CN105425267A - System and method for measuring evolution rate of radon - Google Patents

Abstract

The invention discloses a system and method for measuring the evolution rate of radon. The system does not need a drying tube to dry sample gas, thereby reducing the impact on the evolution rate of radon of the internal dielectric surface of a radon collection cover from a drying agent. In a natural environment, a measurement instrument can accurately measure the instantaneous concentration of radon, and does not need to correct the measured concentration of radon for calculation. The measurement instrument can automatically solve the evolution rate of radon through the measured concentration of radon, and can obtain the value of the evolution rate of radon with no need of a PC for linear fitting processing. An experiment indicates that the measurement error of the radon evolution rate measurement instrument is within the range 5% on a radon evolution rate standard device. After measurement, the evolution rate of radon is directly obtained, thereby meeting the demands of on-site measurement of the evolution rate of radon. The system and method are easy to implement, and are high in measurement efficiency.

Description

System and method for measuring radon exhalation rate

Technical Field

The invention relates toSystem and method for measuring radon exhalation rate。

Background

The latest research result of the radon and lung cancer dangerous epidemiology published by the WHO in 2009 confirms that indoor radon can cause the increase of the lung cancer danger of common people, and a stricter control standard is adopted for the indoor radon. Radon (Radon)The radon exhalation rate measurement method is a preventable and controllable environmental factor, and the radon exhalation rate measurement is the key for searching a source item in environmental radon pollution treatment. International radiation protectionCommittee(ICRP) approval in 4 months 2014 indicated by publication radon radiation protection (ICRP, 2014) No. 126:committeeStrongly suggestState of the countryAnd the administration department should establish a national radon concentration derivation reference level. The level should be as low as 100-300 Bq.m reasonably as possible under the comprehensive consideration of the current economic and social conditions^-3。

The national standard 'environmental pollution control code in civil building engineering (2013 edition)' -GB50325-2010, which is effective at 6/1/2011, more strictly regulates the limit of the radon exhalation rate on the surface of building materials and the surface of soil. The people's republic of ChinaNational State of ChinaStandard GB50325-2010 states that: the standard measurement method for the radon exhalation rate on the surface of the building material is an activated carbon box method, the sample distribution time of the activated carbon box method is 3-7d, and humidity correction and the like are required. The measuring method is used under the condition that the radon exhalation rate does not change greatly.

The main method for measuring the radon exhalation rate on the surface of the medium is an accumulation method, namely, a radon collection cover is tightly buckled on the surface of the medium, and the radon exhalation rate can be reversely deduced by measuring the radon which is precipitated into the radon collection cover within a period of time. The active carbon adsorption method can accurately and directly measure the radon separated out into the radon collection cover, and the radon concentration accumulated in the radon collection cover is very low due to the adsorption effect of the active carbon, so that the leakage and back diffusion effects are very small and can be ignored. However, the activated carbon can adsorb enough radon for gamma spectrum analysis only after a plurality of days, the measurement period is long, and only the stable radon exhalation rate can be measured. And the change rule of the radon concentration in the radon collection cover is measured by other methods, and the leakage and back diffusion effects caused by the high-concentration radon in the radon collection cover must be considered to be corrected, so that the radon exhalation rate on the surface of the medium can be accurately obtained.

The measurement of the radon exhalation rate is greatly influenced by meteorological factors such as air pressure, temperature, humidity and the like, and the measurement time of the activated carbon box method for 3-7d is difficult to meet the radon exhalation requirement of the meteorological factors of the environment with variable sceneInfluence of measurement of the rate of precipitation of radon is eliminated by using a desiccant when the electrostatic collection type radon measuring instrument such as RAD7 measures the precipitation rate of radon, but the precipitation of radon on the surface of a medium to be measured is changed by using the desiccant; in addition, the measured average radon concentration needs to be corrected to obtain the instantaneous radon concentration, the measured radon exhalation rate needs to be calculated by means of the instantaneous radon concentration obtained by correction by a computer, and the measurement result of the radon exhalation rate cannot be directly obtained after the measurement is finished. Only a small part of radon yield measuring instruments can directly give measuring results, such as an ERS-2-s radon-thorium analyzer produced by Germany Tracerlab, and the measuring instruments can directly obtain the results after the measurement is finished, but the measuring results are always low, and the problems of leakage and anti-diffusion influence are not solved. Therefore, it is necessary to designSystem and method for measuring radon exhalation rate。

Disclosure of Invention

The technical problem to be solved by the invention is to provideSystem and method for measuring radon exhalation rateThe radon exhalation rate measuring system and method are easy to implement and high in measuring efficiency.

