JPH0360072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting radioactive substances. More specifically, the present invention relates to a method for detecting radioactive substances using a stimulable phosphor.

Conventionally, the method of measuring the radioactivity of a sample containing a radioactive substance to detect radioactive substances (substances containing radioactive isotopes) contained in a liquid sample involves dissolving a solute (fluorescent agent) in an organic solvent. A well-known liquid scintillation method is a method in which radioactivity in a sample is detected as fluorescence by adding a liquid scintillator to the sample. In this method, a part of the radiation energy emitted from a radioactive substance in a sample is absorbed by a scintillator, and the radioactivity of the radioactive substance is measured by detecting the fluorescence (instantaneous luminescence) emitted from the scintillator. It is.

The liquid scintillation method described above is also applied when samples containing radioactive substances are obtained continuously (or intermittently) by spillage, etc. After a certain amount of the sample is taken, a liquid scintillator is added to the sample. The radioactivity inside is being measured.

For example, as a separation analysis method, a sample solution is injected into a packed tower (column) filled with a packing material such as an adsorbent, and then an appropriate solvent is injected to develop the sample, and the sample components are transferred to the column. Liquid chromatography, which consists of fractionating the flow from a liquid, is well known. This liquid chromatography is also used to separate samples containing radioactive substances, and by measuring the radioactivity of the eluate separated by liquid chromatography, it is possible to separate radioactive substances in the sample. Identification is underway.

In other words, a sample containing radioactive substances separated and developed by liquid chromatography is collected using a fraction collector, a liquid scintillator is added to each fraction, and the fluorescence emitted from the liquid scintillator is collected using a photomultiplier tube. By detecting and counting the electrical pulses, the radioactivity contained in each fraction is measured, and the radioactive substances in the sample are separated and identified.

The liquid scintillation method described above has the advantage of being able to measure the radioactivity even when the radiation emitted from radioactive substances is weak radiation such as α rays and β rays. Widely used to measure radioactivity.

However, when the above conventional liquid scintillation method is used for a liquid sample containing radioactive substances that is obtained continuously (or intermittently) as in the above liquid chromatography, the liquid sample cannot be separated by liquid chromatography. The developed sample is transferred to a large number of scintillation measuring containers (vials).
After fractionation using a fraction collector consisting of a sample, radioactivity is detected for each fractionated volume of the sample by measuring each measurement container with a scintillation counter.

Therefore, in order to accurately separate and identify radioactive substances in a sample by detecting the radioactivity of the separated and developed sample, a larger number of measurement containers are required as fraction collectors.
This also means that the measurement operations for separating the sample solution outflow and detecting radioactivity become complicated.

In addition, in the liquid scintillation method, the scintillator emits light by first exciting the solvent molecules formed by dissolving the solute (fluorescent agent) by the energy of the radiation emitted from the radioactive substance in the liquid sample. This occurs when solute molecules are excited due to collisions between solvent molecules and solute molecules (scintillators). In addition to this process in which radiation energy is transferred from solvent molecules to solute molecules, energy is transferred between solvent molecules due to interactions between solvent molecules in an excited state and solvent molecules in a ground state. This also includes the case where the scintillator is excited after energy is transferred to another solute molecule due to the interaction between the excited solvent molecule and another solute molecule other than the scintillator. Furthermore, this energy transfer occurs not only through interactions between molecules such as collisions, but also when the scintillator absorbs fluorescence emitted from excited solvent molecules or other solute molecules.

However, during this energy transfer process, the excitation energy may be absorbed by some solvent molecules or other solute molecules and then converted into heat, or the fluorescence emitted from the scintillator may be absorbed by the sample. At the same time, quenching phenomena such as absorption by objects also occur.

The liquid scintillator essential in the liquid scintillation method is expensive and requires separation and purification before reuse. Furthermore, since scintillators are usually difficult to recover with high purity, they are not often reused, which also increases measurement costs. Furthermore, there are several problems in handling scintillators that contain used radioisotopes, such as the fact that they are difficult to dispose of.

In addition, in liquid scintillators, the solvent used in combination with the solute (fluorescent agent) is generally an organic substance and is limited, so it is difficult to select a solvent for the sample. Requires some ingenuity in the preparation method.

