CN112363199A - Active carbon radon measuring device and method - Google Patents
Active carbon radon measuring device and method Download PDFInfo
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- CN112363199A CN112363199A CN202011279766.XA CN202011279766A CN112363199A CN 112363199 A CN112363199 A CN 112363199A CN 202011279766 A CN202011279766 A CN 202011279766A CN 112363199 A CN112363199 A CN 112363199A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/204—Measuring radiation intensity with scintillation detectors the detector being a liquid
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Abstract
The invention discloses an active carbon radon measuring device and method. The method comprises the following steps: the scale factor CF and the adsorption saturation time T of the adopted active carbon sampler are measured in advancesThe dried active carbon is loaded into a sampler and then sampling is started, wherein the sampling time is more than the adsorption saturation time T measured in advances(ii) a After sampling is finished, filling the activated carbon in the sampler into a sample box, sealing, then putting the sample box into a nuclear detection instrument, measuring gamma rays or alpha particles generated by radon and daughters thereof, measuring to obtain a counting rate N, and finally obtaining the gas radon concentration C according to the scale factor CF and the measured counting rate N0The calculation formula is C0CF · N. When the active carbon sampler is used for adsorbing and saturating the radon, the radon is measured by the direct proportion relation between the counting rate of the active carbon in the sampler and the concentration of the radon in the gas, and the measurement effect is more accurate.
Description
Technical Field
The invention relates to the field of radon concentration measurement, in particular to an active carbon radon measurement device and method.
Background
Radon gas, which is a natural radiation widely existing in soil, bricks, cement, granite and other major building and finishing materials, is considered as the second most cancer factor next to smoking, and has been listed as one of the 19 most major carcinogenic substances by the world health organization; radon gas is a tracer which can indicate underground mineral deposits, geological structures, earthquakes and the like, so radon gas measurement is widely applied to mineral geology, hydrogeology, engineering geology, disaster geology, environmental geology and the like, particularly to earthquake prediction, and therefore research on radon measurement methods is always a hot spot in the field.
The active carbon radon measuring method comprises an active method and a passive method, wherein the active carbon radon measuring method has the advantages of short measuring time, high collecting efficiency, simple device, low price and the like. The existing active carbon radon measuring method assumes that all radon passing through an active carbon sampler is absorbed by the sampler, and the radon amount absorbed by the active carbon is divided by the gas volume passing through the sampler to obtain the radon concentration in the gas, and the existing method has the problems that the radon absorption efficiency cannot reach 100%, the radon is not uniformly distributed in the active carbon sampler, and the like.
Disclosure of Invention
The invention aims to provide a novel active carbon radon measuring device and method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the utility model provides an active carbon radon measuring device, its sampling head, drying tube, rotor flow meter, filter, active carbon radon sample thief and the aspiration pump that includes nuclear detection instrument and connect gradually, be equipped with flow control valve between active carbon radon sample thief and the aspiration pump, the one end of sampling head is connected the gas that awaits measuring, and the gas flow that awaits measuring is through the sampling head back of admitting air, through drying tube drying, then gets into active carbon radon sample thief after the filter filters, and the active carbon in the active carbon radon sample thief samples the radon in the gas that awaits measuring, and after the sampling, gaseous outflow behind the air pump, the nuclear detection instrument is used for measuring gamma ray or the alpha particle that radon and its daughter that the active carbon gathered produced.
The whole active carbon radon sampler is required to have good air tightness and comprises an air inlet and outlet port, a filter membrane, a sealing ring and active carbon. The air pump needs to have enough air pumping stability, so that the air pumping flow can be kept in a relatively stable state; the nuclear detection instrument is required to be capable of measuring the characteristic gamma rays or alpha particles generated by radon and daughters thereof, and comprises but is not limited to a NaI gamma energy spectrometer and a liquid scintillation counter.
An active carbon radon measuring method comprises the following steps,
step S1: the scale factor CF and the adsorption saturation time T of the adopted active carbon sampler are measured in advances；
Step S2: loading activated carbon dried at 120 ℃ for more than 10 hours into a sampler;
step S3: starting the sampling process by turning on the air pump, wherein the sampling time is longer than the adsorption saturation time T determined in advances；
Step S4: after sampling, filling the activated carbon in the sampler into a sample box, and sealing for more than 3 hours;
step S5: putting the sample box into a nuclear detection instrument to measure gamma rays or alpha particles generated by radon and daughters thereof (if the liquid scintillation counter needs to take out the activated carbon and put the activated carbon into liquid), and measuring to obtain a counting rate N;
step S6: obtaining the radon concentration C of the gas according to the scale factor CF and the measured counting rate N0The calculation formula is C0＝CF·N。
Further, the measuring method of the scale factor CF of the active carbon sampler comprises the following steps:
1) performing active carbon radon measurement at different radon concentrations using the method of claim 1 to obtain an active carbon radon measurement count rate N;
2) simultaneously measuring the radon concentration of gas by using another radon measuring instrument (such as RAD7) while actively measuring the radon by using the activated carbon to obtain a series of radon concentrations C of gas1；
3) The counting rate N of active carbon radon measurement and the radon concentration C of serial gases1And performing linear fitting, wherein the slope obtained by fitting is the scale factor CF.
