JP3559727B2 - Radionuclide absorber and method for measuring radionuclide concentration using it - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an absorber for a radionuclide existing in a gas phase or a liquid phase and a method for measuring the concentration of a radionuclide using the same.
[0002]
[Prior art]
Conventionally, toluene is used as a radionuclide absorber in a liquid, a solvent extraction method is used in which the toluene is added to a liquid in which a radionuclide is present to absorb the radionuclide, and the toluene in which the radionuclide is absorbed is removed from the liquid. A measurement method using a liquid scintillation detector for measuring the concentration of a radionuclide in a toluene solution in which the radionuclide is absorbed by liquid scintillation measurement is generally used. This radionuclide concentration measurement method is suitable for measuring the liquid phase.
[0003]
On the other hand, activated carbon is known as a radionuclide adsorbent in a gas phase, and this activated carbon (powder) is placed in a gas phase in which a radionuclide exists for a certain period of time to adsorb the radionuclide in the gas phase. A method is known in which toluene is used to absorb the radionuclide adsorbed on the activated carbon, and the presence or absence and relative concentration of the radionuclide are measured by measurement using a liquid scintillation detector similar to the above.
[0004]
Absorption means being taken up by another substance, and adsorption means being retained on the surface of a solid or liquid, and is different from absorption entering the solid or liquid.
[0005]
[Problems to be solved by the invention]
However, toluene used in the solvent extraction method is harmful to health, requires not only safety in handling, but also requires special measuring equipment for performing a measuring operation, and requires many man-hours. As described above, it is not suitable for measurement in a gas phase.
[0006]
Although the above activated carbon adsorption method can be measured in the gas phase, it can only measure the presence or absence and relative concentration of radionuclides, but has the fatal drawback that the absolute concentration is difficult to measure and accurate concentration measurement cannot be performed. are doing.
[0007]
[Means for Solving the Problems]
The present invention solves these problems appropriately, and a radionuclide absorber capable of easily and highly reliably measuring radionuclides present in a gas phase or a liquid phase, and a radionuclide using the same. It provides a method for measuring the concentration of nuclides.
[0008]
The radionuclide absorber according to the present invention is composed of an oil-soluble solid polymer substance represented by expanded polystyrene and other solid polymer substances.
[0009]
That is, the radionuclide absorber according to the present invention is an absorber of a radionuclide existing in a gas phase or a liquid phase, and is composed of a solid polymer substance used by being installed in the gas phase or the liquid phase.
[0010]
A solid polymer substance is placed in a gas phase or a liquid phase for a certain period of time to absorb radioactive nuclides, the solid polymer substance having absorbed the radionuclide is dissolved in a solvent, and the above-mentioned gas is determined from the radiation count value of the solution. The concentration of the radionuclide in the phase or liquid phase is measured.
[0011]
The so-called solid polymer substance is applied to a liquid scintillation detector to measure the concentration.
[0012]
The radionuclide absorber made of a solid polymer material represented by the expanded polystyrene is easily available, extremely inexpensive, and safe.
[0013]
By simply pushing the radionuclide absorber composed of the solid polymer substance into the container containing the liquid scintillator, the sample liquid can be obtained without the need for an operation having many opportunities to impair the safety as in the conventional example. By applying a known liquid scintillation detector to, a highly reliable concentration measurement can be performed safely and quickly. The measurement cost is also low.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0015]
The radionuclide absorber 1 according to the present invention is made of a solid polymer substance represented by expanded polystyrene. The solid polymer material is formed into a block having a size suitable for being pushed into the measuring container 2.
[0016]
Alternatively, the powder is used as a sheet or powder, and the powder is housed in a container having ventilation and water permeability, and is placed in a gas phase or a liquid phase.
[0017]
The block or sheet is supported and allowed to stand in a gas phase or a liquid phase with the entire surface exposed as much as possible.
[0018]
As shown in FIGS. 1A and 1B, the radionuclide absorber 1 made of the solid polymer material according to the present invention is formed, for example, of expanded polystyrene in a column, and preferably in a column, as shown in FIG. 1A. .
[0019]
The shape and size of the measurement container 2 for preparing the sample liquid applied to the liquid scintillation detector shown in FIG. 2 are standardized worldwide, and when the diameter is R2, the column of the radionuclide absorber 1 is provided. The diameter R1 of the block 1 'is made substantially equal to R2, and the liquid scintillator 3 in the measurement container 2 (a test solution obtained by dissolving a small amount of an organic fluorescent substance using toluene or xylene as a solvent while gradually pushing in close contact within the diameter). ) And gradually promote dissolution.
[0020]
At this time, in order to prevent the liquid scintillator 3 from overflowing as the column block 1 'is pushed in, through holes 4 opening at both end surfaces are provided in the axis of the column block 1'.
[0021]
As the column block 1 ′ is pushed into the measurement container 2, the liquid scintillator 3 penetrates into the through hole 4 and dissolves the radionuclide absorber 1 composed of the block from the inner surface of the through hole 4.
[0022]
Further, since the liquid scintillator 3 is pushed up into the through hole 4, overflow from the mouth of the measurement container 2 is prevented.
[0023]
As another preferred example, as shown in FIG. 1B, a column block 1 'composed of a column is bisected in the axial direction to form a semi-cylindrical block, and has a long groove 4' along its plane as a suitable example. Form.
[0024]
The through-holes 4 and the long grooves 4 'are means for increasing the contact area with the liquid scintillator 3 and promoting uniform dissolution. As a modified example, a plurality of through-holes 4 are formed from one end face to the other end face of the columnar block 1'. And a case where a plurality of the long grooves 4 ′ are formed. The outer diameter may be a polygonal column or a flat plate.
[0025]
