KR20030083465A - Measuring device and Evaluation system for Radon gas - Google Patents

Abstract

PURPOSE: An apparatus for measuring radon gas and a system for evaluating harmfulness of the radon gas are provided to measure concentration of radon gas existing in an underground space. CONSTITUTION: A hose(102) is installed on a fixed measuring point in longitudinal direction of a bore-hole casing(100) maintaining a bore-hole bored on a ground layer(20) to allow gas to flow therein. A filter holder(101) is mounted on one end of the hose. The filter holder comprising an upper filter cap, an O-ring, a filter and a lower filter cap assembled in order, and prevents infiltration of foreign matters other than underground flowing gas needed for measurement of concentration of radon, and leakage of collected gas from the end of the hose. A Tygon tubing packing member(103) is installed on a point around where the hose passes a ground surface to completely seal the casing so as to prevent leakage on a ground surface joining part, and mixture with atmosphere around the ground surface. The hose is connected with a radon measuring cell(30) installed on the ground through the Tygon tubing packing member. The radon measuring cell is connected with a power source such as an air pump.

Description

Measuring device and evaluation system for Radon gas

The present invention is to provide a radon gas measurement device and radon gas risk assessment system utilized in the underground construction site.

Radon (Rn) is a gaseous substance caused by the radioactive decay of radium (Ra) in the uranium and thorium radioactive series. It has colorless and odorless properties. Big. Radon is the second cause of lung cancer following smoking. Especially, even if the concentration of radium in the indoor atmosphere is very low, radiation can be damaged by the generation of radiation, and radon is steadily affected by soil gas, building materials, and groundwater. There is a serious problem in that it can be introduced into the interior space and distributed in any space on earth.

However, despite the serious problem of radon radioactivity, it is hardly recognized by the public in Korea, and there are insufficient governmental regulatory measures, and the radon gas measurement and radon gas risk assessment system, which is useful at underground construction sites, is applied to construction sites. Is almost absent. Even in foreign countries, a system for measuring radon in a systematic manner cannot be found, and only a device for measuring radon concentration sporadically exists.

Therefore, an object of the present invention is to provide a device for measuring the concentration of radon present in the underground space, and a risk assessment model systemizing these devices.

Figure 1a is a block diagram of a device for measuring the radon concentration in the borehole according to the present invention,

1b is a block diagram of an apparatus for measuring radon concentration in a plurality of boreholes according to the present invention;

1C is a detailed view of a filter holder for collecting radon gas-containing air according to the present invention;

1D is a detailed view of the tygon packing member as the sealing means according to the present invention;

2a is a schematic view of a closed device for measuring radon flux to ground-surface to the atmosphere according to the present invention;

FIG. 2B is a schematic view of an open device for measuring radon flux to ground-surface to the atmosphere according to the present invention; FIG.

Figure 3a is a block diagram showing an apparatus for measuring the divergence rate of radon moving to the pores in the medium according to the present invention,

Figure 3b is a block diagram showing an apparatus for measuring the rate of divergence of radon moving from the production medium of radon to another medium according to the present invention,

Figure 4a is a block diagram showing an apparatus for detecting the radon concentration in the underground space according to the present invention, and

4B is an enlarged perspective view of the container portion of FIG. 4A.

<Description of Signs of Major Parts of Drawings>

(10): radon detector (100): borehole casing (101): filter holder

(102): hose (30): radon measuring cell (200): air pump

120: collecting container (121): rubber packing

The present invention provides a model capable of comprehensively evaluating radon risk in consideration of radon concentration measurement in the underground space, as well as generation, divergence and movement of radon. To this end, the present invention (1) a device for measuring radon in the underground borehole (2) a device for measuring the radon flux emitted to the indicator-air (3) a device for measuring the radon divergence rate and (4) underground space ; Provide a device for measuring the concentration of radon generated and moved in the walls of the cavity (tunnel, tunnel, etc.).

