CN109655865B - Method for measuring radium concentration in water in closed loop mode through total counting of Po-218 and Po-214 - Google Patents
Method for measuring radium concentration in water in closed loop mode through total counting of Po-218 and Po-214 Download PDFInfo
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Abstract
A device and a method for measuring radium concentration in water in a closed-loop mode through total counting of Po-218 and Po-214 comprise a water sample measuring bottle, a bottle cap, an air inlet pipe sleeve, an air outlet pipe sleeve, an air inlet pipe, an air outlet pipe, an air pump, a radon measuring instrument adopting an electrostatic collection method, a flowmeter, a first three-way electromagnetic valve and a second three-way electromagnetic valve; the measuring device is placed in a constant temperature environment, the second air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve are controlled to be opened to be communicated with the external atmospheric environment, or the first air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve are controlled to be opened to form a closed loop air path, the air pump controls air to enter the water sample measuring bottle to bubble, radon in a water sample to be measured is carried out, enters the air pump through the air outlet pipe, then enters the electrostatic collection method radon measuring instrument, and then enters the air inlet end of the air inlet pipe. And calculating the radium concentration in the water according to the ambient temperature, the volume of the water sample to be detected, the volume of the closed loop gas circuit, the radon measuring instrument adopting the electrostatic collection method, the decay counts of Po-218 and Po-214. The device has the advantages of simple structure, convenient operation and short measuring time.
Description
Technical Field
The invention relates to a nuclear radiation detection technology, in particular to a method for measuring radium concentration in water in a closed loop mode by total counting of Po-218 and Po-214.
Background
Radium (Ra-226) is a very toxic osteogenic alpha radionuclide, and its massive deposition in vivo can induce bone cancer or leukemia, thus endangering human health. Radium (Ra-226) has generally higher activity in underground water, and is 1-2 orders of magnitude higher than that of general surface water (river water, lake water, seawater and the like); drinking water sources in many regions of the world are underground water, and underground water in some regions naturally contains high-concentration radium elements or a large amount of radium elements are activated and released into the underground water along with exploitation of different mineral products such as uranium mines and the like, so that great potential safety hazards exist when people use the underground water as the drinking water source, and the concentration of the radium elements contained in the local underground water needs to be monitored for a long time when the drinking water source is selected. In the prior art, the measuring device and the measuring method for the radium element concentration in water are complex and long in measuring time, and a device and a method for rapidly measuring the radium element concentration in water are needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for measuring the radium concentration in water in a closed loop mode by total counting of Po-218 and Po-214, and the method can be used for rapidly obtaining the accurate radium concentration in water.
The technical scheme of the invention is as follows: a method for measuring radium concentration in water in a closed loop mode through total counting of Po-218 and Po-214 is based on a device for measuring radium concentration in water in a closed loop mode through total counting of Po-218 and Po-214.
