JP4936274B2 - Asbestos presence estimation device - Google Patents

Description

  The present invention relates to an apparatus for estimating the presence of asbestos on the other side of a wall contained in an inspection object or blocked by another material in a non-destructive state.

  Asbestos has excellent durability, heat resistance, chemical resistance, and electrical insulation, and is easy to process, so it was very useful in various applications such as construction materials, automotive products, and electrical products. . For this reason, very large amounts have been used until recently. However, the harmfulness of mesothelial seeds and the like caused by asbestos has become a problem, and in Japan, the use ban has been legislated since 1995. Therefore, production is currently prohibited except for some industrial products, but asbestos used during construction may remain in old buildings, and the harmful effects of asbestos exposure have been highlighted.

  For such a problem, a technique for detecting whether or not asbestos is scattered and a technique for how to treat the asbestos when it is found are disclosed.

  From the viewpoint of detection of asbestos, the following knowledge has been disclosed as general knowledge regarding asbestos in products, measurement of dust concentration, and grasping the amount of asbestos in water (see Non-Patent Document 1). Asbestos in products is first pretreated so that it can be measured, and then measured with an optical microscope or X-ray diffraction method.

  Usually, since various chemical components are included in the product, pretreatment is performed so that the asbestos is not lost, so that the product can be detected.

  As the pretreatment, heat treatment, chemical treatment, pulverization treatment and the like can be considered. The characteristics of asbestos for these treatments are as follows. That is, in the heat treatment, chrysotile asbestos gradually loses crystal water from about 400 ° C., and changes to forstlite at about 800 ° C. Therefore, when heat treatment is performed, heat treatment at 500 ° C. or lower, preferably 450 ° C. or lower is preferable.

  In chemical treatment, chrysotile asbestos is strong against alkalinity but weak against strong acid. Therefore, weak acidity (acetic acid, formic acid) is used for acid treatment.

  In the pulverization process, even when pulverizing, if it is pulverized very finely, a part of the surface of chrysotile is altered, which affects analysis.

In consideration of the above points, pre-processing is performed (i) qualitative analysis with an optical microscope (dispersive staining method using a polarizing microscope and phase-contrast microscope), (ii) qualitative analysis with X-ray diffractometry, and presence or absence of asbestos Confirm. Specific analysis methods include the following.
(1) Qualitative analysis by optical microscope (dispersive dyeing method using polarizing microscope, phase contrast microscope) (2) The method using polarizing microscope can discriminate asbestos by the extinction angle even if it is in fiber form. However, some mineral fibers have an extinction angle similar to that of asbestos, so care must be taken.
(3) The disperse dyeing method is a method of judging by coloring using the refractive index of the fiber, but some fibers have a similar refractive index, so care must be taken.
(4) Qualitative and quantitative analysis by the X-ray diffraction method is a method for detecting a fiber form unique to asbestos from an X-ray diffraction pattern. However, some minerals may exhibit the same X-ray diffraction pattern as that of asbestos even when they are not in the form of fibers, and therefore need to be used in combination with the methods (1) to (3). For example, chrysotile has the same diffraction pattern as lizardite and antigolite.

  The method for detecting the asbestos dust concentration is as follows. The floating asbestos fibers are collected with a membrane filter (diameter 25 mm, 47 mm) having a pore diameter of 0.8 μm, the collected membrane filter is made transparent, and the number of asbestos is counted using a 400-fold phase contrast microscope. The asbestos dust concentration is determined by dividing the number of asbestos fibers adhering to the entire membrane filter by the amount of air sucked.

  In this case, the asbestos fibers to be counted are those having a length of 5 μm or more, a width (diameter) of less than 3 μm, and an aspect ratio (length / width) of 3 or more, and referred to as f (fiber). As units of asbestos dust concentration, f / cm 3, f / cc, f / ml, book / cm 3, f / liter, book / liter, etc. are used.

  The method of ascertaining the amount of asbestos in water is as follows. Collect an appropriate amount of target water (tap water, well water, river water, etc.) in a glass bottle or plastic container that has been washed with pure water. The sample is filtered with a suction filtration device having a glass filter base equipped with a membrane filter (diameter 25 to 47 mm) having a pore diameter of 0.4 μm. Organic matter is removed from the filtered filter with a low-temperature ashing device, and the remainder is dispersed in a solvent such as pure water with an ultrasonic cleaner, and a suspension is formed. After vapor deposition, the sample is placed on a TEM mesh, and the filter is dissolved and removed with an appropriate solvent to obtain an observation specimen. The observation specimen is counted by TEM (transmission electron microscope) at a magnification of 10,000 to 40,000.