Furthermore, the present invention integrates the measuring apparatus of (1) to (4) above to provide a system for finding out each radon concentration or divergence rate and efficiently evaluating the risk of radon therefrom.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1. Radon gas measuring device in underground borehole

Radon measurement in boreholes is the measurement of radon concentrations by extracting radon-containing gases directly from the borehole immediately after or at the end of the operation.

In the radon gas measuring apparatus of the present invention for this purpose, as shown in Figure 1a, the hose 102, which allows the internal gas flow in the borehole casing 100 to maintain the borehole drilled in the ground layer 20, the longitudinal direction of the casing The filter holder 101 is installed at a predetermined measuring point along one end of the hose 102. The filter holder 101 is made by assembling the upper filter cap 113, the O-ring 114, the filter 111, and the lower filter cap 112 in order as shown in FIG. 1C. Foreign matter other than underground flow gas, which is necessary for this purpose, is prevented from entering the hose or collecting gas leaking from the hose end. Further, in the vicinity of the hose 102 passing through the ground, a Tygon packing packing member 103 as shown in FIG. 1D is installed to completely seal the casing 100, thereby preventing leakage and indices at the ground joint. The mixing with the atmosphere is prevented, and the hose 102 communicates with the radon measuring cell 30 installed on the ground through the tygon tubing packing member 103. The radon measuring cell 30 is connected to a power source 200 such as an air pump. The radon detector 10 performs quantitative measurement of radon concentration for the gas finally collected in the cell 30. The radon detector 10 may use a known radon detector, which calculates the radon concentration based on the amount of radioactive radon (radon is the only radioactive element present in gaseous form) and informs the user. The measuring device of the present invention having such a configuration drives the air pump 200 connected to the cell 30 to suck the soil gas G from the hose 102 communicated to the inside of the borehole, thereby transferring radon to the cell 30. Collect the gas containing.

In the present invention, the qualitative evaluation of the radon concentration, that is, the contrast between the theoretical value and the measured value and the evaluation can be performed as follows.

First, the calculation of the radon concentration for each depth in relation to FIG. 1 may be generally expressed as follows.

Rn (Z) = Rn (∞) * [1-exp (-Z / L)]

Where Z is the depth of independence, ∞ is the depth of infinity, and L is the diffusion length of the radon atom, representing the distance that can be traveled over the average lifetime of radon (about 5.5 days).

Where Rn (∞)

Rn (∞) = [soil density (g / cm 3) * 1000 (unit correction factor) * Ra (pCi / g) * divergence factor]

Soil Porosity

Obtained through the equation, the soil density, Ra content, soil porosity, etc. are used by the values obtained by general experiments and analysis, the divergence coefficient can be used in the device of Figure 3 to be described later.

L is also

L = [D / (λ * S)] ^0.5 , where λ is the decay constant of radon, 2.1 * 10 ^-6 dps (disintegration per second), S is the soil porosity, and D is the media As the diffusion coefficient of radon at, we use the known values obtained experimentally according to the medium.)

In this way, the radon concentration can be theoretically calculated at the corresponding depth Z and compared with the measurements obtained for each depth in the actual borehole. Radon concentrations are highly variable and potentially uncertain because they are measured in varying air atmospheres. However, if the radon concentration value of the closest data set is determined as a representative value by comparing several groups of measurement values obtained by repeatedly measuring the depths in the borehole with theoretical values, the variable range of the absolute value of the radon concentration Since it is corrected by qualitative data, it is possible to calculate the radon concentration at the corresponding depth more accurately.

Furthermore, the measuring device of the present invention can be utilized for the radon measurement by depth in the borehole, as shown in Figure 1b. In this case, the measuring apparatus is provided with filter holders 101 installed at the ends of the hoses 102, 102,... 102 in the plurality of boreholes according to their respective depths, and each hose 102 is similar to that shown in FIG. 1A. It is likewise connected to each radon measuring cell 30. Since the soil gas (G) collected in the cells (30, 30..30) is collected at different underground depths, such a device can be used to measure radon content at various underground points to determine the radon concentration in the entire borehole. The representative value (average value) can be calculated.