The long groove 4 'is advantageous for wiping the surface after the column block 1' is pulled up from the liquid phase.
[0026]
As the solid polymer substance forming the radionuclide absorber 1, non-expanded polystyrene, polyvinyl methyl resin such as polymethyl methacrylate, polyethylene, and polypropylene can be applied in addition to the expanded polystyrene, but a general-purpose liquid scintillation detection is used. From the viewpoint of application to vessels, foamed or non-foamed polystyrene having oil solubility and polymethyl methacrylate are suitable.
[0027]
The radionuclide absorber 1 can be embedded in the ground and used for detecting radionuclides in the ground, and is included in the concept of gas phase or liquid phase depending on the moisture content in the ground.
[0028]
Hereinafter, an example in which radon concentration measurement was performed using radon in water as a radionuclide and expanded polystyrene as an absorbing substance, that is, a solid polymer substance, will be described. This example does not limit the invention.
[0029]
The expanded polystyrene absorber formed in a prismatic block of 10 (length) × 10 (width) × 50 (length) mm was placed in water containing radon and set for 24 hours or more.
[0030]
When the polystyrene is allowed to stand in water containing radon, the amount of radon absorbed by the polystyrene in the standing time of 24 hours or more becomes a constant value, and it is clear that a distribution law relationship is established between polystyrene and water. (See FIG. 3).
[0031]
The graph of FIG. 3 shows the concentration of radon in polystyrene on the vertical axis and the concentration of radon in water on the horizontal axis. The graph shows that the two are in a straight line (directly proportional) relationship passing through the origin, that is, the distribution rule relationship is established. It indicates that
[0032]
The radon absorption amount (becquerel / g) per unit weight (1 g) of polystyrene for which the distribution rule was established was directly proportional to the radon concentration in water (becquerel / g). This constant of proportionality is called the Radon distribution coefficient in a broad sense.
[0033]
Using the above relationship, the radon concentration in water can be calculated from the concentration of radon absorbed by polystyrene.
[0034]
If, for example, a columnar block 1 'of polystyrene having the same size and shape as described above is used as a standard absorber and its radon distribution coefficient is clarified as a constant, a measured value (Radon The concentration of radon in water can be determined simply by dividing the concentration) by a constant (partition coefficient).
[0035]
That is, as shown in FIG. 2, the expanded polystyrene absorber 1 is pushed into a measuring container 2 containing a liquid scintillator 3 and dissolved therein. Then, the container 2 of the liquid scintillator in which the radon is dissolved is sealed with a lid, and is applied to a liquid scintillation detector.
[0036]
The liquid scintillation detector here is widely used as a radiation measuring instrument worldwide as introduced in, for example, "Maglow Hill Scientific and Technical Dictionary" and "Science Dictionary" edited by International Technology Foundation.
[0037]
The radon concentration in water was calculated by dividing the radiation count value obtained from the liquid scintillation measurement by the radon partition coefficient.
[0038]
The Radon partition coefficient of the expanded polystyrene was about 130 with respect to water. The total error in the radon concentration calculated using this method was 10%.
[0039]
When 2 g of expanded polystyrene is used, radon detection sensitivity and accuracy comparable to the solvent extraction method using toluene as a conventional radionuclide absorber can be achieved in the gas phase and the liquid phase.
[0040]
Absorbent foaming resins represented by the above-mentioned expanded polystyrene include those having a communicating cell structure and those having a non-communicating cell structure. The foaming resin having a communicating cell structure contains a solvent such as a liquid scintillator 3 in the communicating cells. As a result, the contact area with the solvent is large, and the dissolution rate is greatly improved. Also, the density is low and the amount of dissolution is small.
[0041]
【The invention's effect】
According to the present invention, the radionuclide in the liquid phase and the gaseous phase is very easily practically used by standardizing the density, shape and mass of the expanded polystyrene and using a material whose radon partition coefficient is valued. It is possible to determine the concentration.
[0042]
According to the present invention, not only the measurement operation is simple, but also a radionuclide absorber made of a solid polymer substance represented by the above-mentioned expanded polystyrene is easily available, extremely inexpensive, and safe.
[0043]
By simply pushing the radionuclide absorber composed of the solid polymer substance into the measurement container, the sample liquid can be obtained without the need for an operation having many chances of impairing the safety as in the conventional example. By applying the scintillation detector, highly reliable concentration measurement can be performed safely and quickly. The measurement cost is also low.
[Brief description of the drawings]
FIG. 1A is a perspective view of a radionuclide absorber composed of a solid polymer substance formed in a columnar block shape, and FIG. 1B is another example of a radioactive absorber composed of a solid polymer substance formed in a columnar block shape. FIG.
FIG. 2 is a cross-sectional view showing a state in which the column-shaped radionuclide absorber is pushed into and dissolved in a liquid scintillation measurement container.
FIG. 3 is a graph showing a distribution law relationship between a radon concentration in polystyrene and a radon concentration in water.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Radionuclide absorber 1 'Column block 2 Measurement container 3 Liquid scintillator 4 Through hole 4' Long groove

Claims (2)

An absorber of a radionuclide present in a gas phase or a liquid phase, which is composed of a solid polymer substance used by being installed in the gas phase or the liquid phase, wherein the solid polymer substance has a distribution rule. A radionuclide absorber characterized by comprising an oil-soluble expanded polystyrene or a non-expanded polystyrene . An oil-soluble expanded polystyrene or a non-expanded polystyrene in which a distribution rule is established is set in a gas phase or a liquid phase for a certain time to absorb a radionuclide, and the expanded polystyrene or the non-expanded polystyrene absorbing the radionuclide is dissolved in a solvent. A method of dissolving and measuring the concentration of a radionuclide in the gas phase or liquid phase from the radiation count value of the solution.

Images