pipe 3-4 close to the external environment as C(0) ， The value of this radon concentration is the radon concentration in the external environment; at the same time, the radon concentration at the position of the large inlet pipe 3-3 with a length of x from the ventilation chamber 3 is recorded as C(x) .

[0033] B-2. Because the diameter of the small inlet tube 3-5 is much smaller than that of the large inlet tube 3-4, most of the radon leaks out through the large inlet tube 3-4. For ease of calculation, the suction effect of the built-in pump in the RAD7 radon meter 1 and the leakage at the connection of the small inlet tube 3-5 are ignored. The diffusion of radon in the air within the large inlet tube 3-4 follows Fick's Law, as shown in the formula: (1) Where D is the diffusion coefficient of radon in air, with units of m³. 2 / s, with a value of 9.98 * 10 -6 ; x It is the length of the large circular pipe 3-3 inside the air inlet from the ventilation chamber 3, in meters; C(x) The length of the large circular inlet pipe 3-3 within the ventilation chamber 3 is... x Radon concentration at location, in Bqm -3 ; λ Rn It is the attenuation constant of Rn-222, with units of s. -1 The value is 2.1 * 10. -6 .

[0034] when x = 0 At that time, the radon concentration was the average radon concentration in ventilation room 3, i.e., the measured concentration. C(h) The value is also The measured value of RAD7 radon meter 1 C ν (t) ;when x = h At that time, the radon concentration was the average radon concentration in the external environment, that is, the measured radon concentration. C (0) The value of . Solve the above formula (1), and . x = 0 and x = h Substituting the measured values ​​from the two locations into the solution of formula (1), we obtain its general solution, thus obtaining the solution of formula (1) as shown below: C(x) = (2) Where A is C(h) The value of B; B is C(0) The value of .

[0035] The leakage rate of the large circular inlet pipe 3-3 can be calculated using the following formula: (3) in, T 1 This is the leakage rate of the large circular inlet pipe 3-3, measured in Bqm. -2 s -1 ,Will C(0)Substituting into formula (3), the leakage rate of the large circular pipe 3-3 at the air inlet is calculated. T 1 .

[0036] Therefore, the leakage of the large circular inlet pipe 3-3 is calculated using the following formula: T L = T 1 *S (4) in, T L This is the leakage rate of the large circular inlet pipe 3-3, measured in Bqs. -1 S is the cross-sectional area of ​​the large inlet pipe 3-3, in meters (m²). 2 .

[0037] The amount of radon released from the soil surface inside ventilation chamber 3 is obtained by multiplying the radon release rate J measured in an open-loop manner by the bottom area. The calculation formula is as follows: T total = T L *a*b (5) Among them, T total This refers to the amount of radon released from the soil surface inside ventilation chamber 3, measured in Bqs. -1 ; a*b It is the area of ​​the open end of the bottom surface of ventilation chamber 3, in m². 2 .

[0038] Therefore, the ratio of the leakage amount of the large circular inlet pipe 3-3 to the amount of radon released from the soil surface inside the ventilation chamber 3, i.e., the leakage rate X of the large circular inlet pipe 3-3, is calculated using the following formula: X = T L / T total (6) In this embodiment, the average radon concentration measured during open-loop operation is used as follows: C ν1 (t) Calculated open-ring radon release rate J V ±J N It is 34.3 ± 14.8 mBqm -2 s -1 The average radon concentration obtained by measuring in closed-loop conditions is: C ν2 (t) The closed-loop radon release rate J±J was calculated. M It is 39.56 ± 5.66 mBqm -2 s -1 .

[0039] Calculated leakage rate of the intake large pipe 3-3 T 1 was 26.8 mBqm -2 s -1 , the amount of leakage of the intake large pipe 3-3 T L was 0.0427 mBqs -1 , the amount of radon T emitted from the soil surface in the ventilation chamber 3 total was 2.1 mBqs -1 , and the leakage rate X of the intake large pipe 3-3 was 2.04%.