The technical solution of the invention is as follows:

a method for measuring radon exhalation rate is characterized by comprising the following steps:

step 1: taking T as a measurement period, and measuring the radon concentration C after the first measurement period₁And radon concentration C after the ith measurement cycle_i，i≥2：

Step 2: calculating the radon exhalation rate after the ith measurement period according to the following formula:

$J=-\frac{\frac{{\Σ}_{i=1}^n{C}_i\left({\Σ}_{i=1}^n{C_{i-1}}^2\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}\ln \frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}{1-\frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}\frac{V}{TS}$

v is the total volume of the radon collecting cover, a measuring chamber of the measuring system measuring device and a connecting pipe;

s is the bottom area of the radon collection cover;

n is the number of measurements.

The radon concentration in step 1 is determined according to the following formula:

C＝KηHΔN_P(T); [ C is radon concentration of the environment to be measured, C corresponds to C1 and Ci ]

$C_{{222}_{Rn}}={\mathrm{K\ΔN}}_P{\left(T\right)}^{\′}$ The specific derivation formula is: $C_{{222}_{Rn}}={\mathrm{K\ηVR\ΔN}}_P\left(T\right)={\mathrm{K\ΔN}}_P{\left(T\right)}^{\′}$ 】

in the formula, H represents a temperature and humidity correction factor, and delta N represents a first generation daughter of decay radon²¹⁸α particle count, Δ N, of 6.00MeV produced upon Po decay_P(T₀) ' is the semiconductor detector at time T_M0Received²¹⁸α particles generated by Po decay), K is a radon measurement scale factor, η represents detection efficiency, H represents temperature and humidity factors under different temperature and humidity conditions, and T is a measurement period;

k in the formula can be determined through experiments, so that the accuracy and reliability of the measured value of the radon concentration in the detected environment are ensured. K value determination reference patentRadon-measuring instrument scale factor valuing method-201510137825.2The method mainly comprises the following steps:

firstly, determining a scale factor K when the measurement period is 3600s₀Then, determining the radon measuring instrument scale factor K when the measurement period is not 3600s according to the following formula_x(i.e., K corresponding to the present invention):

$K_x=\frac{\frac{1}{{\mathrm{\λ}}_R}(1-e^{-{\mathrm{\λ}}_R{T}_{M0}})-\frac{1}{{\mathrm{\λ}}_P}(1-e^{-{\mathrm{\λ}}_P{T}_{M0}})}{\frac{1}{{\mathrm{\λ}}_R}(1-e^{-{\mathrm{\λ}}_R{T}_{Mx}})-\frac{1}{{\mathrm{\λ}}_P}(1-e^{-{\mathrm{\λ}}_P{T}_{Mx}})}{K}_0;$

wherein λ is_RAnd λ_PAre respectively radon²²²Rn and²¹⁸a decay constant of Po;

T_M0representing the radon measurement time when the measurement period T is 3600 s;

T_Mxindicating radon measurement time of other measurement periods except any measurement period T-3600 s; having a T_Mx＝T-T_s，T_sT is more than or equal to 60s for sampling time_s≤300s；

Wherein,the radon concentration of the detected environment;

ΔN_P(T₀) ' is the semiconductor detector at time T_M0Received²¹⁸α particle counts from Po decay

T is not less than 10 minutes, such as 15 minutes, or 30 minutes.

The radon exhalation rate is measured by a radon exhalation rate measuring device;

the air inlet of the precipitation rate measuring device is connected with the air outlet of the radon collecting chamber through a first air pipe, and a daughter filter (the daughter filter is used for filtering the original daughter in the sampling gas) is arranged on the first air pipe. H ];

the precipitation rate measuring device comprises a measuring chamber, a PIPS detector, a temperature and humidity sensor, a pre-amplification circuit, an amplification forming circuit, a pulse amplitude discrimination circuit, a single chip microcomputer, an energy spectrum peak automatic adjusting circuit, a display screen, an air pump and a high-voltage module;

the structure of the measuring system is prior art.

