JPH0990040A - System and method for reducing radiation exposure and method and instrument for measuring radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation exposure reducing method by which the protective clothing to be worn by workers can be changed in accordance with the surface concentration of radioactivity so that the workers can efficiently work in a facility contaminated with radioactivity and the radiation exposure of the workers can be reduced. SOLUTION: In a radiation exposure reducing method, the radiation exposure of workers is reduced by changing the protective clothing to be worn by the workers in a nuclear facility. In this method, the information on the positions and surface concentrations of radioactivity obtained by means of radioactivity detecting devices 8 and 11 are stored in advance and the secular change of the density of a radioactive material at each location in the facility is calculated 12 from the stored information, and then, the density map of the radioactive material is prepared from the calculated results. At the same time, the protective clothing to be worn by the workers at each location in the facility shown on the map is selectively displayed 13 from the data inputted in advance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation exposure reduction system, a radiation exposure reduction method, a radiation detection method and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the radiation exposure of workers in, for example, nuclear power plants, workers usually wear protective equipment to work. Further, the measurement of the radioactivity density at that time is performed by the direct method or the smear method. The direct method is a method of directly measuring an instrument or a floor surface with a portable Geiger-Muller survey meter (hereinafter abbreviated as GM survey meter) having high detection sensitivity. The smear method, as shown in FIG. 3, wipes the sampling surface 28 with the smear filter paper 21 formed of thick filter paper or the smear filter cloth formed of cloth, and measures with a radioactivity measuring device. .

In this case, the sampling surface is basically 1
It is 00 cm ² , but if it is difficult, it will be done according to the situation. Normally, the circular portion of the smear filter paper 21 is sampled. The rectangular portion is a holding portion. Sumi filter papers are numbered consecutively and sampled continuously. Taking a reactor building as an example, the number of sheets per floor is usually 100 to 200. After the sampling is completed, the radioactivity is measured, but since the level of radioactivity is usually high in such places, there is no equipment such as stairs and a radioactivity measuring instrument is installed in a place where the radioactivity level is low and the measurement is performed. Be seen.

Reference numeral 22 in FIG. 3 is a radioactivity detector (usually GM).
Tube), 26 is a sample holder, 27 is a sample to be measured, 25 is a shield, 23 is a cable, and 24 is a radioactivity measuring instrument. The radioactivity detector 22 has a high detection efficiency GM.
A tube is used, and only the circular portion of the smear filter paper that has been sampled is cut out and measured in the state of reference numeral 27. They are placed in a shield about 5 cm thick with lead to reduce background. Radioactivity measuring device 24
For this, a survey meter or a scaler with a timer is used.

As an automatic smear sampling device, there is known an "automatic smear device" as disclosed in, for example, Japanese Patent Laid-Open No. 2-118483. This automatic smearing device will be described with reference to FIG. 4. Reference numeral 32 is an adhesive tape supply roll, 33 is a winding roll, 36 is a pressing roller, 38 is a wrapping material, and 42 is a floor surface.

The apparatus comprises a pressure roller 3 having an adhesive tape supplied from a supply roll 32 installed near the floor 42.
It is pressed against the floor surface 42 at 6 and a desired length 43 is sampled. After sampling with the pressure roller,
It is covered with a wrapping material 38 and wound up by a winding roll 33. After this, but not described here, the radioactivity is measured using a GM counter.

Further, as a device for automatically sampling and subsequently measuring the radioactivity, there is a "radioactivity contamination inspection device" of Japanese Patent Laid-Open No. 61-112984. The device will be described with reference to FIG. 43 is an adhesive tape supply roll, 42 is a take-up roll 44, 45 is a roller, 46 is a wrapping material, 47 and 48 are wrapping material holding rollers, 49 is a tape holding cylinder, 50 is a radioactivity detector, 51 is a shield, 52 is a cable, 53 is a radioactivity measuring instrument, 54 is a sampling part, 56 is a sampling device lifting device, 55
Is a sampling device rotating device, 57 is a drum can of the object to be measured, and 58 is an object rotating device.