As mentioned above, since the light emitting mechanism of liquid scintillators is complex, the counting efficiency tends to decrease (that is, the detected radioactivity intensity decreases) due to the quenching effect of mixed impurities and the sample itself. For example, fluorescence emitted from a scintillator is easily quenched by oxygen dissolved in the scintillator, or if the sample solution is colored, the colored substance absorbs (ie, quenches) the fluorescence. In addition, when the sample is poorly soluble as mentioned above, it is difficult to make the sample solution into a homogeneous phase, and this heterogeneous phase causes internal absorption of radiation emitted from the sample. be. Therefore, it is necessary to correct for the quenching caused by the various causes mentioned above to accurately determine the sample counting efficiency, which makes the measurement operation complicated.

In order to prevent a decrease in counting efficiency due to the quenching effect of impurities, contaminants, colored substances, etc. mixed into the sample, careful preparation of the sample is required, and the measurer must have a high degree of skill and experience. required.
In addition, sample pretreatment to remove the above-mentioned contaminants has become important.

Furthermore, in the liquid scintillation method,
Radiation measurements of samples are performed in real time. That is, after adding a scintillator to a liquid sample, it is necessary to continuously measure the light emitted from the scintillator for a certain period of time (for example, several minutes to several tens of minutes). When the intensity of the radiation is low, the measurement time (measurement time) is long, and it cannot be said that the measurement efficiency and the operating rate of the measurement device are sufficiently high.

Therefore, when the sample consists of a large number of samples as described above, the waiting time becomes long, which causes problems such as it is difficult to process a large number of samples and it takes time to obtain results. ing. In particular, it is difficult to measure radiation when the radioactive isotope in the sample has a short half-life, and even more difficult when the intensity of the radiation is weak. This also means that the equipment used must be stable for long periods of time (e.g. against dark current drift in photomultiplier tubes), and in order to prevent this This results in either expensive equipment or requiring experience and skill in adjusting the equipment.

The present inventor has conducted extensive research with the aim of solving the above-mentioned problems associated with the conventional liquid scintillation method used to measure the radioactivity of liquid samples containing radioactive substances that are obtained intermittently or continuously. As a result, a long measuring device containing a stimulable phosphor was moved, a liquid sample was continuously dropped or flowed onto the measuring device, and the liquid sample was then absorbed into the measuring device. The inventors have discovered that the above-mentioned problems can be solved or the drawbacks can be reduced by utilizing a method of measuring the radiation energy, and have arrived at the present invention.

That is, in the present invention, a liquid sample containing a radioactive substance is continuously supplied to the surface of a long measuring tool containing a stimulable phosphor, while the measuring tool is moved in the longitudinal direction of the measuring tool. Preferably, the liquid sample is continuously applied to the measuring device so that at least a portion of the radiation energy emitted from the radioactive substance is absorbed by the measuring device, and then the radiation energy is accumulated in the measuring device. The present invention provides a method for detecting radioactive substances, which comprises continuously measuring the radioactivity in the sample by emitting radiation energy as photostimulated light and reading the stimulated light photoelectrically.

In the present invention, "continuous" does not necessarily mean a completely continuous state, but also a semi-continuous state, that is, an intermittent state.

The stimulable phosphor used in the present invention emits light (stimulated luminescence) when it is irradiated with electromagnetic waves (excitation waves) such as visible light and infrared rays after absorbing radiation.
It has the property of showing. Therefore, after the radiation emitted from the radioactive substance of the sample attached to the measuring device containing a stimulable phosphor is absorbed by the measuring device, the measuring device is exposed to electromagnetic waves (such as visible light and infrared rays). By irradiating the sample with excitation light, the accumulated energy proportional to the radiation dose is emitted as fluorescence (stimulated luminescence), and the radioactivity of the sample is measured by photoelectrically reading this fluorescence and converting it into an electrical signal. be able to.

