Device and method for measuring concentration of radon 220 in water and calculating exhalation rate of radon 220 on water surface

Abstract

The invention discloses a device and a method for measuring the concentration of radon 220 in water and calculating the exhaustion rate of radon 220 on the water surface. The device comprises a static floating chamber, an air inlet pipe, an air outlet pipe, a foam plate, a drying bottle and an RAD7 radon measuring instrument. The foam board is arranged around the static floating chamber, the air inlet pipe and the air outlet pipe are respectively installed on the static floating chamber, and the air outlet pipe of the static floating chamber, the drying bottle, the RAD7 emanometer and the air inlet pipe of the static floating chamber are sequentially connected. A static floating chamber is arranged on the surface layer of the water surface of a water sample to be measured, an RAD7 emanometer is started until a system is balanced, and the concentration of radon 220 is measured; and measuring the concentration and flow rate of the radon-220 concentration balance by using a bubbling method, firstly obtaining the actual radon-220 concentration in the water sample to be measured, and then calculating to obtain the radon-220 exhalation rate J of the water surface. The measuring device provided by the invention is simple in structure, convenient to operate and short in measuring time; the measurement method is simple in calculation process and accurate in calculation result, can perform long-term continuous monitoring analysis on the concentration of the radon 220 in the water sample, and provides a basis for subsequent treatment means.

Description

Technical Field

[0001] The present invention relates to a nuclear radiation detection technology, in particular to a device and method for measuring the concentration of radon-220 in water and calculating the radon-220 precipitation rate on the water surface. Background Art

[0002] Radon-220 is a naturally occurring radioactive gas that is usually present in soil and water bodies. It enters the air through precipitation on the water surface, which directly increases the radioactivity level of the air. For example, in areas with abundant hot springs, groundwater resources, or frequent crustal activity, due to the high concentration of radon-220 in the water, the precipitated radon-220 will significantly increase the radiation dose in the surrounding environment, which may have a certain impact on human activities or nearby plants and animals. Therefore, obtaining a more accurate water surface radon-220 precipitation rate is of great significance to the protection of water environment and public health and safety.

[0003] Currently, the main methods for determining the radon-220 exhalation rate from water surfaces include the static accumulation method, the dynamic flow method, and the indirect model method. The static accumulation method involves covering the water surface with a closed container to collect the exhaled radon gas and then calculating the exhalation rate using a diffusion model. However, due to the short half-life of radon-220 (55.6 seconds), it takes a long time to reach equilibrium, resulting in decay losses that seriously affect the accuracy of the calculation. The dynamic flow method continuously extracts air above the water surface and measures the radon concentration in real time, calculating the exhalation rate based on the gas flow rate and interfacial area. However, this method requires a high-sensitivity detector, which is expensive and the calculation process is complex. The indirect model method first establishes an equilibrium relationship between radon-220 and radium-224 in the water and indirectly determines the exhalation rate by measuring the activity of radium-224 in the water. These existing technologies are computationally complex or costly, so it is crucial to find a simple and efficient way to determine the radon-220 exhalation rate from water surfaces. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a device and method for measuring the radon-220 concentration in water and calculating the radon-220 precipitation rate on the water surface.

[0005] The technical solution of the present invention is a device for measuring the radon-220 concentration in water and calculating the radon-220 precipitation rate on the water surface. The device comprises a static floating chamber, an air inlet pipe, an air outlet pipe, a foam plate, a drying bottle, and a RAD7 radon detector. The foam plate is arranged around the static floating chamber and fixedly connected to the static floating chamber. A substance for drying gas is placed in the drying bottle. The air inlet pipe and the air outlet pipe are respectively installed on the static floating chamber. The air outlet pipe is connected to the air inlet end of the drying bottle through a hose. The air outlet end of the drying bottle is connected to the air inlet end of the RAD7 radon detector through a hose. The air outlet end of the RAD7 radon detector is connected to the air inlet pipe of the static floating chamber through a hose.

[0006] A further technical solution of the present invention is: calcium chloride powder is placed in the drying bottle.

