Hybrid radon exhalation rate measurement device and method

Abstract

The application relates to a mixed radon emanation rate measuring device and method, and relates to the technical field of nuclear radiation measurement. The device comprises a radon collection cover, an adsorption and purification device, a radon measuring instrument and a gas pump. The inlet and outlet of the radon collection cover are connected through a gas pipe to form a closed loop, the radon measuring instrument and the gas pump are connected to the gas pipe between the inlet and outlet of the radon collection cover, and the adsorption and purification device is arranged between the gas inlet of the radon collection cover and the radon measuring instrument. The adsorption and purification device is used for adsorbing and purifying the backflow gas flowing to the radon collection cover through the radon measuring instrument when the radon measuring instrument measures the radon concentration in the radon collection cover, so as to reduce the radon concentration of the gas backflowing into the radon collection cover. The application is suitable for occasions with low and high environmental radon concentrations, can avoid the back diffusion phenomenon caused by the excessively high radon concentration in the radon collection cover, can avoid the influence of the pressure generated during flow regulation on the radon seepage and emanation of the surface of the emanation medium, and has high measurement efficiency and accuracy.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation measurement technology, and in particular to a hybrid radon release rate measurement device and method. Background Technology

[0002] Currently, there are two main methods for measuring radon exhalation rate: closed-loop and open-loop. In closed-loop measurement, the radon concentration inside the radon collection hood placed on the medium surface increases over time, leading to back diffusion and inhibiting radon exhalation, thus affecting the accuracy of the measurement results. Furthermore, in closed-loop measurement, the time required for the radon concentration inside the collection hood to reach equilibrium is relatively long (usually around 2 hours), resulting in low measurement efficiency. Chinese patent document CN110456405A discloses a flowmeter-free electrostatic collection method, open-loop method, apparatus, and system for measuring radon exhalation rate. This method employs a typical open-loop measurement approach. Open-loop measurement connects the radon collection hood to the external environment, drawing outside air into the hood via a pump connected to the hood's outlet. This avoids back diffusion caused by excessively high radon concentration inside the hood and allows for reaching radon concentration equilibrium in a relatively short time, significantly improving measurement efficiency. However, the pumping or compressed air flow can cause radon accumulation. The pressure difference between the radon collection chamber and the outside atmosphere can cause internal gas seepage into loose media (such as tailings sand and soil), leading to a discrepancy between the measured radon release rate and the actual radon release rate of the media. (For example, the air pump's operation can create negative pressure inside the radon collection chamber due to air intake resistance, resulting in a higher release rate than under natural conditions.) Furthermore, when the external radon concentration is high (e.g., in a relatively enclosed underground space where long-term accumulation leads to extremely high environmental radon concentrations), introducing outside air into the radon collection chamber will severely affect the accuracy of the measurement results. Therefore, the open-loop measurement method is not suitable for situations with high environmental radon concentrations. Summary of the Invention

[0003] One of the objectives of this invention is to provide a hybrid radon exhalation rate measuring device that can simultaneously achieve high measurement accuracy and measurement efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a hybrid radon emission rate measuring device, comprising a radon collection hood, a radon meter, an adsorption purification device, and an air pump. The inlet and outlet of the radon collection hood are connected by air pipes to form a closed loop. The radon meter and the air pump are connected to the air pipe between the inlet and outlet of the radon collection hood. An adsorption purification device is installed on the air pipe between the air inlet of the radon collection hood and the radon meter. The adsorption purification device is used to adsorb and purify the return gas flowing from the radon meter to the radon collection hood when the radon meter measures the radon concentration inside the radon collection hood, thereby reducing the radon concentration of the gas returning to the radon collection hood.

[0005] Driven by the air pump, the gas to be tested in the radon collection hood flows from its outlet toward the radon meter, then flows back toward the radon collection hood through the radon meter and flows back into the radon collection hood through the air inlet, forming a closed-loop circulation.

[0006] In addition, the adsorption purification device can participate in the entire cycle measurement process. That is, when the radon meter measures the radon concentration of the circulating gas, the adsorption purification device can adsorb and purify the gas flowing through the radon meter and towards the radon collection hood. When the gas flows back into the radon collection hood, it will not have a significant impact on the internal radon concentration (or can even eliminate the impact). This can reduce the influence of the backflowing gas when the radon meter measures the radon concentration of the circulating gas again, resulting in higher measurement accuracy.

[0007] Furthermore, the adsorption purification device has a built-in adsorption material for adsorbing radon.