The tape supplied from the supply roll 43 is pressed by the pressing cylinder 49 on the object 57 to be measured. In this state, the object to be measured 57 is rotated by the rotating device 58,
Sampling a fixed area. After the sampling is completed, the sample is protected by the wrapping material 46, and the radioactivity is measured by the radioactivity detector 50 and the radioactivity measuring device 53. The sampling position can be arbitrarily designated by the sampling device elevating device 56 and the rotating device 55.

[0009]

In order to carry out radioactivity measurement by the radioactivity measurement method and radioactivity measurement device as described above, and to reduce the radiation exposure of workers,
Workers wear protective equipment to work,
In this case, even if the radioactivity density is low, it tends to be heavy protection equipment, that is, it is excessive protection equipment, and there is a dislike that it causes a reduction in work efficiency. Further, in the radioactivity measuring device, naturally these devices are used for their respective purposes, but there are the following problems, and improvements are desired. That is, since the direct method currently used has a high detection lower limit, it is possible to perform measurement only at a position where the background is extremely low, and it is difficult to perform measurement at a position where the background is a little. Further, the window surface of the GM tube type survey meter is a very thin film in order to reduce the absorption of radiation, and if it is hit by a protrusion such as a wire, it is easily damaged. Moreover, since contaminants adhere to the surface, it is necessary to decontaminate the surface frequently.

In the smear method shown in FIG. 2, it is necessary to rub the floor surface directly at the time of sampling, so that the work requires an unreasonable posture. Therefore, it may hurt the lower back. In addition, the target is 100 cm ² when wiping off, but individual differences occur. Different people have different wiping powers. There is less pollution at the place where it was wiped off, so it is necessary to make sure to choose another place for the second time. About 100 at a time
Frequently sampling about one piece may cause cross contamination when carrying the sample in a polyethylene bag.

In the automatic smearing device shown in FIG. 5, the mechanism for pressing the adhesive tape with the roller to sample 100 cm ² becomes complicated and becomes a heavy device. Therefore, it is necessary to move by a dolly. The sampled adhesive tape is 10
Since it is 0 cm ^2, the current GM counter (diameter 5 cm, about 2
It cannot be measured once at 0 cm ² ). It can be measured if the sample is bent, but the β-ray self-shielding and the optical efficiency are somewhat different. It can be obtained by measuring 5 times in that state and summing the measurement results, but the error increases.

The error when the measurement is performed 5 times in the same state is as follows. That is, the measured value is 11 in each measurement.
When the background is 0 cpm and the background is 100 cpm, the net is 10 cpm. The error σ at that time is σ = √
110 = 10.5 cpm, N = 5 in total of 5 times
0 ± 5 × 10.5 = 50 ± 52.5, which is 3σ = 15
It is 7.5 cpm or less, which is below the detection limit.

On the other hand, in the conventional smear method, the measurement can be performed once. The value and error at that time is No = 150
± √150, N = 50 ± 12.2, 3σ = 36.5 cp
m, which is well measured. Thus, the automatic smear method has a worse detection limit than the conventional method.

In the radioactive contamination inspecting apparatus shown in FIG. 5, a vertical and rotational mechanism for surely pressing the adhesive tape to a target sampling point, and γ
It consists of lead shields for shielding wires. It is a very heavy equipment for these and is difficult to move. In addition, since the target area is sampled by pressing the adhesive tape against the object to be measured, there is a possibility that sampling of radioactive material may be partially uncertain.

The present invention has been made in view of the above, and an object thereof is to enable an operator to wear protective equipment according to the radioactivity density, thereby improving the efficiency of work at a radioactive contamination place. A radiation exposure reduction system and a radiation exposure reduction method of this type capable of reducing the radiation exposure amount, and a radiation detection device and method that are lightweight and small and can easily measure the surface contamination density. To provide.