The singlechip controls the air pump to make radon-containing air flow into the measuring chamber at a certain flow rate after passing through the daughter filter, and the sampling time is T_sAfter opening the high-voltage module, by²²²First generation daughter generated by Rn decay²¹⁸The Po with positive charge is adsorbed to the surface of the semiconductor detector under the action of the electrostatic field, and when the daughter decays further, the semiconductor detector identifies the energy of the high-energy α particles generated by the decay and takes the time T-T_sThe working reverse voltage of PIPS detector is 40V, the preamplifier adopts low-electric-noise low-distortion operational amplifier, the signal outputted by preamplifier (charge amplifier whose output amplitude is about 100 mv) is further amplified by main amplifier (amplification is 100 times), then the signal is amplified and formed by amplification and forming circuit, the humiture data of air communicated with measuring cavity is transferred to single-chip computer by humiture sensor, the single-chip computer can calculate threshold number of α particles with different energy according to different temp. conditions, its calculated threshold value and signal amplitude are discriminated into the existent technology, the invented patent is "a method for automatically eliminating PIPSA energy spectrum peak temp. drift and its equipment-201410208477.9 ] the threshold value automatic regulating circuit and pulse amplitude discriminating circuit can together discriminate 6.0Mev energy particles under different temp. conditions, its outputted pulse signal can be fed into single-chip computer, and the pulse signal outputted by pulse amplitude discriminating circuit can be counted, and according to pulse factor current radon concentration C, then its measured concentration can be displayed by TFT screen, its measured radon concentration can be displayed, its measured can be also displayed, its measured_P(T)。

[ PIPS detector means passivation ion implantation semiconductor detector, PIPS detector output pulse signal.

Reference C-K η H Δ N for the relationship between particles and pulse signals [ α ]_P(T), one for each particle detectedGeneration of individual pulse signals

A radon exhalation rate measuring system comprises an exhalation rate measuring device and a radon collection chamber;

the gas inlet of the precipitation rate measuring device is connected with the gas outlet of the radon collecting chamber through a first gas pipe, and a daughter filter is arranged on the first gas pipe;

the precipitation rate measuring device comprises a measuring chamber, a PIPS detector, a temperature and humidity sensor, a pre-amplification circuit, an amplification forming circuit, a pulse amplitude discrimination circuit, a single chip microcomputer, an energy spectrum peak automatic adjusting circuit, a display screen, an air pump and a high-voltage module.

Measuring the radon exhalation rate by adopting the method for measuring the radon exhalation rate;

the PIPS detector and the temperature and humidity sensor are positioned in the measuring chamber.

The invention researches and develops a set of measuring instrument for automatically measuring the radon exhalation rate (namely a measuring system for the radon exhalation rate) based on the technologies of an electrostatic collection method, an automatic temperature and humidity correction technology, an automatic energy spectrum peak adjustment and the like, the measuring instrument finishes linear fitting of numerical values by an internal microprocessor, and directly gives a measuring result of the radon exhalation rate after measurement is finished, thereby realizing accurate and reliable measurement of the radon exhalation rate and meeting the requirement of field measurement.

Has the advantages that:

the reliable measurement of the radon exhalation rate is the key for searching source items in environmental radon pollution treatment. In order to realize reliable measurement of the radon exhalation rate, the invention researches and develops a portable automatic radon exhalation rate measuring system based on the modes of accumulating and collecting radon and measuring radon by an electrostatic collection method, and the measuring system does not need a drying tube to dry sampling gas and reduces the influence of a drying agent on the radon exhalation rate on the surface of a medium in a radon collection cover; under the natural environment, the measuring system can accurately measure the instantaneous radon concentration, and the calculation can be carried out without carrying out data correction on the measured radon concentration; the measuring system can automatically calculate the radon exhalation rate according to the measured radon concentration, and a value of the radon exhalation rate can be obtained without the help of a PC (personal computer) for linear fitting treatment. Experiments show that the measurement error of the radon exhalation rate measuring system on a radon exhalation rate standard device is within 5 percent. The radon exhalation rate can be directly obtained after the measurement is finished, so that the demand of on-site radon exhalation rate measurement is facilitated.