[0007] Another technical solution provided by the present invention is: a method for measuring the concentration of radon-220 in water and calculating the radon-220 precipitation rate of the water surface, including a measurement process and a calculation process, and the specific steps are as follows: 1. Measurement process Place the static float chamber and the foam board surrounding it on the surface of the water sample to be tested, start the pump of the RAD7 radon detector, and the radon-220-containing air in the static float chamber enters the drying bottle through the outlet pipe under the action of the pump for drying, and then enters the RAD7 radon detector; record a set of radon-220 concentration data measured by the RAD7 radon detector at regular intervals until the system reaches equilibrium, that is, the radon-220 concentration measured in the RAD7 radon detector reaches equilibrium.

[0008] The surface water of the water sample to be tested is measured using the bubbling method to measure the radon-220 concentration. When the radon-220 concentration reaches equilibrium, the RAD7 radon detector measures the radon-220 concentration and flow rate.

[0009] 2. Calculation Process The radon-220 concentration in surface water, if the upward and downward convection in the water is not considered, mainly comes from the decay of radium dissolved in the water. Since the water volume during the measurement process is approximately infinite, it is assumed that the radon-220 concentration in the water remains unchanged when measuring the radon-220 precipitation rate on the water surface. At this time, the radon-220 concentration in the static floating chamber is expressed by formula (1): (1) in, c 1 (t) Indicates the concentration of radon-220 in water, in Bq / m 3 ; c 2 (t) Indicates the radon-220 concentration in the static float chamber in Bq / m 3 ; A 1 Indicates the rate at which radon-220 in the air enters the water surface, in m / s; A 2 Indicates the rate at which radon-220 on the water surface enters the air, in m / s; V a Indicates the volume of the gas path, including the volume of the radon hood gas path, the volume of the RAD7 measuring chamber and the volume of the connecting pipes, in m 3 ; S Indicates the surface area of ​​the radon collection cover, in m 2 ; λ represents the radon-220 decay constant, λl Indicates the leakage coefficient.

[0010] Since the half-life of radon-220 is only 55.6 seconds, its decay constant is much larger than S*A 1 / V a , so formula (1) is simplified to: (2) When the radon-220 concentration measured in the RAD7 radon detector reaches equilibrium and approaches a steady state, the following expression is used: (3) Substitute formula (3) and related parameters into formula (2) to calculate the rate at which radon-220 on the water surface enters the air: A 2 The expression is: (4) The radon-220 exhalation rate from the water surface is expressed as the product of the rate at which radon-220 from the water surface enters the air and the radon-220 concentration in the water. Thus, the radon-220 exhalation rate from the water surface is obtained. J The expression is: (5) The expression for calculating the radon-220 concentration in the surface water of the water sample to be tested using the bubble measurement method is: (6) in, c 3 (t) The radon-220 concentration in the bottled water is measured by the bubbling method, and the unit is Bq / m 3 ; c 4 (t) The radon-220 concentration in the water sample gas measured by the bubbling method is expressed in Bq / m 3 ; L The pump flow rate of the RAD7 radon detector using the bubbling method is in L / min. X It is the ratio of radon-220 gas to radon-220 in water at equilibrium, calculated through relevant formulas or obtained through experimental measurements; V 2 The volume of gas sample in the water sample measuring bottle by bubbling method, unit is m 3 ;λ Rn-220 is the radon-220 decay constant.

[0011] After the radon-220 concentration in the bubbling water sample bottle is balanced with the concentration in the internal chamber of the RAD7 radon detector, the radon-220 concentration in the internal chamber of the RAD7 radon detector naturally decays over time due to the gas circulation, resulting in a concentration value that is not the actual radon-220 concentration in the sample bottle. According to the RAD7 radon detector manual, the following is obtained: (7) in, CF 1 is the calibration factor of the RAD7 radon detector, CF 2 is the radon-220 detection efficiency correction factor; c Rn−220 The radon-220 concentration reading of the RAD7 radon detector is in Bq / m 3 ; V 3 The volume of the air path from the outlet of the water sample measuring bottle to the air inlet of the RAD7 radon detector, in m 3 ; V 4 The volume of the internal chamber of the RAD7 radon detector, in m 3 , substitute the result obtained from formula (7) into formula (6) to obtain the actual radon-220 concentration in the water sample to be tested.