The air inlet pipe sleeve and the air outlet pipe sleeve are respectively arranged on the bottle cap, the air inlet pipe is inserted on the air inlet pipe sleeve, the air outlet pipe is inserted on the air outlet pipe sleeve, the air outlet pipe is connected with the air inlet end of the air pump through a hose, the air outlet end of the air pump is connected with the air inlet end of the first three-way electromagnetic valve through a hose, the first air outlet end of the first three-way electromagnetic valve is connected with the air inlet end of the electrostatic collection radon measuring instrument through a hose, the second air outlet end of the first three-way electromagnetic valve is communicated with the atmospheric environment, the air outlet end of the electrostatic collection radon measuring instrument is connected with the air inlet end of the flow meter through a hose, the air outlet end of the flow meter is connected with the air inlet end of the second three-way electromagnetic valve through a hose, the first air outlet end of the second three-way electromagnetic valve is connected with the air inlet end of the air inlet pipe through a hose, and the second air outlet end of the second three-way electromagnetic valve is communicated with the atmospheric environment; the method comprises a measuring process and a calculating process, and comprises the following specific steps:
first, measurement process
A. Placing a device for measuring the radium concentration in the water in a closed loop mode by using the total number Po-218 and Po-214 in a constant-temperature environment, and measuring the environment temperature;
B. pouring a water sample to be detected into the water sample measuring bottle, tightly covering the bottle cap, wherein the air outlet of the air inlet pipe is positioned in the water sample to be detected and close to the bottle bottom of the water sample measuring bottle, and the air inlet of the air outlet pipe is positioned on the liquid level of the water sample to be detected;
C. respectively opening second air outlet ends of a first three-way electromagnetic valve and a second three-way electromagnetic valve, closing the first air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve, starting an air pump, controlling the flow rate of the air pump to be very large, enabling air to enter a water sample to be detected through an air inlet pipe to bubble, simultaneously carrying out radon in the water sample to be detected, entering the first three-way electromagnetic valve through an air outlet pipe, and then entering an atmospheric environment from the second air outlet end of the first three-way electromagnetic valve, wherein the radon concentration in an air path can be considered to be 0 after the air pump is started for 5-30 minutes due to the very large flow rate of the air pump;
D. respectively closing second air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve, opening first air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve so as to form a closed loop air path, controlling the air pump to adjust the flow rate by obtaining the reading of the flow meter, enabling air to enter a water sample to be detected through the air inlet pipe to bubble, simultaneously carrying out radon in the water sample to be detected, entering the air pump through the air outlet pipe to enter the first three-way electromagnetic valve, then entering the electrostatic collection radon measuring instrument from the first air outlet end of the first three-way electromagnetic valve, then entering the second three-way electromagnetic valve from the air outlet end of the flow meter through the flow meter, and then entering the air inlet pipe again from the first air outlet end of the second three-way electromagnetic valve; when the flow rate of the air pump is reduced, the flow rate of the air pump is kept moderate, so that the radon concentration in the measuring cavity of the electrostatic collection radon measuring instrument and the gaseous radon concentration in the water sample measuring bottle synchronously change;
E. measuring with a short measuring period T of 2-20 min;
second, calculating process
And calculating radium concentration in the water sample according to the ambient temperature, the volume of the water sample to be detected, the volume of the closed-loop gas circuit and the reading of the static collection radon detector.
The radon in the water-sampling measuring bottle comes from the decay of the radium in the water. Setting the volume of the water sample as V and the radium activity in the water as ARaAnd then the radium concentration in water is CRaComprises the following steps:
CRa＝ARa/V (1)
water sample measurement bottle for measuring radon concentration C 'in water'RnThe change rule is as follows:
dC'Rn/dt＝CRaλRn-λRn(C'Rn+CRnV1/V)-λlCRnV1/V (2)
in the formula ofRnIs the decay constant of radon; cRnIs the concentration of radon in the closed loop gas circuit; v1The volume of the closed-loop gas circuit comprises the sum of the pipeline volume of the hose, the pipeline volume of the gas inlet pipe, the pipeline volume of the gas outlet pipe, the volume of the internal measuring cavity of the radon measuring instrument adopting the electrostatic collection method and the volume of the upper space of the liquid level of the water sample measuring bottle; lambda [ alpha ]lIs the leakage coefficient;
according to the temperature during measurement, the concentration ratio X of water radon to gaseous radon during balance is obtained by looking up a table, and the concentration ratio X comprises the following components:
C'Rn＝XCRn (3)
substituting formula (3) into formula (2) to obtain:
let the effective decay constant lambdaeComprises the following steps:
equation (4) reduces to:
the initial radon concentration is 0 and the solution of equation (6) is:
because the flow rate of the air pump is moderate, the radon concentration in the measuring cavity of the electrostatic collection method radon measuring instrument and the gaseous radon concentration in the water sample measuring bottle can be considered to be changed synchronously. According to the measurement principle of the electrostatic collection radon meter, the actual measurement of the gaseous radon concentration of the electrostatic collection radon meter is the concentration of Po-218 in the measurement cavity, and the measurement cavity of the electrostatic collection radon meterInternal Po-218 concentration CPoThe change rule of (t) is as follows:
by substituting formula (7) for formula (8)
The initial concentration of Po-218 is 0 and the solution of equation (9) is:
according to radon decay chain, the measuring cavity of the electrostatic collection radon measuring instrument is provided with:
CPb(t)、CBi(t) the concentrations of Pb-214 and Bi-214, respectively; lambda [ alpha ]Pb、λBiThe decay constants of Pb-214 and Bi-214, respectively.