[0016]

That is, the present invention provides a method for reducing the radiation exposure of a worker in a nuclear facility by wearing protective equipment, in which the worker measures the radiation exposure in advance by a radioactivity detector. The information of the measured position and the measured radioactivity density is stored, the secular change of the radioactive material density at each position in the facility is calculated based on this stored information, and the radioactive material density map is created based on this calculation, The necessary protective equipment for the worker at each position in the facility on the map is selectively displayed from previously input data to achieve the intended purpose.

In addition, in a radiation exposure reduction system adapted to reduce the radiation exposure of workers in nuclear facilities by wearing protective equipment, the position of this system and the measured radiation measured in advance by the radioactivity detector are used. A storage device that stores information about active density, a secular change calculation device that calculates the secular change of radioactive material density at each position based on the information of the storage device, and a radioactive material density map based on the output of the calculation device. A protective equipment display device is provided which is created and which selectively displays the required protective equipment for the operator at each position in the facility on the map from the data input in advance.

The measuring method in this case is as follows. That is, a predetermined surface in a nuclear facility is wiped with a sampling means, the wiped sample is measured with a radioactivity measuring instrument, and the radioactive contamination density of the predetermined surface in the facility is measured. In the method, a continuous adhesive tape is used for the sampling means, and the sampling surface is formed smaller than the measurement area of the radioactivity measuring instrument, and a plurality of times until the measurement area required for radioactivity measurement is obtained. The sample collecting operation is repeated to form a measurement sample having a predetermined area, and the radioactive contamination density is measured.

In other words, in such a radiation exposure reduction system, the necessary protective equipment for the worker at each position in the equipment is selected and displayed from the previously input data, so that the worker can adjust the radiation density according to the radiation density. It is possible to wear protective equipment that does not become excessive, so that it is possible to improve the efficiency of work in the radioactive contamination area and reduce the radiation exposure.

Further, the measuring device in this case uses a continuous adhesive tape, operates a plurality of times to a predetermined area with an area smaller than the window surface of the radiation detector, and collects a sample, and then the radiation detector. Therefore, the surface contamination density can be easily measured by making it light and small.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. The radiation exposure reduction system is shown diagrammatically in FIG. In the figure, 8 is a radiation detector, 11 is a radiation measuring device, 12 is a data processing personal computer (storage device 12a, secular change computing device 12b), and 13 is a graph output by the personal computer and displayed on a display device.

A radiation exposure reduction system comprises such a device and operates as follows. That is, the radioactivity density at each position (measurement position) is measured by the radioactivity detecting device, that is, the radiation detector 8 and the radiation measuring device 11, and the radioactivity density information at each position is stored in the storage device 12a. Based on this stored information, the secular change in the radioactive material density at each position is calculated by the secular change calculation device 12b, and a radioactive material density map is created based on the output of this calculation device,
The required protective equipment of the operator at each position in the facility on the map is selected and displayed by the protective equipment display device 13 from the data input in advance. Then, based on this display, the worker wears the protective equipment.

The data of the protective equipment are experimentally or empirically determined in advance, and Table 1 shows an example thereof.

[0024]

[Table 1]

Since the necessary protective equipment for the worker at that time is displayed on the display device in this way, the worker can wear protective equipment according to the radiation density without becoming excessive protective equipment, and It is possible to improve the efficiency of work in a polluted place.

Next, the radiation detector 8 for detecting the radioactive contamination state will be described with reference to FIGS. 1 and 2.
Is an adhesive sampling tape (hereinafter abbreviated as adhesive tape), 2 is an adhesive tape supply roll, 3 is an adhesive tape recovery roll, 4 is an adhesive tape feed roll, 5 is a roll, 6
Is a smear sampling table, 7 is a shield, 9 is a carrying handle, 10 is an adhesive tape protector, 14 is the width of the adhesive tape,
Reference numeral 15 is a bar code reader for position measurement.