[0012] The actual radon-220 concentration in water measured by the bubbling method is the radon-220 concentration in the static float chamber. c 2 (t) , the rate of radon-220 entering the air from the water surface obtained by formula (4) is A 2 Substituting the radon-220 concentration in water obtained from formula (6) into formula (5) yields the radon-220 precipitation rate on the water surface: J .

[0013] Compared with the prior art, the present invention has the following advantages: 1. The device for measuring the radon-220 concentration in water and calculating the radon-220 precipitation rate on the water surface provided by the present invention has a simple structure, is easy to operate, and has a short measuring time.

[0014] 2. The measurement method provided by the present invention is used to calculate the radon-220 precipitation rate of the water surface. The calculation process is simple and the calculation results are accurate. By conducting long-term and continuous monitoring and analysis of the radon-220 concentration in groundwater samples in a certain area, the country can formulate healthy drinking water standards, provide a basis for water pollution control, national disease prevention and treatment, agricultural and animal husbandry water use, etc., and ensure the safety of the groundwater environment and residents' drinking water.

[0015] The detailed structure of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic structural diagram of a device for measuring the radon-220 exhalation rate on a water surface according to the present invention;

[0017] Figure 2 for Figure 1 Top view of the static float chamber 1. DETAILED DESCRIPTION Example 1: Figure 1-2 As shown, a device for measuring radon-220 concentration in water and calculating the radon-220 precipitation rate on the water surface comprises a static float chamber 1, an air inlet pipe 2, an air outlet pipe 3, a foam board 4, a drying bottle 5, and a RAD7 radon detector 6. The foam board 4 is disposed around and fixedly connected to the static float chamber 1, enabling the static float chamber 1 to float on the surface of the water to be measured. The drying bottle 5 contains a substance for drying the gas, such as calcium chloride powder. The air inlet pipe 2 and the air outlet pipe 3 are mounted on the static float chamber 1. The air outlet pipe 3 is connected to the air inlet of the drying bottle 5 via a flexible hose. The air outlet of the drying bottle 5 is connected to the air inlet of the RAD7 radon detector 6 via a flexible hose. The air outlet of the RAD7 radon detector 6 is also connected to the air inlet pipe 2 of the static float chamber 1 via a flexible hose.

[0018] Example 2: A method for measuring the radon-220 concentration in water and calculating the radon-220 precipitation rate on the water surface, as applied to Example 1, includes a measurement process and a calculation process, and the specific steps are as follows: 1. Measurement process The static float chamber 1 and the surrounding foam board 4 are placed on the surface of the water sample 7 to be tested, and the pump of the RAD7 radon detector 6 is started. Under the action of the pump, the radon-220 air in the static float chamber 1 enters the drying bottle 5 through the outlet pipe 3 for drying, and then enters the RAD7 radon detector 6; at regular intervals, in this embodiment, 10 minutes, a set of radon-220 concentration data measured by the RAD7 radon detector 6 is recorded until the system reaches equilibrium, that is, the radon-220 concentration measured in the RAD7 radon detector 6 reaches equilibrium.

[0019] The surface water of the water sample to be tested is measured using the bubbling method to measure the radon-220 concentration. When the radon-220 concentration reaches equilibrium, the RAD7 radon detector measures the radon-220 concentration and flow rate.

[0020] 2. Calculation Process The radon-220 concentration in surface water, if the upward and downward convection in the water is not considered, mainly comes from the decay of radium dissolved in the water. Since the water volume during the measurement process is approximately infinite, it is assumed that the radon-220 concentration in the water remains unchanged when measuring the radon-220 precipitation rate on the water surface. At this time, the radon-220 concentration in the static floating chamber 1 is expressed by formula (1): (1) in, c 1 (t) Indicates the concentration of radon-220 in water, in Bq / m 3 ; c 2 (t) Indicates the radon-220 concentration in the static float chamber 1, in Bq / m 3 ; A 1 Indicates the rate at which radon-220 in the air enters the water surface, in m / s; A 2 Indicates the rate at which radon-220 on the water surface enters the air, in m / s; V a Indicates the volume of the gas path, including the volume of the radon hood gas path, the volume of the RAD7 measuring chamber and the volume of the connecting pipes, in m 3 ; S Indicates the surface area of ​​the radon collection cover, in m 2 ; λ represents the radon-220 decay constant, λ l Indicates the leakage coefficient.