Further, the saturated adsorption time measuring method comprises the following steps: measuring penetration curve of active carbon sampler to radon, the penetration curve measuring device is shown in figure 2Show that the radon-containing material has a certain radon concentration (assumed to be C)0) Gas is continuously introduced into the activated carbon bed and the radon concentration (assumed to be C) of the gas at the outlet is measuredb) The outlet concentration C can be obtained by continuous monitoringbThe relationship with time t is dynamic adsorption penetration curve, and the penetration curve is used
Fitting is carried out to obtain fitting parameters tau and k, the formula is obtained by introducing a Yoon-Nelson model into the radon measuring method and carrying out rigorous mathematical derivation, and in the formula: cbIs the radon outlet concentration (Bq/m)3)，C0Is radon concentration at mouth (Bq/m)3) T is the time (min) for measuring the radon concentration at the outlet, τ is the half-penetration time (min), and k is the rate constant (min)-1) Then substituting tau and k into
The adsorption saturation time T can be obtaineds(min), equation (2) is derived from equation (1) when the exit radon concentration reaches 95% of the entrance radon concentration.
Aiming at the problems that the radon adsorption efficiency of the existing active carbon radon measuring method can not reach 100 percent, the radon is not uniformly distributed in the active carbon sampler and the like, when the radon adsorption of the active carbon sampler is saturated, the radon is measured by adopting the direct proportion relation between the counting rate of the active carbon in the sampler and the radon concentration in the gas, and the problems of the existing method do not exist.
Drawings
Fig. 1 is a schematic view of an active carbon radon measurement device of the present invention.
FIG. 2 is a schematic view of a penetration curve measuring apparatus.
Detailed Description
The technical scheme of the invention is specifically explained below with reference to the accompanying drawings.
As shown in fig. 1, active carbon radon measuring device, it includes nuclear detection instrument and the sampling head, drying tube, rotameter, filter, active carbon radon sample thief and the aspiration pump that connect gradually, be equipped with flow control valve between active carbon radon sample thief and the aspiration pump, the gas that awaits measuring is connected to the one end of sampling head, and the gas stream that awaits measuring is after admitting air through the sampling head, through drying tube drying, then gets into the active carbon radon sample thief after the filter filters, and the active carbon in the active carbon radon sample thief samples the radon in the gas that awaits measuring, and after the sampling, gas flows out behind the air pump, the nuclear detection instrument is used for measuring gamma ray or the alpha particle that radon and its daughter that the active carbon gathered produced.
The air pump needs to have enough air pumping stability, so that the air pumping flow can be kept in a relatively stable state; the nuclear detection instrument is required to be capable of measuring the characteristic gamma rays or alpha particles generated by radon and daughters thereof, and comprises but is not limited to a NaI gamma energy spectrometer and a liquid scintillation counter.
The active carbon radon measuring method adopting the device comprises the following steps,
step S1: the scale factor CF and the adsorption saturation time T of the adopted active carbon sampler are measured in advances；
Step S2: loading activated carbon dried at 120 ℃ for more than 10 hours into a sampler;
step S3: starting the sampling process by turning on the air pump, wherein the sampling time is longer than the adsorption saturation time T determined in advances；
Step S4: after sampling, filling the activated carbon in the sampler into a sample box, and sealing for more than 3 hours;
step S5: putting the sample box into a nuclear detection instrument to measure gamma rays or alpha particles generated by radon and daughters thereof (if the liquid scintillation counter needs to take out the activated carbon and put the activated carbon into liquid), and measuring to obtain a counting rate N;
step S6: obtaining the radon concentration C of the gas according to the scale factor CF and the measured counting rate N0The calculation formula is C0＝CF·N。
The measuring method of the scale factor CF is as follows: 1) performing active carbon radon measurement at different radon concentrations using the method of claim 1 to obtain an active carbon radon measurement count rate N; 2) simultaneously measuring the radon concentration of gas by using another radon measuring instrument (such as RAD7) while actively measuring the radon by using the activated carbon to obtain a series of radon concentrations C of gas1；
3) The counting rate N of active carbon radon measurement and the radon concentration C of serial gases1And performing linear fitting, wherein the slope obtained by fitting is the scale factor CF.