Claims

1. An apparatus for measuring the radon exhalation rate and the radon leakage from the surface of a medium in an open system, characterized in that: It comprises a RAD7 radon detector, a drying tube, a ventilation chamber and a pipeline. The ventilation chamber comprises a cuboid cover with an open lower end, a large-diameter outlet pipe, a small-diameter outlet pipe, a large-diameter inlet pipe, a small-diameter inlet pipe and removable sleeves. A large-diameter outlet pipe is installed on one side of the cuboid cover, and a small-diameter outlet pipe is vertically installed on the large-diameter outlet pipe. The large-diameter outlet pipe and the small-diameter outlet pipe are in communication. Three large-diameter inlet pipes are installed on the other side of the cuboid cover at equal intervals, and each of the other ends of the three large-diameter inlet pipes is provided with a corresponding removable sleeve. A small-diameter inlet pipe is vertically installed on the middle large-diameter inlet pipe, and the middle large-diameter inlet pipe and the small-diameter inlet pipe are in communication. The large-diameter inlet pipe of the ventilation chamber is in communication with the outside atmosphere through the small-diameter inlet pipe thereon. The large-diameter outlet pipe is in communication with the inlet of the drying tube through a pipeline. The outlet of the drying tube is in communication with the inlet of the RAD7 radon detector. The outlet of the RAD7 radon detector is in communication with the atmosphere. When in use, the open lower end of the ventilation chamber is pressed into the soil, the surrounding of the ventilation chamber is sealed with soil, the sleeves on the large-diameter inlet pipes are removed, and the pump built in the RAD7 radon detector sucks gas from the ventilation chamber through the pipeline. The gas is dried by the drying tube and then reaches the internal measuring cavity of the RAD7 radon detector. Finally, the gas is discharged into the atmosphere through the outlet of the RAD7 radon detector.

2. The apparatus for open-loop measurement of radon exhalation rate and radon leakage from a surface of a medium according to claim 1, characterized in that: The length and width of the bottom surface of the cuboid cover are a meters and b meters, respectively. The cross-sectional area of the large-diameter inlet pipe is S, and the length is h meters. The length of the open lower end of the ventilation chamber pressed into the soil is two to six centimeters.