2. Apparatus and method for measuring radon flux to ground-air

The measurement of radon flux to ground-to-air is the measurement of radon flux in ground-layer soil gas (G) that passes through the surface and is released into the atmosphere.

There are two types of apparatus for performing this, the closed type shown in FIG. 2A and the open type shown in FIG. 2B. First, the closed type is described. As shown in FIG. 2A, the edge of the collecting container 120 is wedge. It is fixed to the ground by the mold needle tower 122, and the rubber packing 121 is installed at an approximately halfway point of the container 120 to seal the inner space of the container and the outside atmosphere. Container 120 is a box-shaped rectangular parallelepiped form without a bottom, it is preferable that the height is 30-50cm, the width is 50-80cm, the rubber packing 121 is to be installed about 4-10 along both sides of the container. desirable. Then, the hose 102 passes through the upper surface of the container 120 through the rubber packing 123 for sealing, and at one end thereof, a filter holder 101 for collecting gas is installed. The other end is connected to the radon measuring cell 30 in the same manner as described in FIG. Since it consists of such a structure, the internal space of the container 120 is open only to the ground surface, and will be in the state completely interrupted | blocked with the outside air. In addition, as described in FIG. 1, the air pump 200 is driven to collect gas through the filter holder 101 installed at the end of the hose 102, and then transfer the gas to the cell 30. Only the soil gas diffused and diverged from the ground is collected in the radon measuring cell 30, and the radon concentration is measured using the radon detector 10.

Radon flux is calculated from the following equation based on radon concentration measured with a radon detector.

Flux = measured radon concentration / (measurement time * cross-sectional area)

That is, the radon concentration emitted to the atmosphere from the surface of the unit area per unit time becomes a flux value, in the case of Figure 2 the area of the container is "cross-sectional area".

On the other hand, the open type shown in Figure 2b is removed from the rubber packing 121 in the device of Figure 2a is the same as the closed configuration, in this case, both sides of the container 120 is opened, as a result, the atmosphere in addition to the soil gas The mixed gas is collected and radon flux is measured for the mixed gas. The open case is significant because it measures the radon content in the real human realm. The radon concentration of the mixed gas is lower than the radon concentration measured in the closed type. In addition, the apparatus as described above has the advantage that it is extremely easy to switch between open and closed.

3. Apparatus and method for measuring radon divergence rate

The radon divergence rate measurement according to the present invention measures the emanation rate of radon moved from the medium to the pore and the rate of exhalation delivered from the medium in which radon is generated to another medium (eg, the atmospheric layer). There is a way.

First, as shown in FIG. 3A, an apparatus for performing the former is preferably filled with soil (ground material) in a rectangular column-type sealed container 130, and around the container 130 in the soil. A plurality of water injection passages (131, 131 ... 131) extending up to are provided at equal intervals around the upper and side surfaces of the container. The size of the container is preferably 50-100cm in height, the cross-sectional area is 20cm * 20 cm, it is preferable to install eight water inlets, but is not necessarily limited thereto. Then, filter holders 101 for collecting gas are installed around the top, bottom, and side surfaces of the container 130 (six in this embodiment), and the installation positions thereof may be changed to collect the gas in the soil evenly. Can be. The filter holder 101 is connected to a hose as described in FIG. 1, and the gas collected around each container 130 is delivered to the radon measuring cell 30.

According to the apparatus of the present invention, by supplying water through the water injection passages (131, 131 ... 131), it is possible to measure the radon divergence rate in the soil according to the change in the moisture content. The radon divergence rate here is the concept of the ratio of the number of radon atoms moved to the actual void to the theoretical number of radon atoms produced in the medium. In theory, the number of radon atoms produced is determined by the amount of radon's parent species, radium and uranium, but the number of radon atoms moved to the pores in the actual soil is variable by the physicochemical properties of the medium. Therefore, the radon divergence rate is measured to predict the radon potential of the medium.

