JP7055732B2 - Radiation measuring device and radiation measuring method - Google Patents

Description

Embodiments of the present invention relate to a radiation measuring device and a radiation measuring method.

Conventionally, there is a radiation measuring device that measures radiation such as neutrons emitted from a radioactive substance. For example, there is known a technique of detecting Cherenkov light generated when radiation hits an optical fiber with detectors at both ends of the optical fiber and calculating the incident position of radiation from the time difference of the detection.

Japanese Unexamined Patent Publication No. 6-294871

The shape or size of the object to be measured for radiation may be changed during the operation of the radiation measuring device. In that case, it is necessary to freely change the area where radiation can be measured by the radiation measuring device. However, the above-mentioned technique has a problem that the measured area of radiation cannot be easily changed.

The embodiment of the present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a radiation measurement technique capable of changing the measurement area of radiation.

The radiation measuring device according to the embodiment of the present invention has a radiation detection unit having a tubular portion filled with a rare gas and a wire stretched inside the tubular portion, and a radiation detection unit at one end of the radiation detection unit. It is connected to one terminal and is connected to a signal acquisition unit that acquires a pulse signal based on the current flowing between the tubular portion and the wire due to the incident of radiation, and a second terminal at the other end of the radiation detection unit. A plurality of the radiations, including a connecting cable for connecting the radiation detection unit to the other radiation detection unit, and a measurement unit for measuring the incident of the radiation based on the pulse signal acquired by the signal acquisition unit. The detection units are arranged side by side so as to form a rectangle, and the plurality of the radiation detection units arranged side by side are orthogonal to the longitudinal direction of the tubular part and adjacent to one side of the rectangle. The additional radiation detection unit is arranged in the above .

Embodiments of the present invention provide a radiation measurement technique capable of changing the radiation measurement area.

The block diagram which shows the system of the radiation measuring apparatus of 1st Embodiment. The block diagram which shows the radiation detection part of 1st Embodiment. The block diagram which shows the additional radiation detection part of 1st Embodiment. The graph which shows the waveform of the pulse signal of 1st Embodiment. A flowchart showing a radiation measurement method. A flowchart showing a radiation measurement process. The block diagram which shows the radiation detection part of 2nd Embodiment. The graph which shows the waveform of the pulse signal of 2nd Embodiment. The block diagram which shows the additional radiation detection part of the modification.

(First Embodiment)
Hereinafter, this embodiment will be described with reference to the accompanying drawings. First, the radiation measuring apparatus of the first embodiment will be described with reference to FIGS. 1 to 6.

Reference numeral 1 in FIG. 1 is a radiation measuring device. A neutron beam is exemplified as the radiation R measured by the radiation measuring device 1 of the present embodiment. Further, as an object Q to be measured, a neutron emitting substance that emits neutrons when the content of a radioactive substance is unknown and a criticality occurs is exemplified. In order to determine whether or not criticality has occurred in such an object Q, the detection of neutron rays is an index. Some objects Q have unstable shapes and sizes. In addition, the object Q may be disassembled into a plurality of objects. In addition to the solid object Q, there is also a liquid object. Therefore, it is necessary to appropriately change the measurement area of the radiation R of the radiation measuring device 1 according to the change in the shape or size of the object Q.

As shown in FIG. 1, the radiation measuring device 1 processes a radiation detection unit 3 that detects radiation R emitted from an object Q mounted on a sample table 2 and a signal output from the radiation detection unit 3. The signal processing unit 4 is provided. The radiation detection unit 3 includes a plurality of radiation detection units 5.

The signal processing unit 4 includes a signal acquisition unit 6, an amplifier circuit 7, a setting storage unit 8, a timing unit 9, a measurement unit 10, a data storage unit 11, and a data display unit 12. Further, the measuring unit 10 includes a counting circuit 13, a position specifying unit 14, a waveform identification unit 15, and a noise removing unit 16.

The signal acquisition unit 6 acquires a pulse signal output from the radiation detection unit 3. The amplifier circuit 7 amplifies the pulse signal acquired by the signal acquisition unit 6.

The setting storage unit 8 stores setting information such as the number of radiation detection units 5 constituting the radiation detection unit 3.