[0008] Furthermore, the adsorbent material is activated carbon.

[0009] Furthermore, the aforementioned measuring device also includes a flow meter and a drying tube, which are sequentially arranged on the gas pipe between the outlet of the radon collection hood and the radon meter.

[0010] Another objective of this invention is to provide a hybrid radon exhalation rate measurement method that combines the closed-loop gas path structure and the open-loop calculation model in the above-mentioned device, so that it can simultaneously possess the advantages of both open-loop and closed-loop measurement.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a mixed radon emission rate measurement method, which uses the above-mentioned mixed radon emission rate measurement device for measurement;

[0012] The method includes the following steps:

[0013] 1. Place the radon collection hood on the surface of the medium to be tested, and let the air pump pump the gas to be tested in the radon collection hood into the radon detector at a constant flow rate and then send it back to the radon collection hood so that the radon concentration in the radon detector is balanced with the radon concentration in the radon collection hood.

[0014] 2. Start the radon detector to measure the radon concentration inside the radon collection hood. Record the radon concentration at each measurement cycle ΔT, and record the radon concentrations C1, C2, C3...C1 sequentially. m ...C n Where m is the moment when the radon concentration inside the radon collection hood stabilizes, and n = m + i and i > 5;

[0015] III. Using the above measurements, fit the differential equation for the radon concentration balance inside the radon collection chamber, and then obtain the radon release rate J. The differential equation for the radon concentration balance inside the radon collection chamber is as follows:

[0016]

[0017] In the formula, V is the sum of the internal volume of the radon collection hood and the total volume of the airflow circuit, in meters. 3 C represents the radon concentration inside the radon collection hood, in Bq / m³. 3 t represents the cumulative radon time in seconds; J represents the radon release rate from the surface of the gas ejection medium (the medium under test) in Bq / m³. 2 s; S is the area of ​​the radon collection hood covering the ejected gas medium, in m². 2 ; q represents the air pump circulation flow rate, in L / min; C in The concentration of radon gas re-entering the radon collection hood after adsorption and purification, expressed in Bq / m³. 3 ;λ b Leakage coefficient, in seconds. -1 ;λ l This is the anti-diffusion coefficient, in units of s. -1 λ is the radon decay constant.

[0018] In the above scheme, C in formula (1) can be regarded as the radon concentration of the gas flowing out of the radon collection hood. in This can be considered as the concentration of radon gas entering through the radon collection hood inlet, CC in The difference between the two can be regarded as the actual radon concentration inside the radon collection hood measured by the radon meter. This can transform the original closed-loop calculation model into an open-loop calculation model, making the calculation model more realistic and the results more accurate.

[0019] Furthermore, under the action of the adsorption and purification device, the radon concentration C in the gas returning to the radon collection hood is reduced. in Approaching 0, the above formula simplifies to:

[0020]

[0021] In the formula, the radon concentration C inside the radon collection hood is measured by a radon meter; the starting time of the radon accumulation time t is 0 s; the volume V and cross-sectional area S of the radon collection hood are constant values; λ e Let λ be the equivalent decay constant of radon. e =λ b +λ l +λ; The air pump circulation flow rate q is a constant value.

[0022] Furthermore, solving the above differential equation (2) yields:

[0023]

[0024] In the formula, C0 represents the initial concentration inside the radon collection hood, with units of Bq / m³. 3When the background concentration in the environment is not high, the default value is C0≈0 Bq / m³. 3 .

[0025] By comparing the same time interval ΔT with its corresponding radon concentrations C1, C2, C3, ..., C n By fitting the equations described above, we can obtain J and λ. e The value of .

[0026] Furthermore,

[0027] when Therefore, the radon concentration inside the radon collection hood tends to be constant, meaning the radon concentration does not change with time. Hence:

[0028]

[0029] When q >> λ e V, then λ e This can be ignored; formula (4) above can be simplified to:

[0030]

[0031] Furthermore, let Where C0≈0;

[0032] Equation (3) simplifies to: C(t) = A(1-e -Bt ).

[0033] Furthermore,

[0034] The equilibrium concentration is approximately equal to the value A. The radon exudation rate J on the surface of the medium to be tested is calculated by combining the value A with formula (4).

[0035] Or, when q >> λ e V, combined with B value and formula (5), calculate the radon release rate J on the surface of the gas medium to be tested.

[0036] Furthermore, the measurement time of the radon detector shall not exceed the effective time of the adsorption and purification device; that is, the measurement work of the radon detector shall be carried out before the adsorption and purification device fails.