[0021] Since the half-life of radon-220 is only 55.6 seconds, its decay constant is very large, on the order of 10 -2 , much greater than S*A 1 / V a , the order of magnitude is 10 -5 ~10 -6 , so formula (1) is simplified to: (2) When the radon-220 concentration measured by the RAD7 radon detector 6 reaches equilibrium and approaches a steady state, the following expression is obtained: (3) Substitute formula (3) and related parameters into formula (2) to calculate the rate at which radon-220 on the water surface enters the air: A 2 The expression is: (4) The radon-220 exhalation rate from the water surface is expressed as the product of the rate at which radon-220 from the water surface enters the air and the radon-220 concentration in the water. Thus, the radon-220 exhalation rate from the water surface is obtained. J The expression is: (5) The expression for calculating the radon-220 concentration in the surface water of the water sample to be tested using the bubble measurement method is: (6) in, c 3 (t) The radon-220 concentration in the bottled water is measured by the bubbling method, and the unit is Bq / m 3 ; c 4 (t) The concentration of radon-220 in the gas bottle of water sample measured by bubbling method is Bq / m 3 ; L The pump flow rate of the RAD7 radon detector using the bubbling method is in L / min. X It is the ratio of radon-220 gas to radon-220 in water at equilibrium, calculated through relevant formulas or obtained through experimental measurements; V 2 The volume of gas sample in the water sample measuring bottle by bubbling method, unit is m 3 ;λ Rn-220 is the radon-220 decay constant.

[0022] After the radon-220 concentration in the bubbling water sample bottle is balanced with the concentration in the internal chamber of the RAD7 radon detector, the radon-220 concentration in the internal chamber of the RAD7 radon detector naturally decays over time due to the gas circulation, resulting in a concentration value that is not the actual radon-220 concentration in the sample bottle. According to the RAD7 radon detector manual, the following is obtained: (7) in, CF 1 is the calibration factor of the RAD7 radon detector, CF 2 is the radon-220 detection efficiency correction factor; c Rn−220 The radon-220 concentration reading of the RAD7 radon detector is in Bq / m 3 ; V 3 The volume of the air path from the outlet of the water sample measuring bottle to the air inlet of the RAD7 radon detector, in m 3 ; V 4 The volume of the internal chamber of the RAD7 radon detector, in m 3 Substituting the result obtained from formula (7) into formula (6), the actual radon-220 concentration in the water sample to be tested is obtained.

[0023] The actual radon-220 concentration in water measured by the bubbling method is the radon-220 concentration in the static float chamber 1. c2 (t) The rate of radon-220 entering the air from the water surface obtained by formula (4) is A 2 Substituting the radon-220 concentration in water obtained from formula (6) into formula (5) yields the radon-220 precipitation rate on the water surface: J .

Claims

1. A device for measuring the concentration of radon-220 in water and calculating the radon-220 precipitation rate on the water surface, characterized by: The device comprises a static floating chamber, an air inlet pipe, an air outlet pipe, a foam board, a drying bottle and a RAD7 radon detector. The foam board is arranged around the static floating chamber and fixedly connected to the static floating chamber. A substance for drying gas is placed in the drying bottle. The air inlet pipe and the air outlet pipe are respectively installed on the static floating chamber. The air outlet pipe is connected to the air inlet end of the drying bottle through a hose. The air outlet end of the drying bottle is connected to the air inlet end of the RAD7 radon detector through a hose. The air outlet end of the RAD7 radon detector is connected to the air inlet pipe of the static floating chamber through a hose.

2. The device for measuring the concentration of radon-220 in water and calculating the radon-220 precipitation rate on the water surface as claimed in claim 1, characterized in that: Place calcium chloride powder in a drying bottle.

