JP3350202B2 - Concrete contamination judgment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining radioactive contamination, and more particularly to a method for determining radioactive contamination when decontaminating or dismantling concrete structures.

[0002]

2. Description of the Related Art Conventionally, when decontaminating a wall surface or a floor surface of a concrete structure contaminated with radioactivity, the surface is cut. As a known means of cutting the concrete surface and performing radioactive decontamination in this way, the reference "CLEAN"
-CUT REMOVAL SYSTEM FOR C
ONCRETE DECONTAMINATION
(T. Funakawa et. Al., Proc.
of The 1st JSME / ASME Join
t Int. Conf. on Nucl. En
g. , 2, pp. 109-114, (issued in 1991)).

[0003] As shown in FIG. 12, a decontamination apparatus 1 cuts a concrete surface, and concrete dust resulting from the cutting is collected by a concrete dust collection apparatus 2.
That is, when decontaminating the concrete surface 3 contaminated with radioactivity by the decontamination apparatus 1, the cutting teeth 4a of the cutting means 4 shown in FIG. The dust 5 is collected by the concrete dust collection device 2. The concrete dust 5 is separated into a very fine dust 5a and another dust by a bag filter 6 shown in FIG. 14, and the very fine dust 5a is sucked by a blower 8 and collected by a filter 7, while the other dust is collected. Is collected in the container 9.

In order to judge concrete contamination, after cutting the wall or floor of a concrete structure contaminated with radioactivity, concrete powder or concrete-containing cutting powder generated when cutting the surface is sampled. Then, the radioactivity is measured, the presence or absence of radioactive contamination is confirmed from the measurement result, and it is determined whether to stop the surface cutting or to re-cut the surface.

[0005]

However, as described above, if sampling is performed after cutting, when radioactive contamination is localized, a portion without radioactive contamination is sampled, and vice versa. Because it is possible, accurate determination of radioactive contamination cannot be made. In addition, it is inefficient because the cutting operation is interrupted.

The present invention has been made in view of the above circumstances, and clearly determines the end of decontamination of concrete without losing the accuracy of the determination of radioactive contamination of concrete, and interrupts the work by sampling. It is an object of the present invention to provide an efficient method for determining concrete contamination.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a method for decontaminating a radioactively contaminated concrete structure or for cutting from one surface during demolition. The generated concrete powder is absorbed, the radiation from the radionuclide contained in the sucked concrete powder is detected, the contamination of the concrete structure is determined, and the counting of the radiation dose for determining the contamination is performed n times. When performed, (n-2) times more than (n-1) times, and n times more than or equal to (n-1) times, the cut surface of the concrete structure To
This is a method of determining that there is no contamination .

[0008] Claim 2 is, in concrete contamination determination method according to claim 1, wherein, when detecting the radiation from radionuclides in concrete powder, of decontamination means and dismantling means performing decontamination and dismantling, either A radiation detecting means for detecting radiation from radioactive nuclides contained in the concrete powder is provided near one of the concrete powders, and the radiation detecting means directly detects the radiation.

[0009]

[0010] In claim 2, the radiation in the detection of radiation from radionuclides in concrete powder, of decontamination means and dismantling means, in the vicinity of either one, from radionuclides in concrete powder By installing radiation detection means for detecting concrete, and by directly detecting radiation with this radiation detection means, it is possible to determine contamination of the concrete structure during either decontamination or demolition of the concrete structure. it can.

In the present invention, when detecting radiation from radioactive nuclides contained in concrete powder, radiation from radioactive nuclides contained in concrete powder is detected near one of the decontamination means and the dismantling means. By installing the radiation detecting means to detect the radiation directly by the radiation detecting means, it is possible to determine the contamination of the concrete structure during one of the decontamination and the demolition of the concrete structure.

[0012]

[0013]

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 to FIG. 4 are block diagrams showing a decontamination apparatus using a first embodiment of the concrete contamination judging method according to the present invention. Parts that are the same as or correspond to those of the conventional configuration will be described using the same reference numerals.

As shown in FIG. 1 and FIG.
When decontaminating the concrete surface 3 which has been contaminated by radioactivity, the cutting means 4 of the decontamination device 1 rotates to cut the concrete surface 3, and the concrete dust 5a by this cutting is removed from the concrete dust collection device 2 Is collected by The concrete dust 5a is separated into very fine dust 5a and other dust by the bag filter 6, and the very fine dust 5a is sucked by the blower 8 and collected by the filter 7, while the other dust 5a is Collected in the container 9.

