WO2021238348A1 - 基于固体核径迹的放射性氡、钍射气子体浓度检测方法 - Google Patents

基于固体核径迹的放射性氡、钍射气子体浓度检测方法 Download PDF

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WO2021238348A1
WO2021238348A1 PCT/CN2021/081193 CN2021081193W WO2021238348A1 WO 2021238348 A1 WO2021238348 A1 WO 2021238348A1 CN 2021081193 W CN2021081193 W CN 2021081193W WO 2021238348 A1 WO2021238348 A1 WO 2021238348A1
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concentration
progeny
radon
track density
thoron
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PCT/CN2021/081193
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English (en)
French (fr)
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曹磊
兰长林
吴鹏
王晓涛
党磊
方芳
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北京市化工职业病防治院
兰州大学
生态环境部核与辐射安全中心
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Publication of WO2021238348A1 publication Critical patent/WO2021238348A1/zh

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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
    • G01T1/167—Measuring radioactive content of objects, e.g. contamination
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T5/00—Recording of movements or tracks of particles; Processing or analysis of such tracks
    • G01T5/02—Processing of tracks; Analysis of tracks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • the invention relates to the technical field of solid nuclear track detection, in particular to a solid nuclear track-based method for detecting the concentration of radioactive radon and thoron progeny.
  • the exposure caused by radon and its daughters should be attributed to the additional public exposure caused by natural radiation sources.
  • the increase in natural exposure caused by human activities was included in 4 priority areas of concern and research
  • radioactive hazards rank first: for example, radioactive radon, thoron and their progeny, lung cancer caused by radon is a random effect of ionizing radiation , Its incidence is positively correlated with the cumulative dose of long-term inhalation of radon and its progeny. Radon, thoron and its progeny are the first environmental cause of lung cancer induced by non-smokers.
  • the main methods of common accumulation measurement of radon/thoron decay progeny include solid nuclear track, activated carbon cartridge and electret method.
  • the basic principle of passive accumulation measurement of radon thoron jet gas is carried out by the diffusion chamber body: after the measured radon thoron jet gas enters the measurement chamber, the radon thoron jet gas and its series of decay daughters release ⁇ particles, ⁇ Particles can form damage tracks on the CR-39 solid nuclear track film.
  • the density of damage tracks per unit area has a proportional relationship with the concentration of radon and thoron.
  • the proportional relationship can be used to determine the radiation dose.
  • the existing body core track detection technology has some obvious defects, such as: 1. In the measurement of lower concentration, the data dispersion is high; 2. It can only measure the average level of radon gas or radon progeny concentration. The daughter body has no resolution; 3. When the high permeability filter membrane is used, thoron gas (220Rn) and its daughter body have a great influence on the result.
  • the present invention provides a solid nuclear track-based method for detecting the concentration of radioactive radon and thoron progeny, including the following operations:
  • Step S100 The air containing the target ejaculate (i.e. radon and/or thorium ejaculation) is drawn into the sampling space, and after the target ejaculation and the target ejaculation sub-body reach the radioactive balance, the target is treated in the sampling space Concentration detection of ejaculatory sub-body;
  • target ejaculate i.e. radon and/or thorium ejaculation
  • Step S200 The sampling space is pumped out, and the target ejection gas in the mixed radioactive aerosol is drawn out of the sampling space (that is, the radon ejection gas and thoron ejection gas are pumped out, so that the radon ejection gas progeny Po-218 , Po-214, and thorium progeny Bi-212, Po-212 are left in the sampling space); note that the release of ⁇ particles cannot cause the response of the CR39 solid nuclear track detection element; because the energy of the released ⁇ particles is different, so Its range in the aluminum filter membrane is different, so it is better to attenuate the remaining energy is also different;
  • Step S300 the target ejection sub-body remaining after the air extraction in the sampling space is blocked on the deposited sampling filter;
  • Step S400 deposit the ⁇ particles released by the target ejection sub-body on the sampling filter membrane, and then pass through the sampling diffusion cavity and the aluminum filter membrane to be incident on the CR39 solid nuclear track detection element to form a damage track;
  • Step S500 After the accumulation measurement is completed, take out the CR39 solid nuclear track detection element, measure the track density after etching, and quantitatively analyze the concentration of the target emanation progeny.
  • the target jet includes radon jet and/or thoron jet
  • the target jet daughter includes radon jets and/or thoron jet daughters.
  • the aluminum filter membrane is four aluminum filter membranes with different thicknesses;
  • the aluminum filter membrane with a thickness of 100 ⁇ m forms a background channel
  • the aluminum filter film with a thickness of 1.0-3.0 ⁇ m forms the first channel T I , which can receive radon progeny Po-218, Po-214 alpha particles and thoron progeny Bi-212, Po-212 And finally ensure that the remaining energy of the above-mentioned alpha particles after the attenuation of the thickness of the aluminum filter membrane is 3 ⁇ 5 MeV, so as to form a response on the CR39 solid nuclear track detection element;
  • the aluminum filter film with a thickness of 10.0-15.0 ⁇ m forms the second channel T II , which can receive the alpha particles of the radon progeny Po-214 and the alpha particles of the thoron progeny Po-212, and finally ensure that they pass through the
  • the remaining energy of the alpha particles after the attenuation of the thick aluminum filter membrane is 3 ⁇ 5 MeV, thus forming a response on the CR39 solid nuclear track detection element;
  • the aluminum filter film with a thickness of 20.0-25.0 ⁇ m forms the third channel T III to receive the alpha particles of the thorium progeny Po-212, and finally ensure that the above-mentioned alpha particles after the attenuation of the aluminum filter film of this thickness are left
  • the energy is 3 ⁇ 5MeV, so as to form a response on the CR39 solid nuclear track detection element.
  • the target ejaculate progeny before quantitatively analyzing the concentration of the target ejaculate progeny, it also includes the following operation steps: analyzing and judging the current detected air components, and judging that the current air contains only radon ejaculate (i.e. radon ejaculate). Room), either only contains thoron gas, or contains radon gas and thoron gas.
  • radon ejaculate i.e. radon ejaculate
  • Room either only contains thoron gas, or contains radon gas and thoron gas.
  • Quantitative analysis of the concentration of target ejection sub-body specifically includes the following steps:
  • Step S510 After judgment and analysis, if the current air contains only radon gas (that is, in the radon chamber), decay and accumulate at a preset time, measure the track density on each channel, and calculate the net track of each subbody Density; the net track density of each daughter includes the net track density of Po-218 and the net track density of Po-214;
  • Step S520 Substituting the net track density of each sub-body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th species and the concentration of the sub-body, and correspondingly solve the corresponding net track density of the sub-body C i (t) is the concentration of the i-th seed body in time t; the net track density of Po-218 obtained by the previous steps is used to calculate the daughter body concentration of Po-218; the net track density of Po-214 obtained by the previous steps Solve the progeny concentration of Po-214;
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • C i (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S530 Measure and obtain the mean values of multiple sub-body balance factors F;
  • Step S540 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Po-218, and the progeny concentration of Po-214 into the equilibrium equivalent radon concentration relationship formula, and reverse the progeny concentration of Pb-214 to obtain Pb- Progeny concentration of 214;
  • Step S550 Solve the reduced balance factor of radon daughters.
  • the reduced balance factor of radon daughters is defined as:
  • Quantitative analysis of the concentration of target ejection sub-body specifically includes the following steps:
  • Step S610 After judgment and analysis, if the current air contains only thorium, decay and accumulate through the preset time, measure the track density on each channel, and calculate the net track density of each sub-body;
  • the net track density includes the net track density of Bi-212 and the net track density of Po-212;
  • Step S620 Substituting the net track density of each child body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th species and the child body concentration, and correspondingly solve the corresponding net track density of the child body C i (t) is the concentration of the i-th seed body in time t; the net track density of Bi-212 obtained by the previous steps is used to calculate the daughter body concentration of Bi-212; the net track density of Po-212 obtained by the previous steps Solve the progeny concentration of Po-212;
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • C i (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S630 Measure and obtain the average value of multiple sub-body balance factors F;
  • Step S640 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Bi-212, and the progeny concentration of Po-212 into the equilibrium equivalent thorium concentration relationship formula, and reverse the progeny concentration of Pb-212;
  • Step S650 Solve the definition of reduced balance factor for thoron gas and its daughters.
  • Quantitative analysis of the concentration of target ejection sub-body specifically includes the following steps:
  • Step S710 After judgment and analysis, if the current air contains radon gas and thorium gas, decay and accumulate through the preset time, measure the track density on each channel, and calculate the net track density of each subbody;
  • the net track density of the daughter body includes the net track density of Po-218, the net track density of Po-214, the net track density of Bi-212, and the net track density of Po-212;
  • Step S720 Substituting the net track density of each child body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th nuclide and the child body concentration, and correspondingly solve the corresponding net track density of the child body C i (t) is the concentration of the i-th seed body in time t; the net track density of Po-218 obtained by the previous steps is used to calculate the daughter body concentration of Po-218; the net track density of Po-214 obtained by the previous steps Solve the progeny concentration of Po-214; solve the Bi-212 progeny concentration by the net track density of Bi-212 obtained by the previous steps; solve the progeny concentration of Po-212 by the net track density of Po-212 obtained by the aforementioned steps Body concentration
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • C i (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S730 Measure and obtain the mean values of multiple sub-body balance factors F;
  • Step S740 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Po-218 and the progeny concentration of Po-214 into the equilibrium equivalent radon concentration relationship formula, and reverse the progeny concentration of Pb-214 to obtain Pb- Progeny concentration of 214;
  • the reduced balance factor of radon daughters is defined as:
  • Step S750 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Bi-212, and the progeny concentration of Po-212 into the equilibrium equivalent thorium concentration relationship formula, and reverse the progeny concentration of Pb-212;
  • the air containing radon/thoron is pumped in to block the radon/thoron progeny on the filter membrane of the sampling head, and then The alpha particles released by the daughter are incident on the CR39 solid nuclear track detection element to form a damage track, and the radon/thoron gas is pumped out by the air pump.
