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

Abstract

The device comprises a static floating chamber, an air inlet pipe, an air outlet pipe, foam plates, a drying bottle and an RAD7 emanometer, the foam plates are arranged on the periphery of the static floating chamber, the air inlet pipe and the air outlet pipe are respectively installed on the static floating chamber, and the drying bottle is installed on the air inlet pipe. The static floating chamber gas outlet pipe, the drying bottle, the RAD7 emanometer and the static floating chamber gas inlet pipe are connected in sequence. 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 radon concentration is measured; and measuring the radon concentration balance concentration and flow rate by using a bubbling method, firstly obtaining the radon concentration in the water sample to be measured, and then calculating the radon exhalation rate of the water surface. The measuring device provided by the invention is simple in structure, convenient to operate and short in measuring time; the measuring method is simple in calculation process and accurate in calculation result, the radon concentration in the water sample can be continuously monitored and analyzed for a long time, and a basis is provided for subsequent treatment means.

Description

Technical Field

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

[0002] Radon is a naturally radioactive gas that is usually found 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 radon concentration in the water, the precipitated radon will significantly increase the radiation dose in the surrounding environment, which may have a certain impact on human activities or nearby animals and plants. Therefore, obtaining a more accurate water surface radon precipitation rate is of great significance to water environmental protection and public health and safety.

[0003] Water bodies are important media for radon migration, and their radon concentration directly affects the radon exchange process at the water-air interface. When the radon dissolved in water reaches a certain concentration, it will be released from the water surface into the atmosphere through diffusion and convection. This process is called radon exhalation. The radon exhalation rate is usually expressed as the radon activity released per unit area per unit time, and is a key parameter for assessing the impact of radiation on the water environment. In practical applications, hot springs, groundwater, water bodies around uranium mines, and discharge water from nuclear facilities all need to monitor the radon exhalation rate.

[0004] At present, the methods for measuring radon concentration in water mainly include bubbling method, liquid scintillation counting method and electrostatic collection method. The bubbling method is widely used in field measurement because of its simple operation and low cost. Its principle is to purge the radon dissolved in water with carrier gas and detect it. Liquid scintillation counting method has high sensitivity, but requires a complex sample pretreatment process. The electrostatic collection method uses the electron-bearing body produced by radon decay for measurement, which is suitable for the detection of low-concentration radon. These methods have their own advantages and disadvantages and need to be selected according to the specific application scenario. The existing technologies mentioned above have the problems of complex calculations or high costs. Therefore, it is very necessary to achieve simple and efficient acquisition of water surface radon exhalation rate. Summary of the invention

[0005] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and to provide a device and method for measuring the radon concentration in water and calculating the radon exhalation rate on the water surface.

[0006] The technical solution of the present invention is: a device for measuring the radon concentration in water and calculating the radon exhalation rate of the water surface, including a static floating chamber, an intake pipe, an exhaust 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 intake pipe and the exhaust pipe are respectively installed on the static floating chamber. The exhaust pipe is connected to the intake end of the drying bottle through a hose. The exhaust end of the drying bottle is connected to the intake end of the RAD7 radon detector through a hose. The exhaust end of the RAD7 radon detector is connected to the intake pipe of the static floating chamber through a hose.

[0007] A further technical solution of the present invention is: the substance for drying gas placed in the drying bottle is calcium chloride powder.

[0008] Another technical solution provided by the present invention is: a method applied to the device for measuring the radon concentration in water and calculating the radon exhalation rate of the water surface, including a measurement process and a calculation process. The specific steps are as follows:

[0009] I. Measurement process

[0010] Place the static floating chamber and the surrounding foam board on the water surface layer of the water sample to be measured. Start the pump of the RAD7 radon detector. The radon-containing air in the static floating chamber enters the drying bottle through the exhaust pipe under the action of the pump for drying, and then enters the RAD7 radon detector. Record the radon concentration data measured by the RAD7 radon detector at regular intervals until the system reaches equilibrium, that is, the radon concentration measured in the RAD7 radon detector reaches equilibrium.