Drawings

FIG. 1 shows a schematic view of aThe principle of the system for automatically measuring the radon exhalation rateDrawing (A)；

FIG. 2For measuring device circuit structureDrawing (A)；

FIG. 3The measuring process of the radon exhalation rateDrawing (A)。

Detailed Description

Will be combined as followsDrawingsThe invention is further illustrated in detail with specific examples:

example 1:

the radon exhalation rate measurement principle is explained as follows:

1. method for measuring radon exhalation rate

Automatic radon exhalation rate measurementAs shown in figure 1As shown, the sampling pump is started to pump the radon-containing air in the measured environment at the QL/min flow rate for a time Δ T (not less than 1 minute), and at this time, the radon concentration in the measurement chamber is the radon concentration C in the radon collection chamber when the initial time T is 0₀Then, a radon collecting cover with the volume of (V-delta V1) and the bottom area of S is buckled on the surface with the radon exhalation rate of the measured medium of J, a closed measuring chamber with the volume of delta V is connected with the radon collecting cover through 2 silicone tubes with the internal volume of delta V1 to form a loop, after a certain time T-delta T is collected, a sampling pump is started to mix the radon collecting chamber with the radon in the measuring chamber for delta T time at the flow rate of QL/min, and the radon concentration in the measuring chamber is the time TRadon concentration C of Radon accumulating chamber₁Then, repeatedly measuring with T (more than 10min) as a period, and measuring a series of radon concentration data C in radon collecting chambers with equal time intervals_i. Due to the existence of leakage and counter-diffusion rate R, the radon concentration change of the radon collecting chamber can be expressed by the formula (1)

$\frac{dC}{dt}=\frac{JS}{V}-\mathrm{\λ}C-RC---\left(1\right)$

(1) In the formulaThe change of radon concentration caused by the radon precipitated into the radon collecting chamber in unit time; lambda is the decay constant of radon; t is the radon collecting time.

Let lambda_eλ + R; namely t is 0 moment, the concentration of radon in the radon collection chamber is C₀. (1) The solution of formula (II) is

$C\left(t\right)=\frac{JS}{{\mathrm{\λ}}_e}(1-e^{-{\mathrm{\λ}}_{e}t})+C_0{e}^{-{\mathrm{\λ}}_{e}t}---\left(2\right)$

And (3) continuously measuring by taking T as a measurement period, wherein the change of radon concentration in the two adjacent measurement sets of radon chambers is in the following relation:

$C_i=\frac{JS}{{\mathrm{\λ}}_e}(1-e^{-{\mathrm{\λ}}_{e}t})+C_{i-1}{e}^{-{\mathrm{\λ}}_{e}t}---\left(3\right)$

order to $a=\frac{JS}{{\mathrm{\λ}}_e}(1-e^{-{\mathrm{\λ}}_{e}t}),b=e^{-{\mathrm{\λ}}_{e}t},$ Then there are:

C_i＝a+bC_i-1(4)

in order to improve the measurement accuracy, multiple measurements are carried out, a and b are calculated by using least square method and linear fitting, and finally, lambda is calculated_eAnd J.

2. Method for calculating radon exhalation rate

The microprocessor used for data acquisition and data processing of the measuring instrument can only complete algebraic operation and can not directly perform linear fitting processing. The automatic measurement method converts linear fitting into algebraic operation. Performing linear fitting on n data to obtain an equation of y ═ a + bx, and minimizing deviation square sum according to least square method

$R^2(a,b)\≡\underset{i=1}{\overset{n}{\Σ}}{\[y_i-f(x_i,a_1,a_2,\mathrm{...}{a}_n)\]}^2=0---\left(5\right)$

Solving the equation (5) to obtain a, b and C in the linear equation (4)_i＝y_i，C_i-1＝x_iAnd then a and b are as follows:

$a=\frac{{\Σ}_{i=1}^n{C}_i\left({\Σ}_{i=1}^n{C_{i-1}}^2\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}---\left(6\right)$

$b=\frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}---\left(7\right)$

$J=-\frac{\frac{{\Σ}_{i=1}^n{C}_i\left({\Σ}_{i=1}^n{C_{i-1}}^2\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}\ln \frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}{1-\frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}\frac{V}{TS}---\left(8\right)$

the measuring instrument transplants the formula (8) algorithm into a microprocessor of the measuring instrument, and after the 2 nd measuring period is finished, the measured radon concentration is substituted into the formula (8) after the measurement of each measuring period is finished, so that the radon exhalation rate J is automatically measured.

T is a measurement period; the value of T is not less than 10 minutes;

v is the total volume of the radon collecting cover and the measuring instrument measuring and connecting pipe.