[0037] Furthermore, when using activated carbon as the adsorption material, it is best to control the air pump circulation flow rate to be less than 1.5 L / min.

[0038] Where m is the moment when the radon concentration inside the radon collection hood stabilizes, and n = m + i and i > 5, the accuracy of the measurement results can be guaranteed.

[0039] Compared to existing open-loop measurement methods, this invention does not introduce ambient air into the radon collection hood. Instead, it installs an adsorption purification device at the air inlet of the radon collection hood. The high-concentration radon-containing air discharged from the radon meter is treated by the adsorption purification device and then returned to the radon collection hood. This ensures that the air intake and exhaust of the radon collection hood are always in a balanced state, avoiding the problem of negative pressure forming inside the hood due to air pump resistance, which would cause the radon release rate to be higher than the value under natural conditions. Furthermore, only one air pump is needed to adjust the inlet and outlet flow rates of the radon collection hood, making it simple in structure and easy to use. Since it does not require the introduction of ambient air, this device is suitable for special situations involving high-concentration environments and high-radon-producing media. At the same time, this invention can achieve radon concentration equilibrium and accurate measurement in a short time (0.5-1 hour), just like the open-loop measurement method, ensuring the efficiency of the measurement work. Compared to existing closed-loop measurement methods, this invention can stabilize the radon concentration at the gas-solid interface inside the radon collection hood at a low level during the measurement process. This not only improves measurement efficiency but also effectively reduces the impact of back diffusion on the radon release rate measurement, thereby more accurately measuring the radon release rate on the surface of the ejected medium. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the radon exudation rate measuring device in the embodiment;

[0041] Figure 2 This is a schematic diagram of the cumulative radon concentration fitting curve (1 L / min) in the example;

[0042] Figure 3 This is a schematic diagram of the cumulative radon concentration fitting curve in the example (1.50 L / min);

[0043] Figure 4 This is a schematic diagram of the radon penetration curve adsorbed by activated carbon in the examples.

[0044] In the picture:

[0045] 1—Radon collection hood; 2—Flow meter; 3—Adsorption purification device

[0046] 4 - Air pump; 5 - Radon detector; 6 - Drying tube. Detailed Implementation

[0047] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0048] Unlike existing closed-loop and open-loop measurement methods, this embodiment provides a hybrid device for measuring radon release rate. The device's gas path adopts a closed-loop circulation structure for intake and exhaust. By setting an adsorption purification device 3 at the intake front end of the circulation gas path (the air inlet of the radon collection hood 1), the return air entering the radon collection hood 1 is treated. Based on this, the calculation is performed using the calculation model of open-loop measurement. This avoids the situation where the negative pressure generated by the operation of the air pump 4 leads to an overestimation of the radon release rate, and also eliminates the problem of introducing external high-radon concentration air affecting the accuracy of the measurement results. At the same time, there is no situation where excessive accumulation of radon concentration leads to back diffusion, and the radon release rate can be accurately measured in a short time.

[0049] Based on the same technical concept, this embodiment also provides a method for determining the radon release rate on the surface of a scattering gas medium. This method uses a hybrid radon release rate measuring device to measure the radon release rate of the medium.

[0050] Figure 1 The overall structure of the measuring device is shown, which mainly includes a radon collection hood 1, a flow meter 2, a drying tube 6, a radon detector 5, a precisely adjustable air pump 4, and an adsorption purification device 3. The radon collection hood 1 has two vents, corresponding to the inlet and outlet respectively. A gas flow meter 2 (a high-precision flow meter can be used) is installed at the outlet and connected to the drying device (drying tube 6) containing desiccant and the radon detector 5. A precisely adjustable air pump 4 is then connected in series with the adsorption purification device 3 (activated carbon is used as the adsorbent material in the adsorption purification device 3). The outlet of the adsorption purification device 3 is connected to the inlet of the radon collection hood 1, thus forming a circulating gas path. Furthermore, these components can be connected via air pipes, and the closed loop can be connected in series. Also, the adsorbent material (activated carbon) should be removable and replaceable to facilitate timely replacement according to its service life. As can be seen from the figure, the flow meter 2, drying tube 6, radon meter 5, air pump 4, and adsorption purification device 3 are sequentially arranged on the air pipe between the air outlet and air inlet of the radon collection hood 1. Of course, the connection order of these components can also be adjusted according to actual needs.