[0011] Take the water surface layer water of the water sample to be measured and use the bubbling method to measure the radon concentration and flow rate measured by the RAD7 radon detector when the radon concentration reaches equilibrium.

[0012] II. Calculation process

[0013] The radon-220 concentration in the water on the water surface, if the up and down convection in the water is not considered, mainly comes from the decay of radium dissolved in the water. Since the water volume is approximately infinite during the measurement process, assuming that the radon-220 concentration in the water remains unchanged when measuring the radon-220 exhalation rate of the water surface, the radon-200 concentration in the static floating chamber is expressed by formula (1):

[0014]

[0015] Among them, c(t) represents the radon concentration in the static floating chamber 1, with the unit of Bq / m 3 ; A1 represents the rate of radon in the air entering the water surface, with the unit of m / s; A2 represents the rate of radon on the water surface entering the air, with the unit of m / s; V represents the gas path volume, including the volume of the gas path in the static floating chamber, the volume of the measurement chamber in the RAD7 radon detector, and the volume of the connecting pipeline, with the unit of m 3; S represents the surface area of the static floating chamber, in m 2 ; c(H2o) represents the radon concentration in water, in Bq / m 3 ; λ represents the radon decay constant, λ l Indicates the leakage coefficient.

[0016] Let the effective decay constant of radon be e for:

[0017]

[0018] Substituting formula (2) into formula (1) yields the following expression:

[0019]

[0020] The radon exhalation rate of the water surface is expressed by the product of the rate at which radon from the water surface enters the air and the radon concentration in the water. Therefore, the expression of the radon exhalation rate J of the water surface is:

[0021] J=A2c(H2o) (4)

[0022] The expression for calculating the radon concentration in the surface water of the water sample to be tested by the bubble measurement method is:

[0023] c(H2O)=CF×c read ×K (5)

[0024] Where CF is the calibration factor of the RAD7 radon detector, C read is the reading value of the radon concentration in water measured by the RAD7 radon detector through the bubbling method, and K is the conversion coefficient; the calculation formula of the conversion coefficient K is:

[0025]

[0026] Among them, V1 is the volume of the water sample to be measured by the bubbling method, the unit is m 3 ; V2 is the volume of the gas circuit in the bubbling method measurement, in m 3 ; t1 is the measurement count start time, t2 is the measurement count end time, the unit is s; λ Po-218 is the decay constant of Po-218; L is the flow rate of the RAD7 radon detector in the bubbling method, in L / m 3 ; X is the distribution ratio of the radon concentration in gas and the radon concentration in water by the bubbling method; Substitute formula (6) into formula (5) to calculate the radon concentration in water.

[0027] Since A2 is a constant at the same temperature, the radon exhalation rate J on the water surface can be obtained by substituting the value of A2 and the radon concentration c(H2o) in water calculated in formula (5) into formula (4).

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The closed-loop device for rapidly measuring radon concentration in water and calculating radon exhalation rate on the water surface provided by the invention has a simple structure, is easy to operate and takes a short measuring time.

[0030] 2. The measurement method provided by the present invention is used to measure the radon concentration in water and calculate the radon exhalation rate on the water surface. The calculation process is simple and the calculation result is accurate. It can conduct long-term and continuous monitoring and analysis of the radium concentration in groundwater samples in a certain area, so as to formulate healthy drinking water standards for the country, 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.

[0031] The detailed structure of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of a device for measuring radon exhalation rate on a water surface according to the present invention;

[0033] Figure 2 It is a top view of the static floating chamber 1. DETAILED DESCRIPTION

[0034] Embodiment 1: Figure 1-2 As shown, the device for measuring the radon concentration in water and calculating the radon exhalation rate on the water surface comprises a static floating 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 arranged around the static floating chamber 1 and is fixedly connected to the static floating chamber 1, so that the static floating chamber 1 can float on the water surface to be measured. A substance for drying gas, such as calcium chloride powder, is placed in the drying bottle 5. The air inlet pipe 2 and the air outlet pipe 3 are respectively installed on the static floating chamber 1, the air outlet pipe 3 is connected to the air inlet end of the drying bottle 5 through a hose, the air outlet end of the drying bottle 5 is connected to the air inlet end of the RAD7 radon detector 6 through a hose, and the air outlet end of the RAD7 radon detector 6 is connected to the air inlet pipe 2 of the static floating chamber 1 through a hose.