S is the bottom area of the radon collection cover;

n is the number of measurements;

ci is the radon concentration measured at the current time;

ci-1 is the last radon concentration measured.

3. Circuit design of measuring instrument

The radon exhalation rate is measured by measuring radon concentrations of the radon collection chamber at different moments for multiple times and calculating by using a least square method and linear fitting, and the reliable measurement of the radon concentration is the key for measuring the radon exhalation rate.

The hardware circuit of the precipitation rate measuring device mainly comprises a measuring chamber, a PIPS detector, a temperature and humidity sensor, a pre-amplification circuit, an amplification forming circuit, a pulse amplitude discrimination circuit, a single chip microcomputer, an energy spectrum peak automatic regulating circuit, a TFT display screen, an air pump and a high-voltage module. Structure frame of continuous measuring instrument systemAs shown in figure 2As shown.

4. Internal value processing procedure of measuring instrument

In consideration of the requirements of different measuring environments, 3 measuring period options of 15 minutes, 30 minutes and 60 minutes are set, and the flow of the measuring instrumentAs shown in figure 3As shown.

After the RaA is measured, the measured radon concentration is calculated, and after the 2 nd period is measured, the measured radon exhalation rate is calculated according to a formula (8), so that the automatic measurement of the radon exhalation rate is realized.

Test results and analysis

1 Effect of temperature on Radon concentration measurement

The temperature and humidity influence experiment of the measuring instrument is carried out in a radon chamber of the university of south China, the radon concentration of a standard radon chamber is adjusted to be about 2000Bq/m3, and the temperature of the radon chamber is controlled to be 25 ℃. Radon measuring instrumentThe measuring period is set to 60min, and each temperature point is continuously measured for 8 periods; placing the emanometer in a high-low temperature experiment box, adjusting the radon meter by using the high-low temperature experiment box at 5 ℃ as a step length to control the measurement temperature of the emanometer, and obtaining the measurement resultAs shown in Table 1As shown.

TABLE 1Measurement of radon concentration under different temperature conditions

TABLE 1The experimental measurement results in (1) show that the relative standard deviation of the measurement results is within 5% under the temperature condition of 0-45 ℃.

PQ2000 belongs to a high-precision radon measuring instrument, and the PQ2000 measurement is taken as a reference standard in the radon measurement at present.

2. Effect of relative humidity on Radon concentration measurement

The experiment of the influence of temperature on radon concentration measurement is carried out in a standard radon chamber of the university of south China, and the concentration of the standard radon chamber is adjusted to increase the concentration of the standard radon chamber to 3000Bq.m^-3About, the temperature of the standard radon indoor environment is controlled at 19.0 ℃, and the relative humidity is controlled at 30% and 90%. And connecting the radon measuring device with the standard radon chamber, and turning on a power supply of the experimental device to measure under the condition that the radon concentration in the environment of the standard radon chamber is stable. Measurement results under different humidity conditionsAs shown in Table 2As shown.

TABLE 2The measurement results of radon chamber under the conditions of set temperature of 19.0 ℃, relative humidity of 30% and relative humidity of 90%

TABLE 2The result shows that the relative deviation of the radon concentration measured by the automatic measuring device under different humidity conditions, no matter under the condition that the environment humidity of the standard radon chamber is high or lowAre all within 5%. The result shows that the collecting effect of the measuring instrument is basically not influenced when the measuring instrument is used for measuring at the normal temperature and the relative humidity of 30-90 percent.

This radon exhalation rate automatic measuring device through the structure of optimizing the measurement chamber, improves the radon collection efficiency, adopts temperature automatic compensation to revise^[15-17]The accuracy of radon concentration measurement and the reliable measurement of radon exhalation rate are ensured.

3 radon exhalation rate measurement accuracy test

A radon laboratory of the university of south China establishes 1 set of radon exhalation rate reference device and provides a measurement object with stable exhalation rate, and the reference value of the radon exhalation rate is measured by a scintillation chamber method and an activated carbon box gamma spectrumMethod ofThe radon exhalation rate reference value of the No. 1 standard device with the same fixed value is (1.48 +/-0.05) Bq.m^-3And the radon exhalation rate reference value of the No. 2 standard device is (2.60 +/-0.08) Bq.m^-3And the reference value of radon exhalation rate of the No. 3 standard device is (0.39 +/-0.02) Bq.m^-3. The radon exhalation rate performance test experiment is carried out on a radon exhalation rate standard device of the university of south China.