Therefore, according to the present invention, by continuously dropping (or flowing down) a liquid sample containing a radioactive substance onto a moving long measurement device, separation as in liquid chromatography, etc. can be performed. For a sample that is developed and flows out continuously, the sample can be continuously attached to the measuring tool, and radiation from the sample can be continuously absorbed by the measuring tool. Also,
By irradiating the measurement tool that stores this radiation energy with appropriate excitation light, the radiation energy stored in the measurement tool can be continuously read out as stimulated luminescence. In other words, it is possible to continuously detect radioactive substances in separated and developed samples.
This makes it possible to separate and identify radioactive substances with high precision.

Furthermore, according to the present invention, since the emission time of photostimulated light is instantaneous, the measurement time of photostimulated light can be set regardless of the radiation intensity of the sample. The readout operation after the radiation energy from the sample is continuously stored in the measurement tool only takes several seconds to several tens of seconds, which can shorten the measurement time.

Conventionally, a scintillator was added to each container of the sample collected using a fraction collector, and then the radioactivity was measured using a scintillation counter. However, according to the present invention, the measuring device containing the above-mentioned stimulable phosphor is moved in the longitudinal direction of the measuring device, and the sample is continuously placed on the measuring device. By attaching the measurement device to the target and then moving it further to read out the radiation energy stored in the measurement device, it is possible to perform both of the above operations in one step (on line). In this respect as well, the time required for conventional measurements can be shortened and the measurement operation can be greatly simplified.

Therefore, the operating rate of the measuring device can be increased and the number of measurements can be increased. Furthermore, this means that
This means that even when using a radioactive isotope with a short half-life and low radiation intensity, measurements can be made with high accuracy under the same conditions (measurement time, temperature, etc.).
Further, according to the present invention, it is possible to perform radiation measurements with high precision under the same conditions by simply preparing a set of a measuring device and a measuring tool.

Furthermore, the operation of moving the measuring tool containing the stimulable phosphor, the adhesion of the sample to the measuring tool, the operation of absorbing and accumulating radiation emitted from the sample into the measuring tool, and the operation of absorbing and accumulating radiation in the measuring tool. It is possible to automate the radiation energy readout operation, thereby further improving the workability.

Furthermore, the present invention does not require a conventional scintillator, and since the measuring instrument used in the present invention is made of plastic material or the like, it is very easy to handle. For example, by making the measuring device in the form of a thread-like material or a woven fabric, it is possible to increase the adsorption of the liquid sample, that is, the ease with which the sample absorbs into the measuring device, and the amount of water released from the sample can be increased. At the same time, radiation can be efficiently absorbed by the stimulable phosphor of the measurement tool, and at the same time, after use, the measurement tool can be washed with an appropriate solvent to remove any adhering samples, and then irradiated with appropriate light. By erasing the stored energy that remains in the
Can be used repeatedly. This makes it possible to reduce measurement costs. By repeatedly and continuously using the measuring tool in this manner, it is possible to greatly simplify the operation by automating the measurement.

In radiation measurement, the method of the present invention does not require a solvent, unlike the liquid scintillation method described above. Therefore, there is no need to particularly select a solvent or prepare a sample as in a liquid scintillator. In the present invention, the above-mentioned quenching phenomenon, especially the quenching phenomenon for fluorescence, does not occur. Therefore, there is no need to perform complicated extinction correction (determination of counting efficiency) for measuring the radioactivity of a sample, and the measurement operation is simplified in this respect as well.

Therefore, since there is no particular need to remove impurities contained in the sample, there is no need for conventional sample pretreatment, and a high degree of skill and care based on experience is required when preparing the sample. It's something you don't do. In this respect as well, radiation measurement of the sample can be easily performed.

Below, a measuring tool containing a stimulable phosphor that is suitably used in detecting a radioactive substance according to the present invention will be described.