  • four aluminum filter membranes with different thicknesses are designed in this program.
  • the energy of each sub-body is attenuated to CR39 and the energy is 3-5MeV to ensure that the CR39 response product is accurate; at the end of the cumulative measurement Then, take out the CR39 solid nuclear track detector, measure the track density after etching, and quantitatively analyze the concentration of radon/thoron gas and its progeny.
  • the above-mentioned measurement method has higher detection efficiency, and can effectively realize radon/thoron gas and sub-body resolution, accumulation or continuous sampling of radon/thoron gas measurement of sub-body.
  • Figure 1 is a schematic diagram of the diameter change of the damage track formed on the CR39 solid nuclear track detection element by ⁇ particles with the energy change under a certain etching condition discovered by the present invention
  • FIG. 2 is a schematic diagram of the principle of alpha particles received on aluminum filter membranes of different thicknesses found in an embodiment of the present invention
  • FIG. 3 is a schematic flow chart of a method for detecting the concentration of radioactive radon and thoron progeny based on solid nuclear tracks according to an embodiment of the present invention
  • FIG. 4 is a schematic structural diagram of a sampling device for detecting the concentration of radioactive radon and thoron progeny based on solid nuclear tracks provided by an embodiment of the present invention
  • Fig. 5 is a schematic diagram of the exploded structure of the sampling device in Fig. 4.
  • Fig. 6 is a schematic diagram of the correlation between the measurement results obtained by the detection method implemented by the method of the present invention and the measurement results obtained from the Tomas three-segment method of the filter membrane.
  • Label 1- sampling space; 2- deposition sampling filter membrane; 3- sampling diffusion cavity; 4- aluminum filter membrane; 5-CR39 solid nuclear track detection element.
  • the method for detecting the concentration of radioactive radon and thorium progeny based on solid nuclear tracks in this embodiment includes the following steps: Air ejected) into the sampling space (that is, in fact a semi-enclosed air sampling space), after the target ejection and the target ejection sub-body reach the radioactive balance, the target ejection sub-body is implemented in the sampling space Concentration detection; step S200: the sampling space is pumped, and the target ejection gas in the mixed radioactive aerosol is pumped out of the sampling space (that is, the radon ejection gas and thoron ejection gas are pumped out, so that the radon ejection gas is specifically ejected Po-218, Po-214, and thorium progeny Bi-212, Po-212 remained in the sampling space); note that the release of ⁇ particles cannot cause the response of the CR39 solid nuclear track detection element; due to the release of the energy of ⁇ particles Different, so its range in the aluminum filter membrane
  • a semi-closed sampling space is designed, and a deposition sampling filter membrane, a sampling diffusion chamber, an aluminum filter membrane and a CR39 solid nuclear track detection element are designed in the sampling space.
  • the specific installation direction is shown in Figure 4, in the sampling space 1 (that is, in the housing of the detection device), it is arranged in sequence from one end to the other in the gas release direction, and a deposition sampling filter membrane 2 and a sampling diffusion chamber are arranged in sequence along the installation direction. 3.
  • the basic principle of the measurement is: the air containing radon thoron jet is fed into the above-mentioned sampling space, while the radon thoron jet is sucked away, and the daughters of radon thoron jet are deposited on the sampling filter membrane, and then in a certain amount of time. During the accumulation time, the radon thoron progeny releases alpha particles through a series of decay progeny.
  • the technical solution of this application can form the most active damage track on the CR-39 solid nuclear track film, which can guarantee higher final detection accuracy; 2. It can only be measured Obtain the average level of radon gas or radon progeny concentration, without distinguishing radon and progeny (the technical solution of this application can receive the decayed alpha particles of each progeny in the four channels above, and extract the radon and thoron ejection gases (Separate), so that only the concentration of radon progeny and thoron progeny can be detected, so as to realize the separate discrimination of progeny); 3.
  • the target jet includes radon jet and/or thoron jet
  • the target jet daughter includes radon jet and/or thoron jet daughter.
  • the aluminum filter membrane consists of four aluminum filter membranes with different thicknesses; among them, the aluminum filter membrane with a thickness of 100 ⁇ m forms a background channel;
  • the aluminum filter film with a thickness of 1.0-3.0 ⁇ m forms the first channel T I , which can receive radon progeny Po-218, Po-214 alpha particles and thoron progeny Bi-212, Po-212 Alpha particles (that is, all four kinds of decayed alpha particles), and finally ensure that the remaining energy of the alpha particles after attenuation by the thickness of the aluminum filter membrane is 3 ⁇ 5 MeV, so as to form a response on the CR39 solid nuclear track detection element ;
  • the aluminum filter film with a thickness of 10.0-15.0 ⁇ m forms the second channel T II , which can receive the alpha particles of the radon progeny Po-214 and the alpha particles of the thoron progeny Po-212, and finally ensure that they pass through the
  • the remaining energy of the alpha particles after the attenuation of the thick aluminum filter membrane is 3 ⁇ 5 MeV, which forms a response on the CR39 solid nuclear track detection element;
  • the aluminum filter film with a thickness of 20.0-25.0 ⁇ m forms the third channel T III to receive the alpha particles of the thorium progeny Po-212, and finally ensure that the above-mentioned alpha particles after the attenuation of the aluminum filter film of this thickness are left
  • the energy is 3 ⁇ 5MeV, so as to form a response on the CR39 solid nuclear track detection element;
  • the first channel T I (aluminum filter film with a thickness of 1.0-3.0 ⁇ m) can be used for radon progeny Po-218, Po-214 and thoron progeny Bi-212 (36%, 6.2 MeV) alpha particle track measurement; the second channel T II (10.0-15.0 ⁇ m thick aluminum filter membrane), to achieve the alpha particle track measurement of the radon progenitor Po-214; the third channel T III (20.0 -25.0 ⁇ m thick aluminum filter membrane), to achieve the measurement of the alpha particle track of the thorium progenitor Po-212; background channel T 0 (100 ⁇ m thick aluminum filter membrane), gas interference elimination and the diameter of the background channel Track deduction.
  • Rn222 and Rn220 are gaseous, but other nuclides are solid, for example: the nuclide Rn222 (gas) decays into Po- 218 (solid state), the above-mentioned Po-218 is solid; after decay, it can form bound and unbound daughters. I don’t need to say too much about the unbound daughters, because the unbound daughters can be formed.
  • the unbound progeny will be pumped away along the air; as for the bound progeny, the radon thoron emission is released through decay, and the Po-218, Po-214 and thoron emission in the radon progeny Bi-212 and Po-212 of the gas progeny; after pumping, the radon progeny Po-218, Po-214 and the Bi-212 and Po-212 of the thoron progeny will be deposited on the sedimentary sampling filter ⁇ The membrane.
  • radioactive mixed aerosols include radon gas, thoron gas, Po-218 and Po-214 of radon gas progeny, Bi-212 and Po-212 of thoron progeny body, among which, radon gas and thoron progeny The gas is pumped away, and the remaining radon progeny and thoron progeny can be detected;
  • R air is the average range, in cm; E is the alpha particle energy, in MeV.
  • R Al is the average range, in ⁇ m; E is the energy of the alpha particles, in MeV.
  • a m is the molecular weight or atomic mass constant, ⁇ is the density, g cm -3 .
  • the aluminum filter membrane designed by the present invention is actually divided into four aluminum filter membranes of different thickness on the circumferential area (as shown in Figure 5, the aluminum filter membrane is actually fan-shaped into four channels). After the aluminum filter membranes of different thicknesses, the energy of each different sub-body is attenuated.
  • the sampler used in the above application has a 4-channel sampling head assembly for the radon/thoron progeny resolution, which can accurately estimate the radon/thoron progeny concentration and closely conform to the requirements of national standards. It is the first in China technology.
  • Po-214 and Po-212 will pass through the second channel T II , and only the 8.8 released by Po-212 on the third channel Alpha particles with MeV energy can reach; since the track density of only Po-212 is formed on the third channel T III , the number of Po-212 on the third channel can be calculated, because of the above Po-218 and Po-214 And among Bi-212 and Po-212 nuclides, only Po-212 has the highest energy, and only Po-212 releases alpha particles with 8.8MeV energy that can reach the third channel (the energy of alpha particles released by other daughter nuclides is too low , Resulting in limited range, so the alpha particles released by other daughter nuclides cannot be shot on the third channel at all), so the number of Po-212 nuclides can be judged based on this.
  • the original 7.7MeV for example: Po-214
  • the energy of Po-214 is 7.7MeV
  • alpha particles begin to undergo radiation attenuation, and first pass through air attenuation (for example, attenuation of 2MeV).
  • the remaining energy is 5.7MeV
  • continue to attenuate through the 10.0-15.0 ⁇ m thick aluminum filter film after calculation and analysis, it is found that the remaining energy of 5.7MeV attenuation through 10.0-15.0 ⁇ m thick aluminum sheet is 3 ⁇ 5MeV energy)
  • the alpha particles deposited (fired) on the CR39 film are exactly the alpha particles with an energy of 3 to 5 MeV.
  • the original 8.8-9MeV (such as Bi-212, the energy of Bi-212 is well known to be 8.8MeV, see Figure 2) alpha particles start to undergo radiation attenuation, first pass air attenuation (air attenuation 2MeV), and then the rest The energy is about 6.6MeV, and then it is attenuated after passing through a 20.0-25.0 ⁇ m thick aluminum sheet; at this time, the alpha particles pass through the thicker aluminum sheet, the more their energy attenuates, and the final attenuation to CR39 film is 3 ⁇ Alpha particles with 5MeV energy.
  • this application designs aluminum sheets (attenuation channels) of different thicknesses and sizes, and finally we get the result that after attenuation through different channels, the final radiation to the CR39 sheet is all alpha particles with energies of 3 to 5 MeV.