And adjusting the air conditioner to ensure that the temperature of the radon exhalation rate standard measuring chamber is 25 ℃ and the relative humidity is 51 percent. The automatic radon exhalation rate measuring device adopts the volume of the radon collecting cover, the total volume V of the measuring chamber and the silicone tube to be 0.0057m³The bottom area S of the radon collecting cover is 0.066m²The measurement period is 15 min. The measurement results of the radon collecting cover buckled on the standard radon exhalation rate devices No. 1, No. 2 and No. 3 are listedTABLE 3In

TABLE 3Result measured on radon exhalation rate standard measuring device

TABLE 3The measurement result of the exhalation rate of radon is calculated based on the measured instantaneous radon concentration. And the radon concentration measurement result does not need to be corrected, and the radon is directly calculated according to the formula (10)Value of the precipitation rate.

According to the measurement result, the experimental measurement value and the reference value are better in accordance.TABLE 3The method shows that the measured value of the multi-fitting experiment is closer to the reference value along with the increase of the measurement times of each group of measurement data, the change of the measurement result after 4 measurement periods is very small, and the deviation of the result obtained through 7 measurement periods and the reference value is within 5 percent.

4 field application measurement

(1) Site measuring point 1

The point 1 for automatically measuring the radon exhalation rate is on a hill in an industrial park in the Zhuhui area of the Hengyang city and is original soil,TABLE 4Measurement data the first day was the result of the measurement during the afternoon raindrop.

TABLE 4On-site measurement point 1 radon exhalation rate measurement result

TABLE 4The measured data shows that the radon precipitation value of the soil surface at the time of the measurement is 0.12Bq.m^-2.s^-1。

(2) Site measuring point 2

The point 2 for automatically measuring the radon exhalation rate is a tailing pond, and the field measurement point 2 measures the measurement result of the radon exhalation rate for 8 measurement periodsAs shown in Table 5As shown.

TABLE 5On-site measurement point 2 radon exhalation rate measurement result

TABLE 5The measured data shows that the radon precipitation value of the measuring point is 0.24Bq.m^-2.s^-1. The measurement results of the measurement point 1 and the measurement point 2 show that the stability of the measurement results is good.

Conclusion

1) The automatic radon exhalation rate measuring instrument is researched based on the modes of accumulating radon collection and measuring radon by an electrostatic collection method, is based on the modes of accumulating radon collection and measuring radon by the electrostatic collection method, does not need a drying tube to dry sampling gas, and reduces the influence of a drying agent on the exhalation rate of the radon on the surface of a medium in a radon collection chamber;

2) when the humidity is measured under the normal temperature measurement condition, the relative humidity is measured under the condition of 30-90%, and the collection efficiency is not influenced;

3) when the temperature of the measuring instrument adopting the energy spectrum peak automatic adjustment technology is between 5.2 and 44.9 ℃, the radon concentration is accurately measured;

4) the automatic measuring instrument can accurately measure the instantaneous radon concentration and can calculate without correcting the measured radon concentration;

5) the single-chip built-in program of the automatic measuring instrument can automatically calculate the radon exhalation rate according to the measured radon concentration, and a value of the radon exhalation rate can be obtained without the help of a PC (personal computer) to perform linear fitting treatment.

Experiments show that the measurement error of the radon exhalation rate measuring instrument on a radon exhalation rate standard device is within 5 percent. The radon exhalation rate can be directly obtained after the measurement is finished, and the demand of rapid and reliable measurement of the on-site radon exhalation rate is facilitated. The measuring device provides important guarantee for improving the monitoring and evaluation level of radon pollution in the environment of China, the measurement and control level of radon exhalation rate of building materials, the resource survey, the geological research, the earthquake prediction level and the like by taking radon as tracer nuclides.

Claims (5)

1. A method for measuring radon exhalation rate is characterized by comprising the following steps:

step 1: taking T as a measurement period, and measuring the radon concentration C after the first measurement period₁And radon concentration C after the ith measurement cycle_i，i≥2；

Step 2: calculating the radon exhalation rate after the ith measurement period according to the following formula:

$J=-\frac{\frac{{\Σ}_{i=1}^n{C}_i\left({\Σ}_{i=1}^n{C_{i-1}}^2\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}\ln \frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}{1-\frac{n\left({\Σ}_{i=1}^n{C}_{i-1}{C}_i\right)-{\Σ}_{i=1}^n{C}_{i-1}\left({\Σ}_{i=1}^n{C}_i\right)}{n{\Σ}_{i=1}^n{C_{i-1}}^2-{\left({\Σ}_{i=1}^n{C}_{i-1}\right)}^2}}\frac{V}{TS}$

v is the total volume of the radon collecting cover, a measuring chamber of the measuring system measuring device and a connecting pipe;

s is the bottom area of the radon collection cover;

n is the number of measurements.

