CN101609154A - Measure the method for precipitation rate of radon - Google Patents

Abstract

A kind of method of measuring precipitation rate of radon, comprise measuring process and computation process, to collect the radon cover is buckled on the testing medium surface, or medium packed in the collection radon cover collecting chamber, constant duration measures one group of radon concentration data, according to formula (9), nonlinear fitting obtains precipitation rate of radon with the radon concentration data that measures.Or utilizing 20 minutes later measurement data according to formula (10), nonlinear fitting obtains precipitation rate of radon.

Description

Measure the method for precipitation rate of radon

Technical field

The present invention relates to a kind of nuclear radiation detection technology, particularly a kind of method of measuring precipitation rate of radon.

Background technology

Radon mainly comes from separating out of dielectric surface in the air ambient, and the main method of measuring media surface precipitation rate of radon has accumulative and active carbon adsorption.Active carbon adsorption is to utilize activated charcoal to separating out the absorption of radon, measures by the γ spectrum that the radon decay that is adsorbed in the activated charcoal is produced and obtains precipitation rate of radon, and this method Measuring Time is long, be difficult for realizing robotization; Accumulative mainly is the average radon eduction rate that is used to measure in a period of time, has important statistical significance and reference value.Use the electrostatic collection formula precipitation rate of radon instrument of accumulative simple, convenient and rapid, can measure immediately and provide the result and obtained using more widely with it.Current use accumulative all is the radon that adopts a collection radon cover trapping medium to separate out, and measures the Changing Pattern of radon concentration in the collection radon cover then, measurement data is carried out match obtain radon concentration.Because in measuring radon concentration process fast, radon concentration is rising always, radon and its decay daughter polonium 218 can not reach balance, by measuring the anti-concentration that pushes away radon of α particle counting that polonium 218 decays are emitted, the concentration of the radon that obtains is on the low side, and therefore the precipitation rate of radon that adopts existing computing method to obtain is also on the low side.

Summary of the invention

The present invention seeks to overcome the above-mentioned deficiency of prior art and disclose a kind of method of measuring precipitation rate of radon, this method comprises measuring process and computation process, it is by revising existing computing method, solved when measuring in the collection radon cover radon concentration, because radon concentration is rising always, radon and its decay daughter polonium 218 can not reach balance, cause the radon concentration problem on the low side that measures, the precipitation rate of radon more accurately that obtains.

Technical scheme of the present invention is: a kind of method of measuring precipitation rate of radon, it comprises measuring process and computation process.

One, measuring process:

The collection radon cover of an opening is buckled on the testing medium surface, or in packing medium into collection radon cover collecting chamber airtight, because the radon atom in the medium is under diffusion and seepage effect, the effusion surface enters collection radon cover collecting chamber, causes collecting the radon cover and collects the Indoor Niton concentration change.Pump will collect radon in the radon cover collecting chamber with constant flow rate always and pump into measuring chamber after by drying tube and filter membrane filtering daughter, flow velocity 0.5-2 liter/minute, make radon concentration balance in radon concentration and the collection radon cover collecting chamber of measuring chamber.

The semiconductor detector is arranged in the measuring chamber, and semiconductor detector is connected with secondary instrument, surveys the α particle counting that polonium 218 decays are emitted.At the bottom of the measuring chamber and between wall and the semiconductor detector in addition the 50-100 volt/centimetre electric field, make the polonium 218 of the positively charged that radon decay back produces under electric field action, be adsorbed onto on the semiconductor detector face at a high speed, improve detection efficiency.

The radon concentration that measures is the mean concentration in the Measuring Time, and concrete corresponding which time point is difficult to determine.This method adopts short time interval measurement, both measures once in 1-5 minute, just can be similar to think and the centre of the corresponding Measuring Time of radon concentration that measures can reduce Measuring Time and grow the radon concentration time corresponding uncertainty that causes; Short time interval may cause statistic fluctuation bigger like this, can remedy by increasing measurement point, does not increase total Measuring Time.

Only measure the anti-radon concentration that pushes away of α particle counting that polonium 218 decays are emitted, can get rid of the interference of thoron fully, reduced the complexity of measuring system simultaneously, reduced cost, improve reliability.Constant duration measures one group of radon concentration data, considers to leak and the antidiffusion influence, simultaneously radon and its decay daughter polonium 218 is carried out non-equilibrium correction, just can obtain radon eduction rate on medium furface more accurately.