A suction port 10 is provided in a flow path between the bag filter 6 and the filter 7, and a part of the very fine dust 5 a is sucked from the suction port 10 by using a dust collecting device 11. The ultrafine dust 5a sucked by the dust collector 11 is adsorbed by a thin filter of the dust sampler 12 to release β from the contaminated radionuclides in the concrete.
Detect lines. This detection result is converted into a count by the signal processing system 13, converted into an amount of radioactivity by the calculating means 14, and the count of β-rays is displayed on the display means 15. Assuming that the count at that time is C, the amount of radioactivity A per cutting unit area is obtained from the count C by the calculating means 14.

As shown in FIGS. 2 and 3, the dust sampler 12 includes a sheet filter 16, a feed roller 17a for sequentially feeding the sheet filter 16, and a winding roller for winding the sequentially fed sheet filter 16. 17b, and β-ray detecting means 18 as radiation detecting means for detecting β-rays emitted from the contaminated radionuclides of the ultrafine dust 5a in the concrete adsorbed on the sheet filter 16.

As shown in FIG. 1, the concrete dust collecting device 2 is provided with a moving means 19 such as wheels, and can travel freely. The moving amount of the moving means 19 is set on an axle 19a of the moving means 19. A rotary encoder 20 for detection is attached.

Next, the operation of this embodiment will be described.

The concrete contamination determination according to the present embodiment is executed as shown in the flowchart of FIG. That is, the area S1 of the concrete surface 3 to be cut in advance
And the cutting width L are input to the calculating means 14 (step s).
1) After the arithmetic means 14 sets the number of cuts n = 0, the cutting means 4 starts cutting the concrete surface 3 (steps s2 to s3).

Next, the moving amount R1 of the moving means 19 is obtained by the rotary encoder 20 attached to the axle 19a of the moving means 19, and the cutting area S2 is calculated from the width W of the cutting means 4 and the moving amount R1 of the moving means 19. 14 (step s5), the area S of the concrete surface 3
1 is equal to the cutting area S2 (step s
6), the calculation means 14 sets the number of cuts n = n + 1,
The cutting is stopped, the measurement of β-rays by the β-ray detecting means 18 is stopped (steps s7 to s9), and the radioactivity A is obtained (step s10).

When cutting is performed n times when the area S1 of the concrete surface 3 is constant, the amount of radioactivity when the number of cuts is n is A [n], and the amount of radioactivity when the number of cuts is [n-1] is A
[N-1], the radioactivity at the time of cutting [n-2] times is A
When [n−2] is satisfied, if the number of cuts n ≧ 3 (steps s11 to s12), the process proceeds to step s13.

## EQU1 ## A [n-2]> A [n-1]

## EQU2 ## If both equations of A [n-1] ≤A [n] are satisfied, it is determined that the decontamination of the concrete is completed, and this is displayed on the display means 15 (steps s14 to s15).

Step s12 and step s1
In No. 3, if no, the process proceeds to step s16, moves the sheet filter 16, and then returns to step s3.

As described above, in this embodiment, the surface 3 of the concrete is decontaminated by cutting it with the decontamination device 1, and the concrete dust 5 sucked from the inlet 10 is contaminated in the concrete by the β-ray detecting means 18. Β-rays emitted from radionuclides are detected and converted into coefficients by the signal processing system 13,
The calculation means 14 converts it into radioactivity. The result is displayed on the display unit 15.

When the surface of the concrete 3 to be decontaminated is cut n times and the radioactivity is equivalent to the evaluation of radionuclides contained in nature, the radioactive contamination has been removed and the concrete has been removed. Can be determined.

FIGS. 5 to 7 show a cutting section of a dismantling apparatus using a second embodiment of the concrete contamination judging method according to the present invention. The same parts as those in the first embodiment will be described with the same reference numerals. This embodiment is a concrete contamination judging method for removing the contaminated concrete by cutting the wall of the concrete structure into small blocks by the cutting means instead of the cutting means 4 of the first embodiment.