Next, the apparatus for measuring the divergence rate according to the movement of the medium is the same as shown in Figure 3b, filling the ground material such as soil only in the lower portion of the container 130 so that the air is present in the upper portion, the water inlet 131 Is installed to connect to the soil, and the hose and filter holder for collecting the gas is disposed in the vessel 130 portion where the air is present is different from the apparatus of Figure 3a. In addition, the separation membrane 132 is used between the soil and the air in the container 130 is configured to block the soil gas and air in the first step.

The method of using such a device is not the same as measuring the radon in the pores of the ground material but the rate of divergence of the radon gas moved to the atmosphere after moving to the pores. Can be. That is, in the initial stage, air and soil are separated by the separator 132 and water is injected into the soil, and after a suitable time, the separator 132 is separated to measure the content of radon gas moved into the air. The divergence rate of radon gas transferred from one medium (soil) to the second medium (air) can be known.

The measurement of the radon divergence rate using the apparatus demonstrated above, after finding out the actual radon measurement amount,

Rn (∞) = [soil density (g / cm 3) * 1000 (unit correction factor) * Ra (pCi / g) * divergence factor]

Soil Porosity

The theoretical radon concentration value obtained by setting the divergence rate to 100% is found and compared. For example, a medium capable of producing 100 pCi / L. If the test result is 30 pCi / L, the divergence rate is 30%.

4. Radon Concentration Evaluation System and Method in Underground Space

This method measures the radon concentrations generated and transported from the walls of underground spaces (cavities, tunnels). Since radon concentrations in underground work places directly affect human health, it is necessary to quantitatively and qualitatively evaluate the inflow of radon from the underlying medium into the ground air.

The apparatus of the present invention for achieving this object is provided with a collecting container 150 on the wall and / or bottom surface of the underground tunnel, and the rubber clay or silicon injection material, such as shown in Figure 4a The sealing material 151 is used to seal the both and fix the container 150 at the same time. As shown in FIG. 4B, a portion of the filter holder and the hose for collecting the gas is positioned in the inner space of the container 150 to collect the gas emitted from the underground wall.

In underground cavities, the mass balance associated with radon can be expressed by the equation

SE = λVCin + QCin-QCout

Where S is the surface area of the cavity, E is the amount of radon diverged per unit time from the unit area, λ is the decay constant of radon, V is the volume of the cavity, Q is the amount of air flow per unit time (ventilation), and Cin is inside the cavity The radon concentration of Cout is the radon concentration outside the cavity. Since Cout is much smaller than Cin, it is ignored.

Cin = SE / (λV + Q)

Becomes

When the collection container of FIG. 4 is experimented using the same concept as that of FIG. 2, the value of E can be inferred, and Cin can be theoretically calculated from the average value of the E values. Furthermore, it can be seen that by properly adjusting the Q, that is, the ventilation amount, the radon concentration value can be reduced below the regulation value.

5. Utilization of the integrated system of the present invention

The present invention has another feature in that radon concentration, divergence rate, etc. can be measured according to the above-described items 1 to 4, and the radon risk can be effectively evaluated based on these results. For example, in the case of subway construction, after the drilling rig at the beginning of the construction, the radon concentration is calculated for each depth in the ground, and the overall evaluation (radon potential of the ground) is performed, and the flux in the surface is measured to the upper atmosphere of radon Find the divergence rate of. Next, the degree of radon divergence of the soil is determined by determining the divergence rate considering the porosity and the presence of other media, and finally, measuring the radon concentration in the actual underground workplace. This last step is to measure the radon concentration that most affects the human body. If the radon concentration is higher than the reference value, the cause is due to, for example, excessive radon content in the ground (Fig. 1), whether the amount is largely out of the surface (Fig. 2), or the divergence rate is high (Fig. 3). Alternatively, it is possible to accurately determine whether or not the ventilation amount is small from the measured data and the theoretical value, so that appropriate countermeasures can be taken. This integrated model provides a systematic system for evaluating radon risks in the ground.

Conventional techniques for measuring radon concentrations have remained only to detect concentration at a certain point, but it is necessary to accurately determine whether radon concentration is excessive and its cause by considering various environments and variables (concentration, flux, divergence rate, etc.). It is a feature of the present invention that it can.