After Bi-214 is degraded into Po-214, the half life of the Po-214 is only 164us, and the concentration of the Bi-214 can be considered as the concentration of the Po-214; namely:
CPo214(t) is the concentration of Po-214.
The concentrations of Pb-214, Bi-214, and Po-214 at the time of initial measurement were 0, and the results were obtained according to the following equations (11) and (13):
firstly, the electrostatic collection method radon measuring instrument is subjected to measurement and calibration for 30-120 minutes in a standard radon chamber under the condition that radon is balanced with Po-218 and Po-214 to obtain:
C0＝k1m1＝k2m2 (16)
m1、m2counts per unit time of the decay emission of the high energy alpha particles of Po-218 and Po-214, respectively; c0Is the radon concentration of a standard radon chamber; k is a radical of1、k2Is a scale factor.
Since the measurement period T is short, the average count rate of each measurement period is the count rate at the midpoint of the measurement period. For the nth measurement period there are:
m1(n)、m2(n) the count rates of radioactive decay at the nth measurement cycle for Po-218 and Po-214, respectively. Substituting the formulas (10) and (15) into the formula (17), and fitting nonlinear data according to the formula (17) to the data of all measurement periods to obtain the radium concentration in water.
Compared with the prior art, the invention has the following advantages:
1. the device for measuring the radium concentration in water in a closed loop mode by using the total counting number Po-218 and Po-214 is simple in structure, convenient to operate and short in measuring time.
2. The method for measuring radium concentration in water in a closed loop mode through total counting of Po-218 and Po-214 has the advantages that the calculation process of radium concentration in water is simple, the obtained radium concentration result is accurate, healthy drinking water standards can be established for the country through long-term continuous monitoring and analysis of radium concentration in a groundwater water sample in a certain area, bases are provided for water pollution treatment, national disease prevention and treatment, water for agriculture and animal husbandry and the like, and the safety of the groundwater environment and drinking water for residents is guaranteed.
The detailed structure of the invention is further described below in conjunction with the drawings and the detailed description.
Drawings
FIG. 1 is a schematic structural diagram of a device for measuring radium concentration in water in a total counting closed-loop manner by Po-218 and Po-214 according to the present invention.
Detailed Description
As shown in fig. 1, the device for measuring radium concentration in water in a closed-loop manner by total counting at Po-218 and Po-214 comprises a water sample measuring bottle 1, a bottle cap 2, an air inlet pipe sleeve 3, an air outlet pipe sleeve 4, an air inlet pipe 5, an air outlet pipe 6, an air pump 7, an electrostatic collection radon measuring instrument 8, a flowmeter 9, a first three-way electromagnetic valve 10 and a second three-way electromagnetic valve 11.
An air inlet pipe sleeve 3 and an air outlet pipe sleeve 4 are respectively arranged on a bottle cap 2, an air inlet pipe 5 is inserted on the air inlet pipe sleeve 3, an air outlet pipe 6 is inserted on the air outlet pipe sleeve 4, the air outlet pipe 6 is connected with an air inlet end of an air pump 7 through a hose, an air outlet end of the air pump 7 is connected with an air inlet end of a first three-way electromagnetic valve 10 through a hose, a first air outlet end of the first three-way electromagnetic valve 10 is connected with an air inlet end of an electrostatic collection method radon measuring instrument 8 through a hose, a second air outlet end of the first three-way electromagnetic valve 10 is communicated with the atmospheric environment, an air outlet end of the electrostatic collection method radon measuring instrument 8 is connected with an air inlet end of a flowmeter 9 through a hose, an air outlet end of the flowmeter 9 is connected with an air inlet end of a second three-way electromagnetic valve 11 through a hose, a first air outlet end of the second three-way electromagnetic valve 11 is connected with an air inlet end of the air inlet pipe 5 through a hose, and a second air outlet end of the second three-way electromagnetic valve 11 is communicated with the atmospheric environment.