The timekeeping unit 9 includes a real-time clock and is used to identify the time when the pulse signal is acquired. It is also used to measure the elapsed time from the time when one pulse signal is acquired.

The data storage unit 11 stores various data such as the radiation count value or the incident position measured by the measurement unit 10. The data display unit 12 displays the data stored in the data storage unit 11.

The measuring unit 10 performs a process of measuring the incident of radiation R based on the pulse signal acquired by the signal acquisition unit 6.

The counting circuit 13 performs a process of counting the number of times the radiation R is detected. The position specifying unit 14 performs a process of specifying the incident position of the radiation R based on the difference in acquisition time between the initial wave of the pulse signal and the reflected wave of the pulse signal.

The waveform identification unit 15 performs a process of discriminating between the initial wave of the pulse signal and the reflected wave of the pulse signal based on the amplitude and wavelength. The noise removing unit 16 performs a process of removing the waveform of the pulse signal that becomes noise.

The measurement unit 10 included in the signal processing unit 4 is realized by executing a program stored in a memory or an HDD by a CPU.

The system of this embodiment has hardware resources such as a CPU, ROM, RAM, and HDD, and is composed of a computer in which information processing by software is realized by using hardware resources by executing various programs by the CPU. Will be done.

As shown in FIG. 2, in the initial state, the radiation detection unit 3 is configured by using the three radiation detection units 5. The radiation detection unit 5 has a cylindrical portion 17 having a cylindrical shape and a wire 18 stretched inside the tubular portion 17. The inside of the tubular portion 17 is filled with a rare gas such as argon gas or xenon gas.

The plurality of radiation detection units 5 are arranged so that the tubular portions 17 are parallel to each other, and the tubular portions 17 are arranged in contact with each other or in close proximity to each other. That is, a plurality of radiation detection units 5 are arranged side by side in one direction (in the vertical direction of the paper surface in FIG. 2). Then, the radiation detection units 5 are integrated with each other by a predetermined fixing jig, and a rectangular (quadrangular) flat plate-shaped radiation detection unit 3 is formed. Further, the rectangular area of the radiation detection unit 3 when these radiation detection units 5 are integrated is the measurement area of the radiation R. The radiation detection units 3 arranged side by side in this way and forming a rectangular shape are brought close to the object Q to measure the radiation R (see FIG. 1).

One predetermined radiation detection unit 5 is connected to the signal acquisition unit 6 of the signal processing unit 4 via the base cable 19. In each radiation detection unit 5, a first terminal 21 is provided at one end, and a second terminal 22 is provided at the other end.

The signal acquisition unit 6 is connected to the first terminal 21 at one end of the radiation detection unit 5, and acquires a pulse signal based on the current flowing between the tubular portion 17 and the wire 18 due to the incident radiation R.

In the following description, the side close to the signal acquisition unit 6 in terms of an electric circuit will be described as the base end side. That is, in each radiation detection unit 5, the terminal on the proximal end side is the first terminal 21, and the terminal on the opposite end is the second terminal 22. Further, the signal acquisition unit 6 will be described with the farthest end of the electric circuit as the end.

A connecting cable 20 is connected to the second terminal 22 of the radiation detection unit 5A on the most proximal side. This connecting cable 20 is connected to the first terminal 21 of another radiation detection unit 5. That is, the second terminal 22 of the radiation detection unit 5 of 1 and the first terminal 21 of the other radiation detection unit 5 are connected by the connecting cable 20. Further, a connecting cable 20 is connected to the second terminal 22 of the other radiation detection unit 5, and this connecting cable 20 is connected to the first terminal 21 of the radiation detection unit 5B at the end. That is, a plurality of radiation detection units 5 are connected in series as an electric circuit by the connecting cable 20.

The base cable 19 and the connecting cable 20 consist of a general coaxial cable. A coaxial cable has a circular shape in cross-sectional view, an internal conductor is provided on the central axis, the internal conductor is covered with an insulator, an external conductor is provided around the inner conductor, and the periphery thereof is covered with a protective coating. It is a thing. In the coaxial cable, the inner conductor is connected to the wire 18, and the outer conductor is connected to the tubular portion 17.