Two, computation process:

To collect the radon cover and be buckled on the testing medium surface, and at this moment collect the interior radon concentration change of radon cover and can use formula (1) to describe:

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

For the unit interval precipitate into the variation that the radon that collects in the radon cover causes radon concentration; J is a measured medium surface precipitation rate of radon; S is the floorage of collection radon cover; V is collection radon cover spatial volume; The radon concentration change that λ C causes for the decay that collects radon in the radon cover; RC is the leakage of radon and the radon concentration change that antidiffusion causes in the collection radon cover; λ=2.1 * 10 ^-6s ^-1Disintegration constant for radon; C is accumulation t radon concentration constantly in the collection radon cover; R is the leakage and the antidiffusion rate of radon; T is the time of collection radon.

Make λ _e=λ+R; Make that ENVIRONMENT RADON CONTENT is C ₀, promptly during t=0, the concentration of radon is C in the collection radon cover ₀Formula (1) separate for:

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

$\≈\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-e^{-{\mathrm{\λ}}_{e}t})---\left(2\right)$

Because in measuring radon concentration process fast, radon concentration is rising always, radon and its decay daughter polonium 218 can not reach balance, and by measuring the anti-concentration that pushes away radon of α particle counting that polonium 218 decays are emitted, the concentration of the radon that obtains is on the low side.

Adopt following method correction:

Its daughter is by the filter membrane filtering when entering the sample cavity of RAD7 for radon, and the radon decay in measuring chamber can be described as:

$\frac{\mathrm{dC}}{\mathrm{dt}}=-\mathrm{\λC}---\left(3\right)$

$\begin{array}{c}\frac{d{C}_{\mathrm{Po}}}{\mathrm{dt}}={\mathrm{\λ}}_{\mathrm{Po}}C-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}\\ C_{\mathrm{Po}}\left(0\right)=0\end{array}---\left(4\right)$

C _PoExpression 218Po concentration; λ _PoBe the 218Po disintegration constant, equal 0.0037s ^-1

The half life period of radon is 3.8235d; The half life period of 218Po is 3.10min.When think measure during radon concentration constant, formula (4) separate for:

$C_{\mathrm{Po}}\left(t\right)=C(1-e^{-{\mathrm{\λ}}_{\mathrm{Po}}t})---\left(5\right)$

Be longer than 20min when the time, 218Po and radon balance, formula (5) can be reduced to:

C _Po(t)＝C????(6)

The measuring principle of radon concentration is from formula (6).Utilize formula (2), (4) just can obtain 218Po decay rule among the RAD7:

$\frac{d{C}_{\mathrm{Po}}}{\mathrm{dt}}=\frac{\mathrm{JS}{\mathrm{\λ}}_{\mathrm{Po}}}{{\mathrm{\λ}}_{e}V}(1-e^{-{\mathrm{\λ}}_{e}t})-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}---\left(7\right)$

Solve:

$C_{\mathrm{Po}}\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(8\right)$

Comparison expression (8), (6) can obtain the radon concentration value that the RAD7 actual measurement obtains:

$C_1\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(9\right)$

$=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-\frac{{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})$

Formula (9) is exactly the revised theoretical model that utilizes the electrostatic collection method to measure precipitation rate of radon fast, obtains precipitation rate of radon according to formula (9) nonlinear fitting.

General λ when sealing is better _e＜λ _Po, when t＞20 minute,

Less than 0.012, with this understanding,

Formula (9) can be reduced to:

$C_1\left(t\right)=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1+\frac{{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})---\left(10\right)$

According to formula (10), utilize 20 minutes later measurement data nonlinear fittings also can obtain precipitation rate of radon.

The present invention compared with prior art has following characteristics:

1, considered the interference of leakage and antidiffusion influence and thoron, and through type (9) or formula (10) measures precipitation rate of radon correction fast to utilizing the electrostatic collection method, obtain radon eduction rate on medium furface more accurately.

2, compare with active carbon adsorption, install simply, easy to operate, be fit to on-the-spotly to measure in real time, shortened Measuring Time simultaneously, satisfied the needs that precipitation rate of radon is measured fast.