The stimulable phosphor used in the present invention is a phosphor that exhibits stimulated luminescence when irradiated with radiation and then with excitation light as described above, but from a practical point of view, the wavelength is 400~ The phosphor is preferably a phosphor that exhibits stimulated luminescence in the wavelength range of 300 to 500 nm by excitation light in the 800 nm range. Examples of such stimulable phosphors include SrS:Ce, Sm, SrS:Eu, described in U.S. Pat. No. 3,859,527.
Phosphors expressed by composition formulas such as Sm, ThO ₂ :Er, and La ₂ O ₂ S:Eu, Sm, described in Japanese Patent Application Laid-Open No. 12142/1982
ZnS: Cu, Pb, BaO・xAl ₂ O ₃ : Eu [However, 0.8
≦x≦10], and M ²⁺ O・xSiO ₂ :A [however,
M ²⁺ is Mg, Ca, Sr, Zn, Cd, or Ba;
A is Ce, Tb, Eu, Tm, Pb, Tl, Bi, or
A phosphor represented by a composition formula such as Mn, and x is 0.5≦x≦2.5] (Ba _1-xy , Mg _x , Ca _y ) is described in JP-A-12143-1983. FX: aEu ²⁺ [However, X
is at least one of Cl and Br,
A phosphor represented by the composition formula: x and y are 0<x+y≦0.6 and xy≠0, and a is 10 ^-6 ≦a≦5×10 ^-2 JP-A-12144-1987 stated in the issue
LnOX: xA [However, Ln is La, Y, Gd, and
At least one of Lu, X is at least one of Cl and Br, A is at least one of Ce and Tb, and x is 0<x<0.1
A phosphor expressed by the composition formula of (Ba _1-x , M〓 _x )FX:yA [where M〓 is Mg,
At least one of Ca, Sr, Zn, and Cd, X is at least one of Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho,
At least one of Nd, Yb, and Er, x is 0≦x≦0.6, and y is 0≦y≦0.2] JP-A-55-160078 M listed in the official bulletin
FX・xA: yLn [However, M〓 is Ba, Ca, Sr,
At least one of Mg, Zn, and Cd, A
are BeO, MgO, CaO, SrO, BaO, ZnO,
Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ ,
ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and
At least one of ThO ₂ , Ln is Eu, Tb,
Ce, Tm, Dy, Pr, H ₀ , Nd, Yb, Er, Sm,
and at least one of Gd, X is Cl,
At least one of Br, and I,
x and y are respectively 5×10 ^-5 ≦x≦0.5 and 0<y≦0.2] A phosphor is described in JP-A-56-116777 (Ba _{1- x} , M〓 _x )F ₂・aBaX ₂ :yEu, zA [However,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium; X is at least one of chlorine, bromine, and iodine; A is at least one of zirconium and scandium;
a, x, y, and z are each 0.5≦a≦1.25,
0≦x≦1, 10 ^-6 ≦y≦2×10 ^-1 , and 0<z
≦10 ^-2 ], described in Japanese Patent Application Laid-Open No. 57-23673, (Ba _1-x , M〓 _x )F ₂・aBaX ₂ :yEu, zB ,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium;
10 ^-6 ≦y≦2×10 ^-1 and 0<z≦2×10 ^-1 ] A phosphor is described in JP-A-57-23675 (Ba _{1 -x} , M〓 _x )F ₂・aBaX ₂ :yEu, zA [However,
M〓 is beryllium, magnesium, calcium,
at least one of strontium, zinc, and cadmium; X is at least one of chlorine, bromine, and iodine; A is at least one of arsenic and silicon; a, x, y, and z are each 0.5 ≦a≦1.25, 0≦x≦1, 10 ^-6
≦y≦2×10 ^-1 , and 0<z≦5×10 ^-1 ], M as described in Japanese Patent Application No. 167498/1983 filed by the present applicant 〓OX: xCe [However, M〓 is Pr,
Nd, Pm, Sm, Eu, Tb, Dy, _H0 , Er, Tm,
is at least one trivalent metal selected from the group consisting of Yb, and Bi, X is one or both of Cl and Br, and x is 0<x<0.1]. The represented phosphor is Ba _1-x M _x/2 L _x/2 FX:yEu ²⁺ [However,
M represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs; L represents Sc, Y, La, Ce, Pr, Nd, Pm,
Sm, Gd, Tb, Dy, H ₀ , Er, Tm, Yb, Lu,
represents at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl; X is Cl,
represents at least one halogen selected from the group consisting of Br, and I; and x is 10 ^-2 ≦
x≦0.5, y is 0<y≦0.1] BaFX xA:yEu ²⁺ [However, ,X is
is at least one halogen selected from the group consisting of Cl, Br, and I; A is a fired product of a tetrafluoroboric acid compound; and x is
10 ^-6 ≦x≦0.1, y is 0<y≦0.1] BaFX xA: yEu described in Japanese Patent Application No. 158048/1983 filed by the present applicant ²⁺ [However, X is
at least one halogen selected from the group consisting of Cl, Br, and I; A is a hexafluoro compound consisting of a monovalent or divalent metal salt of hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid; and x is 10 ^-6 ≦x≦0.1, and y is 0<y≦0.1. BaFX xNaX′: aEu ²⁺ described in Application No. 166320/1989 [However,
X and X′ are each at least one of Cl, Br, and I, and x and a are 0<x≦2 and 0<a≦0.2, respectively]; ^M〓FX . is a kind of alkaline earth metal; X and X' are Cl, Br, and I, respectively.
at least one halogen selected from the group consisting of; A is at least one transition metal selected from V, Cr, Mn, Fe, Co, and Ni; and x is 0<x≦2, y is 0<y≦
0.2, and z is 0<z≦10 ^-2 ], M〓FX・aM〓X′ described in the specification of Japanese Patent Application No. 184455/1983 filed by the present applicant.・bM′〓X″ ₂・cM〓
X″′ ₃・xA:yEu ²⁺ [However, M〓 is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; M〓 is Li, Na, K,
is at least one kind of alkali metal selected from the group consisting of Rb, and Cs; M′〓 is Be and
is at least one divalent metal selected from the group consisting of Mg; M is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl; A is a metal oxide; X is Cl, Br,
and at least one kind of halogen selected from the group consisting of I; X′, X″ and X″′ are F,
at least one kind of halogen selected from the group consisting of Cl, Br, and I; and a is 0≦
a≦2, b is 0≦b≦10 ^-2 , c is 0≦c≦10 ^-2 ,
and a+b+c≧10 ^-6 ; x is 0<x≦0.5,
y is 0<y≦0.2], and the like.