As shown in FIG. 5, the cutting device is provided with a cutting means 21 for cutting the wall surface of the concrete structure instead of the cutting means 4 of the first embodiment. A laser distance meter 22 for obtaining a distance from the means 21 is attached and fixed, and a suction port 10 for sucking the concrete dust 5 from the dust collecting device 11 is arranged near the cutting means 21.

As in the first embodiment, the dust sampler 12 includes a sheet filter 16, a delivery roller 17a for sequentially delivering the sheet filter 16, and a winding roller 17b for winding the sequentially delivered sheet filter 16. And β-ray detecting means 18 as radiation detecting means for detecting β-rays emitted from the contaminated radionuclides of the concrete dust 5 in the concrete adsorbed on the sheet filter 16.

Next, the operation of this embodiment will be described.

The concrete dust 5 generated by cutting the concrete surface 3 by the cutting means 21 is sucked from the suction port 10 by the dust collecting device 11, and the concrete dust 5 is adsorbed on the thin filter to detect β rays. Sampler 1
The β-rays emitted from the contaminated radionuclides in the concrete are detected by the β-ray detecting means 18 of 2 and converted into coefficients by the signal processing system 13 and converted into radioactivity by the calculating means 14.
The result is displayed on the display unit 15.

That is, as shown in FIG. 6, the distance Ra between the concrete surface 3 and the cutting means 21 is initially determined by using the laser distance meter 22, and the cutting distance R2 is calculated from the feeding amount Rb of the cutting means 21. In FIG. 7 (A), ΔR is defined as the cutting distance from 0 to R1, and the concrete dust 5 corresponding to ΔR is adsorbed without sending out the sheet filter 16, and when the cutting distance reaches R1, the sheet filter 16 is removed. The feed roller 17a feeds out r parts.

As shown in FIG. 7B, the sheet filter 16 sent out is designated as r1, and β rays emitted from the concrete dust 5 for r1 are detected by the β ray detecting means 18 and the count at that time is detected. Is C1, this C1
Is input to the calculating means 14. When the same process is performed from the cutting distance R1 to R [n + 1] by the cutting distance ΔR, as shown in FIG. 7C, the sheet filter 16 to be measured for β rays is r [n], and β Line count is C
[N].

At this time,

## EQU3 ## C [n-2]> C [n-1]

## EQU4 ## If both of C [n-1] ≤C [n] are satisfied, it is determined from the cutting distance R [n + 1] that there is no contamination in the preceding concrete.

As described above, in the present embodiment, β-rays from the concrete surface 3 after cutting are detected by the β-ray detecting means 18 as radiation detecting means, converted into coefficients by the signal processing system 13, and calculated by the calculating means. Converted to radioactivity at 14. The result is displayed on the display unit 15. When the surface of the concrete 3 to be decontaminated is cut n times and the radioactivity is equivalent to the evaluation of radionuclides contained in nature, the radioactive contamination has been removed, and the contamination of the concrete is judged. Becomes possible.

FIGS. 8 to 10 show a decontamination apparatus using a third embodiment of the concrete contamination judging method according to the present invention. The same parts as those in the first embodiment will be described with the same reference numerals.

This embodiment is directed to a method of judging concrete contamination by sucking concrete dust generated by decontamination means or demolition means, measuring β-rays of radioactivity in concrete from the suction path, and judging contamination of concrete. This is a method of determining concrete contamination by combining a method of measuring radioactive γ-rays in concrete contained in a container for temporarily storing concrete dust generated by dismantling to determine concrete contamination.

As shown in FIG. 8, a container 9 for temporarily storing the concrete dust 5 is disposed in the concrete dust collecting device 2 for collecting the cut concrete dust 5. Ge detector 24 as radiation detecting means (γ-ray detecting means) for detecting radioactive γ-rays 23 in the concrete housed in the concrete, and this Ge detector 2
4, a collimator 25 as shielding means for shielding the γ-rays 23, and an elevator 26 for raising and lowering the Ge detector 24 and the collimator 25 in the depth direction of the container 9 are installed and accommodated in the container 2. The gamma rays 23 of the concrete dust 5 are measured.

The storage state of the concrete dust 5 in the container 2, that is, the height L of the concrete dust 5 is measured by a level meter 27 which is mounted offset on the upper part of the container 2. When the height L is obtained by the level meter 27, the Ge detector 23 and the collimator 24 are raised by the height L by the elevator 26.