Below in conjunction with the drawings and specific embodiments the present invention is further described.

Description of drawings

Accompanying drawing 1 is a dielectric surface measuring process synoptic diagram;

Accompanying drawing 2 is particle or cake mass measuring process synoptic diagram.

Embodiment

Embodiment: a kind of method of measuring precipitation rate of radon, it comprises measuring process and computation process.

One, measuring process:

As shown in Figure 1 and Figure 2, will collect radon cover 5 and be buckled on the testing medium surface, or medium is packed in the collection radon cover collecting chamber, wherein Fig. 1 is a dielectric surface measuring process synoptic diagram, and Fig. 2 is particle 8 or block 7 material measuring process synoptic diagram.Because the radon atom in the medium is under diffusion and seepage effect, the effusion surface enters collection radon cover 5 collecting chambers, causes collecting radon cover 5 and collects the Indoor Niton concentration change.Pump 6 will collect radon in radon cover 5 collecting chambers with constant flow rate always and pump into measuring chamber 2 after by drying tube 4 and filter membrane 3 filtering daughters, flow velocity 0.5-2 liter/minute, make radon concentration balance in radon concentration and collection radon cover 5 collecting chambers of measuring chamber 2.

Semiconductor detector 9 is arranged in the measuring chamber 2, and semiconductor detector 9 is connected with secondary instrument 1, surveys the α particle counting that polonium 218 decays are emitted.Between 2 ends of measuring chamber and wall and semiconductor detector 9 in addition the 50-100 volt/centimetre electric field, make the polonium 218 of the positively charged that radon decay back produces under electric field action, be adsorbed onto at a high speed on 9 of the semiconductor detectors, improve detection efficiency.

The radon concentration that measures is the mean concentration in the Measuring Time, and concrete corresponding which time point is difficult to determine.This method adopts short time interval measurement, both measured once in 1-5 minute, just can be similar to and think the centre of the corresponding Measuring Time of the radon concentration that measures, can reduce the long radon concentration time corresponding uncertainty that causes of Measuring Time, short time interval may cause statistic fluctuation bigger like this, can remedy by increasing measurement point, not increase total Measuring Time.

Only measure the anti-radon concentration that pushes away of α particle counting that polonium 218 decays are emitted, can get rid of the interference of thoron fully, reduced the complexity of measuring system simultaneously, reduced cost, improve reliability.

Constant duration measures one group of radon concentration data, considers to leak and the antidiffusion influence, simultaneously radon and its decay daughter polonium 218 is carried out non-equilibrium correction, just can obtain radon eduction rate on medium furface more accurately.

Twice measurement data on standard precipitation rate of radon analogue means sees the following form, and the reference value of precipitation rate of radon is 1.48Bqm ^-2s ^-1, the calibration factor of surveying instrument (RAD7) is 1.02.

Measuring Time	Measurement data (Bq/m 3)	Revised data (the Bq/m of calibration factor 3)	Measuring Time	Measurement data (Bq/m 3)	Revised data (the Bq/m of calibration factor 3)
						??13:41:00	??1700	??1734	??15:40:00	??1650	??1683
??13:43:00	??1930	??1968.6	??15:42:00	??925	??943.5
						??13:45:00	??1470	??1499.4	??15:44:00	??2090	??2131.8
??13:47:00	??2450	??2499	??15:46:00	??3390	??3457.8
						??13:49:00	??3970	??4049.4	??15:48:00	??3650	??3723
??13:51:00	??5670	??5783.4	??15:50:00	??4180	??4263.6
						??13:53:00	??6240	??6364.8	??15:52:00	??7620	??7772.4
??13:55:00	??9300	??9486	??15:54:00	??7100	??7242
						??13:57:00	??9700	??9894	??15:56:00	??9550	??9741
??13:59:00	??12100	??12342	??15:58:00	??8880	??9057.6