[0035] Embodiment 2: A method for measuring radon concentration in water and calculating radon exhalation rate on a water surface applied to Embodiment 1 includes a measurement process and a calculation process, and the specific steps are as follows:

[0036] 1. Measurement process

[0037] Place the static floating chamber 1 and the surrounding foam board 4 on the water surface of the water sample 7 to be measured. Start the pump of the RAD7 radon detector 6. The radon-containing air in the static floating chamber 1 enters the drying bottle 5 through the air outlet pipe 3 under the action of the pump for drying, and then enters the RAD7 radon detector 6; at regular intervals, in this embodiment, a set of radon concentration data measured by the RAD7 radon detector 6 is recorded every 10 minutes until the system reaches equilibrium, that is, the radon concentration measured in the RAD7 radon detector 6 reaches equilibrium.

[0038] When the radon concentration reaches equilibrium by measuring the surface water of the water sample to be measured using the bubbling method, measure the radon concentration and flow rate obtained by the RAD7 radon detector.

[0039] II. Calculation process

[0040] The radon-220 concentration in the water surface water, if the up and down convection in the water is not considered, mainly comes from the decay of the dissolved radium in the water. Since the water volume is approximately infinite during the measurement process, assuming that the radon-220 concentration in the water remains unchanged when measuring the radon-220 release rate on the water surface, the radon-200 concentration in the static floating chamber 1 is expressed by formula (1):

[0041]

[0042] Among them, c(t) represents the radon concentration in the static floating chamber 1, with the unit of Bq / m 3 ; A1 represents the rate of radon in the air entering the water surface, with the unit of m / s; A2 represents the rate of radon on the water surface entering the air, with the unit of m / s; V represents the gas path volume, including the volume of the gas path in the static floating chamber 1, the volume of the measurement chamber in the RAD7 radon detector 6 and the volume of the connecting pipeline, with the unit of m 3 ; S represents the surface area of the static floating chamber 1, with the unit of m 2 ; c(H2o) represents the radon concentration in the water, with the unit of Bq / m 3 ; λ represents the radon decay constant, λ l represents the leakage coefficient.

[0043] Let the effective decay constant λ of radon e be:

[0044]

[0045] Substitute formula (2) into formula (1) to obtain the following expression:

[0046]

[0047] The radon release rate on the water surface is expressed by the product of the rate of radon on the water surface entering the air and the radon concentration in the water. Therefore, the expression for the radon release rate J on the water surface is obtained as:

[0048] J=A2c(H2o) (4)

[0049] The expression for calculating the radon concentration in the surface water of the water sample to be tested by the bubble measurement method is:

[0050] c(H2O)=CF×c read ×K (5)

[0051] Where CF is the calibration factor of the RAD7 radon detector 6, C read is the reading value of the radon concentration in water measured by the RAD7 radon detector 6 through the bubbling method; K is the conversion coefficient, and its calculation formula is:

[0052]

[0053]

[0054] Among them, the expressions of M and N are as above, V1 is the volume of the water sample to be measured by the bubbling method, the unit is m 3 ; V2 is the volume of the gas circuit in the bubbling method measurement, in m 3 ; t1 is the measurement count start time, t2 is the measurement count end time, the unit is s; λ Po-218 is the decay constant of Po-218; L is the flow rate of the RAD7 radon detector in the bubbling method, in L / m 3 ; X is the distribution ratio of the radon concentration in gas and water by the bubbling method, which is calculated by the relevant formula or experimentally measured. Substituting formula (6) into formula (5) to calculate the radon concentration in water, the radon concentration in water calculated by the bubbling method is equal to the radon concentration in water measured by the static floating chamber 1.