However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphors, but any phosphor that exhibits stimulated luminescence when irradiated with radiation and then irradiated with excitation light. It may be.

The elongated measuring tool used in the present invention includes:
For example, natural polymer substances, plastic substances, glass, etc. containing stimulable phosphor particles in a dispersed state may be formed into tapes, or spun into fibers and then thread-like products (e.g., twisted threads). )
Alternatively, it can be processed into textiles.

Examples of the above natural polymeric substances include proteins such as gelatin, polysaccharides such as dextran,
Alternatively, natural polymeric substances such as gum arabic can be mentioned. Examples of plastic materials include polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride/vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, wire Examples include synthetic polymeric substances such as polyester.

The measuring tool, for example, uses the above-mentioned stimulable phosphor and material in a suitable solvent (for example, lower alcohol,
After dispersing the stimulable phosphor in the above material by dissolving or suspending it in a chlorine atom-containing hydrocarbon, ketone, ester, or ether, or by subjecting it to heat treatment, it is formed into a long shape. It can be obtained by

In order to protect the measuring device from chemical deterioration and physical impact, the molded article may be covered with a protective film made of a transparent polymeric material such as polyethylene or polyethylene terephthalate.

In the present invention, the diameter, width, length, and amount of stimulable phosphor contained in the elongated measuring device thus obtained are determined depending on the amount, density, and measurement conditions of the sample. can be suitably selected.

Further, the measuring tool may be provided with liquid adsorption properties. In order to impart liquid adsorption properties to the measuring device, in addition to making the measuring device structurally liquid-absorbent by making it a thread-like material or a woven fabric as described above,
For example, this can be done by processing the surface of the measuring tool.

As a method of making the measuring device liquid-absorbing through surface processing, the surface of the molded article (or protective film) may be subjected to physical treatment such as roughening treatment; corona discharge, high-frequency discharge, glow discharge, activated plasma, etc. Electrical treatment; treatment with light such as ultraviolet rays or laser; activation treatment such as flame treatment, and applying hydrophilic or lipophilic natural polymeric substances; synthetic polymeric substances; and a method of providing a liquid adsorption layer made of paper such as filter paper, fibrous material such as gauze, etc.