  • the researchers configured 4 channels (that is, four aluminum filter membranes) of different thicknesses and sizes.
  • T i to represent the track density value measured on the i-th channel, unit: trs/cm 2 .
  • the first channel T I (referred to as the first channel, that is, the aluminum filter film with a thickness of 1.0-3.0 ⁇ m), realizes the treatment of radon sub-bodies Po-218, Po-214 and thoron sub-bodies Bi-212 (36%, 6.2MeV) ⁇ particle track measurement
  • the second channel T II (referred to as the second channel, that is, 10.0-15.0 ⁇ m thickness of aluminum filter membrane), to achieve the ⁇ particle track measurement of radon progeny Po-214 Particle track measurement
  • the third channel T III (referred to as the third channel, that is, 20.0-25.0 ⁇ m thick aluminum filter membrane), to achieve the measurement of the alpha particle track of the thorium progeny Po-212
  • the background channel T 0 ie 100 ⁇ m
  • the thickness dimension design of the aluminum filter membrane is obtained by an empirical formula (not the core technical point of this application, which will not be repeated), but the energy of all sub-body attenuation through air is fixed (air attenuation 1MeV or 2MeV according to the design). Note that the sub-body track density of the above background channel needs to be deducted:
  • the track density caused by the 8.8MeV alpha particles released by Po-212 measured on T III can be expressed as:
  • the track density caused by the release of 7.7MeV alpha particles from Po-214 measured on T II is expressed as:
  • T I track density measured Po-218 6.0MeV release of ⁇ particles is caused by the expression:
  • T 0 background track density, and used to eliminate the influence of radon gas (Rn-222) and thoron gas (Rn-220).
  • Rn-222 radon gas
  • Rn-220 thoron gas
  • the air containing radon/thoron gas is drawn in to block the radon/thoron progeny on the deposition sampling filter, and then The alpha particles released by the radon/thoron progeny deposited on the deposited sampling filter membrane are energy attenuated by the aluminum filter membranes of different thicknesses, and are incident on the CR39 solid nuclear track detection element to form damage tracks.
  • the radon/thoron radiation The air is pumped out by the air pump. After the accumulation measurement is over, take out the CR39 solid nuclear track detector, measure the track density after etching, and then quantitatively analyze the concentration of radon/thoron progeny.
  • Equilibrium equivalent concentration refers to the concentration when the short-lived progeny is in radioactive equilibrium.
  • the measurement mainly considers the effects of uranium-based progeny and thorium-based progeny nuclides, which is the equilibrium equivalent radon concentration or Equilibrate the equivalent thorium concentration.
  • Alpha potential concentration refers to the total energy of alpha particles released when radon thorium daughter nuclide completely decays into uranium-based nuclide Pb-210 (RaD) or thorium-based nuclide Pb-208 (ThD).
  • RaD uranium-based nuclide
  • ThD thorium-based nuclide
  • the effective diameter of the circular or elliptical track formed by the ⁇ particles of 3 to 5 MeV on the CR39 element is the largest. With good resolution, it can be distinguished and quantitatively measured more accurately, as shown in Figure 1.
  • the target jet progeny Before quantitatively analyzing the concentration of the target jet progeny, it also includes the following steps: Analyze and judge the current detected air components, and determine whether the current air contains only radon jets (that is, in the radon chamber), or only thoron jets. , Or contain radon gas and thoron gas.
  • Quantitative analysis of the concentration of target ejection sub-body specifically includes the following steps:
  • Step S510 After judgment and analysis, if the current air contains only radon gas (that is, in the radon chamber), decay and accumulate at a preset time, and measure the track density on each channel to calculate the net track density of each subbody ;
  • the net track density of the above-mentioned daughters includes the net track density of Po-218 and the net track density of Po-214;
  • Step S520 Substituting the net track density of each sub-body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th species and the concentration of the sub-body, and correspondingly solve the corresponding net track density of the sub-body C i (t) is the concentration of the i-th seed body in time t; the net track density of Po-218 obtained by the previous steps is used to calculate the daughter body concentration of Po-218; the net track density of Po-214 obtained by the previous steps Solve the progeny concentration of Po-214;
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • C i (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S530 Measure and obtain the mean values of multiple sub-body balance factors F;
  • Step S540 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Po-218, and the progeny concentration of Po-214 into the equilibrium equivalent radon concentration relationship formula, and reverse the progeny concentration of Pb-214 to obtain Pb- Progeny concentration of 214;
  • the average value of the equilibrium equivalent radon concentration EECRn is: 1097Bqm -3 h; at the medium concentration, the equilibrium equivalent The average value of the radon concentration EECRn is: 3568Bqm -3 h -1 ; at high concentration, the average value of the equilibrium equivalent radon concentration EECRn is: 7645Bqm -3 h -1 ;
  • Step S550 Solve the reduced balance factor of radon daughters.
  • the reduced balance factor of radon daughters is defined as:
  • the track density of the second channel II mainly comes from Po-214.
  • the quantitative analysis of the concentration of the target ejaculatory progeny specifically includes the following operation steps:
  • Step S610 After judgment and analysis, if the current air contains only thorium, decay and accumulate through the preset time, and measure the track density on each channel to calculate the net track density of each sub-body;
  • the net track density includes the net track density of Bi-212 and the net track density of Po-212;
  • Step S620 Substituting the net track density of each child body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th species and the child body concentration, and correspondingly solve the corresponding net track density of the child body C i (t) is the concentration of the i-th seed body in time t; the net track density of Bi-212 obtained by the previous steps is used to calculate the daughter body concentration of Bi-212; the net track density of Po-212 obtained by the previous steps Solve the progeny concentration of Po-212;
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • Ci (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S630 Measure and obtain the average value of multiple sub-body balance factors F;
  • Step S640 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Bi-212, and the progeny concentration of Po-212 into the equilibrium equivalent thorium concentration relationship formula, and reverse the progeny concentration of Pb-212;
  • Equation 6 Equation 6
  • Step S650 Solve the definition of reduced balance factor for thoron gas and its daughters.
  • the quantitative analysis of the concentration of the target ejaculatory progeny specifically includes the following operation steps:
  • Step S710 After judgment and analysis, if the current air contains radon gas and thorium gas, decay and accumulate through the preset time, and measure the track density on each channel to calculate the net track density of each subbody;
  • the net track density of the daughter body includes the net track density of Po-218, the net track density of Po-214, the net track density of Bi-212, and the net track density of Po-212;
  • Step S720 Substituting the net track density of each child body into the formula for the relationship between the net track density caused by the alpha particles released by the i-th nuclide and the child body concentration, and correspondingly solve the corresponding net track density of the child body C i (t) is the concentration of the i-th seed body in time t; the net track density of Po-218 obtained by the previous steps is used to calculate the daughter body concentration of Po-218; the net track density of Po-214 obtained by the previous steps Solve the progeny concentration of Po-214; solve the Bi-212 progeny concentration by the net track density of Bi-212 obtained by the previous steps; solve the progeny concentration of Po-212 by the net track density of Po-212 obtained by the aforementioned steps Body concentration
  • Si -nuclear is the net track density caused by the alpha particles released by the i-th nuclide, in trs ⁇ cm -2 ;
  • ⁇ is the scale coefficient (sensitivity coefficient) of the solid nuclear track detector, in trs ⁇ Cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ;
  • C i (t) is the concentration of the i-th seed body within t, the unit is kBq ⁇ m -3 ⁇ h -1 ;
  • t is the measurement accumulation time, the unit Is h;
  • Step S730 Measure and obtain the mean values of multiple sub-body balance factors F;
  • Step S740 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Po-218 and the progeny concentration of Po-214 into the equilibrium equivalent radon concentration relationship formula, and reverse the progeny concentration of Pb-214 to obtain Pb- Progeny concentration of 214;
  • the reduced balance factor of radon daughters is defined as:
  • Step S750 Substitute the above-mentioned multiple progeny balance factors, the progeny concentration of Bi-212, and the progeny concentration of Po-212 into the equilibrium equivalent thorium concentration relationship formula, and reverse the progeny concentration of Pb-212;
  • the final inverse solution obtains the concentration of each subbody and the average value of the reduced balance factor, which is the final target calculation result obtained by the technology of the present invention.
  • the balance factor and the equilibrium equivalent (radon) concentration it should be noted that the balance factor F: is the total alpha potential of the radon daughters actually existing in the air and the total alpha potential of the radon daughters when the radon concentration in the air reaches the radioactive equilibrium.
  • Ratio. Equilibrium equivalent (radon) concentration EECRn The activity concentration of radon when radon and its short-lived decay products are in equilibrium and have the same alpha potential concentration as the actual non-equilibrium mixture.
  • the SI unit is Bq ⁇ m -3 .
  • the progeny is called the equilibrium equivalent (radon) potential concentration.
  • the RTM-2100 radon gas meter is used to monitor the radon gas concentration, and the WLM-2000 radon progeny meter to monitor the radon progeny ⁇ potential concentration.
  • the concentration of radon and its progeny shows a consistent change trend.
  • the alpha potential concentration of radon daughters increased, the concentration of radon gas did not change significantly, and the measured balance factor F ranged from 0.15 to 0.53.
  • the radon source of the standard radon chamber comes from Ra-226, and there is a trace amount of Ra-224.
  • the calculation shows:
  • the scale coefficient (sensitivity coefficient) ⁇ of CR39 used in the experiment for ⁇ particle response is about 2.1trs ⁇ cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 , the cumulative time in formula 1 is 48h, and it is calculated by formula (1 ) It can be seen that at low concentrations, the average value of the equilibrium equivalent radon concentration EEC Rn is: 1096.73Bqm -3 h ⁇ 1097Bqm -3 h;
  • the above 32 refers to the average value of the second channel T II value, the third channel value is not considered, where 1 refers to the average value of the T 0 value;
  • 2.1 is the scale coefficient ⁇ , 48 refers to 48 hours; so by the formula 1 Obtain the progeny concentration of Po-214;
  • C Pb-214 is about -362Bqm -3 h -1 , and the absolute value is 362Bqm -3 h -1 ; that is, Pb-214 is a ⁇ -decay daughter.