The adhesive tape from the supply roll 2 passes through the smear sampling table 6, the roll 5, the inside of the shield 7, the adhesive tape feed roll 4, and the adhesive tape recovery roll 3. . In this state, the radiation measuring instrument 11
At the same time, go to the target site with the handle 9. Sampling is performed at the target location, but the method is as follows. The radiation detector 8 is usually a GM tube having a window diameter of 5 cm and a surface area of about 20 cm ² .

The standard sampling area in the Smear method is 100 cm ^2. Generally, the conversion count is often obtained in this state. The smear sampling table 6 of the present invention has a diameter of 5 cm and a surface area of 20 cm ² . Therefore, in order to collect 100 cm ² of area for smear measurement, the sample is collected by moving the different points and stamping five times.
The sampling method may be continuous or staggered as long as the same position is not sampled. After that, the adhesive tape feed roll 4 is rotated to move the sampling surface to the position of the radiation detector 8.

After that, as described above, in this state, measurement is performed by the radiation measuring instrument, the measurement is stored in the memory, the measurement position is read by the bar code reader 15, and the measurement is stored in the memory. The adhesive tape is made by sticking an adhesive material on paper, cloth, aluminum or the like. The part where the adhesive tape contacts the device is when it passes between the shields 7 and when it passes the tape feed roll 4. If the adhesive tape touches the equipment and becomes sticky, problems may occur such as stopping movement or cutting the tape. In order to prevent this trouble, the adhesive tape protector 10 is used. This protector is made of paper tape soaked in tetrafluoroethylene (hereinafter referred to as Teflon, which is a commercial product) or oil so that the tape does not stick easily, and prevents the tape from adhering.
The adhesive tape feed roll 4 is also made of a similar material that does not easily stick.

In addition, a guide roller is provided on the opposite side to reliably feed the tape. The signal obtained by the radiation detector 8 is measured by the radiation measuring device 11, and is stored in the memory attached to the radioactivity measuring device together with the information on the position read by the barcode reader. The memory is stored in a certain amount using an IC card or a memory card and then transferred to a personal computer. The personal computer processes the data, creates and outputs maps for each floor, and calculates and outputs the average contamination density. Also, the time-dependent change of pollution at the target location is output as in 13.

The above-mentioned adhesive tape feeding mechanism will be described in detail with reference to FIGS. 6 to 8. 1, 3, 4, 6, 7 are the same as those in FIGS. 1 and 2, 71 is a guide roller, 7
2 is a stepping motor for feeding the adhesive tape, and 73 is a belt for rotating the winding roller. The adhesive tape from which the sample is sampled by the smear sampling table portion 6 is moved to the position of the radiation detector 8 by the adhesive tape feed roll 4. The adhesive tape feed roll is provided with a stepping motor 72 to give necessary rotation. In addition, adhesive tape feed roll 4
Is equipped with a guide roller for preventing the tape from being idly fed, so that the adhesive tape can be reliably fed.

The adhesive tape is finally wound up on the collecting roll 3, but is equipped with a winding roller rotating belt 73 for rotating this roll. The collecting roller is rotated more than the stepping motor 72, but the belt is slippery and rotates as much as necessary.

A method of setting the adhesive tape will be described with reference to FIG. The shield is divided into 7 and 76.
Reference numeral 7 is called an upper shield, and 76 is called a lower shield. The upper shield has anti-adhesion 10 and the lower shield has anti-adhesion 10A. Screw 7 when setting adhesive tape
7, remove the upper and lower shields, set the tape, and fix with screws 78 when finished.

The tape feed amount sampled by the adhesive tape will be described with reference to FIG. Smear sampling table 6
When the sample is sampled a plurality of times, the radioactive substance is accumulated at the position 81 on the tape. When the sampling is completed, 1 in Fig. 1
The position information is read by the bar code reader shown in FIG. 1, and the tape is moved to the position 82 by the adhesive tape feeding roller 4 by moving the stepping motor 72 shown in FIG.

