Файл: Исследование суточных вариаций поровой активности радона в поверхностных грунтах удк 550. 42 546. 296 551. 51.docx

is optional knowledge of the value of the advection velocity, since it is based on the use of already measured values of radon volumetric activity in soil air on depth up to 1 meters. Method developed in 3rd options.

First option method By estimates density flow radon

In this method, you can limit yourself to one measurement of the volume activity soil radon and use information O physical geological parameters soils For estimates values ???? _∞ . Denote

measured on depth h concentration radon ???? ⁽ ℎ ⁾ = ???? _ℎ .

Substitute in

the equation (2)
(2)

Express coefficient at exhibitor in next form
(3)

In accordance with Fick's law and taking into account radiological transferintensity flow radon determined expression (4).
(4)

with taking into account (2) at ???? = 0 expression (4) will accept

view

(5)

Let's write down expression (6) rewriting the equation (5), With taking into account (3) we getformula For estimates density flow radon With surfaces land By measured on certain depth volumetric activity radon in soil air.
(6)

At absence credible information O physical and geological soil parameters instead of values ???? _∞ Can use in calculations, along with With ???? _ℎ , meaning voluminous activity radon, measured on another

depth.

Second option method By estimates density flow radon

When measurements volumetric activity radon produced on depths that differ by 2 times, the second option is more useful method By estimates density flow radon. Substitute in the equation (2) values ^{of radon volumetric activity}

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^???? 1 ^{and ????} 2 ^{measured at depths ℎ} 1 ^{and ℎ2}

_ ^{we get expressions (7) and (2;7)}

???? ₁ = ???? _∞ ⁽ 1 − ???????????? ^{−????ℎ 1 )} , (7)

???? ₂ = ???? _∞ ⁽ 1 − ???????????? ^{−????ℎ 2 )} , (8)

Where

Express ???? and ???? _∞ through ???? ₁ and ???? ₂ . in case, When ℎ2 _{_} = 2ℎ ₁ , systemequations (7; 8) It has simple analytical solution. Denote

???????????? ^{−????ℎ 1} = , Then ???????????? ^{−????ℎ 2} = ???????????? ^{−2????ℎ 1} = ???? ² and equations (7; 8) accept view
???? ₁ = ???? _∞ ⁽ 1 − ???? ⁾ , (9)

???? ₂ = ???? _∞ ⁽ 1 − ???? ^{2 )} , (10)

^{Dividing ????} 2 ^{and ????} 1 ^{and taking a logarithm both parts equations,} we getformula For ????
(11)


Expression For ???? _∞ through measured voluminous activity radon

^???? 1 ^{and ????} 2 ^{looks next way}

(12)

Transforming equation (5), taking into account (11) and (12),

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we obtain a formula for estimating the RFD from the earth's surface using radon pore activities measured at depths that differ by a factor of 2
(13)

Third option method By estimates density flow radon

When measurements volumetric activity radon produced on depths that differ by a factor of , the third option is more useful method By estimates density flow radon.

^{At this ℎ2} _ ^{=???? ∙ ℎ1 ,} _ ^{ratio ????} 1 ^{and ????} 2 ^{is equal to ???? ,}

Having made several transformations with equations (9) and (10), we obtain the expression (14)
???????????? ^_ − ???? + ⁽ 1 − ???? ⁾ = 0. (14)
The resulting nonlinear equation (14) in the general case cannot be solved analytically, however, numerical methods allow solving this equation to determine the unknown quantity .

The advection velocity is expressed in terms of the desired value

???? in the following way

(15)

Meaning equilibrium voluminous activity radon in soilair

equals

(16)

Taking into account relations (15) and (16), the expression for the radon flux density takes the form
(17)

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Static and dynamic methods measurements

pushing off from designs funded cameras, which used to measure the flux density of radon from the ground surface, measurement methods can be subdivided on two main:

static (Cumulative camera All time be in closed condition. measurements produced directly on accumulated quantityradon in the accumulation chamber, with subsequent measurement, the accumulation camera ventilated.) The method is used more frequently. Dynamic (take place continuous circulation air in storage chamber).

3. Detectors for measuringpore activity of radon in the surface soil.

Highly sensitive scintillation intelligent detection unit designed to measure the flux density of alpha particles from contaminated surfaces in the range from 0.1 ppm (min·cm² ).


Figure 3. Scheme installations for measurements density flow radon from the surface soil
where 1 is a storage chamber designed to measure the RFD from the soil surface. The camera is installed in the ground so that the distance from the ground surface to the detector is 10 cm; 2 - detection unit BDPA-01 and BDPB-01.

Applications: Radioecology, sanitary and epidemiological supervision , nuclear industry, fire services, emergency rescue services, civil defense, scientific research.
Table 2 shows the main characteristics of the detection units BDPA-01, BDPB-01 for measuring the density of ionizing radiation fluxes.

Table 2. Main characteristics of detection units

Alpha radiation detection units
Detector	Alpha particle flux density measureme nt range	239 Pu surface activity measurement range	Pu alpha particle fluence measureme nt range	Energy range	239 Pu Alpha Sensitivity imp∙s -1 / part∙min -1 .cm -2	Overall dimensions, weight
	Limit of basic relative measurement error					Degree of protection
Scintil . ZnS ( Ag ) 30cm 2	0.1-10 5 ppm -1 .cm -2	3.4∙10 -3 - 3.4∙10 3 Bq∙cm -2	1-3∙10 6 part∙cm -2	4-7 MeV	0.15	Ø80x196 mm 0.5 kg
	±20%					IP64
Beta radiation detection units
	Beta	Surface	Measurem
Detector	particle flux density measureme nt range	activity measurement range 90 Sr + 90 Y	ent range of fluence of 239 Pu beta particles	Energy range	Sensitivity to beta radiation of the 90Sr+90Y source imp∙s -1 / part∙min -1 .cm -2	Overall dimensions, weight
	Limit of basic relative measurement					Degree of
	error					protection
Scintil . Plastic	1-5∙10 5 part∙min -1 .cm -2	4.4∙10 -2 - 2.2∙10 4 Bq∙cm -2	1-3∙10 6 part∙cm -2	155keV- 3.5 MeV	0.3	Ø80x196m m 0.5 kg
	±20%					3.5 MeV

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The method of monitoring the radon flux density from the soil surface consists of the use of a scintillation (or semiconductor) α - particle detector and an accumulation chamber.

α -particle detector is installed inside the accumulation chamber so that its film is located no closer than 10 cm from the soil surface. Such a limitation makes it possible to exclude the “background”, which

can be determined by detecting α -particles resulting from the decay of soil radionuclides.



Figure 4. Scheme of installation of a device for monitoring the density of radon flux from the soil surface
The accumulation chamber has ventilation holes for partial discharge of soil gas and for maintaining a semi-equilibrium concentration of radon inside the accumulation chamber. The number and size of holes are chosen in accordance with the condition that the pulse count rate inside the accumulation chamber must be at least 10 times greater than the pulse count rate in the open atmosphere at the same distance from the scintillation α-detector film from the soil surface. This allows us to reduce the statistical error of the measurement results.

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