[0051] The measurement method mainly includes the following steps:

[0052] (1) Before starting the measurement, connect the measuring device as described above, turn on the air pump 4, adjust the flow rate, control the flow rate Q, and then quickly place the radon collection hood 1 on the surface of the medium to be measured. After the flow meter 2 reading stabilizes, start the radon meter 5 to begin measuring the radon concentration inside the radon collection hood 1. After each certain measurement cycle ΔT, record the radon concentrations C1, C2, C3...C m ...C n To ensure the accuracy of the measurement results, m represents the moment when the radon concentration inside radon collection hood 1 stabilizes; n = m + i, where i is generally greater than 5.

[0053] (2) The above measurements are used to fit the differential equation of radon concentration balance in the radon hood, and then the value of radon release rate J is obtained.

[0054] The differential equation for the radon concentration equilibrium inside the radon collection hood is:

[0055]

[0056] Where V is the sum of the internal volume of the radon collection hood 1 and the total volume of the airflow circuit it belongs to, in m³. 3 C represents the radon concentration inside radon collection hood 1, in Bq / m³. 3 t represents the cumulative radon time in seconds; J represents the radon deposition rate on the surface of the ejector medium in Bq / m³. 2 s; S is the area of ​​the radon collection hood 1 covering the ejected gas medium, in m². 2 ; q represents the air pump 4 circulation flow rate, in L / min; C in The radon concentration after adsorption and purification before re-entering the radon collection hood 1 is expressed in Bq / m³. 3 ;λ b Leakage coefficient, in seconds. -1 ;λ l This is the anti-diffusion coefficient, in units of s. -1 λ is the radon decay constant, typically taken as 2.1 × 10⁻⁶. -6 s -1 .

[0057] Let λ e Let λ be the equivalent decay constant of radon, then we have λ e =λ b +λ l +λ. In the closed-loop process of this device, due to the adsorption and purification device 3 installed at the inlet of the radon collection hood 1, the radon concentration C of the gas re-entering the radon collection hood 1 through circulation is reduced. in Extremely low, can be considered as: C in ≈0Bqm -3 Therefore, the above formula can be simplified to:

[0058]

[0059] The radon concentration C inside the radon collection hood 1 is measured by the radon meter 5; the radon accumulation time t starts at 0 s; the volume V and cross-sectional area S of the radon collection hood 1 are constants; the equivalent decay coefficient λ... e For unknown quantity (leakage coefficient λ) b anti-diffusion coefficient λ l (This is an unknown quantity); the circulation flow rate q of the air pump 4 is generally set to a fixed value in the experiment.

[0060] Solving the above differential equation yields:

[0061]

[0062] Wherein, C0 represents the initial concentration inside radon collection hood 1, in units of Bq / m³. 3 When the background concentration in the environment is not high, C0≈0 is assumed to be zero. That is, under low concentration conditions, the initial concentration C0 inside the radon collection chamber is assumed to be 0 and can be ignored.

[0063] By using the same time interval ΔT, the corresponding radon concentrations C1, C2, C3..., C... n By fitting the above equations, we can obtain J and λ. e The value of .

[0064] when and This can be considered as the concentration reaching a point of near-stability, meaning the concentration does not change over time. Therefore:

[0065]

[0066] When q >> λ e V, then λ e This can be ignored; formula (4) above can be simplified to:

[0067]

[0068] Based on the above conditions, the condition that must be met is C. in ≈0Bqm -3 Therefore, the selection of adsorption materials is particularly important. Here is an example of an adsorption material:

[0069] Activated carbon is known to have good adsorption capacity for radon, but as the adsorption time increases, its adsorption capacity gradually decreases until it breaks through (loses its purification ability). The specific process is as follows: Figure 4 As shown in the figure, the horizontal axis represents the adsorption time t; the vertical axis represents the radon concentration C; T p Indicates the penetration time; T e This indicates the effective time (i.e., the time during which the low concentration is maintained). The effective time is an important criterion for determining the continuous working capability of the device.

[0070] In this device, after determining the type and amount of activated carbon, the flow rate of activated carbon (i.e., the air pump circulation flow rate q) is one of the variables affecting the adsorption process and is also an important factor in determining the effective operating time of the device.

[0071] We selected coconut shell activated carbon as the adsorbent. Here, we used the same type and amount of activated carbon and conducted breakthrough time experiments by changing different flow rates q. The results are as follows:

[0072] Table 1 Effective Time of Activated Carbon

[0073]

[0074] We found that as the flow rate increases, the effective time of activated carbon gradually decreases, indicating that the higher the flow rate, the shorter the effective usage time of the adsorption purification device 3. In actual measurements, specific analysis should be performed based on the specific circumstances.