The method for carrying out Po-218 and Po-214 total counting closed-loop measurement on radium concentration in water by adopting the measuring device comprises a measuring process and a calculating process, and comprises the following specific steps:
first, measurement process
A. Placing a device for measuring the radium concentration in the water in a closed loop mode by total counting of Po-218 and Po-214 in a constant temperature environment, and measuring the environment temperature;
B. pouring a water sample to be detected into the water sample measuring bottle 1, tightly covering the bottle cap 2, enabling the air outlet of the air inlet pipe 5 to be positioned in the water sample to be detected and close to the bottle bottom of the water sample measuring bottle 1, and enabling the air inlet of the air outlet pipe 6 to be positioned on the liquid level of the water sample to be detected;
C. respectively opening second air outlet ends of a first three-way electromagnetic valve 10 and a second three-way electromagnetic valve 11, closing the first air outlet ends of the first three-way electromagnetic valve 10 and the second three-way electromagnetic valve 11, starting an air pump 7, controlling the flow rate of the air pump 7 to be very large, enabling air to enter a water sample to be detected through an air inlet pipe 5 to bubble, simultaneously carrying out radon in the water sample to be detected, entering the air pump 7 through an air outlet pipe 6 to enter the first three-way electromagnetic valve 10, and then entering an atmospheric environment from the second air outlet end of the first three-way electromagnetic valve 10, wherein the radon concentration in an air path can be considered to be 0 after the air pump 7 is started for 5-30 minutes due to the very large flow rate of the air pump 7;
D. respectively closing second air outlet ends of a first three-way electromagnetic valve 10 and a second three-way electromagnetic valve 11, opening the first air outlet ends of the first three-way electromagnetic valve 10 and the second three-way electromagnetic valve 11 to form a closed loop air path, controlling an air pump 7 to reduce the flow rate by obtaining the reading of a flow meter 9, enabling air to enter a water sample to be detected through an air inlet pipe 5 to bubble, simultaneously carrying out radon in the water sample to be detected, entering the air pump through an air outlet pipe 6 to enter the first three-way electromagnetic valve 10, then entering an electrostatic collection method radon measuring instrument 8 from the first air outlet end of the first three-way electromagnetic valve 10, then entering the second three-way electromagnetic valve 11 from the air outlet end of the flow meter 9 through the flow meter 9, and then entering the air inlet pipe 5 again from the first air outlet end of the second three-way electromagnetic valve 11; when the flow rate of the air pump 7 is reduced, the flow rate of the air pump 7 is kept moderate, so that the radon concentration in the measuring cavity of the electrostatic collection method radon measuring instrument 8 and the gaseous radon concentration in the water sample measuring bottle 1 synchronously change;
E. measuring with short measuring period T of 2-20 min;
second, calculating the process
And calculating the radium concentration in the water sample according to the environment temperature, the volume of the water sample to be detected, the volume of the closed-loop gas circuit and the reading of the radon measuring instrument 8 by the electrostatic collection method.