  • the calculation shows:
  • the scale coefficient (sensitivity coefficient) ⁇ of CR39 response to ⁇ particles used in the experiment is about 2.1 trs ⁇ cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 , and it can be seen from formula 1 that at medium concentration, the equilibrium equivalent radon The average value of the concentration EEC Rn is: 3568Bqm -3 h -1 ;
  • the calculation shows:
  • the scale coefficient (sensitivity coefficient) ⁇ of CR39 used in the experiment for ⁇ particle response is about 2.1 trs ⁇ cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 , it can be seen from formula (1) that when the concentration is high, the balance
  • the average value of the equivalent radon concentration EEC Rn is: 7645Bqm -3 h -1 ;
  • the measured balance factor F is 0.34;
  • the sampling method recommended by the "Standard Measurement Method for Radon in Ambient Air" GB14582-1993 was used to measure the low, medium and high concentrations of radon indoors.
  • the concentration of radon and its daughters were measured.
  • the alpha count rate at 3 moments after the filter is sampled is measured, and the progeny concentrations of 218 Po, 214 Pb and 214 Bi uranium series nuclides are calculated respectively, and the results are listed in the table 4.
  • the radon concentration is consistent with the aerosol dynamics of the daughter 214 Pb (good linear relationship), which can be confirmed from the measurement results obtained by the filter membrane Tomas three-stage method and the method of the present invention, as shown in the figure 6.
  • the correlation coefficient between radon concentration and daughter 214 Pb calculated by the present invention is 99.94%, which shows that this method can improve the reliability of radon and daughter concentration measurement to a certain extent.
  • the relative deviation of the result is shown in Table 4.
  • the maximum deviation is about 13.5%, which shows the feasibility of this method ( The following table is attached table 4).
  • the calculation shows:
  • the scale factor (sensitivity coefficient) ⁇ of CR39's response to alpha particles is approximately 2.1 trs ⁇ cm -2 ⁇ kBq -1 ⁇ m 3 ⁇ h -1 ,
  • the average value of the radon concentration C Rn is: 86.8Bqm -3 h -1 ; the average value of the thoron gas concentration is: 30.8Bqm -3 h -1
  • the main application formula is formula 1;
  • the main application formula is formula 1;
  • the application formula is formula 1.
  • the balance factor is measured radon: 0.38-0.39
  • the balance factor according to formula Formula 2 may be thrust reverser relational formula obtained Pb-214 concentration: Pb-214 is the absolute value of the mean concentration C Pb-214 34.7Bqm -3 h about - 1 ;
  • the measured thoron gas balance factor is 0.0018-0.0918, and the average value is 0.0293.
  • the Pb-212 concentration can be inversely deduced: the Pb-212 concentration range is 3.6-3.9 Bqm -3 h -1 , and the average value is 3.69 Bqm -3 h -1 .

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Abstract

一种基于固体核径迹的放射性氡、钍射气子体浓度检测方法，抽入含氡/钍射气的空气，将氡/钍射气的子体阻留在采样头滤膜上，然后子体释放的α粒子入射至CR39固体核径迹探测元件上形成损伤径迹，同时，氡/钍射气被气泵抽出。设计了四个不同厚度的铝过滤膜，在经过四个不同厚度的铝过滤膜后确保各子体衰减到CR39后能量均为3-5MeV，确保CR39响应积准确；在累积测量结束后，取出CR39固体核径迹探测器，蚀刻后测量径迹密度，定量分析氡/钍射气及其子体的浓度。

Description

基于固体核径迹的放射性氡、钍射气子体浓度检测方法 技术领域
本发明涉及固体核径迹检测技术领域，尤其是涉及一种基于固体核径迹的放射性氡、钍射气子体浓度检测方法。
背景技术
氡及其子体引起的照射应归于天然辐射源引起的公众附加照射，在联合国原子能辐射效应科学委员会UNSCEAR第56届会议中，将人类活动引起的天然照射增加列入4个优先关注和研究领域之一，以报告形式，专门论述了居室中氡及其子体引起体内照射剂量贡献以及放射性核素发射γ射线引起体外照射剂量贡献的复合作用。
2006年，UNSCEAR报告中指出，居民终生(75年)处在氡浓度为100Bq·m-3环境中所致肺癌的超额相对危险因子为0.16。相比于室内环境存在着数种有害物质(例如，甲醛、苯等)，放射性危害居于首位：举例说明，放射性氡、钍射气及其子体，氡所致肺癌属电离辐射的随机性效应，其发生机率与长期吸入氡及其子体的累积剂量正相关，氡、钍射气及其子体的照射是非吸烟者诱发肺癌的首位环境病因。研究人员发现，居室内天然辐射照射对人类健康的影响正在逐步显现，然而降低居室内氡浓度和控制氡及子体危害的核心是实现对居室氡/钍射气及其衰变子体浓度的准确评价和测量。
目前，常见的氡/钍射气衰变子体的累积测量的主要方法包括固 体核径迹、活性炭盒和驻极体方法。研究发现与本申请技术方案最为接近的现有检测方法是：利用CR-39固体核径迹探测器实施的固体核径迹检测技术；目前，采用CR-39固体核径迹探测器(片)及扩散室体对氡钍射气进行被动累积式测量，其基本原理是：所测量的含氡钍射气空气进入测量室后，氡钍射气及其一系列衰变子体释放α粒子，α粒子可在CR-39固体核径迹片上形成损伤径迹，单位面积上的损伤径迹密度与氡钍射气浓度具有比例关系，利用比例关系可测定辐射剂量。但现有的体核径迹检测技术存在一些明显缺陷，例如：1、较低浓度测量中，数据离散性高；2、只能测量得到氡气体或氡子体浓度的平均水平，对氡及子体无分辨；3、采用高渗透率滤膜时，钍射气(220Rn)及其子体对结果影响大。
发明内容
本发明提供的一种基于固体核径迹的放射性氡、钍射气子体浓度检测方法，包括如下操作：
步骤S100：将抽入含目标射气(即氡射气和/或钍射气)的空气到采样空间内，待目标射气及目标射气子体达到放射性平衡后，在采样空间内对目标射气子体实施浓度检测；
步骤S200：对采样空间进行抽气，将混合放射性气溶胶中的目标射气抽出采样空间(即抽气抽走的是氡射气、钍射气，这样具体将氡射气子体Po-218、Po-214、钍射气子体Bi-212、Po-212留在了采样空间内)；注意释放β粒子无法造成CR39固体核径迹探测元件的响应；由于释放α粒子的能量不同，因此 其在铝过滤膜中的射程是不同的，因此最好衰减剩下的能量也不同；
步骤S300：将采样空间中抽气剩下的目标射气子体被阻留在沉积采样滤膜上；
步骤S400：沉积采样滤膜上的目标射气子体释放的α粒子并先后经过采样扩散腔、铝过滤膜入射至CR39固体核径迹探测元件上形成损伤径迹；
步骤S500：在累积测量结束后，取出CR39固体核径迹探测元件，蚀刻后测量径迹密度，定量分析目标射气子体的浓度。
优选的，作为一种可实施方案；目标射气包括氡射气和/或钍射气，且目标射气子体包括氡射气子体和/或钍射气子体。
优选的，作为一种可实施方案；铝过滤膜为四个不同厚度的铝过滤膜；
其中，厚度为100μm厚度的铝过滤膜形成了本底通道；
厚度为1.0-3.0μm厚度的铝过滤膜形成了第一通道T I，实现接收氡射气子体Po-218、Po-214的α粒子以及钍射气子体的Bi-212、Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
厚度为10.0-15.0μm厚度的铝过滤膜形成了第二通道T II，实现接收氡射气子体Po-214的α粒子以及钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～ 5MeV，从而在CR39固体核径迹探测元件上形成响应；
厚度为20.0-25.0μm厚度的铝过滤膜形成了第三通道T III，实现接收钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应。