When no radiation R is incident on the radiation detection unit 5, no current flows between the tubular portion 17 and the wire 18. Here, when the radiation R is incident on the radiation detection unit 5, the rare gas existing between the tubular portion 17 and the wire 18 is ionized, and a current flows between the tubular portion 17 and the wire 18. A pulse signal based on this current is generated on the wire 18.

The pulse signal generated in the wire 18 flows from the incident position P of the radiation R to the first direction C1 toward the proximal end side and the second direction C2 toward the opposite side. The pulse signal flowing in the first direction C1 is first acquired by the signal acquisition unit 6. On the other hand, the pulse signal flowing in the second direction C2 flows to the other radiation detection unit 5 via the connecting cable 20, and further flows to the radiation detection unit 5B at the end.

Then, it is reflected by the second terminal 22B of the radiation detection unit 5B at the end. Since one side of the terminal second terminal 22B is in an electrically open state, impedance mismatch occurs and the pulse signal is reflected. The reflected pulse signal runs backward in the transmitted path and flows to the signal acquisition unit 6. The pulse signal first acquired by the signal acquisition unit 6 is referred to as an initial wave W1, and the pulse signal reflected by the terminal second terminal 22B at the end is referred to as a reflected wave W2.

FIG. 4 is a graph showing the waveform of the pulse signal acquired by the signal acquisition unit 6. In this way, a waveform having two peaks, the initial wave W1 and the reflected wave W2, is acquired. The reflected wave W2 arrives after the initial wave W1 arrives. Then, the incident position P of the radiation R can be specified based on the difference D between the acquisition times of the initial wave W1 and the reflected wave W2. For example, when the incident position P is close to the signal acquisition unit 6, the time difference D becomes large, and when the incident position P is far from the signal acquisition unit 6, the time difference D becomes small. That is, the time difference D is proportional to the electric circuit distance from the incident position P to the terminal second terminal 22B at the end. By doing so, the incident position P of the radiation R can be specified by a simple process. By specifying the incident position P, it is possible to specify the approximate position of generation of the radiation R in the object Q.

The incident position P may be specified as long as the radiation detection unit 5 that has detected at least the radiation R can be specified by the plurality of radiation detection units 5.

The pulse signal generated in the wire 18 is reflected by the second terminal 22B which is the terminal, and is also reflected by the signal acquisition unit 6 on the proximal end side. That is, the initial wave W1 and the reflected wave W2 are reciprocated many times between the second terminal 22B at the end and the signal acquisition unit 6, and a waveform of a pulse signal that becomes noise is generated. Therefore, the noise reduction unit 16 (see FIG. 1) performs a process of stopping the acquisition of the pulse signal for a certain period of time after the signal acquisition unit 6 acquires the reflected wave. This noisy waveform weakens each time it makes a round trip and disappears in a short time. The pulse signal acquisition stop processing is continued for a time until the noise disappears. By doing so, it is possible to reduce erroneous detection based on a pulse signal that becomes noise.

Further, when the impedance of the connecting cable 20 is bent due to the bending, a plurality of secondary and tertiary reflected waves W2 may be generated. Since such a reflected wave W2 is an unnecessary pulse signal, that is, electrical noise, it is eliminated by the pulse signal acquisition stop processing. By doing so, it is possible to reduce erroneous detection and improve the accuracy of the radiation R counting function.

As shown in FIG. 3, the radiation detection unit 5 can be added. For example, in the initial state (see FIG. 2), the connection cable 20 is connected to the second terminal 22 of the radiation detection unit 5 at the end in a state where the three radiation detection units 5 are connected in series as an electric circuit. The first terminal 21 of the radiation detection unit 5 for expansion is further connected to the connection cable 20. Further, an additional radiation detection unit 5 is added, and five radiation detection units 5 are connected. In this way, the five radiation detection units 5 are arranged side by side in one direction (in the vertical direction of the paper in FIG. 3).

By connecting the radiation detection units 5 with the connecting cable 20 to form the radiation detection unit 3, the number of the radiation detection units 5 can be easily increased. Then, the measurement area of the radiation R can be expanded. Further, even if a plurality of radiation detection units 5 are added, it is not necessary to increase the signal processing unit 4 (measurement unit 10), and the incident of radiation R can be measured by one signal processing unit 4. Further, the number of radiation detection units 5 may be reduced to reduce the measurement area of radiation R. In the present embodiment, the measurement area of the radiation R can be easily changed by increasing or decreasing the number of the radiation detection units 5 according to the shape or size of the object Q.