On the other hand, a β-ray detecting means 29 as a radiation detecting means is installed in the suction pipe 28 for sucking the concrete dust 5, and the β-ray of the sucked concrete dust 5 is detected by the β-ray detecting means 29. You.

Next, the operation of this embodiment will be described.

In FIG. 9A, when the Ge detector 24 is at the position of the height Ld, the γ-rays 23 from below the concrete dust 5 are shielded by the collimator 25 and are not detected by the Ge detector 24. Therefore, the volume of the concrete dust 5 measured by the Ge detector 24 is as shown in FIG.
S1. The volume S1 corresponds to the amount V1 of concrete cut by the cutting means 4.

When the measurement of the γ-rays 23 of the concrete dust 5 by the Ge detector 24 at the height Ld is completed and the amount of concrete cut thereafter is ΔV as shown in FIG. 9B, Ge detection is performed. The volume of the concrete dust 5 measured by the vessel 24 is ΔS. Therefore, the increase in the volume of the concrete dust 5 becomes ΔS, and the height of the concrete dust 5 indicated by the level meter 27 increases by ΔL. Therefore, the Ge detector 24 and the collimator 25 are raised by ΔL by the elevator 26, and the measurement of the γ-ray 23 is started.

In general, Ge detectors are known to have excellent energy resolution, and Ge detectors are often used for nuclide analysis. As shown in FIG.
The γ-rays 23 detected in 4 are converted into coefficients by the signal processing system 13 and converted into counts for each energy by the calculating means 14. The result is displayed on the display unit 15.

Here, when the gamma ray energy of the concrete contaminating nuclide is known in advance, the gamma ray energy of the concrete contaminating nuclide is stored in the calculating means 14, and the gamma ray energy is displayed on the display means 15, and the concrete You can check for contamination. This is shown in FIGS. 10A and 10B.
Shown in At the same time, the concrete dust 5 of ΔS in FIG.
9 detects β-rays. The amount Cg of β-rays detected at this time is due to β-rays from naturally occurring radionuclides in addition to β-rays from concrete-contaminated nuclides.

The amount of naturally occurring radionuclides in the volume ΔS of the concrete dust 5 is determined by the Ge detector 24 as γ.
By quantifying from the measurement result of the line 23, the contribution amount Cb of the β-ray of the naturally occurring radionuclide is calculated using the calculating means 14, and the contribution amount Cb of the β-ray is subtracted from the amount Cg of the β-ray. And the amount Cn of β-rays from the concrete contaminating nuclide can be obtained. When the amount of β-rays Cn becomes 0, it is determined that the contamination of the concrete has been removed.

As described above, in this embodiment, the storage height of the container 9 for storing the concrete dust 5 is determined by the level meter 27, and is set below the Ge detector 24 as γ-ray detection means in accordance with the height. The collimator 25 is moved up and down by using an elevator 26. Γ detected by the Ge detector 24
The line 23 located below the collimator 25 is blocked, and is not detected by the Ge detector 24. The γ-rays 23 below the collimator 25 are from the concrete surface 5 after cutting, and the γ-rays 23 detected by the Ge detector 24 are from the concrete surface 5 during cutting. If the radioactivity detected by the Ge detector 24 is equivalent to the evaluation of radioactive nuclides contained in nature or the gamma ray of a specific energy from the contaminated nuclide reaches an undetectable level, radioactive contamination Has been removed, and it is possible to determine the contamination of concrete.

As described above, according to the present embodiment, even if the concrete-contaminated nuclide is a nuclide that does not emit gamma rays, it is possible to determine whether the concrete is contaminated.

It should be noted that the present invention is not limited to the above-described embodiment, and the second embodiment and the third embodiment as shown in FIG.
Even if the contamination of concrete is determined by combining the examples, the radioactivity can be measured while cutting or cutting the concrete, and the determination of the contamination due to the local presence of the radioactive contamination or the interruption of the work can be performed. It is possible to judge concrete contamination efficiently. In FIG. 11, the same parts as those in the second and third embodiments are denoted by the same reference numerals.

[0050]

As described above, according to the first aspect of the present invention, concrete powder generated from one of decontamination and demolition of a radioactively contaminated concrete structure is sucked, In addition to detecting radiation from radioactive nuclides contained in the sucked concrete powder, and cutting the concrete structure n times, determining the number of radioactive cuts and terminating the cutting, the concrete structure Contamination of the concrete structure can be determined during either decontamination and demolition.