[0075] In practical applications, the appropriate adsorption material and dosage should be selected based on the measurement time, especially the internal circulation flow rate. The measurement time should be less than the breakthrough time of the adsorption purification device 3. During actual testing, a suitable measurement cycle should be selected based on the flow rate and the volume of the radon collection hood 1.

[0076] In existing closed-loop designs, the radon concentration of the gas returning to the radon collection hood 1 is not considered; instead, it is simply treated as a single unit C. This leads to radon precipitated on the surface of the medium continuously re-entering the radon collection hood 1 and the radon meter 5. Due to the limited volume of the radon collection hood 1, back diffusion is prone to occur, resulting in inaccurate measurement data. In contrast, this embodiment not only considers the impact of the returning gas on the radon concentration inside the radon collection hood 1 but also provides a solution: an adsorption purification device 3 is installed at the air inlet of the radon collection hood 1. This adsorption purification device 3 adsorbs and purifies the returning gas, thus reducing the radon concentration C returning to the radon collection hood 1. in The radon concentration can approach zero, greatly reducing (almost eliminating) the influence of the backflow gas on the radon concentration inside the radon collection hood 1. Therefore, the equilibrium differential equation of this embodiment is more realistic, and the adsorption purification device 3 adsorbs the backflow gas, almost eliminating the influence of the backflow gas on the radon concentration inside the radon collection hood 1, making the results more accurate.

[0077] Unlike existing technologies, this invention considers the impact of accumulated radon concentration in a closed-loop system on radon release. By purifying the inlet gas, it effectively eliminates the influence of back diffusion on radon release rate measurement. Simultaneously, this circulation structure effectively reduces leakage and maintains stable ambient humidity. This invention is applicable to both low and high ambient radon concentration environments and combines the features of both closed-loop and open-loop measurement methods, avoiding the back diffusion effect caused by excessive accumulated radon concentration. Compared to existing open-loop measurement methods, it can control the pressure difference between the radon collection hood 1 and the outside air to be zero. In contrast, the closed-loop measurement method can more effectively reduce leakage and can perform measurements under special conditions of high concentration environments and high radon-producing media, while improving measurement accuracy.

[0078] In addition, this embodiment also conducted actual tests on the device, as detailed below.

[0079] To verify the universality of flow rate for precipitation rate measurement, this embodiment uses two flow rates (1 L / min and 1.5 L / min).

[0080] The internal volume of radon collection hood 1 was pre-measured to be approximately 3.14 L, and the coverage area was approximately 0.0314 m². 2 Adjust the air pump 4 to set different flow rates q of 1L / min and 1.5L / min respectively. After the flow meter 2 reading stabilizes, place the radon collection hood 1 on the surface of the medium to be measured, turn on the radon meter 5, and collect the radon concentration C1, C2, C3...C1 inside the radon collection hood 1 at regular intervals. m ...C n In this experiment, the measurement period was different depending on the flow rate. For example, when q was 1 L / min, the measurement period was 5 min; when q was 1.5 L / min, the measurement period was 3 min.

[0081] The concentration results obtained from the experiment were subjected to curve fitting.

[0082] For ease of calculation, we let

[0083] Equation (3) simplifies to: C(t) = A(1-e -Bt (7).

[0084] The results of fitting the experimental data can be found in [reference]. Figure 2 The diagram shows a cumulative radon concentration fitting curve (1 L / min). Figure 3 The diagram shows the cumulative radon concentration fitting curve (1.50 L / min).

[0085] The fitting results are shown in the table below:

[0086] Table 2 Fitting Results

[0087] 1±0.01 946.40±35.24 0.0053±0.0011 0.84 1.50±0.01 637.64±42.62 0.00796±0.0025 0.73

[0088] Considering the mathematical characteristics of the fitted curve, the equilibrium concentration is approximately equal to the value of A. Combining equation (4), the radon release rate J on the surface of the gas-ejecting medium can be preliminarily calculated. Furthermore, combining the value of B, we find that q >> λ e V, therefore formula (5) also applies.

[0089] Table 3. Calculation results of radon exhalation rate

[0090]

[0091]

[0092] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any content that does not depart from the technical solution of the present invention shall still fall within the patent scope of the technical solution of the present invention.