优选的，作为一种可实施方案；定量分析目标射气子体的浓度之前还包括如下操作步骤：对当前被检测空气组分进行分析判断，判断当前空气中是只含氡射气(即氡室中)，或者只含有钍射气，或者含有氡射气和钍射气。
定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S510：经过判断分析，若当前空气中是只含氡射气(即氡室中)，则通过预设时间衰变累积，测量获得各个通道上的径迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度；
步骤S520：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；
即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
Figure PCTCN2021081193-appb-000001
Figure PCTCN2021081193-appb-000002
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S530：测量得到多个子体平衡因子F均值；
步骤S540：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
平衡当量氡浓度关系公式表述为：
Figure PCTCN2021081193-appb-000003
Figure PCTCN2021081193-appb-000004
步骤S550：求解氡子体的约化平衡因子，氡子体的约化平衡因子定义为：
F Rn＝0.105F Po-218+0.381F Po-214          公式3。
定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S610：经过判断分析，若当前空气中是只含钍射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Bi-212的净径迹密度、Po-212的净径迹密度；
步骤S620：将上述各个子体的净径迹密度代入第i种核素释 放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
Figure PCTCN2021081193-appb-000005
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S630：测量得到多个子体平衡因子F均值；
步骤S640：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
平衡当量钍射气浓度关系公式表述为：
Figure PCTCN2021081193-appb-000006
步骤S650：求解钍射气及子体的约化平衡因子定义，钍射气及子体的的约化平衡因子定义为：F Tn＝0.084F Bi-212
即公式7。
定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S710：经过判断分析，若当前空气中是含氡射气以及钍射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度以及Bi-212的净径迹密度、Po-212的净径迹密度；
步骤S720：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
Figure PCTCN2021081193-appb-000007
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S730：测量得到多个子体平衡因子F均值；
步骤S740：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
平衡当量氡浓度关系公式表述为：
Figure PCTCN2021081193-appb-000008
Figure PCTCN2021081193-appb-000009
求解氡子体的约化平衡因子，氡子体的约化平衡因子定义为：
F Rn＝0.105F Po-218+0.381F Po-214         公式3；
步骤S750：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
平衡当量钍射气浓度关系公式表述为：
Figure PCTCN2021081193-appb-000010
求解钍射气及子体的约化平衡因子定义，钍射气及子体的的约化平衡因子定义为：F Tn＝0.084F Bi-212
即公式7；
本发明实施例至少存在如下方面的技术优势：
在上述技术方案中，环境中氡钍射气及其子体达到放射性平衡后，抽入含氡/钍射气的空气，将氡/钍射气子体阻留在采 样头滤膜上，然后子体释放的α粒子入射至CR39固体核径迹探测元件上形成损伤径迹，氡/钍射气被气泵抽出。另外本方案设计了四个不同厚度的铝过滤膜，在经过四个不同厚度的铝过滤膜后确保各子体衰减到CR39后能量均为3-5MeV，确保CR39响应积准确；在累积测量结束后，取出CR39固体核径迹探测器，蚀刻后测量径迹密度，定量分析氡/钍射气及其子体的浓度。上述测量方法具有更高探测效率，可以有效实现氡/钍射气及子体分辨，累积或连续采样子体的氡/钍射气测量。
附图说明
图1为本发明研究发现的某一蚀刻条件下随能量变化α粒子在CR39固体核径迹探测元件上形成的损伤径迹直径变化示意图；
图2为本发明实施例发现的不同厚度的铝过滤膜上接收的α粒子原理示意图；
图3为本发明实施例提供的基于固体核径迹的放射性氡、钍射气子体浓度检测方法的流程示意图；
图4为本发明实施例提供的基于固体核径迹的放射性氡、钍射气子体浓度检测实施的采样设备结构示意图；
图5为图4中的采样设备爆炸结构示意图。
图6为本发明方法实施的检测方法得到测量结果与从滤膜Tomas三段法得到测量结果的相关性示意图。
标号：1-采样空间；2-沉积采样滤膜；3-采样扩散腔；4-铝过滤膜；5-CR39固体核径迹探测元件。
具体实施方式
如图3所示，本实施例基于固体核径迹的放射性氡、钍射气子体浓度检测方法，包括如下步骤：步骤S100：将抽入含目标射气(即氡射气和/或钍射气)的空气到采样空间内(即实际上为一种半封闭的空气采样空间)，待目标射气及目标射气子体达到放射性平衡后，在采样空间内对目标射气子体实施浓度检测；步骤S200：对采样空间进行抽气，将混合放射性气溶胶中的目标射气抽出采样空间(即抽气抽走的是氡射气、钍射气，这样具体将氡射气子体Po-218、Po-214、钍射气子体Bi-212、Po-212留在了采样空间内)；注意释放β粒子无法造成CR39固体核径迹探测元件的响应；由于释放α粒子的能量不同，因此其在铝过滤膜中的射程是不同的，因此最好衰减剩下的能量也不同；步骤S300：将采样空间中抽气剩下的目标射气子体被阻留在沉积采样滤膜上；步骤S400：沉积采样滤膜上的目标射气子体释放的α粒子并先后经过采样扩散腔、铝过滤膜入射至CR39固体核径迹探测元件上形成损伤径迹；步骤S500：在累积测量结束后，取出CR39固体核径迹探测元件，蚀刻后测量径迹密度，定量分析目标射气子体的浓度。
在本申请的上述技术方案中，其设计了一个半封闭式的采样空间，同时在采样空间内设计了沉积采样滤膜、采样扩散腔、铝过滤膜以及CR39固体核径迹探测元件。具体安装方向如图4所示，在采样空间1(即检测设备的壳体内)内自气体释放方向自一端至另一端依次设置， 沿着设置方向依次设置有沉积采样滤膜2、采样扩散腔3、铝过滤膜4以及CR39固体核径迹探测元件5；同时在采样空间侧壁处设置有供给氡钍射气被抽走的侧壁通孔。
测量的基本原理是：将含氡钍射气空气送入到上述采样空间内，同时氡钍射气被抽气吸走，氡钍射气的子体则被沉积采样滤膜上，此后在一定的累积时间内，氡钍射气子体经过一系列衰变子体释放α粒子，然而本申请设计了四个衰减通道(即不同厚度的铝过滤膜形成的通道)，这样不同类型子体释放的α粒子在经过对应厚度的铝过滤膜衰减后其能量所剩3～5MeV能量，这样可在CR-39固体核径迹片(即CR39固体核径迹探测元件)上形成最为积极的损伤径迹(为后续进行子体浓度计算检测提升了可靠的高精度数据基础)，利用上述单位面积上的损伤径迹密度求解各个子体的净径迹密度；然后定量分析目标射气子体的浓度(具体通过平衡当量氡浓度关系公式，反推某子体浓度以及约化平衡因子)；因此说，本发明的技术方案其克服了现有技术中固体核径迹检测技术存在的技术缺陷，例如：1、较低浓度测量中，数据离散性高(本申请技术方案可在CR-39固体核径迹片上形成最为积极的损伤径迹，其可保障最终检测精度更高)；2、只能测量得到氡气体或氡子体浓度的平均水平，对氡及子体无分辨(本申请技术方案可在四个通道上述接收各个子体衰变的α粒子，并且将氡射气以及钍射气抽出去(分离出去)，从而只检测氡射气子体、钍射气子体的浓度，实现对子体的单独分辨)；3、采用高渗透率滤膜时，钍射气(220Rn)及其子体对结果影响大(本申请技术方案避免了高渗透 率滤膜，同样也避免了因高渗透率滤膜产生的技术缺陷)。目标射气包括氡射气和/或钍射气，且目标射气子体包括氡射气子体和/或钍射气子体。需要说明的是，对采样空间进行抽气处理，这样经过采样空间进行抽气，抽气剩下的就是氡/钍射气子体(即氡射气子体、钍射气子体)。
铝过滤膜为四个不同厚度的铝过滤膜；其中，厚度为100μm厚度的铝过滤膜形成了本底通道；
厚度为1.0-3.0μm厚度的铝过滤膜形成了第一通道T I，实现接收氡射气子体Po-218、Po-214的α粒子以及钍射气子体的Bi-212、Po-212的α粒子(即四种衰变的α粒子都有)，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
厚度为10.0-15.0μm厚度的铝过滤膜形成了第二通道T II，实现接收氡射气子体Po-214的α粒子以及钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
厚度为20.0-25.0μm厚度的铝过滤膜形成了第三通道T III，实现接收钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
在本实施中，第一通道T I(1.0-3.0μm厚度的铝过滤膜)，实现对氡射气子体Po-218、Po-214和钍射气子体Bi-212(36％，6.2MeV) 的α粒子径迹测量；第二通道T II(10.0-15.0μm厚度的铝过滤膜)，实现对氡射气子体Po-214的α粒子径迹测量；第三通道T III(20.0-25.0μm厚度的铝过滤膜)，实现对钍射气子体Po-212的α粒子径迹测量；本底通道T 0(100μm厚度的铝过滤膜)，气体干扰排除及对本底通道的径迹扣除。
在本实施中，上述氡射气在经过衰变放射过程中，气体的只有是Rn222和Rn220是气体状态的，然而其他的核素是固态的，例如：核素Rn222(气体)衰变成Po-218(固态)，上述Po-218就是固态的；经过衰变可以形成结合态子体和非结合态子体，关于非结合态子体就不用太多赘述了，因为非结合态子体可以形成了团簇，然后非结合态子体就会顺着空气被抽走了；关于结合态子体，氡钍射气经过衰变释放，氡射气子体中的Po-218、Po-214以及钍射气子体的Bi-212、Po-212；在进行抽气后，氡射气子体Po-218、Po-214以及钍射气子体的Bi-212、Po-212会沉积在沉积采样滤膜上。上述放射性混合气溶胶包括氡射气、钍射气，氡射气子体的Po-218、Po-214、钍射气子体的Bi-212、Po-212，其中，氡射气、钍射气被抽走了，剩下的氡射气子体，钍射气子体可以进行检测；