The radon in the water sampling bottle 1 comes from the decay of radium in the water. Setting the volume of the water sample as V and the radium activity in the water as ARaThen the radium concentration in water is CRaComprises the following steps:
CRa＝ARa/V (1)
water sample measuring bottle1 radon concentration C 'in water'RnThe change rule is as follows:
dC'Rn/dt＝CRaλRn-λRn(C'Rn+CRnV1/V)-λlCRnV1/V (2)
in the formula ofRnIs the decay constant of radon; cRnIs the concentration of radon in the closed loop gas circuit; v1The volume of the closed-loop gas circuit comprises the sum of the pipeline volume of the hose, the pipeline volume of the gas inlet pipe 5, the pipeline volume of the gas outlet pipe 6, the volume of the internal measuring cavity of the radon measuring instrument 8 by the electrostatic collection method and the volume of the upper space of the liquid level of the water sample measuring bottle 1; lambda [ alpha ]lIs the leakage coefficient.
According to the temperature during measurement, a table is looked up to obtain the concentration ratio X of water radon to gaseous radon during balance, and the concentration ratio X comprises the following components:
C'Rn＝XCRn (3)
substituting formula (3) into formula (2) to obtain:
let the effective decay constant lambdaeComprises the following steps:
equation (4) reduces to:
the initial radon concentration is 0 and the solution of equation (6) is:
because the flow rate of the air pump 7 is moderate, the radon concentration in the measuring cavity of the electrostatic collection radon measuring instrument 8 and the radon concentration in the water sample measuring bottle 1 can be consideredThe concentration of the gaseous radon is changed synchronously. According to the measurement principle of the electrostatic collection radon detector 8, the actual measurement of the gaseous radon concentration of the electrostatic collection radon detector 8 is the concentration of Po-218 in the measurement cavity, and the concentration C of Po-218 in the measurement cavity of the electrostatic collection radon detector 8PoThe change rule of (t) is as follows:
by substituting formula (7) for formula (8)
The initial concentration of Po-218 is 0 and the solution of equation (9) is:
according to the radon decay chain, the measuring cavity of the electrostatic collection radon measuring instrument 8 is provided with:
CPb(t)、CBi(t) the concentrations of Pb-214 and Bi-214, respectively; lambdaPb、λBiThe decay constants of Pb-214 and Bi-214, respectively.
After Bi-214 is degraded into Po-214, the half life of the Po-214 is only 164us, and the concentration of the Bi-214 can be considered as the concentration of the Po-214; namely:
CPo214(t) is the concentration of Po-214.
The concentrations of Pb-214, Bi-214, and Po-214 at the time of initial measurement were 0, and the results were obtained according to the following equations (11) and (13):
the electrostatic collection method radon detector 8 firstly carries out measurement calibration for 30-120 minutes in a standard radon chamber under the condition that radon is balanced with Po-218 and Po-214 to obtain:
C0＝k1m1＝k2m2 (16)
m1、m2counts per unit time of the decay emission of the high energy alpha particles of Po-218 and Po-214, respectively; c0Is the radon concentration of a standard radon chamber; k is a radical of1、k2Is a scale factor.
Since the measurement period T is short, the average count rate for each measurement period is the count rate at the midpoint of the measurement period. For the nth measurement period there are:
m1(n)、m2(n) the count rates of radioactive decay at the n-th measurement cycle for Po-218 and Po-214, respectively. Substituting the formulas (10) and (15) into the formula (17), and fitting the data of all measurement periods according to the formula (17) to obtain the radium concentration in the water by nonlinear data fitting.