The present invention described above includes (1) an apparatus for measuring radon in an underground borehole, (2) an apparatus for measuring radon flux emitted from an indicator-atmosphere, and (3) an apparatus for measuring radon divergence rate, and (4) an underground space. Devices are provided to measure radon concentrations generated and transported on the wall, so in each case it is possible to accurately measure radon concentrations, fluxes and divergence rates. Each of these devices is novel and unknown in the prior art.

Furthermore, the present invention provides a system for efficiently evaluating the risk of radon by incorporating the measuring device of (1) to (4) above, thereby assessing the radon concentration systematically and overall, as well as the risk factors of radon. It can be analyzed, and the countermeasure can be taken.

Claims (8)

A borehole casing for retaining boreholes perforated in the ground layer; A hose installed in the borehole casing along a longitudinal direction, one end of which is equipped with a filter holder for collecting air containing radon gas, and the other end of which is connected to a radon measuring cell installed on the ground; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; Radon detector for measuring the radon concentration from the air collected in the radon measuring cell; consisting of an apparatus for measuring the concentration of radon gas in the underground borehole. A collecting container installed on the ground in a sealed state with an external atmosphere; A hose installed through the upper surface of the container, the filter holder installed at one end thereof is located inside the container, and the other end thereof is connected to a radon measuring cell; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; A radon detector for measuring radon concentration from air collected in the radon measuring cell; And a radon flux from the ground to the atmosphere. A collecting container installed on the ground in communication with the outside atmosphere; A hose installed through the upper surface of the container, the filter holder installed at one end thereof is located inside the container, and the other end thereof is connected to a radon measuring cell; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; And a radon detector for measuring radon concentration from air collected in the radon measuring cell, the radon flux being measured from the ground surface to the atmosphere. A columnar sealed container filled with soil therein; A plurality of water injection passages installed at equal intervals around the upper and side surfaces of the vessel and extending into the soil of the vessel; A filter holder installed at a predetermined point of the container and collecting radon-containing gas in the soil of the container at one end thereof, and the other end of which is connected to a radon measuring cell; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; A radon detector for measuring radon concentration from air collected in the radon measuring cell; Apparatus, characterized in that for measuring the divergence rate of radon moved to the pores of the soil. A column-type closed container configured to fill air at the upper part and soil at the lower part, and separate the air layer and the soil layer; A plurality of water injection passages installed around a side of the container surrounding the soil layer and extending into the soil of the container; A filter holder installed at a predetermined point surrounding the air layer of the vessel and collecting the radon-containing gas of the air layer at one end thereof, and the other end of which is connected to a radon measuring cell; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; A radon detector for measuring radon concentration from air collected in the radon measuring cell; The device is characterized in that for measuring the divergence rate of radon moved from the air gap in the soil to the air layer. A container which is installed in a sealed state with air outside by sealing a lower portion thereof to a wall surface and / or a bottom surface of an underground space; A filter holder installed inside the container and collecting radon-containing gas at one end thereof, and the other end of which is connected to a radon measuring cell through the container; A power source connected to said radon measuring cell for providing power to suck radon gas containing air; A radon detector for measuring radon concentration from air collected in the radon measuring cell; The device is characterized in that for measuring the radon gas concentration in the underground space. A device for measuring the radon gas concentration according to the depth in the underground borehole; A device for measuring radon flux from the surface to the atmosphere; An apparatus for measuring radon divergence rate in consideration of soil porosity of the ground; A device for measuring the divergence rate of radon moving from the soil to the air layer; And Radon risk assessment system, characterized in that consisting of; device for measuring the concentration of radon in the underground space. Measuring the radon gas concentration according to the depth in the underground borehole; Measuring radon flux from the surface to the atmosphere; Measuring a radon divergence rate in consideration of the soil porosity of the ground; Measuring the divergence rate of radon moving from the soil to the air layer; And Measuring the radon concentration in the underground space; risk assessment method of radon, characterized in that consisting of.