如图1所示，我方研究发现了上述某一蚀刻条件下随能量变化α粒子在CR39固体核径迹探测元件上形成的损伤径迹直径变化示意图；我方研究人员基于以上研究发现，3～5MeV能量的α粒子在CR39固体核径迹探测元件(即简称CR39元件或CR39片子)上形成圆形或椭圆形径迹的有效直径最大，分辨率好，可较为准确的加以区分并定量 测量。基于上述认识，即3～5MeV能量的α粒子在CR39片子上的响应最好，因此针对不同的子体设计出不同厚度的铝过滤膜；需要保障无论何种子体衰变释放的α粒子，最终经过不同厚度铝过滤膜能量衰减后的α粒子到达CR39片子都只剩下都3～5MeV能量；即保障不同子体释放的α粒子在经过不同厚度的铝过滤膜后(即经过铝滤过率能量衰减后)在CR39片子上得到最好的响应(最后保障每个通道上的α粒子都是3～5MeV能量的α粒子)。
另外，我方研究人员对α粒子射程以及衰减规律进行了分析，分析结果如下：
研究发现能量范围在4～8MeV之间的α粒子在空气中的射程与能量的经验公式可表述为：
Figure PCTCN2021081193-appb-000011
其中，R air为平均射程，单位：cm；E为α粒子能量，单位MeV。
研究还发现能量范围在4～10MeV之间的α粒子在铝中的射程与能量的经验公式可表述为：
Figure PCTCN2021081193-appb-000012
其中，R Al为平均射程，单位：μm；E为α粒子能量，单位MeV。A m为分子量或原子质量常数，ρ为密度，g cm -3。
基于以上认识，我方研究设计了四个不同厚度的铝过滤膜(即四 个通道)，设计要求保障氡射气子体、钍射气子体释放的α粒子，先后经过采样扩散腔(一段空气能量衰减一小部分)、不同厚度铝过滤膜(纯铝介质中能量衰减一大部分)最终入射至CR39固体核径迹探测元件上(即最终衰减到CR39的α粒子能量仅剩下3～5MeV能量)形成最优化最积极准确的损伤径迹。本发明设计了的铝过滤膜其实际上在圆周面积上被分割四个不同厚度的铝过滤膜(如图5所示，铝过滤膜其实际上被扇形分割成四种通道)，在经过四个不同厚度的铝过滤膜后确保各个不同子体的能量进行衰减。上述应用的采样器，其氡/钍射气子体分辨设置具有4通道的采样头组件，较为准确的估计了氡/钍射气子体浓度，与国家标准要求紧密贴合，在国内属于首创技术。
分析上述图2可知，所有子体都穿过本底通道后才能进入其他通道；首先，氡射气，钍射气都被抽走了，这样第一通道T I上原则上会有Po-218、Po-214以及钍射气的Bi-212、Po-212穿过，第二通道T II上原则上会有Po-214以及Po-212穿过，第三通道上只有Po-212释放的8.8MeV能量的α粒子能够到达；由于第三通道T III上形成只有Po-212的径迹密度，那么就可以推算出第三通道上的Po-212的数量，因为上述Po-218、Po-214以及Bi-212、Po-212核素中只有Po-212能量最高，只有Po-212其释放的8.8MeV能量的α粒子能够到达第三通道上(其他子体核素释放的α粒子能量太低，导致射程有限，所以其他子体核素释放的α粒子根本射不到第三通道上)，所以据此可以判断出Po-212核素的数量。
如图2所示，关于释放能量衰减的研究：因为各个子体不同，所以其释放的α粒子的能量是不一样的，但是本发明设计要求从沉积采样滤膜上他发射到CR39上面的那个距离是一定的(根据不同子体释放α粒子的射程固定推荐设计四个不同厚度的铝过滤膜)，因此本申请设计四个通道；本实施例设计了不同厚度的铝片以适应不同的子体放射，以保证辐射到预设铝过滤膜上对应接收衰减后的α粒子的能量正好都是3～5MeV能量的α粒子；举例说明，1.0-3.0μm厚度的铝过滤膜(或称铝片)是针对Po-218、Bi-212设计的，因为Po-218、Bi-212他的能量在6.0到6.2MeV之间，这样的话Po-218、Bi-212经过空气，α粒子发射经过空气后α粒子也会损失一部分能量(即α能量，计算空气大概损失1MeV)，α粒子继续发射经过很薄的铝片(即1.0-3.0μm的铝过滤膜)，经过该第一通道继续能量继续衰减，最后衰减得到正好那个3～5MeV能量的α粒子；然而由于3～5MeV能量的α粒子响应最高。
同时举例说明，原7.7MeV(例如：Po-214，众所周知Po-214的能量是7.7MeV，参见图2)的α粒子开始实施放射衰减，先经过空气衰减(例如衰减2MeV)这样的话(此时剩下能量为5.7MeV)，继续经过10.0-15.0μm厚的铝过滤膜继续衰减(经过计算分析发现5.7MeV经过10.0-15.0μm厚的铝片衰减剩下的能量为3～5MeV能量)，最后沉积(射)在CR39片子的α粒子正好是3～5MeV能量的α粒子。
同时再举例说明，原8.8-9MeV(例如Bi-212，众所周知Bi-212的能量是8.8MeV，参见图2)的α粒子开始实施放射衰减，先经过空 气衰减(空气衰减2MeV)，然后剩下能量为6.6MeV左右呢，然后经过20.0-25.0μm厚的铝片再进行衰减；此时α粒子经过厚度更厚的铝片后，其能量衰减也越多，最后衰减射到CR39片子是3～5MeV能量的α粒子。
本申请技术方案，本申请设计了不同厚度的尺寸的铝片(衰减通道)，最终我们得到结果是经过不同通道衰减后，最后辐射到CR39片子都是3～5MeV能量的α粒子。
综上分析，研究人员配置不同厚度尺寸的4个通道(即四个铝过滤膜)。定义T i表示第i个通道上测量到的径迹密度值，单位：trs/cm 2。在实际的实施例中，第一通道T I(简称第一通道，即1.0-3.0μm厚度的铝过滤膜)，实现对氡射气子体Po-218、Po-214和钍射气子体Bi-212(36％，6.2MeV)的α粒子径迹测量；第二通道T II(简称第二通道，即10.0-15.0μm厚度的铝过滤膜)，实现对氡子体Po-214的α粒子径迹测量；第三通道T III(简称第三通道，即20.0-25.0μm厚度的铝过滤膜)，实现对钍子体Po-212的α粒子径迹测量；本底通道T 0(即100μm厚度的铝过滤膜)，气体干扰排除及对本底通道的径迹密度扣除。上述铝过滤膜的厚度尺寸设计则由经验公式获得(非本申请核心技术点，对此不再赘述)，然而所有子体经过空气衰减能量都是固定的(根据设计空气衰减1MeV或2MeV)。注意上述本底通道的子体径迹密度需要进行扣除：
T III上测得Po-212释放8.8MeV的α粒子引起的径迹密度可以表述为：
S Po-212＝T III；S Bi-212＝1.563×T III
T II上测得Po-214释放7.7MeV的α粒子引起的径迹密度表述为：
S Po-214＝T II–T III
T I上测得Po-218释放的6.0MeV的α粒子引起的径迹密度表述为：
S Po-218＝T I–T II+T III–[1.563×T III]＝T I–T II–0.563×T III
T 0，本底径迹密度，并用于对氡气(Rn-222)和钍射气(Rn-220)影响的排除。在T I、T II和T III径迹结果中扣除T 0，获得各通道净径迹密度(注意此时得到是各通道净径迹密度，不是径迹密度)；上述应用方法为极差法。
需要说明的是，环境中氡钍射气及其子体达到放射性平衡后，抽入含氡/钍射气的空气，将氡/钍射气的子体阻留在沉积采样滤膜上，然后沉积在沉积采样滤膜上的氡/钍射气子体释放的α粒子经过不同厚度的铝过滤膜能量衰减，入射至CR39固体核径迹探测元件上形成损伤径迹，同时，氡/钍射气被气泵抽出。在累积测量结束后，取出CR39固体核径迹探测器，蚀刻后测量得到径迹密度，然后再定量分析氡/钍射气子体的浓度。
然而在计算氡/钍射气子体的浓度，需要引入一个平衡因子的概念，在进氡射气子体/钍射气子体的浓度测量时，实际上是通过平衡因子反推推导计算的，具体方法如下：
根据理论分析：平衡当量浓度(EEC)是指实际存在短寿命子体处于放射性平衡时的浓度，测量中主要考虑铀系子体及钍系子体核素的影响，即为平衡当量氡浓度或平衡当量钍浓度。α潜能浓度是指氡 钍子体核素完全衰变为铀系核素Pb-210(RaD)或钍系核素Pb-208(ThD)时，所释放α粒子的能量总和。处于平衡状态时，铀系和钍系短寿命子体物理量的衰变特性列入表1。
表1 处于平衡状态时，铀系和钍系短寿命子体物理量的衰变特性
Figure PCTCN2021081193-appb-000013
注：
Figure PCTCN2021081193-appb-000014
和
Figure PCTCN2021081193-appb-000015
采用固体核径迹方法测量α粒子损伤径迹时，根据能量权窗理论，在某一蚀刻条件下，3～5MeV的α粒子在CR39元件上形成圆形或椭圆形径迹的有效直径最大，分辨率好，可较为准确的加以区分并定量测量，见图1。
定量分析目标射气子体的浓度之前还包括如下操作步骤：对当前被检测空气组分进行分析判断，判断当前空气中是只含氡射气(即氡室中)，或者只含有钍射气，或者含有氡射气和钍射气。
定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S510：经过判断分析，若当前空气中是只含氡射气(即氡室中)，则通过预设时间衰变累积，测量获得各个通道上的径迹密度求解各子体的净径迹密度；上述各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度；
步骤S520：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；
即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
Figure PCTCN2021081193-appb-000016
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S530：测量得到多个子体平衡因子F均值；
步骤S540：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
根据表1数据可知，平衡当量氡浓度关系公式表述为：
Figure PCTCN2021081193-appb-000017
Figure PCTCN2021081193-appb-000018
需要说明的是，上述公式2中
Figure PCTCN2021081193-appb-000019
氡气体被抽出，因而Rn-222释放的α粒子未形成CR39响应；同时，铀系衰变链上的子体Po-218衰变为Pb-214，Pb-214衰变为Bi-214，Bi-214衰变为Po-214，历经1次α衰变和2次β衰变，上述Pb-214和Bi-214的β衰变对CR39无影响，即径迹贡献来源于Po-218和Po-214；关于各个浓度范围内，平衡当量氡浓度EECRn的均值都是一种整体浓度监测设备获得的测量数据，举例说明，在低浓度时，平衡当量氡浓度EECRn的均值为：1097Bqm -3h；中浓度时，平衡当量氡浓度EECRn的均值为：3568Bqm -3h -1；高浓度时，平衡当量氡浓度EECRn的均值为：7645Bqm -3h -1；
步骤S550：求解氡子体的约化平衡因子，氡子体的约化平衡因子定义为：
F Rn＝0.105F Po-218+0.381F Po-214       公式3；
另外验证一下，需要说明的是，因此，氡子体Po-218和Po-214的浓度与第一通道I上测量到CR39径迹密度的关系表述为：
Figure PCTCN2021081193-appb-000020
Figure PCTCN2021081193-appb-000021
同理可得，第二通道II的径迹密度主要来自Po-214。
Figure PCTCN2021081193-appb-000022