Incidentally, in the present invention, the surface treatment of the measuring instrument as described above does not need to be carried out on the entire surface; for example, when the measuring instrument is tape-shaped, it is sufficient that it is carried out on only one surface. Further, the above-mentioned thread-like material or fabric may also be subjected to the above-mentioned surface treatment in order to further enhance the liquid adsorption property.

The measuring device used in the present invention is preferably made of a filamentous material made of plastic fiber or glass fiber containing a stimulable phosphor, from the viewpoints of adsorption of the measuring device to liquid samples, possibility of reuse, and automatic continuous repeated measurements. Particularly preferred are fabrics or fabrics.

However, the measuring tool used in the present invention is not limited to the above-mentioned measuring tool, and may be a long-sized measuring tool that contains a stimulable phosphor and that can continuously adhere and absorb a liquid sample that is dropped or flowed down. Any material having the shape can be used.

Next, referring to the example of the measuring device shown in FIG. 1 of the attached drawings, we will discuss the radioactive substance detection operation according to the present invention using the elongated measuring tool containing the above-mentioned stimulable phosphor. explain.

FIG. 1 shows a schematic diagram of an example of a radiation measuring device for detecting radioactive substances contained in a continuously dropped liquid sample.

The sample to be measured in the present invention, ie, the liquid sample containing a radioactive substance, may be a solution or a suspension, and may be colored.

Furthermore, any type of radiation emitted from the radioactive substance in the sample can be measured, such as α rays, β rays, γ rays, proton rays, neutron rays, light rays, meson rays, and cosmic rays. That is, radiation from any radionuclide can be measured.

First, the liquid sample 3 is placed on the measurement tool 1 containing the elongated stimulable phosphor from the lower part of the sample container 2.
is dripped. The measuring tool 1 is transferred in the direction of the arrow 4, and the part of the measuring tool 1 to which the sample is attached enters the radiation energy storage section 5. In the storage section 5, at least a portion of the radiation energy emitted from the radioactive substance in the sample is absorbed and stored in the measurement tool 1. The accumulation time of this radiation energy varies depending on the strength of the radioactivity of the radioactive substance contained in the sample, the concentration of the substance, the shape of the measuring instrument, the intensity of stimulated luminescence, etc., but it is usually several seconds to several tens of seconds. It takes. Therefore, the transfer speed is adjusted so that the time for passing through the storage section 5 matches the desired storage time.
Note that in the storage section 5, the sample on the measuring tool 1 may be dried by heating the measuring tool 1 at the same time.

The part of the measurement tool 1 that has come out of the storage section 5 and has the sample attached thereto is transferred in the direction of the arrow 6 and enters the stored energy readout section 7 . In the reading section 7, the part of the measuring tool 1 to which the sample is attached is irradiated with excitation light 9 emitted from the light source 8. The beam diameter of this excitation light 9 preferably has a width at least in the direction perpendicular to the transport direction with respect to the sample attachment site.

When the part of the measurement tool 1 to which the sample is attached is irradiated with excitation light, it emits stimulated luminescence with an amount of light proportional to the accumulated radiation energy, and this light enters a photodetector 10 such as a photomultiplier tube. do. The photodetector 10 has a filter attached thereto that transmits only light in the wavelength region of stimulated luminescence and cuts out light in the wavelength region of excitation light, so that only stimulated luminescence can be detected. is used. Stimulated luminescence detected by the photodetector 10 is converted into an electrical signal, amplified to an electrical signal of an appropriate level by an amplifier 11, and then input to the display/recording device 12.

The display/recording device 12 displays the level of the obtained electrical signal, for example, the count value of electrical pulses, as a digital value. Examples of the display/recording device 12 include one that scans a photosensitive material with a laser beam or the like and records it optically, one that displays it electronically on a CRT, etc., and one that displays an X-ray image displayed on a CRT or the like using a video printer. Display and recording devices based on various principles can be used, such as those that record on a heat-sensitive recording material using heat rays, and those that record on a heat-sensitive recording material using heat rays.