Claims (1)
1. The method for measuring the radium concentration in water in a closed-loop manner by utilizing the device for measuring the radium concentration in water in a closed-loop manner by utilizing the total counting of Po-218 and Po-214 is characterized in that the device for measuring the radium concentration in water in a closed-loop manner by utilizing the total counting of Po-218 and Po-214 comprises a water sample measuring bottle, a bottle cap, an air inlet pipe sleeve, an air outlet pipe sleeve, an air inlet pipe, an air outlet pipe, an air pump, a radon measuring instrument by an electrostatic collection method, a flowmeter, a first three-way electromagnetic valve and a second three-way electromagnetic valve;
the air inlet pipe sleeve and the air outlet pipe sleeve are respectively arranged on the bottle cap, the air inlet pipe is inserted on the air inlet pipe sleeve, the air outlet pipe is inserted on the air outlet pipe sleeve, the air outlet pipe is connected with the air inlet end of the air pump through a hose, the air outlet end of the air pump is connected with the air inlet end of the first three-way electromagnetic valve through a hose, the first air outlet end of the first three-way electromagnetic valve is connected with the air inlet end of the electrostatic collection radon measuring instrument through a hose, the second air outlet end of the first three-way electromagnetic valve is communicated with the atmospheric environment, the air outlet end of the electrostatic collection radon measuring instrument is connected with the air inlet end of the flow meter through a hose, the air outlet end of the flow meter is connected with the air inlet end of the second three-way electromagnetic valve through a hose, the first air outlet end of the second three-way electromagnetic valve is connected with the air inlet end of the air inlet pipe through a hose, and the second air outlet end of the second three-way electromagnetic valve is communicated with the atmospheric environment;
the method is characterized by comprising a measuring process and a calculating process, and the method comprises the following specific steps:
first, measurement process
A. Placing a device for measuring the radium concentration in the water in a closed loop mode by total counting of Po-218 and Po-214 in a constant temperature environment, and measuring the environment temperature;
B. pouring a water sample to be detected into the water sample measuring bottle, tightly covering the bottle cap, wherein the air outlet of the air inlet pipe is positioned in the water sample to be detected and close to the bottle bottom of the water sample measuring bottle, and the air inlet of the air outlet pipe is positioned on the liquid level of the water sample to be detected;
C. respectively opening second air outlet ends of a first three-way electromagnetic valve and a second three-way electromagnetic valve, closing first air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve, starting an air pump, controlling the flow rate of the air pump to be very large, enabling air to enter a water sample to be detected through an air inlet pipe to be bubbled, simultaneously carrying out radon in the water sample to be detected, entering the first three-way electromagnetic valve through an air outlet pipe, and then entering an atmospheric environment from the second air outlet end of the first three-way electromagnetic valve, wherein the radon concentration in an air path can be considered to be 0 after the air pump is started for 5-30 minutes due to the very large flow rate of the air pump;
D. respectively closing second air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve, opening first air outlet ends of the first three-way electromagnetic valve and the second three-way electromagnetic valve so as to form a closed loop air path, controlling the air pump to adjust the flow rate by obtaining the reading of the flow meter, enabling air to enter a water sample to be detected through the air inlet pipe to bubble, simultaneously carrying out radon in the water sample to be detected, entering the air pump through the air outlet pipe to enter the first three-way electromagnetic valve, then entering the electrostatic collection radon measuring instrument from the first air outlet end of the first three-way electromagnetic valve, then entering the second three-way electromagnetic valve from the air outlet end of the flow meter through the flow meter, and then entering the air inlet pipe again from the first air outlet end of the second three-way electromagnetic valve; when the flow rate of the air pump is reduced, the flow rate of the air pump is kept moderate, so that the radon concentration in the measuring cavity of the electrostatic collection radon measuring instrument and the gaseous radon concentration in the water sample measuring bottle synchronously change;
E. measuring by adopting a short measuring period, wherein the measuring period T is 2-20 minutes;
second, calculating process