Claims

1. A method for measuring the radon exhalation rate using a mixed-type method, characterized in that, The radon emission rate is measured using a hybrid radon emission rate measuring device. The hybrid radon emission rate measuring device includes a radon collection hood (1), a radon meter (5), an adsorption purification device (3), and an air pump (4). The inlet and outlet of the radon collection hood (1) are connected by an air pipe to form a closed loop. The radon meter (5) and the air pump (4) are connected to the air pipe between the inlet and outlet of the radon collection hood (1). An adsorption purification device (3) is provided between the air inlet of the radon collection hood (1) and the radon meter (5). The adsorption purification device (3) is used to adsorb and purify the return gas flowing from the radon meter (5) to the radon collection hood (1) when the radon meter (5) measures the radon concentration in the radon collection hood (1), thereby reducing the radon concentration of the gas returning to the radon collection hood (1). The method includes the following steps:

1. Place the radon collection hood (1) on the surface of the medium to be tested, and let the gas pump (4) pump the gas to be tested in the radon collection hood (1) into the radon meter (5) at a constant flow rate and then send it back to the radon collection hood (1) so that the radon concentration in the radon meter (5) is balanced with the radon concentration in the radon collection hood (1); 2. Start the radon meter (5) and measure the radon concentration inside the radon collection hood (1). Record the radon concentrations C1, C2, C3...C at equal time intervals ΔT. m ...C n Where m is the moment when the radon concentration inside the radon collection hood (1) stabilizes, n = m + i and i > 5; III. Using the above measurements, fit the differential equation for the radon concentration balance inside the radon collection chamber, and then obtain the radon release rate J. The differential equation for the radon concentration balance inside the radon collection chamber is as follows: （1）； In the formula, V is the sum of the internal volume of the radon collection hood (1) and the total volume of the airflow circuit, in m³. 3 C represents the radon concentration inside the radon collection hood (1), in units of Bq / m³. 3 t represents the cumulative radon time in seconds; J represents the radon exudation rate on the surface of the test medium in Bq / m³. 2 s; S is the area of ​​the radon collection hood (1) covering the medium to be measured, in m². 2 ; The air pump (4) circulation flow rate is expressed in L / min; C in The concentration of radon gas re-entering the radon collection hood (1) after adsorption and purification is expressed in Bq / m³. 3 ; Leakage coefficient, in seconds. -1 ; This is the anti-diffusion coefficient, in units of s. -1 ; is the radon decay constant.

2. The method for measuring the mixed radon exhalation rate according to claim 1, characterized in that: Under the action of the adsorption purification device (3), the radon concentration C of the gas flowing back into the radon collection hood (1) is reduced. in Approaching 0, the above formula simplifies to: （2）； In the formula, the radon concentration C inside the radon collection hood (1) is measured by the radon meter (5); the starting time of the radon accumulation time t is 0s; the volume V and cross-sectional area S of the radon collection hood (1) are both constant values. Let be the equivalent decay constant of radon. ; Air pump (4) circulation flow rate It is a constant value.

3. The method for measuring the mixed radon exhalation rate according to claim 2, characterized in that: Solving the above differential equation (2) yields: （3）； In the formula, The initial concentration inside the radon collection hood (1) is expressed in Bq / m³. 3 When the background concentration in the environment is not high, the default is... Bq / m 3 ; By using the same time interval ΔT, the corresponding radon concentrations C1, C2, C3..., C... n By fitting the equations described above, we can obtain J and... The value of .

4. The method for measuring the mixed radon exhalation rate according to claim 3, characterized in that: when , Then the radon concentration inside the radon collection hood (1) tends to stabilize, hence: （4）； when Then Ignoring this, the above formula (4) simplifies to: （5）。 5. The method for measuring the mixed radon exhalation rate according to claim 4, characterized in that: make ; ;in, ; Equation (3) simplifies to: .

6. The method for measuring the mixed radon exhalation rate according to claim 5, characterized in that: The equilibrium concentration is approximately equal to the value of A. Combine the value of A with formula (4) to calculate the radon exudation rate J on the surface of the medium to be tested. Or, when The radon release rate J on the surface of the gas medium to be tested is calculated by combining the B value with formula (5).

7. The method for measuring the mixed radon exhalation rate according to claim 1, characterized in that: The measurement time of the radon meter (5) shall not exceed the effective time of the adsorption purification device (3).

8. The method for measuring the mixed radon exhalation rate according to claim 1, characterized in that: The adsorption purification device (3) is equipped with an adsorption material for adsorbing radon.

9. The method for measuring the mixed radon exhalation rate according to claim 1, characterized in that: The mixed radon emission rate measuring device also includes a flow meter (2) and a drying tube (6), which are arranged between the outlet of the radon collection hood (1) and the radon meter (5).

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