At this time, the tape surface sampled last time reaches the measurement position 83 of the radioactivity detector 8 and is measured. When the measurement for a certain period of time is completed, the stepping motor is moved to move the tape to an intermediate point between 82 and 83, that is, a portion where radioactive material is not sampled. When the movement is completed, the background is measured for a certain period of time. An adjusting rod 84 is provided as a mechanism for adjusting the amount of movement of the adhesive tape by the stepping motor. This adjusting rod adjusts the position of the roll 5 so as to surely reach the detection surface of the radioactivity detector.

FIG. 1 shows the shield surrounding the detector.
This will be described with reference to FIG. The shield used this time is made of aluminum and has a thickness of 5 mm. The shielding effect is evaluated as follows.

[0037]

[Formula 1] ⁶⁰ Co β-ray 0.318 MeV ⁵⁸ Co β-ray 0.475 MeV ⁵⁴ Mm β-ray None ⁵¹ Cr β-ray None Radioactive substances contained in piping, pumps, valves, etc. of nuclear power plants are the above-mentioned four nuclides. Since it is over 90%, the objective can be achieved if these can be shielded. Γ that occurs at the same time
The wire cannot be shielded with 5 mm of aluminum.
However, the detection efficiency for γ-rays of GM counter is 10 for β-rays.
Since it is less than%, β rays are mainly shielded. γ-rays can be canceled in the background measurement, which is performed after the measurement of the sampling unit.

Since the maximum range of 0.5 MeV β-rays in aluminum is about 1 mm, sufficient shielding can be achieved with 5 mm. The weight of the 5 mm shield is 1.9 kg.
It is. If it is this weight, it can be carried easily.

If a nuclide that is a fissile substance is detected, the energies of these β rays are as follows.

[0040]

(2) ⁹⁰ Sr β ray 0.546 MeV ⁹⁰ Y β ray 2.28 ¹³¹ I β ray 0.606 ¹³⁴ Cs β ray 0.658 ¹³⁷ Cs β ray 0.512 Therefore, even when a fissile substance is detected. The object can be achieved by using aluminum 7 mm as the maximum shielding thickness. Target area, eg 5FL of reactor building
After the measurement of etc. is completed, the measured data is carried in a floppy disk, a memory card, an IC card, etc. and input to a personal computer. After this, a color map showing the pollution situation can be created using a personal computer, and a graph of the secular change of pollution as shown at 13 in FIG. 1 can be created. It also automatically outputs instructions for protective equipment according to the pollution situation. That is, if it is 4 Bq / cm ² or less, the above-mentioned Table 1
As shown in, half-face mask, B wear, rubber gloves, protective helmet are worn.

As described above, by using the lightweight and small-sized device, it is possible to continuously measure the surface contamination density on site without any individual difference. This improves work efficiency, eliminates the risk of damage to the radiation detector, and prevents measurement errors due to cross contamination. In addition, it becomes possible to consistently give instructions for protective equipment, and it is possible to prevent a reduction in work efficiency due to excessive equipment.

[0042]

As described above, according to the present invention, the necessary protective equipment for the worker at each position in the equipment is selected and displayed from the data input in advance, so that the worker can reduce the radiation density. It is possible to wear appropriate protective equipment, and it is possible to improve the efficiency of work in a radioactive contamination place and reduce the radiation exposure amount without becoming excessive protective equipment. The measuring device uses a continuous adhesive tape, and a sample is taken by operating the area smaller than the window surface of the radiation detector multiple times to a predetermined area, and then the radiation detector is used for measurement. Thus, the surface contamination density can be easily measured.

[Brief description of drawings]

FIG. 1 is a diagram showing a radiation exposure reduction system and a radiation detection apparatus of the present invention.

FIG. 2 is a plan view showing a radiation detecting apparatus of the present invention.

FIG. 3 is a vertical sectional side view showing a conventional radiation detection apparatus.