Calculating radium concentration in the water sample according to the environment temperature, the volume of the water sample to be detected, the volume of the closed-loop gas circuit and the reading of the static collection radon detector;
radon in water in the water sample measuring bottle comes from decay of radium in the water; setting the volume of the water sample as V and the radium activity in the water as ARaThen the radium concentration in water is CRaComprises the following steps:
CRa＝ARa/V (1)
water sample measurement bottle for measuring radon concentration C 'in water'RnThe change rule is as follows:
dC'Rn/dt＝CRaλRn-λRn(C'Rn+CRnV1/V)-λlCRnV1/V (2)
in the formula ofRnIs the decay constant of radon; cRnIs the concentration of radon in the closed loop gas circuit; v1The volume of the closed-loop gas circuit comprises the sum of the pipeline volume of the hose, the pipeline volume of the gas inlet pipe, the pipeline volume of the gas outlet pipe, the volume of the internal measuring cavity of the radon measuring instrument adopting the electrostatic collection method and the volume of the upper space of the liquid level of the water sample measuring bottle; lambdalIs the leakage coefficient;
according to the temperature during measurement, the concentration ratio X of water radon to gaseous radon during balance is obtained by looking up a table, and the concentration ratio X comprises the following components:
C'Rn＝XCRn (3)
substituting formula (3) into formula (2) to obtain:
let the effective decay constant lambdaeComprises the following steps:
equation (4) reduces to:
the initial radon concentration is 0 and the solution of equation (6) is:
because the flow rate of the air pump is moderate, the radon concentration in the measuring cavity of the electrostatic collection method radon measuring instrument and the gaseous radon concentration in the water sample measuring bottle can be considered to be changed synchronously; according to the measurement principle of the electrostatic collection radon meter, the actual measurement of the gaseous radon concentration of the electrostatic collection radon meter is the concentration of Po-218 in a measurement cavity, and the concentration C of Po-218 in the measurement cavity of the electrostatic collection radon meterPoThe change rule of (t) is as follows:
by substituting formula (7) for formula (8)
The initial concentration of Po-218 is 0 and the solution of equation (9) is:
according to radon decay chain, the measuring cavity of the electrostatic collection radon measuring instrument is provided with:
CPb(t)、CBi(t) the concentrations of Pb-214 and Bi-214, respectively; lambdaPb、λBiThe decay constants of Pb-214 and Bi-214, respectively;
after Bi-214 is degraded into Po-214, the half life of the Po-214 is only 164us, and the concentration of the Bi-214 can be considered as the concentration of the Po-214; namely:
CPo214(t) is the concentration of Po-214;
the concentrations of Pb-214, Bi-214, and Po-214 at the time of initial measurement were 0, and the results were obtained according to the following equations (11) and (13):
firstly, the electrostatic collection method radon measuring instrument is subjected to measurement and calibration for 30-120 minutes in a standard radon chamber under the condition that radon is balanced with Po-218 and Po-214 to obtain:
C0＝k1m1＝k2m2 (16)
m1、m2counts per unit time of the decay emission of the high energy alpha particles of Po-218 and Po-214, respectively; c0Is the radon concentration of a standard radon chamber; k is a radical of1、k2Is a scale factor;
because the measuring period T is short, the average counting rate of each measuring period is the counting rate of the midpoint of the measuring period; for the nth measurement period there are:
m1(n)、m2(n) the count rates of radioactive decay at the n-th measurement cycle for Po-218 and Po-214, respectively; substituting the formulas (10) and (15) into the formula (17), and fitting the data of all measurement periods according to the formula (17) to obtain the radium concentration in the water by nonlinear data fitting.
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| CN109655864B (en) * | 2018-12-21 | 2022-06-21 | 衡阳师范学院 | Method for measuring radium concentration in water by Po-218 and Po-214 total counting closed-loop two-stage method |
| CN109655868B (en) * | 2018-12-21 | 2022-08-02 | 衡阳师范学院 | Method for rapidly measuring radium concentration in water by closed-loop electrostatic collection method |
| CN109655863B (en) * | 2018-12-21 | 2022-06-21 | 衡阳师范学院 | Method for measuring radium concentration in water in two cycles of closed-loop electrostatic collection |
| CN109655862B (en) * | 2018-12-21 | 2022-06-21 | 衡阳师范学院 | Method for partially integrating and measuring radium concentration in water by closed-loop electrostatic collection method |
| CN109655866B (en) * | 2018-12-21 | 2022-08-12 | 衡阳师范学院 | Method for measuring radium concentration in water by closed-loop electrostatic collection two-stage method |
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