The saturated adsorption time measuring method comprises the following steps: measuring penetration curve of active carbon sampler to radon, and measuring device of penetration curve as shown in FIG. 2, which will contain a certain radon concentration (assumed as C)0) Gas is continuously introduced into the activated carbon bed and the radon concentration (assumed to be C) of the gas at the outlet is measuredb) The outlet concentration C can be obtained by continuous monitoringbThe relationship with time t is dynamic adsorption penetration curve, and the penetration curve is used
Fitting is carried out to obtain fitting parameters tau and k, the formula is obtained by introducing a Yoon-Nelson model into the radon measuring method and carrying out rigorous mathematical derivation, and in the formula: cbIs the radon outlet concentration (Bq/m)3)，C0Is radon concentration at mouth (Bq/m)3) T is the time (min) for measuring the radon concentration at the outlet, τ is the half-penetration time (min), and k is the rate constant (min)-1) Then substituting tau and k into
The adsorption saturation time T can be obtaineds(min), equation (2) is derived from equation (1) when the exit radon concentration reaches 95% of the entrance radon concentration.
The above are preferred embodiments of the present invention, and all changes made according to the technical scheme of the present invention that produce functional effects do not exceed the scope of the technical scheme of the present invention belong to the protection scope of the present invention.
Claims (5)
1. An active carbon radon measurement method is characterized in that: which comprises the following steps of,
step S1: the scale factor CF and the adsorption saturation time T of the adopted active carbon sampler are measured in advances；
Step S2: loading the dried active carbon into a sampler;
step S3: starting the sampling process by turning on the air pump, wherein the sampling time is longer than the adsorption saturation time T determined in advances；
Step S4: after sampling, filling the activated carbon in the sampler into a sample box, and sealing for more than 3 hours;
step S5: putting the sample box into a nuclear detection instrument to measure gamma rays or alpha particles generated by radon and daughters thereof, and measuring to obtain a counting rate N;
step S6: obtaining the radon concentration C of the gas according to the scale factor CF and the measured counting rate N0The calculation formula is C0＝CF·N。
2. The active carbon radon measurement method of claim 1, wherein: the measuring method of the scale factor CF of the active carbon sampler comprises the following steps:
1) performing active carbon radon measurement at different radon concentrations using the method of claim 1 to obtain an active carbon radon measurement count rate N;
2) measuring the radon concentration of gas by using another radon measuring instrument while actively measuring radon by using the activated carbon to obtain a series of radon concentrations C of gas1；
3) The counting rate N of active carbon radon measurement and the radon concentration C of serial gases1And performing linear fitting, wherein the slope obtained by fitting is the scale factor CF.
3. The active radon measurement method as claimed in claim 1, wherein the active radon measurement method is characterized in thatCharacterized in that: saturation adsorption time TsThe measuring method comprises the following steps: measuring the penetration curve of the active carbon sampler to radon to obtain the radon-containing concentration of C0The gas is continuously introduced into the activated carbon bed and the radon concentration C of the gas at the outlet is measuredbThe outlet concentration C can be obtained by continuous monitoringbAs a function of time t, i.e. dynamic adsorption breakthrough curves, using the breakthrough curves
Fitting to obtain fitting parameters tau and k, wherein: cbIs the radon outlet concentration (Bq/m)3)，C0Is radon concentration at mouth (Bq/m)3) T is the time (min) for measuring the radon concentration at the outlet, τ is the half-penetration time (min), and k is the rate constant (min)-1) Then substituting tau and k into
The adsorption saturation time T can be obtaineds(min)。
4. The active carbon radon measurement method of claim 1, wherein: the drying in the step 2 is to dry the activated carbon at 120 ℃ for more than 10 hours.
5. An active carbon radon measuring device which characterized in that: it includes nuclear detection instrument and the sampling head, drying tube, rotameter, filter, active carbon radon sample thief and the aspiration pump that connect gradually, be equipped with flow control valve between active carbon radon sample thief and the aspiration pump, the gas that awaits measuring is connected to the one end of sampling head, and the gas stream that awaits measuring admits air through the sampling head after, through drying tube drying, then gets into active carbon radon sample thief after the filter filters, and the active carbon in the active carbon radon sample thief samples the radon in the gas that awaits measuring, and after the sampling, gaseous outflow behind the air pump, nuclear detection instrument is used for measuring gamma ray or the alpha particle that radon and its daughter that the active carbon gathered produced.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113341448A (en) * | 2021-05-31 | 2021-09-03 | 青海省核工业核地质研究院(青海省核工业检测试验中心) | Portable radon measuring instrument for detecting radon concentration in air of public place |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113341448A (en) * | 2021-05-31 | 2021-09-03 | 青海省核工业核地质研究院(青海省核工业检测试验中心) | Portable radon measuring instrument for detecting radon concentration in air of public place |
| CN113341448B (en) * | 2021-05-31 | 2023-08-15 | 青海省核工业核地质研究院(青海省核工业检测试验中心) | Portable radon measuring instrument for detecting radon concentration in air in public place |
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