FIG. 4 is a side view showing a sampling state by a conventional automatic sampling device.

FIG. 5 is a partially cutaway side view showing a conventional radioactive contamination inspection device.

FIG. 6 is a front view of an adhesive tape drive mechanism of the radiation detecting apparatus of the present invention.

FIG. 7 is a side view of the adhesive tape drive mechanism of the radiation detecting apparatus of the present invention.

FIG. 8 is a plan view of an adhesive tape drive mechanism of the radiation detecting apparatus of the present invention.

FIG. 9 is a vertical cross-sectional side view showing the periphery of the adhesive tape portion of the radiation detecting apparatus of the present invention.

FIG. 10 is a side view of the radiation detecting apparatus of the present invention.

[Explanation of symbols]

1 ... Adhesive tape, 2 ... Tape supply roll, 3 ... Tape collection roll, 4 ... Tape drive roller, 6 ... Smear intake table, 7 ... Shield, 8 ... Radioactivity detector, 11 ... Radioactivity measuring instrument, 12 ... Personal computer, 13 ... Output result, 14 ... Adhesive tape width, 72 ... Tape driving stepping motor.

Claims (7)

[Claims] 1. A radiation exposure reduction method for reducing the radiation exposure of a worker in a nuclear facility when the worker wears protective equipment, in which the position previously measured by a radioactivity detector and the measured radiation density are measured. Information is stored, the secular change of radioactive material density at each position in the equipment is calculated based on this stored information, and a radioactive material density map is created based on this calculation, and at each position in the equipment on the map. A method for reducing radiation exposure, characterized in that the protective equipment required by the operator is selected and displayed from previously input data. 2. In a radiation exposure reduction system adapted to reduce the radiation exposure of workers in nuclear facilities by wearing protective equipment, information on the position previously measured by a radioactivity detector and the measured radioactivity density. With a storage device that stores, a secular change calculation device that calculates the secular change of the radioactive material density at each position based on the information of the storage device, and create a radioactive material density map based on the output of the calculation device, A radiation exposure reduction system characterized by comprising a protective equipment display device for selectively displaying the necessary protective equipment for workers at respective positions in the equipment on the map from previously input data. 3. A predetermined surface in a nuclear facility is wiped by a sampling means, and the wiped sample is measured by a radioactivity measuring instrument to measure the radioactive contamination density of the predetermined surface in the facility. In the radiation measuring method described above, a continuous adhesive tape is used for the sampling means, and the sampling surface is formed smaller than the measurement area of the radioactivity measuring instrument until the measurement area of the radioactivity measuring instrument is reached. A radiation measuring method characterized in that a plurality of sampling operations are repeated to form a measurement sample having a predetermined area, and the radioactive contamination density is measured. 4. The radiation measuring method according to claim 3, wherein the continuous adhesive tape is moved after the radioactive substance on the target surface is measured, and then the background is measured. 5. A predetermined surface in a nuclear facility is wiped off,
A radiation measuring device comprising a sample collecting means for collecting a sample and a radioactivity measuring device for measuring the radioactivity of the wiped sample, and a radiation measuring device adapted to measure the radioactive contamination density of a predetermined surface in the facility, The sampling means is formed of a continuous adhesive tape, and its sampling surface is formed smaller than the measurement area of the radioactivity measuring instrument, so that the sampling operation is repeated to obtain a measurement sample of a predetermined area. A radiation measuring device characterized by being formed. 6. A radiation measuring apparatus according to claim 4, wherein a cloth impregnated with ethylene tetrafluoride or oil is used for a portion of the apparatus which comes into contact with the continuous adhesive tape. 7. The device is provided with a roller for moving the adhesive tape from which a sample is taken to the radiation measuring instrument, and the sample collecting part of the adhesive tape is accurately moved to a predetermined position of the radiation measuring instrument on this roller. 5. The radiation measuring apparatus according to claim 4, further comprising a position adjusting mechanism.