3. A method for measuring the concentration of radon-220 in water and calculating the radon-220 precipitation rate on a water surface according to claim 1 or 2, characterized in that: Including measurement process and calculation process, the specific steps are as follows:

1. Measurement process Place the static float chamber and the foam board surrounding it on the surface of the water sample to be tested. Start the pump of the RAD7 radon detector. The radon-220-containing air in the static float chamber is pumped through the outlet pipe into the drying bottle for drying, and then enters the RAD7 radon detector. Record a set of radon-220 concentration data measured by the RAD7 radon detector at regular intervals until the system reaches equilibrium, that is, the radon-220 concentration measured by the RAD7 radon detector reaches equilibrium. Take the surface water of the water sample to be tested and use the bubble method to measure the radon-220 concentration. When the radon-220 concentration reaches equilibrium, the radon-220 concentration and flow rate measured by the RAD7 radon detector are obtained.

2. Calculation Process The radon-220 concentration in surface water, if the upward and downward convection in the water is not considered, mainly comes from the decay of radium dissolved in the water. Since the water volume during the measurement process is approximately infinite, it is assumed that the radon-220 concentration in the water remains unchanged when measuring the radon-220 precipitation rate on the water surface. At this time, the radon-220 concentration in the static floating chamber is expressed by formula (1): （1） in, c 1 (t) Indicates the concentration of radon-220 in water, in Bq / m 3 ; c 2 (t) Indicates the radon-220 concentration in the static float chamber in Bq / m 3 ; A 1 Indicates the rate at which radon-220 in the air enters the water surface, in m / s; A 2 Indicates the rate at which radon-220 on the water surface enters the air, in m / s; V a Indicates the volume of the gas path, including the volume of the radon hood gas path, the volume of the RAD7 measuring chamber and the volume of the connecting pipes, in m 3 ; S Indicates the surface area of ​​the radon collection cover, in m 2 ; λ represents the radon-220 decay constant, λ l Indicates leakage coefficient; Since the half-life of radon-220 is only 55.6 seconds, its decay constant is much larger than S*A 1 / V a , so formula (1) is simplified to: （2） When the radon-220 concentration measured in the RAD7 radon detector reaches equilibrium and approaches a steady state, the following expression is used: （3） Substitute formula (3) and related parameters into formula (2) to calculate the rate at which radon-220 on the water surface enters the air: A 2 The expression is: （4） The radon-220 exhalation rate from the water surface is expressed as the product of the rate at which radon-220 from the water surface enters the air and the radon-220 concentration in the water. Thus, the radon-220 exhalation rate from the water surface is obtained. J The expression is: （5） The expression for calculating the radon-220 concentration in the surface water of the water sample to be tested using the bubble measurement method is: （6） in, c 3 (t) The radon-220 concentration in the bottled water is measured by the bubbling method, and the unit is Bq / m 3 ; c 4 (t) The radon-220 concentration in the water sample gas measured by the bubbling method is expressed in Bq / m 3 ; L The pump flow rate of the RAD7 radon detector using the bubbling method is in L / min. X It is the ratio of radon-220 gas to radon-220 in water at equilibrium, calculated through relevant formulas or obtained through experimental measurements; V 2 The volume of gas sample in the water sample measuring bottle by bubbling method, unit is m 3 ;λ Rn-220 is the radon-220 decay constant; After the radon-220 concentration in the bubbling water sample bottle is balanced with the concentration in the internal chamber of the RAD7 radon detector, the radon-220 concentration in the internal chamber of the RAD7 radon detector naturally decays over time due to the gas circulation, resulting in a concentration value that is not the actual radon-220 concentration in the sample bottle. According to the RAD7 radon detector manual, the following is obtained: （7） in, CF 1 is the calibration factor of the RAD7 radon detector, CF 2 is the radon-220 detection efficiency correction factor; c Rn−220 The radon-220 concentration reading of the RAD7 radon detector is in Bq / m 3 ; V 3 The volume of the air path from the outlet of the water sample measuring bottle to the air inlet of the RAD7 radon detector, in m 3 ; V 4 The volume of the internal chamber of the RAD7 radon detector, in m 3 , substitute the result obtained from formula (7) into formula (6) to obtain the actual radon-220 concentration in the water sample to be tested; The actual radon-220 concentration in water measured by the bubbling method is the radon-220 concentration in the static float chamber. c 2 (t) , the rate of radon-220 entering the air from the water surface obtained by formula (4) is A 2 Substituting the radon-220 concentration in water obtained from formula (6) into formula (5) yields the radon-220 precipitation rate on the water surface: J .

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