在本发明实施例的具体技术方案中，定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S610：经过判断分析，若当前空气中是只含钍射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度求解各子体的净径迹密度；上述各子体的净径迹密度包括Bi-212的净径迹密度、Po-212的净径迹密度；
步骤S620：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
Figure PCTCN2021081193-appb-000023
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度， 单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S630：测量得到多个子体平衡因子F均值；
步骤S640：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
根据表1数据可知，平衡当量钍射气浓度关系公式表述为：式6；
Figure PCTCN2021081193-appb-000024
需要说明的是，钍射气被抽出，因而Rn-220释放的α粒子未形成CR39响应。钍系衰变链上，Bi-212经β衰变至Po-212的分支比为64％，Po-212半衰期极短，仅为299ns，Po-212经α衰变为稳定核素Pb-208，可将其视为与Bi-212同时释放α粒子，则Bi-212衰变时，以64％几率放出8.8MeV的α粒子，以36％几率释放6.2MeV的α粒子而衰变为Tl-208。根据表1数据，可将平衡当量钍射气浓度EECTn表述为：
Figure PCTCN2021081193-appb-000025
即上述公式6；
步骤S650：求解钍射气及子体的约化平衡因子定义，钍射气及子体的的约化平衡因子定义为：F Tn＝0.084F Bi-212
即公式7；
另外验证一下，上述第三通道III的径迹密度来自Bi-212的α衰变子体Po-212，则
Figure PCTCN2021081193-appb-000026
(即公式8)
在本发明实施例的具体技术方案中，定量分析目标射气子体的浓度，具体包括如下操作步骤：
步骤S710：经过判断分析，若当前空气中是含氡射气以及钍射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度求解各子体的净径迹密度；上述各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度以及Bi-212的净径迹密度、Po-212的净径迹密度；
步骤S720：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
Figure PCTCN2021081193-appb-000027
其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数(灵敏系数)，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
步骤S730：测量得到多个子体平衡因子F均值；
步骤S740：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
根据表1数据可知，平衡当量氡浓度关系公式表述为：
Figure PCTCN2021081193-appb-000028
Figure PCTCN2021081193-appb-000029
求解氡子体的约化平衡因子，氡子体的约化平衡因子定义为：
F Rn＝0.105F Po-218+0.381F Po-214         公式3；
步骤S750：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
根据表1数据可知，平衡当量钍射气浓度关系公式表述为：
Figure PCTCN2021081193-appb-000030
求解钍射气及子体的约化平衡因子定义，钍射气及子体的的约化平衡因子定义为：F Tn＝0.084F Bi-212
即公式7；
综上本发明实施例涉及的技术方案其最终反推求解得到了各子体的浓度以及约化平衡因子的均值，这是本发明技术最终得到的目标计算结果。关于平衡因子以及平衡当量(氡)浓度需要说明的是，平衡因子F:是空气中实际存在的氡子体的总α潜能与该空气中跟氡浓度达到放射性平衡时的氡子体总α潜能之比。平衡当量(氡)浓度EECRn：氡与其短寿命衰变产物处于平衡状态，并具有与实际非平衡混合物相同的α潜能浓度时氡的活度浓度，SI单位为Bq·m -3。对子体称为平衡当量(氡)潜能浓度。
下面对本发明上述技术方案配合具体应用案例进行说明：
实验案例一
标准氡室内，分别采用RTM-2100氡气体测量仪监测氡气体浓度，WLM-2000氡子体测量仪监测氡子体α潜能浓度。未通入气溶胶时，氡及其子体的浓度呈一致变化趋势。通入气溶胶后，氡子体α潜能浓度升高，氡气体的浓度变化差异不明显，测量得到的平衡因子F范围在0.15至0.53之间。标准氡室的氡源来自Ra-226，存在微量Ra-224，可以认为衰变生成的钍系子体Bi-212浓度很低，其释放的α粒子不致引起CR39的响应，则不需考虑第三通道T III的测量计数，因此此时的净径迹密度S Po-214＝T II；
S Po-218＝T I-T II。
测量及数据处理结果如下：
在低浓度时，平衡氡子体浓度与刻度实验结果如下表1：
表1低浓度时(900～1300Bq/m 3h)，氡子体浓度与净径迹密度刻度实验结果(时间48h)
Figure PCTCN2021081193-appb-000031
依据测量数据，计算可知：
1、实验采用的CR39对α粒子响应的刻度系数(灵敏系数)ε约为2.1trs·cm -2·kBq -1·m 3·h -1，公式1中累计时间为48h，由式(1)可知，低浓度时，平衡当量氡浓度EEC Rn的均值为：1096.73Bqm -3h≈1097Bqm -3h；
2、Po-214累积浓度均值为C Po-214＝(32-1)/2.1≈15.4kBq·m -3，除以48个小时，Po-214的子体浓度约为321Bqm -3h -1；其中上述32是指第二通道T II值的均值，第三通道数值不考虑，其中的1指T 0值的均值；2.1为刻度系数ε，48是指48小时；这样由该公式1可以获得Po-214的子体浓度；
3、Po-218累积浓度均值为C Po-218＝(93-32-1)/2.1≈29.37kBq·m -3，除以48个小时，Po-218的子体浓度约为612Bqm -3h -1；其中上述93是 指第一通道T I值的均值，32是指第二通道T II值的均值，第三通道数值不考虑，其中的1指T 0值的均值；2.1为刻度系数ε，48是指48小时；这样由该公式1可以获得Po-218的子体浓度；
4、测量得平衡因子F均值(0.41+0.25+0.35)/3＝0.34；
5、依据公式2平衡当量氡浓度EEC Rn，实际上也反应了平衡因子的关系；即平衡当量氡浓度EEC Rn为测量得平衡因子F均值即0.34；由此可反推得到Pb-214浓度：0.34＝0.105×612+0.381×321+0.514×C Pb-214可知：平衡时，反推得到Pb-214浓度均值为C Pb-214约为-362Bqm -3h -1，取其绝对值为362Bqm -3h -1；即Pb-214是β衰变子体，为保持平衡关系，计算时其C Pb-214值为负，最终求解应当取其浓度均值的绝对值即为362Bqm -3h -1。上述C Pb-214在公式2计算过程如下：上述C Pb-214的浓度均值绝对值为{0.105×612+0.381×321-0.34}除以0.514最终等于362Bqm -3h -1；在公式2中，因Bi-214会立即衰变成Po-214,所以代入公式2中与0.381份额匹配的是Po-214的321Bqm -3h -1。
6、约化平衡因子均值：F Rn＝0.105×(605/1097)+0.381×(294/1097)＝0.170；这样根据上述公式3可以计算得到该约化平衡因子的均值。
实验案例2：中浓度时，平衡氡子体浓度与刻度实验结果表2：
表2 中浓度时(3300～3900Bq/m 3h)，氡及子体浓度与净径迹密度刻度实验结果(时间10h)
Figure PCTCN2021081193-appb-000032
Figure PCTCN2021081193-appb-000033
依据测量数据，计算可知：
1、实验采用的CR39对α粒子响应的刻度系数(灵敏系数)ε约为2.1trs·cm -2·kBq -1·m 3·h -1，由公式1可知，中浓度时，平衡当量氡浓度EEC Rn的均值为：3568Bqm -3h -1；
2、Po-214累积浓度均值为C Po-214＝(23-1)/2.1≈10.25kBq·m -3，除以10个小时，即浓度约为1025Bqm -3h -1；
3、Po-218累积浓度均值为C Po-218＝(62-23-1)/2.1≈17.72kBq·m -3，除以10个小时，即浓度约为1772Bqm -3h -1；
4、测量得平衡因子F均值(0.31+0.35+0.43)/3＝0.36；
5、依据公式2平衡因子关系可得到Pb-214浓度：0.36＝0.105×1772+0.381×1025+0.514×C Pb-214可知：Pb-214浓度均值绝对值为C Pb-214约为1121Bqm -3h -1；即C Pb-214的浓度均值绝对值为{0.105×1772+0.381×1025-0.34}除以0.514最终等于1121Bqm -3h -1；注意在公式2中，因Bi-214会立即衰变成Po-214,所以代入公式2中与0.381份额匹配的是Po-214的1025Bqm -3h -1；
6、约化平衡因子均值：F Rn＝0.105×(1772/3568)+0.381× (1025/3568)＝0.162；这样根据上述公式3可以计算得到该约化平衡因子的均值。
实验案例3：高浓度时，平衡氡子体浓度与刻度实验结果表3：
表3 高浓度时(6500～8300Bq/m 3h)，氡及子体浓度与净径迹密度刻度实验结果(时间5h)
Figure PCTCN2021081193-appb-000034
依据测量数据，计算可知：
1、实验采用的CR39对α粒子响应的刻度系数(灵敏系数)ε约为2.1trs·cm -2·kBq -1·m 3·h -1，由式(1)可知，高浓度时，平衡当量氡浓度EEC Rn的均值为：7645Bqm -3h -1；
2、Po-214累积浓度均值为C Po-214≈(19-1)/2.1＝8.89kBq·m -3，除以5个小时，即浓度约为1777Bqm -3h -1；其中上述19是指第二通道T II值的均值，第三通道数值不考虑，其中的1指T 0值的均值；2.1为刻度系数ε，5是指5小时；这样由该公式1可以获得Po-214的子体浓度；
3、Po-218累积浓度均值为C Po-218≈(69-19-1)/2.1＝23.17kBq·m -3，除以5个小时，即浓度约为4635Bqm -3h -1；其中上述69是指第一通道T I值的均值，19是指第二通道T II值的均值，第三通道数值不考虑，其中的1指T 0值的均值；2.1为刻度系数ε，5是指5小时；这样由该公式1可以获得Po-218的子体浓度；
4、测量得平衡因子F为0.34；
5、依据公式2平衡因子关系可得到Pb-214浓度：0.34＝0.105×4635+0.381×1777+0.514×C Pb-214：Pb-214浓度均值为C Pb-214约为2263Bqm -3h -1；
6、约化平衡因子均值：F Rn＝0.105×(4635/7645)+0.381×(1777/7645)＝0.152；这样根据上述公式3可以计算得到该约化平衡因子的均值。