In addition, as patent documents, an invention (see Patent Document 1) that quantitatively grasps asbestos of a specific composition using a map obtained based on element composition information and shape information, hydrofluoric acid, concentrated sulfuric acid, etc. As a chemical screening method that can be used without using any dangerous chemicals, a technology that allows pre-treatment with an organic acid and then a non-oxidizing inorganic acid to make it possible to use a color reagent (see Patent Document 2), etc. Is disclosed.
JP 2005-233658 A JP 2000-88838 A Japan Asbestos Association website (as of March 13, 2006) http://www.jaasc.or.jp/index.html

  The above asbestos detection method is basically a method of sampling asbestos at a place and examining information such as what kind of asbestos it is. Since the building etc. in which asbestos is used are very old buildings, it may be unknown even where the asbestos was used.

  Since sampling is partial destruction, there is a risk that asbestos will be scattered, and there is a need for non-destructive detection of asbestos. Until now, methods for detecting asbestos non-destructively have been disclosed. There was no technology.

  The present invention was created to solve the above-described problems, and relates to an apparatus for nondestructively estimating the presence of asbestos by measuring the radiation dose from a radioactive substance in asbestos.

  Asbestos has undergone hydrothermal transformation, and rock-forming minerals such as olivine, serpentinite, and amphibolite are deformed into fibers, and natural radionuclides uranium and thorium, which are earth elements, Contains more than soil.

  The radiation dose of asbestos is not much different from the radiation from natural objects. However, the content of uranium and thorium is slightly higher than that of normal soil. Therefore, when very sensitive radiation measurement is performed, the generation pattern is different from that of normal soil. Therefore, by examining the generation pattern (energy and the number of generations) of radiation and making it a map, the difference from normal soil or so-called radiation sources can be clearly separated.

  More specifically, a radiation generation pattern is obtained using a highly sensitive radiation detector such as a germanium detector, and the presence of asbestos is estimated from the generation pattern.

  According to the present invention, since the presence of asbestos can be estimated nondestructively, it is possible to determine what kind of processing is necessary before actual asbestos processing.

  The block diagram of the asbestos presence estimation apparatus (10) of this invention is shown in FIG. The asbestos presence estimation device (10) includes a radiation detector (12), a preamplifier (14), a multi-channel analyzer (16), and a processing device (18). The radiation detector (12) is a part for detecting radiation, and there are detectors such as silicon, germanium, cadmium tellurium, mercury iodide, gallium arsenide, and a high-purity germanium detector is desirable.

  Radiation detectors made from ultra high purity germanium are called intrinsic germanium or high purity germanium detectors. This high purity germanium crystal is provided with a P-type and N-type semiconductor layer facing each other in a flat plate shape or a coaxial shape, and an electrode is attached to each of the semiconductor layers. Usually, a voltage of about 5000 volts is supplied to the electrode and cooled to the temperature of liquid nitrogen (−196 degrees), whereby the energy spectrum of gamma rays can be measured with ultrahigh resolution.

  This high-purity germanium outputs a signal corresponding to energy when radiation enters. The preamplifier (14) applies a reverse voltage to the radiation detector (12), and amplifies the output signal so that the subsequent multi-channel analyzer (16) can handle it. The multi-channel analyzer (16) receives the output of the preamplifier by arranging a number of filters having a constant energy width in parallel, and outputs the energy width of the filter and the number of counts within a predetermined time. The detector (12), preamplifier (14), and multichannel analyzer (16) are collectively referred to as a detector. The processing device (18) is usually a personal computer. In recent years, multi-channel analyzers are also in the form of a board connected to a personal computer, and can be seen as a single PC.

  The processing device (18) controls the entire asbestos presence estimation device (10) and displays the energy value and the count number as a graph on the display screen based on the data of the multi-channel analyzer (16). Further, the processing device (18) determines whether or not there is a possibility of the presence of asbestos from the graph pattern displayed on the display screen and displays it.

  FIG. 2 shows the configuration of the processing device (18). The processing device (18) is basically a software process, and the hardware configuration includes a CPU (20), memories (24 and 32), an input / output control unit (22), a display device driving unit (26), and a display. (28).