2. The method for measuring radon exhalation rate according to claim 1, wherein the radon concentration in step 1 is determined according to the following formula:

C＝KηHΔN_P(T)；

$C_{{222}_{Rn}}={\mathrm{K\ΔN}}_P{\left(T\right)}^{\′}$

wherein H represents temperatureHumidity correction factor, Δ N, denotes the first generation daughter of radon decay²¹⁸α particle count, Δ N, of 6.00MeV produced upon Po decay_P(T₀) ' is the semiconductor detector at time T_M0Received²¹⁸α particles generated by Po decay), K is a radon measuring scale factor, η represents detection efficiency, H represents temperature and humidity factors under different temperature and humidity conditions, and T is a measurement period.

3. The method of measuring radon exhalation rate as claimed in claim 1, wherein T is not less than 10 minutes.

4. The method for measuring the radon exhalation rate according to any one of claims 1 to 3, wherein the radon exhalation rate is measured using a radon exhalation rate measuring device;

the gas inlet of the precipitation rate measuring device is connected with the gas outlet of the radon collecting chamber through a first gas pipe, and a daughter filter is arranged on the first gas pipe;

the precipitation rate measuring device comprises a measuring chamber, a PIPS detector, a temperature and humidity sensor, a pre-amplification circuit, an amplification forming circuit, a pulse amplitude discrimination circuit, a single chip microcomputer, an energy spectrum peak automatic adjusting circuit, a display screen, an air pump and a high-voltage module; the singlechip controls the air pump to make radon-containing air flow into the measuring chamber at a certain flow rate after passing through the daughter filter, and the sampling time is T_sAfter opening the high-voltage module, by²²²First generation daughter generated by Rn decay²¹⁸The Po with positive charge is adsorbed to the surface of the semiconductor detector under the action of the electrostatic field, and when the daughter decays further, the semiconductor detector identifies the energy of the high-energy α particles generated by the decay and takes the time T-T_sCounting internally; the working reverse voltage of the PIPS detector is 40V, the preamplifier adopts a low-electric-noise low-distortion operational amplifier, the signal output by the preamplifier (the output amplitude of a charge amplifier is about 100 mv)) is further amplified by a main amplifier (the amplification is 100 times), then the signal is amplified and formed by an amplifying and forming circuit, and a temperature and humidity sensor transmits the temperature and humidity data of the air communicated with the measuring cavity to a single chipThe machine is characterized in that a single chip microcomputer calculates threshold value number threshold value automatic adjusting circuits of α particles with different energies according to different temperature conditions and a pulse amplitude discrimination circuit to discriminate α particles with 6.0Mev energies under different temperature conditions, pulse signals output by the automatic adjusting circuits and the pulse amplitude discrimination circuit are sent to the single chip microcomputer, the single chip microcomputer counts the pulse signals output by the pulse amplitude discrimination circuit, the single chip microcomputer calculates the current radon concentration C according to a pulse count value and a scale factor, the measured radon concentration C is displayed through a TFT display screen, and the radon concentration C is K η H delta N_P(T)。

5. A measuring system for radon exhalation rate is characterized by comprising an exhalation rate measuring device and a radon collecting chamber;

the gas inlet of the precipitation rate measuring device is connected with the gas outlet of the radon collecting chamber through a first gas pipe, and a daughter filter is arranged on the first gas pipe;

the precipitation rate measuring device comprises a measuring chamber, a PIPS detector, a temperature and humidity sensor, a pre-amplification circuit, an amplification forming circuit, a pulse amplitude discrimination circuit, a single chip microcomputer, an energy spectrum peak automatic adjusting circuit, a display screen, an air pump and a high-voltage module.

Measuring the radon exhalation rate by using the method for measuring radon exhalation rate according to claim 4;

the PIPS detector and the temperature and humidity sensor are positioned in the measuring chamber.