3. A method applied to the device for measuring the radon exhalation rate and the radon leakage of the surface of a medium according to any one of claims 1-2, comprising the measurement and calculation of the radon exhalation rate and the measurement and calculation of the radon leakage: A. Measurement and calculation of the radon exhalation rate A-1, start RAD7 radon detector, remove the sleeve on the three large circular tube of the air inlet, the pump built-in RAD7 radon detector through the pipeline from the ventilation chamber suction gas, the gas in the environment through the ventilation chamber, drying tube into the RAD7 radon detector, RAD7 radon detector records the concentration of radon, and multiple measurements take the average, the average value of the radon concentration data in the environment is recorded as C 0 (t) ; A-2, the lower end of the ventilation chamber opening is pressed into the position of two to six centimeters from the surface of the medium soil to be measured, the soil around the ventilation chamber is sealed, and the sleeves on the three large circular tubes of the air inlet are removed; start the RAD7 radon detector, the pump built-in the RAD7 radon detector sucks gas from the ventilation chamber through the pipeline, the gas is dried through the drying tube and then reaches the internal measuring cavity of the RAD7 radon detector, and finally the gas is discharged to the atmosphere through the outlet of the RAD7 radon detector through the pipeline, and the radon in the medium soil to be measured is separated into the ventilation chamber along with the flow of the gas; the measurement period of the RAD7 radon detector is set to 30 minutes, and the measurement times are 16 times, because the radon concentration in the ventilation chamber at the beginning of the measurement does not reach equilibrium, in order to ensure the accuracy of the measurement, the first 4 groups of data are discarded, and the measurement data of the last 6 hours are calculated, and the average value of the radon concentration in the medium soil to be measured measured at the open loop is recorded as C ν1 (t) ; A-3, the sleeve of the three air inlet large pipe of the ventilation chamber is all sleeved, and the gas outlet of the RAD7 radon measurement instrument and the small pipe of the air inlet large pipe on the middle air inlet are connected through the pipeline; the RAD7 radon measurement instrument is started, the pump built in the RAD7 radon measurement instrument sucks the gas from the ventilation chamber through the pipeline, the gas is dried through the drying pipe and reaches the internal measurement cavity of the RAD7 radon measurement instrument, finally the gas reenters the ventilation chamber through the pipeline from the gas outlet of the RAD7 radon measurement instrument, the radon in the medium soil to be measured is separated into the ventilation chamber along with the flow of the gas, the measurement cycle of the RAD7 radon measurement instrument is set to 10 minutes, and the measurement times are 12 times, since the radon concentration in the ventilation chamber does not reach the balance at the beginning of measurement, in order to ensure the accuracy of measurement, therefore, the first 4 groups of data are discarded, the measurement data of the last 8 groups of data is calculated, and the average value of the radon concentration measured in the closed loop is recorded as C ν2 (t) ; A-4, the average value of radon concentration measured by open loop is C ν1 (t) The open loop radon exhalation rate J is calculated V ±J N , J N is the standard deviation of open loop exhalation rate; the average value of radon concentration measured by closed loop is C ν2 (t) The closed loop radon exhalation rate J±J M , J M is the standard deviation of closed loop exhalation rate, the open loop radon exhalation rate is compared with the closed loop radon exhalation rate, if the open loop radon exhalation rate J V is greater than the closed loop radon exhalation rate J, then the size of the inlet section circle S is increased, and the length of the inlet pipe h is reduced, if the open loop radon exhalation rate J V is less than the closed loop radon exhalation rate J, then the removable sleeve on the large circular pipe of the inlet is put on one by one, until the open loop radon exhalation rate J V is within one standard deviation of the closed loop radon exhalation rate J, the average value of radon concentration measured by open loop at this time is recorded as C ν1 (t) The corresponding radon exhalation rate is J ν , that is, the medium surface radon exhalation rate measured by open loop B. Measurement and calculation of the radon leakage B-1, when the open-loop radon exhalation rate and the closed-loop radon exhalation rate are within a standard deviation range during the measurement of A-4, record the radon concentration of the large circular pipe close to the ventilation chamber end of the measurement inlet as C(h) The value of the radon concentration is the average radon concentration in the ventilation chamber; record the radon concentration of the large circular pipe close to the external environment end of the measurement inlet as C(0) ， The value of the radon concentration is the radon concentration in the external environment; at the same time, record the radon concentration of the large circular pipe in the measurement inlet at a position with a length of x from the ventilation chamber as C (x) ; B-2. Since the diameter of the small-diameter inlet pipe is much smaller than that of the large-diameter inlet pipe, most of the radon is leaked out of the large-diameter inlet pipe. In order to facilitate the calculation of the leakage of radon, the pumping effect of the built-in pump of the RAD7 radon detector and the leakage at the connection of the small-diameter inlet pipe are ignored. The diffusion of radon in the air in the large-diameter inlet pipe satisfies Fick's law, and the formula is: （1） wherein D is the diffusion coefficient of radon in air, with units of m 2 / s, with a value of 9.98*10 -6 ; x is the length of the large circular pipe from the air inlet to the ventilation chamber, with units of m; C(x) is the length of the large circular pipe from the air inlet to the ventilation chamber x , with units of Bq / m -3 ; λ Rn is the decay constant of Rn-222, with units of s -1 , with a value of 2.1*10 -6 ; When x = 0 the radon concentration is the average radon concentration in the ventilation chamber, i.e. the value of C(h) measured by the RAD7 radon detector C ν (t) ; when x = h the radon concentration is the average radon concentration in the outside environment, i.e. the value of C(0) measured; solving equation (1) and substituting the measured values of x = 0 and x = h into the solution of equation (1) gives the general solution of equation (1) as follows: C(x)= （2） wherein A is C(h) the value of B is C(0) the value of B is Therefore, the leakage rate of the large-diameter inlet pipe can be calculated by the following formula: （3） wherein, T 1 is the leakage rate of the large circular tube of the air inlet, in Bqm -2 s -1 , the C(0) leakage rate of the large circular tube of the air inlet is calculated by substituting formula (3) T 1 ; Furthermore, the leakage of the large-diameter inlet pipe can be calculated by the following formula: T L = T 1 *S （4） wherein, T L is the leakage of the large circular intake pipe, in Bqs -1 ; S is the cross-sectional circular area of the large circular intake pipe, in m 2 .

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