??14:01:00	??14300	??14586	??16:00:00	??13600	??13872
						??14:03:00	??13400	??13668	??16:02:00	??11700	??11934
??14:05:00	??14900	??15198	??16:04:00	??13900	??14178
						??14:07:00	??15400	??15708	??16:06:00	??15400	??15708
??14:09:00	??17000	??17340	??16:08:00	??15700	??16014
						??14:11:00	??17200	??17544	??16:10:00	??16600	??16932
??14:13:00	??20000	??20400	??16:12:00	??16200	??16524
						??14:15:00	??20800	??21216	??16:14:00	??17800	??18156
??14:17:00	??19900	??20298	??16:16:00	??20000	??20400
						??14:19:00	??21700	??22134	??16:18:00	??21400	??21828
??14:21:00	??24400	??24888	??16:20:00	??21100	??21522
						??14:23:00	??23400	??23868	??16:22:00	??21800	??22236
??14:25:00	??26300	??26826	??16:24:00	??23800	??24276
						??14:27:00	??23700	??24174	??16:26:00	??24900	??25398
??14:29:00	??26000	??26520	??16:28:00	??23400	??23868
						??14:31:00	??27700	??28254	??16:30:00	??25600	??26112
??14:33:00	??22000	??22440	??16:32:00	??28500	??29070
						??14:35:00	??26200	??26724	??16:34:00	??29300	??29886
??14:37:00	??30800	??31416	??16:36:00	??29900	??30498
						??14:39:00	??29000	??29580	??16:38:00	??28600	??29172
??14:41:00	??30200	??30804	??16:40:00	??27300	??27846
						??14:43:00	??32000	??32640	??16:42:00	??30000	??30600
??14:45:00	??33900	??34578	??16:44:00	??31100	??31722
						??14:47:00	??31000	??31620	??16:46:00	??28800	??29376
??14:49:00	??33100	??33762	??16:48:00	??30100	??30702
						??14:51:00	??35200	??35904	??16:50:00	??29500	??30090
??14:53:00	??33900	??34578	??16:52:00	??28000	??28560
						??14:55:00	??34000	??34680	??16:54:00	??33100	??33762
??14:57:00	??34600	??35292	??16:56:00	??37200	??37944
						??14:59:00	??34700	??35394	??16:58:00	??40500	??41310
??15:01:00	??30900	??31518	??17:00:00	??36600	??37332
						??15:03:00	??33900	??34578	??17:02:00	??37300	??38046
??15:05:00	??34900	??35598	??17:04:00	??34900	??35598
						??15:07:00	??36500	??37230	??17:06:00	??36000	??36720
??15:09:00	??41300	??42126	??17:08:00	??37400	??38148
						??15:11:00	??38500	??39270	??17:10:00	??34100	??34782
??15:13:00	??40100	??40902	??17:12:00	??40300	??41106
						??15:15:00	??38800	??39576	??17:14:00	??40400	??41208
??15:17:00	??41700	??42534	??17:16:00	??40300	??41106
						??15:19:00	??40500	??41310	??17:18:00	??38400	??39168

Two, computation process: state:

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

For the unit interval precipitate into the variation that the radon that collects in the radon cover causes radon concentration; J is a measured medium surface precipitation rate of radon; S is the floorage of collection radon cover; V is collection radon cover spatial volume; The radon concentration change that λ C causes for the decay that collects radon in the radon cover; RC is the leakage of radon and the radon concentration change that antidiffusion causes in the collection radon cover; λ=2.1 * 10 ^-6s ^-1Disintegration constant for radon; C is accumulation t radon concentration constantly in the collection radon cover; R is the leakage and the antidiffusion rate of radon; T is the time of collection radon.

Make λ _e=λ+R; Make that ENVIRONMENT RADON CONTENT is C ₀, promptly during t=0, the concentration of radon is C in the collection radon cover ₀Formula (1) separate for:

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

$\≈\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-e^{{\mathrm{\λ}}_{e}t})---\left(2\right)$

Because in measuring radon concentration process fast, radon concentration is rising always, radon and its decay daughter polonium 218 can not reach balance, and by measuring the anti-concentration that pushes away radon of α particle counting that polonium 218 decays are emitted, the concentration of the radon that obtains is on the low side.With experimental data be: 1.28Bqm according to the precipitation rate of radon that formula (2) obtains ^-2s ^-1And 1.17Bqm ^-2s ^-1, with reference value 1.48Bqm ^-2s ^-1Differ bigger.