关于本发明应用的检测方法的实验数据验证说明：
为验证本发明中氡及子体浓度测量的具体实施例，同时采用《环境空气中氡的标准测量方法》GB14582-1993推荐的抽气滤膜采样方法对氡室内低浓度、中浓度和高浓度氡浓度及其子体浓度进行了测量。根据氡子体浓度测量的Tomas三段法原理，测量滤膜采样后3个时刻的α计数率，分别计算 218Po、 214Pb和 214Bi铀系核素的子体浓度，将结果列入表4。
表4 滤膜Tomas三段法与本发明测量及计算结果的比较
Figure PCTCN2021081193-appb-000035
Figure PCTCN2021081193-appb-000036
放射性平衡条件下，氡浓度与子体 214Pb的气溶胶动力学行为具有一致性(良好线性关系)，从滤膜Tomas三段法及本发明方法获得的测量结果中均可以得到证实，见图6，本发明计算得到的氡浓度与子体 214Pb的相关系数为99.94％，说明了该方法在一定程度上提高氡及子体浓度测量的可靠性。取滤膜Tomas三段法与RTM-2100氡气体测量仪测量平衡氡浓度相近结果比较，得到结果的相对偏差值见附表4，最大偏差约为13.5％，说明了这一方法的可行性(下表为附表4)。
Figure PCTCN2021081193-appb-000037
实验案4：某地下室内，温湿度较大，氡钍射气具有积聚条件。采用德国RTM-2100氡/钍射气气体测量仪，测量地下室内氡/钍射气浓度，结果见表5。
表5 累积测量氡钍射气与净径迹密度实验结果(时间10days)
Figure PCTCN2021081193-appb-000038
Figure PCTCN2021081193-appb-000039
依据测量数据，计算可知：
1、CR39对α粒子响应的刻度系数(灵敏系数)ε约为2.1trs·cm -2·kBq -1·m 3·h -1，
2、放射性平衡时，氡浓度C Rn的均值为：86.8Bqm -3h -1；钍射气浓度的均值为：30.8Bqm -3h -1
2、Po-214累积浓度为C Po-214≈(33-18-1)/2.1＝6.67kBq·m -3，这里计算除以时间应当是240小时即10day,浓度约为27.8Bqm -3h -1；主要应用公式为公式1；
3、Po-218累积浓度为C Po-218≈(63-18-0.563×13-1)/2.1＝17.47kBq·m -3，这里计算除以时间应当是240小时即10day，浓度约为72.8Bqm -3h -1；主要应用公式为公式1；
4、Bi-212累积浓度为C Bi-212≈(1.563×13-1)/2.1＝9.76kBq·m -3，除以时间应当是240，即浓度约为40.7Bqm -3h -1；主要应用公式为公式1。
5、测量得到氡平衡因子为：0.38-0.39，依据式公式2平衡因子关系公式可反推得到Pb-214浓度：Pb-214浓度均值绝对值为C Pb-214约为34.7Bqm -3h -1；
6、测量得到钍射气平衡因子为：0.0018-0.0918，均值为0.0293。依据式公式6平衡因子关系公式，可反推得到Pb-212浓度：Pb-212浓度范围为3.6-3.9Bqm -3h -1，均值为3.69Bqm -3h -1。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (7)

  1. 一种基于固体核径迹的放射性氡、钍射气子体浓度检测方法，其特征在于，包括如下操作步骤：
    步骤S100：将抽入含目标射气的空气到采样空间内，待目标射气及目标射气子体达到放射性平衡后，在所述采样空间内对目标射气子体实施浓度检测；
    步骤S200：对所述采样空间进行抽气，将所述混合放射性气溶胶中的目标射气抽出所述采样空间；
    步骤S300：将所述采样空间中抽气剩下的目标射气子体被阻留在沉积采样滤膜上；
    步骤S400：所述沉积采样滤膜上的目标射气子体释放的α粒子并先后经过采样扩散腔、铝过滤膜入射至CR39固体核径迹探测元件上形成损伤径迹；
    步骤S500：在累积测量结束后，取出所述CR39固体核径迹探测元件，蚀刻后测量径迹密度，定量分析目标射气子体的浓度。
  2. 根据权利要求1所述的基于固体核径迹的放射性氡、钍射气子体浓度检测方法，其特征在于，所述目标射气包括氡射气和/或钍射气，且所述目标射气子体包括氡射气子体和/或钍射气子体。
  3. 根据权利要求2所述的基于固体核径迹的放射性氡、钍 射气子体浓度检测方法，其特征在于，所述铝过滤膜为四个不同厚度的铝过滤膜；
    其中，厚度为100μm厚度的铝过滤膜形成了本底通道；
    厚度为1.0-3.0μm厚度的铝过滤膜形成了第一通道T I，实现接收氡射气子体Po-218、Po-214的α粒子以及钍射气子体的Bi-212、Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
    厚度为10.0-15.0μm厚度的铝过滤膜形成了第二通道T II，实现接收氡射气子体Po-214的α粒子以及钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应；
    厚度为20.0-25.0μm厚度的铝过滤膜形成了第三通道T III，实现接收钍射气子体Po-212的α粒子，并最终保证经过该厚度铝过滤膜衰减后的上述α粒子所剩能量为3～5MeV，从而在CR39固体核径迹探测元件上形成响应。
  4. 根据权利要求3所述的基于固体核径迹的放射性氡、钍射气子体浓度检测方法，其特征在于，所述定量分析目标射气子体的浓度之前还包括如下操作步骤：对当前被检测空气组分进行分析判断，判断当前空气中是只含氡射气，或者只含有钍射气，或者含有氡射气和钍射气。
  5. 根据权利要求4所述的基于固体核径迹的放射性氡、钍 射气子体浓度检测方法，其特征在于，所述定量分析目标射气子体的浓度，具体包括如下操作步骤：
    步骤S510：经过判断分析，若当前空气中是只含氡射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度；
    步骤S520：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；
    即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
    Figure PCTCN2021081193-appb-100001
    其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
    步骤S530：测量得到多个子体平衡因子F均值；
    步骤S540：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
    所述平衡当量氡浓度关系公式表述为：
    Figure PCTCN2021081193-appb-100002
    步骤S550：求解氡子体的约化平衡因子，所述氡子体的约化平衡因子定义为：
    F Rn＝0.105F Po-218+0.381F Po-214     公式3。
  6. 根据权利要求4所述的基于固体核径迹的放射性氡、钍射气子体浓度检测方法，其特征在于，
    所述定量分析目标射气子体的浓度，具体包括如下操作步骤：
    步骤S610：经过判断分析，若当前空气中是只含钍射气，则通过预设时间衰变累积，测量获得各个通道上的径迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Bi-212的净径迹密度、Po-212的净径迹密度；
    步骤S620：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
    即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
    Figure PCTCN2021081193-appb-100003
    Figure PCTCN2021081193-appb-100004
    其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
    步骤S630：测量得到多个子体平衡因子F均值；
    步骤S640：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
    所述平衡当量钍射气浓度关系公式表述为：
    Figure PCTCN2021081193-appb-100005
    步骤S650：求解钍射气及子体的约化平衡因子定义，所述钍射气及子体的的约化平衡因子定义为：F Tn＝0.084F Bi-212
    即公式7。
  7. 根据权利要求4所述的基于固体核径迹的放射性氡、钍射气子体浓度检测方法，其特征在于，
    所述定量分析目标射气子体的浓度，具体包括如下操作步骤：
    步骤S710：经过判断分析，若当前空气中是含氡射气以及钍射气，则通过预设时间衰变累积，测量获得各个通道上的径 迹密度，求解各子体的净径迹密度；各子体的净径迹密度包括Po-218的净径迹密度、Po-214的净径迹密度以及Bi-212的净径迹密度、Po-212的净径迹密度；
    步骤S720：将上述各个子体的净径迹密度代入第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式中，对应求解该子体的净径迹密度所对应的C i(t)为t时间内第i种子体浓度；通过前述步骤得到的Po-218的净径迹密度求解Po-218的子体浓度；通过前述步骤得到的Po-214的净径迹密度求解Po-214的子体浓度；通过前述步骤得到的Bi-212的净径迹密度求解Bi-212的子体浓度；通过前述步骤得到的Po-212的净径迹密度求解Po-212的子体浓度；
    即第i种核素释放的α粒子引起的净径迹密度与子体浓度关系公式为；
    Figure PCTCN2021081193-appb-100006
    其中，S i-nuclear为第i种核素释放的α粒子引起的净径迹密度，单位为trs·cm -2；ε为固体核径迹探测器的刻度系数，单位为trs·cm -2·kBq -1·m 3·h -1；C i(t)为t时间内第i种子体浓度，单位为kBq·m -3·h -1；t为测量累积时间，单位为h；
    步骤S730：测量得到多个子体平衡因子F均值；
    步骤S740：将上述多个子体平衡因子以及Po-218的子体浓度、Po-214的子体浓度，代入平衡当量氡浓度关系公式中，反推Pb-214的子体浓度，从而获得Pb-214的子体浓度；
    所述平衡当量氡浓度关系公式表述为：
    Figure PCTCN2021081193-appb-100007
    求解氡子体的约化平衡因子，所述氡子体的约化平衡因子定义为：
    F Rn＝0.105F Po-218+0.381F Po-214     公式3；
    步骤S750：将上述多个子体平衡因子以及Bi-212的子体浓度、Po-212的子体浓度，代入平衡当量钍射气浓度关系公式中，反推Pb-212的子体浓度；
    所述平衡当量钍射气浓度关系公式表述为：
    Figure PCTCN2021081193-appb-100008
    求解钍射气及子体的约化平衡因子定义，所述钍射气及子体的的约化平衡因子定义为F： Tn＝0.084F Bi-212
    即公式7。
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