[0055] Since A2 changes very little at the same temperature, it is considered to be a constant. It is obtained by theoretical calculation or experimental measurement. The value of A2 and the radon concentration in water c(H2o) calculated in formula (5) are substituted into formula (4) to obtain the radon exhalation rate J on the water surface.

Claims

1. A device for measuring radon concentration in water and calculating radon exhalation rate on the water surface, characterized by: It includes a static floating chamber, an intake pipe, an 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 intake pipe and the outlet pipe are respectively installed on the static floating chamber. The outlet pipe is connected to the intake end of the drying bottle through a hose. The outlet end of the drying bottle is connected to the intake end of the RAD7 radon detector through a hose. The outlet end of the RAD7 radon detector is connected to the intake pipe of the static floating chamber through a hose.

2. The device for measuring radon concentration in water and calculating radon exhalation rate on water surface as claimed in claim 1, characterized in that: The substance for drying gas placed in the drying bottle is calcium chloride powder.

3. A method for calculating the radon exhalation rate on the water surface by measuring the radon concentration in water according to claim 1 or 2, characterized in that: It includes a measurement process and a calculation process, and the specific steps are as follows. I. Measurement process Place the static floating chamber and the surrounding foam board on the water surface of the water sample to be measured. Start the pump of the RAD7 radon detector. The radon-containing air in the static floating 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 the radon concentration data measured by the RAD7 radon detector at regular intervals until the system reaches equilibrium, that is, the radon concentration measured in the RAD7 radon detector reaches equilibrium. Take the water on the water surface of the water sample to be measured and use the bubbling method to measure the radon concentration and flow rate when the radon concentration reaches equilibrium measured by the RAD7 radon detector. II. Calculation process The radon-220 concentration in the water on the water surface, if the up and down convection in the water is not considered, mainly comes from the decay of radium dissolved in the water. Since the water volume in the measurement process is approximately infinite, assume that the radon-220 concentration in the water remains unchanged when measuring the radon-220 evolution rate on the water surface. At this time, the radon-200 concentration in the static floating chamber is expressed by formula (1): Among them, c(t) represents the radon concentration in the static floating chamber 1, with the unit of Bq / m 3 ; A1 represents the rate of radon in the air entering the water surface, with the unit of m / s; A2 represents the rate of radon in the water surface entering the air, with the unit of m / s; V represents the volume of the gas path, including the volume of the gas path in the static floating chamber, the volume of the measurement chamber in the RAD7 radon detector, and the volume of the connecting pipeline, with the unit of m 3 ; S represents the surface area of the static floating chamber, with the unit of m 2 ; c(H2o) represents the radon concentration in the water, with the unit of Bq / m 3 ; λ represents the radon decay constant, λ l represents the leakage coefficient; Let the effective decay constant of radon be λ e be: Substitute formula (2) into formula (1) to obtain the following expression: The radon evolution rate on the water surface is expressed by the product of the rate of radon entering the air on the water surface and the radon concentration in the water. Therefore, the expression for the radon evolution rate J on the water surface is obtained as: J = A2c(H2o) (4) The expression for calculating the radon concentration in the surface water layer of the water sample to be measured by using the bubbling measurement method is: c(H2O) = CF × c read × K (5) Among them, CF is the calibration factor of the RAD7 radon detector, and C read is the reading value of the RAD7 radon detector for measuring the radon concentration in water by the bubbling method. K is the conversion coefficient, and its calculation formula is: Among them, V1 is the volume of the water sample to be measured taken by the bubbling method, with the unit of m 3 ; V2 is the volume of the gas circuit in the bubbling method measurement, with the unit of m 3 ; t1 is the start time of the measurement count, t2 is the end time of the measurement count, with the unit of s; λ Po-218 is the decay constant of Po-218; L is the flow rate of the RAD7 radon detector in the bubbling method measurement, with the unit of L / m 3 ; X is the distribution ratio of the radon concentration in the bubbling method gas to the radon concentration in water; substituting formula (6) into formula (5) to calculate the radon concentration in water; Since A2 is a constant value at the same temperature, substitute the value of A2 and the radon concentration c(H2o) calculated in formula (5) into formula (4) to obtain the radon evolution rate J on the water surface.

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