Adopt following method correction:

Its daughter is by the filter membrane filtering when entering the sample cavity of RAD7 for radon, and the radon decay in measuring chamber can be described as:

$\frac{\mathrm{dC}}{\mathrm{dt}}=-\mathrm{\λC}---\left(3\right)$

$\begin{array}{c}\frac{d{C}_{\mathrm{Po}}}{\mathrm{dt}}={\mathrm{\λ}}_{\mathrm{Po}}C-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}\\ C_{\mathrm{Po}}\left(0\right)=0\end{array}---\left(4\right)$

C _PoExpression 218Po concentration; λ _PoBe the 218Po disintegration constant, equal 0.0037s ^-1

The half life period of radon is 3.8235d; The half life period of 218Po is 3.10min.When think measure during radon concentration constant, formula (4) separate for:

$C_{\mathrm{Po}}\left(t\right)=C(1-e^{-{\mathrm{\λ}}_{\mathrm{Po}}t})---\left(5\right)$

Be longer than 20min when the time, 218Po and radon balance, formula (5) can be reduced to:

C _Po(t)＝C????(6)

The measuring principle of radon concentration is from formula (6).Utilize formula (2), (4) just can obtain 218Po decay rule among the RAD7:

$\frac{{\mathrm{dC}}_{\mathrm{Po}}}{\mathrm{dt}}=\frac{\mathrm{JS}{\mathrm{\λ}}_{\mathrm{Po}}}{{\mathrm{\λ}}_{e}V}(1-e^{-{\mathrm{\λ}}_{e}t})-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}---\left(7\right)$

Solve:

$C_{\mathrm{Po}}\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(8\right)$

Comparison expression (8), (6) can obtain the radon concentration value that the RAD7 actual measurement obtains:

$C_1\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(9\right)$

$=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-\frac{{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})$

Formula (9) is exactly the revised theoretical model that utilizes the electrostatic collection method to measure precipitation rate of radon fast, obtains precipitation rate of radon according to formula (9) nonlinear fitting.

General λ when sealing is better _e＜λ _Po, when t＞20 minute,

Less than 0.012, with this understanding, formula (9) can be reduced to:

$C_1\left(t\right)=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1+\frac{{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})---\left(10\right)$

According to formula (10), utilize 20 minutes later measurement data nonlinear fittings also can obtain precipitation rate of radon.With experimental data be: 1.58Bqm according to the precipitation rate of radon that formula (10) obtains ^-2s ^-1, 1.43Bqm ^-2s ^-1Approaching with reference value.

Claims (2)

1, a kind of method of measuring precipitation rate of radon, it comprises measuring process and computation process,

One, measuring process:

To collect the radon cover is buckled on the testing medium surface, or medium packed in the collection radon cover collecting chamber, because the radon atom in the medium is under diffusion and seepage effect, the effusion surface enters collection radon cover collecting chamber, cause collecting the radon cover and collect the Indoor Niton concentration change, pump will collect with constant flow rate always and pump into measuring chamber after radon in the radon cover collecting chamber leaches daughter by drying tube and filter membrane, flow velocity 0.5-2 liter/minute, make radon concentration balance in radon concentration and the collection radon cover collecting chamber of measuring chamber;

The semiconductor detector is arranged in the measuring chamber, semiconductor detector is connected with secondary instrument, survey the α particle counting that polonium 218 decays are emitted, at the bottom of the measuring chamber and between wall and the semiconductor detector in addition the 50-100 volt/centimetre electric field, make the polonium 218 of the positively charged that radon decay back produces under electric field action, be adsorbed onto on the semiconductor detector face at a high speed, improve detection efficiency;

The radon concentration that measures is the mean concentration in the Measuring Time, concrete corresponding which time point is difficult to determine, adopt short time interval measurement, both measured once in 1-5 minute, just can be similar to and think and the centre of the corresponding Measuring Time of the radon concentration that measures can reduce the long radon concentration time corresponding uncertainty that causes of Measuring Time, short time interval may cause statistic fluctuation bigger like this, can remedy by increasing measurement point, not increase total Measuring Time;

Only measure the anti-radon concentration that pushes away of α particle counting that polonium 218 decays are emitted, can get rid of the interference of thoron fully, constant duration measures one group of radon concentration data, consider to leak and the antidiffusion influence, simultaneously radon and its decay daughter polonium 218 are carried out non-equilibrium correction, just can obtain radon eduction rate on medium furface more accurately;

Two, computation process:

To collect the radon cover and be buckled on the testing medium surface, and at this moment collect the interior radon concentration change of radon cover and can use formula (1) to describe:

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

For the unit interval precipitate into the variation that the radon that collects in the radon cover causes radon concentration, J is a measured medium surface precipitation rate of radon, S is the floorage of collection radon cover, V is collection radon cover spatial volume, the radon concentration change that λ C causes for the decay that collects radon in the radon cover, RC is the leakage of radon and the radon concentration change that antidiffusion causes in the collection radon cover, λ=2.1 * 10 ^-6s ^-1Be the disintegration constant of radon, C is accumulation t radon concentration constantly in the collection radon cover, and R is the leakage and the antidiffusion rate of radon, and t is the time of collection radon;

Make λ _e=λ+R; Make that ENVIRONMENT RADON CONTENT is C ₀, promptly during t=0, the concentration of radon is C in the collection radon cover ₀, formula (1) separate for:

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

$\≈\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-e^{-{\mathrm{\λ}}_{e}t})---\left(2\right)$

It is characterized in that: because in measuring radon concentration process fast, radon concentration is rising always, radon and its decay daughter polonium 218 can not reach balance, and by measuring the anti-concentration that pushes away radon of α particle counting that polonium 218 decays are emitted, the concentration of the radon that obtains is on the low side;

Adopt following method correction:

Its daughter is by the filter membrane filtering when entering the sample cavity of RAD7 for radon, and the radon decay in measuring chamber can be described as:

$\frac{\mathrm{dC}}{\mathrm{dt}}=-\mathrm{\λC}---\left(3\right)$

$\frac{{\mathrm{dC}}_{\mathrm{Po}}}{\mathrm{dt}}={\mathrm{\λ}}_{\mathrm{Po}}C-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}---\left(4\right)$

C _Po(0)＝0

C _PoExpression 218Po concentration; λ _PoBe the 218Po disintegration constant, equal 0.0037s ^-1

The half life period of radon is 3.8235d; The half life period of 218Po is 3.10min, when think measure during radon concentration constant, formula (4) separate for:

$C_{\mathrm{Po}}\left(t\right)=C(1-e^{-{\mathrm{\λ}}_{\mathrm{Po}}t})---\left(5\right)$

Be longer than 20min when the time, 218Po and radon balance, formula (5) can be reduced to:

C _Po(t)＝C??????????????????????????????????????????(6)

The measuring principle of radon concentration utilizes formula (2), (4) just can obtain 218Po decay rule among the RAD7 from formula (6):

$\frac{{\mathrm{dC}}_{\mathrm{Po}}}{\mathrm{dt}}=\frac{\mathrm{JS}{\mathrm{\λ}}_{\mathrm{Po}}}{{\mathrm{\λ}}_{e}V}(1-e^{-{\mathrm{\λ}}_{e}t})-{\mathrm{\λ}}_{\mathrm{Po}}{C}_{\mathrm{Po}}---\left(7\right)$

Solve:

$C_{\mathrm{Po}}\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(8\right)$

Comparison expression (8), (6) can obtain the radon concentration value that the RAD7 actual measurement obtains:

$C_1\left(t\right)=\frac{\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}({\mathrm{\λ}}_e-{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}+{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t})}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}}---\left(9\right)$

$=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1-\frac{{\mathrm{\λ}}_e{e}^{-{\mathrm{\λ}}_{\mathrm{Po}}t}-{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})$

Formula (9) is exactly the revised theoretical model that utilizes the electrostatic collection method to measure precipitation rate of radon fast, obtains precipitation rate of radon according to formula (9) nonlinear fitting.

2, a kind of method of measuring precipitation rate of radon according to claim 1 is characterized in that: general λ when sealing is better _e＜λ _Po, when t＞20 minute, Less than 0.012, with this understanding, formula (9) can be reduced to:

$C_1\left(t\right)=\frac{\mathrm{JS}}{{\mathrm{\λ}}_{e}V}(1+\frac{{\mathrm{\λ}}_{\mathrm{Po}}{e}^{-{\mathrm{\λ}}_{e}t}}{{\mathrm{\λ}}_e-{\mathrm{\λ}}_{\mathrm{Po}}})---\left(10\right)$

According to formula (10), utilize 20 minutes later measurement data nonlinear fittings also can obtain precipitation rate of radon.

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