  The input / output control unit (22) controls data exchange with the multi-channel analyzer (16). The internal clock (30) measures the time inside the processing device (18). The internal clock may use a register in the CPU (20) described later, or may be realized by software processing. The memory (24) and the external memory (32) store data and use it for processing. The display driver (26) controls data transfer to the display (28), display timing, and display data handling. The display drive unit (26) and the display (28) are collectively referred to as a display unit.

  The CPU (20) controls the entire processing device (18) and operates mainly by a program on the memory (24). Processing unique to the present application will be described separately based on the flow. Further, the CPU (20) is also referred to as a processing unit when performing a flow process described later.

  Next, a measurement example for determining whether or not there is a possibility of the presence of asbestos will be described. 3 to 7 show some typical measurement results with high-purity germanium (hereinafter referred to as “germa”).

  FIG. 3 shows the measurement results of natural soil. The vertical axis is a logarithmic display with the count number. The horizontal axis is energy. Even in natural soil, radiation is emitted, but the measurement results are as shown in FIG. 40K is the radiation emitted by potassium and is normally present in nature. In this case, such a result can be obtained by measuring for one hour.

  FIG. 4 shows the measurement results of aluminum. Since aluminum has no radiation source, it shows a low count over the measured energy range. 40K potassium is counted as in FIG.

  Comparing FIG. 3 and FIG. 4, 60 to 64 in FIG. 3 indicate high values not found in aluminum. This is radiation contained in normal soil.

  FIG. 5 shows the measurement results for Co60 (cobalt 60) used as the standard radiation source. High counts are seen over a very wide energy range. In particular, a remarkable peak is seen in the high energy band of the reference numerals 68 and 69. Also, the measurement time is short and it can be seen that a lot of radiation is emitted.

  FIG. 6 shows the measurement result of Ba 133 (barium 133), which is also used as a standard radiation source, and a large amount of radiation is observed in a relatively low energy band portion.

  FIG. 7 shows the measurement results of a substance containing asbestos. The distance is 10 mm and the measurement time is 1 hour. Although the detection pattern itself is very close to natural soil, there is a portion with a large number of counts in a wide range. This is due to radiation from radioactive materials such as uranium and thorium left in asbestos. Although the difference from natural soil is slight, reference numerals 71, 72, and 73 in FIG. 7 are clearly several times as large as those of natural soil. Specifically, the peak 71 is 646 counts, which is 8 times larger than soil with the same energy band (count number is 80). Similarly, the peak 72 is 453 counts, and the peak 73 is 105 counts, which are 7.1 times at 63 counts and 5.8 times at 18 counts, respectively, when compared with soil of the same energy band. Moreover, the total weight of the sample is 46 g of asbestos against 163 g of soil.

  Since these originate from radioactive materials such as uranium and thorium, which are radiation sources, the observed energy band is limited, and the presence of asbestos is estimated even if only that energy band is measured. .

  FIG. 8 shows a flow of measurement processing for asbestos estimation. This flow is performed by the CPU (20) shown in FIG. 1 and is a software process. With reference to FIG. 8, the measurement start is started by an instruction to the processing device (18) (S1000). The processing device (18) instructs the multi-channel analyzer (16) to start measurement and starts the internal clock (30).

  Each time the radiation detector (12) senses radiation, it outputs a signal to the preamplifier (14). The preamplifier (14) transmits measurement data to the multi-channel analyzer (16). The multi-channel analyzer (16) transmits the measured energy band and the count number to the processing device (18). The processing device (18) receives this data each time (S1002).

  The processing device (18) additionally records the count number in an energy band memory prepared in advance each time data is received. For example, 30 counts are added to the memory area corresponding to 500 eV. Then, the count number of all energy bands is calculated (S1004).

  Next, the measurement time is checked (S1006). Since this measurement routine ends with measurement for a fixed time, the measurement ends when the measurement time exceeds Tmax (S1012). On the other hand, if the count number exceeds a certain amount (Dmax) at a time equal to or shorter than Tmax, it is regarded as an abnormal measurement (S1008).

  For example, as shown in FIG. 5, in the case of exceeding 290,000 counts in only 100 seconds, the presence of a radioactive substance stronger than the presence of asbestos is expected. Accordingly, in such a case, the abnormality measurement process (S1010) is performed and the process ends (S1014). With the above flow, measurement data in which the count number for each energy band is recorded can be obtained.