In addition, by providing a data processing circuit in the display/recording device 12, the radioactivity intensity can be determined based on the readout efficiency (luminous efficiency of stimulated luminescence) and radiation energy accumulation time input in advance from the obtained digital value. After calculating the amount or concentration of the radioactive substance per each attachment site (or reading pixel of stimulated luminescence) of the sample by calculating the radioactivity intensity per molecule of the target radioactive substance, It is possible to display and record the obtained data.

Note that in the present invention, it is of course possible to use methods other than those exemplified above as a method for reading the radiation energy of the sample accumulated in the measuring tool.

On the other hand, the measuring tool 1 that has come out from the reading section 7 is wound up and collected by the winding machine 13.

Note that the operations according to the radioactive substance detection method of the present invention are not limited to the above-mentioned operations, and include, for example, the moving speed of the measuring device, the dropping speed of the liquid sample, the reading speed of the measuring device, and the measuring device of the sample. By setting the upward drop position and the reading position of the stored energy in the measuring tool, the entire measurement operation can be automated.

In addition, for example, before collecting (rolling up) the measurement tool with the sample attached, samples can be collected only from areas where radioactive substances have been detected based on the obtained data, and the target radioactive substance can be efficiently separated. It is also possible to do so.

A used measuring tool can be reused by cleaning it with a suitable solvent and then erasing the energy remaining in the measuring tool by irradiating it with light or the like. Therefore, continuous reuse is possible by incorporating and automating the operations of cleaning the used measuring device and erasing the remaining energy into the measurement process after reading out the measuring device without collecting the measuring device. becomes.

Alternatively, by cleaning the measuring device after absorbing and accumulating radiation energy in the measuring device, for example, if the sample is colored, the next readout operation will remove the radiation from the measuring device. Light emission can be read easily and with high accuracy.

The method for detecting radioactive substances of the present invention can be suitably used especially when the liquid sample is in a small amount, and can detect radioactive substances contained in the small amount of sample with high precision and quickly. It is possible to do so.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of an example of a radiation measuring device for detecting radioactive substances contained in a liquid sample that is continuously dropped. 1: Measuring tool containing a stimulable phosphor, 2:
sample container, 3: liquid sample, 4: transfer direction, 5: storage section, 6: transfer direction, 7: reading section, 8: light source,
9: excitation light, 10: photodetector, 11: amplifier, 1
2: Display and recording device, 13: Winding machine.

Claims (1)

[Claims] 1. While continuously supplying a liquid sample containing a radioactive substance onto the surface of a long measuring tool containing a stimulable phosphor, the measuring tool is moved in the longitudinal direction of the measuring tool. The liquid sample is continuously deposited on the measuring device by causing at least a part of the radiation energy emitted from the radioactive substance to be absorbed by the measuring device, and then the liquid sample is accumulated in the measuring device. A method for detecting radioactive substances, which comprises continuously measuring the radioactivity in the sample by emitting radiation energy as photostimulated light and reading the stimulated light photoelectrically. 2. The method for detecting a radioactive substance according to claim 1, wherein the measuring tool is a tape made of a plastic material containing the stimulable phosphor. 3. The method for detecting a radioactive substance according to claim 1 or 2, characterized in that the measuring device has liquid adsorption properties. 4. The method for detecting a radioactive substance according to claim 1, wherein the measuring device is a filament or fabric made of plastic fiber containing the stimulable phosphor. 5. The method for detecting a radioactive substance according to claim 1, wherein the measuring device is a filament or fabric made of glass fibers on the surface of which the stimulable phosphor is dispersed. 6. The stimulable phosphor according to any one of claims 1 to 5, wherein the stimulable phosphor is a divalent europium-activated alkaline earth metal fluorohalide phosphor. Detection method for radioactive substances. 7. The method for detecting a radioactive substance according to any one of claims 1 to 5, wherein the stimulable phosphor is a rare earth element-activated rare earth oxyhalide phosphor. 8. The method for detecting a radioactive substance according to claim 1, wherein the method for detecting a radioactive substance comprises measuring the concentration of the radioactive substance in the liquid sample.