Thus, it is possible to provide an efficient concrete contamination determination method without interrupting the work due to sampling without losing the accuracy of the determination of the radioactive contamination of the concrete.

[0052] According to claim 2, when detecting the radiation from radionuclides in concrete powder, of decontamination means and dismantling means, in the vicinity of either one, from radionuclides in concrete powder By installing radiation detection means for detecting radiation, and by directly detecting radiation with this radiation detection means, it is possible to judge contamination of concrete structures during either decontamination or demolition of concrete structures. Can be. Therefore, in addition to the effect of the first aspect, the radiation detection accuracy can be improved.

[0053]

[Brief description of the drawings]

FIG. 1 shows a first example of a concrete contamination determination method according to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram which shows the decontamination apparatus using an Example.

FIG. 2 is a configuration diagram showing an attached state of a suction port in FIG. 1;

FIG. 3 is an enlarged configuration diagram showing a dust sampler and a dust collection device in FIG. 1;

FIG. 4 is a flowchart illustrating the operation of a control system according to the first embodiment.

FIG. 5 is a second example of the concrete contamination determination method according to the present invention.
The block diagram which shows the disassembly apparatus which used the Example.

FIG. 6 is an explanatory view showing the operation of the cutting means in FIG.

FIGS. 7A, 7B, and 7C are explanatory diagrams showing the relationship between the cutting means and the sheet-like film in FIG. 5;

FIG. 8 shows a third example of the concrete contamination judging method according to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram which shows the decontamination apparatus using an Example.

FIGS. 9A and 9B are explanatory diagrams illustrating a method of measuring γ-rays according to a third embodiment.

FIGS. 10A and 10B are spectrum diagrams showing the relationship between γ-ray energy and counting in the third embodiment.

FIG. 11 is an overall configuration diagram showing an apparatus using the second and third embodiments of the method for judging concrete contamination according to the present invention.

FIG. 12 is a schematic view showing a general decontamination apparatus and a concrete dust collection apparatus.

FIG. 13 is an enlarged view showing a cutting means of the decontamination apparatus in FIG.

FIG. 14 is a configuration diagram showing a decontamination device and a concrete dust collection device of FIG. 12;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 decontamination device 2 concrete dust collection device 3 concrete surface 4 cutting means 5 concrete dust 9 container 10 suction port 12 dust sampler 13 signal processing system 14 arithmetic means 15 display means 16 sheet filter 18 β-ray detection means (radiation detection means ) 19 Moving means 21 Cutting means 22 Laser distance meter 23 γ-ray 24 Ge detector (radiation detecting means) 25 Collimator (shielding means) 26 Elevator 27 Level meter

Continuation of the front page (56) References JP-A-3-4191 (JP, A) JP-A-2-263188 (JP, A) JP-A-3-41386 (JP, A) JP-A-3-51788 (JP) JP-A-56-79979 (JP, A) JP-A-4-1061491 (JP, A) JP-A-62-282288 (JP, A) JP-A-63-122869 (JP, A) 4-99998 (JP, A) JP-A-5-45467 (JP, A) JP-A-5-333155 (JP, A) JP-B-31-1992 (JP, B1) (58) Fields investigated (Int. Cl. ^7, DB name) G01T 7/02 G01T 1/169 G21F 9/30 535 G21F 9/30 ZAB

Claims (2)

(57) [Claims] 1. A method for absorbing radiation from a radionuclide contained in the sucked concrete powder by absorbing concrete powder generated during cutting from one of surfaces during decontamination and demolition of a concrete structure contaminated with radioactivity. To detect
When the concrete structure is judged to be contaminated, and the radiation dose for judging the contamination is counted n times, (n
(N-2) times more than -1) times, and (n-1)
When n times are greater than or equal to n times, it is determined that the cut surface of the concrete structure is free of contamination.
Concrete contamination determination method, characterized by a constant. 2. The method for judging concrete contamination according to claim 1, wherein when detecting radiation from radionuclides contained in the concrete powder, one of decontamination means and demolition means for performing decontamination and demolition. A method for judging concrete contamination, comprising: installing radiation detecting means for detecting radiation from radionuclides contained in the concrete powder in the vicinity, and directly detecting the radiation with the radiation detecting means.