  Next, a flow of processing for pattern analysis of the measurement data will be described with reference to FIG. The processing flow is preferably started automatically after the measurement routine is completed (S1030), but may be started based on a user instruction. The above measurement data is sequentially read into the memory (S1032). The measurement data to be read is a pair of energy band and count number.

  It is determined whether the read data is a predetermined energy band (S1034). Since the radiation source of asbestos is a radioactive element such as uranium or thorium, it can be assumed that the radiation count value in a predetermined energy band is always high. In this pattern analysis, the count value of the energy band is checked. Therefore, if it is not an energy band to be checked, the process returns to reading of measurement data (N branch in S1034).

  If it is the desired energy band, it is determined whether or not the count number is a certain value (Dth) or more. This is because there is no possibility of asbestos if the count value is below a certain value. If it is above a certain value, it is recorded in the condition list (S1036). The condition list is a list that records whether or not the count number of the energy band to be checked is greater than or equal to a certain value. For example, it is a list that records whether or not the count number is greater than or equal to a certain value in the energy bands 71, 72, and 73 in FIG.

  This operation is continued until there is no more data to be read (S1040). When all measurement data has been read, this routine is terminated (S1042). After this routine is completed, a condition list indicating whether or not the count of the predetermined energy band is greater than or equal to a certain value can be obtained.

  Next, FIG. 10 shows a flow for determining whether there is a risk of asbestos and instructing display based on the determination. This routine starts immediately after the pattern analysis routine shown in FIG. 9 ends (S1060). First, the measurement data read into the memory is displayed on the screen (S1062). Next, it is confirmed whether or not the condition list is satisfied (S1064). If there is a count greater than or equal to a predetermined value in all the predetermined energy bands, it is next determined whether or not an abnormal end has occurred (S1068). In particular, when a radioactive substance having a high radioactivity is measured, it becomes a certain value or more in a predetermined energy band, but this must be distinguished from the presence of asbestos.

  If not abnormally terminated, the fact that there is a high possibility of the presence of asbestos is displayed on the display screen (S1070). The execution of the processing here is realized by transferring the contents displayed on the display drive unit (26) by the CPU (20) and displaying it on the display (28) by the display drive unit (26). FIG. 11 shows a display example. On the display unit (28), a plot (80) of measurement results and a display (82) indicating the possibility of the presence of asbestos are displayed.

  If it is an abnormal end, a display to that effect (84) is made (S1072). FIG. 12 shows a display example. If the condition list is not satisfied, it is determined that there is no asbestos, and a display to that effect (86) is made (S1074). FIG. 13 shows a display example.

  This completes the pattern analysis (S1076). When this routine is completed, it is possible to display whether or not the presence of asbestos is estimated on the display screen.

The figure which shows the structure of the asbestos measuring apparatus of this invention Diagram showing the internal configuration of the processing equipment Result of measuring normal soil Result of measuring aluminum Result of measurement of cobalt 60 Results of measuring barium 133 As a result of measuring asbestos content The figure which shows the flow of measurement operation of the asbestos measuring device Diagram showing the flow of pattern analysis operation for measurement results The figure which shows the flow which judges the result from pattern analysis The figure which shows the example which displays the existence of asbestos Figure showing an example of a display that has a radioactive substance and calls attention The figure which shows the example which displays that there is no asbestos

Explanation of symbols

12 detector 14 preamplifier 16 multi-channel analyzer 18 processor 20 CPU
28 Display section

Claims (7)

A radiation detector for detecting radiation;
An asbestos presence estimation apparatus comprising: a processing unit that performs at least a determination process for determining the possibility of the presence of asbestos based on a detection value from the radiation detection unit.   The asbestos presence estimation apparatus according to claim 1, wherein the determination process of the presence possibility of the asbestos is a determination based on a count number of a specific energy band of the detected value.   The asbestos presence estimation apparatus according to claim 1, wherein the processing unit further performs an abnormality determination process for determining the possibility of the presence of a radioactive substance based on the detection value.   The asbestos presence estimation apparatus according to claim 1, wherein the display unit displays the detected amount in two dimensions.   The asbestos presence estimation apparatus according to claim 1, wherein the radiation detection unit includes a detector using germanium.   The asbestos presence estimation apparatus according to claim 2, wherein the specific energy band is an energy band corresponding to uranium and thorium as radiation sources.   The asbestos presence estimation apparatus according to claim 2 or 6, wherein the specific energy band is an energy band excluding an energy band corresponding to potassium as a radiation source.