The relationship between the acquisition time difference D between the initial wave W1 and the reflected wave W2 and the incident position P of the radiation R changes according to the number of connected radiation detection units 5. Therefore, the setting information indicating the number of connected radiation detection units 5 is stored in the setting storage unit 8. The setting information also includes information on the lengths of the radiation detection unit 5, the base cable 19, and the connecting cable 20. Then, based on the difference D between the setting information and the acquisition time, the position specifying unit 14 performs a process of specifying the incident position P. Further, since the initial wave W1 and the reflected wave W2 are superimposed on the wire 18 and propagated, the incident position P can be specified by a circuit having a simple configuration.

The count value, which is the number of times the radiation R is detected counted by the counting circuit 13, and the incident position P of the radiation R specified by the position specifying unit 14 are stored in the data storage unit 11. It should be noted that these pieces of information are stored in the data storage unit 11 as digital signals together with the measurement time. Then, the data stored in the data storage unit 11 can be displayed on the data display unit 12. The distribution of the radiation R generation position in the object Q may be aggregated and displayed on the data display unit 12 based on the count value of the radiation R, the incident position P, and the measurement time.

Next, the radiation measuring method executed by the radiation measuring device 1 will be described with reference to the flowchart of FIG. The effect of passively occurring on the radiation measuring device 1 will be described. The block diagram shown in FIG. 1 will be referred to as appropriate.

As shown in FIG. 5, first, in step S11, the user of the radiation measuring device 1 connects one end of the base cable 19 to the first terminal 21A of the radiation detection unit 5A on the most base end side. Then, the other end of the base cable 19 is connected to the signal acquisition unit 6 of the signal processing unit 4.

In the next step S12, the user connects the connecting cable 20 to the second terminal 22 of the radiation detection unit 5A on the most proximal side, and connects the connecting cable 20 to the first terminal 21 of the other radiation detection unit 5. do. By sequentially performing this, a plurality of radiation detection units 5 are connected in series as an electric circuit by a connecting cable 20.

In the next step S13, the user stores various setting information including the number of connected radiation detection units 5 in the setting storage unit 8.

In the next step S14, the user starts measuring the radiation R emitted from the object Q using the radiation measuring device 1. That is, the radiation measuring device 1 starts executing the radiation measuring process.

Next, the radiation measurement process executed by the radiation measurement device 1 will be described with reference to the flowchart of FIG. The effect of passively occurring on the radiation measuring device 1 will be described. The block diagram shown in FIG. 1 will be referred to as appropriate. This process is a process that is repeated at regular time intervals.

As shown in FIG. 6, first, in step S21, the signal processing unit 4 determines whether or not the temporary stop timer indicating that the acquisition of the pulse signal is temporarily stopped is being counted. Here, if the stop timer is once counting (YES in step S21), the process ends. On the other hand, if the stop timer is not counting once (NO in step S21), the process proceeds to step S22.

In the next step S22, the signal acquisition unit 6 determines whether or not a pulse signal has been acquired. Here, if the pulse signal has not been acquired (NO in step S22), the process ends. On the other hand, when the pulse signal is acquired (YES in step S22), the process proceeds to step S23.

In the next step S23, the waveform identification unit 15 determines whether or not the acquired pulse signal is the initial wave W1 based on the amplitude and the wavelength. Here, if the pulse signal is not the initial wave W1 (NO in step S23), the process proceeds to step S25 described later. On the other hand, when the pulse signal is the initial wave W1 (YES in step S23), the process proceeds to step S24.

In the next step S24, the measuring unit 10 stores the acquisition time of the initial wave W1 in the data storage unit 11 and ends the process.

In step S25, which proceeds when the pulse signal is not the initial wave W1, the waveform identification unit 15 determines whether or not the acquired pulse signal is the reflected wave W2 based on the amplitude and wavelength. Here, if the pulse signal is not the reflected wave W2 (NO in step S25), the process ends. On the other hand, when the pulse signal is the reflected wave W2 (YES in step S25), the process proceeds to step S26.

In the next step S26, the measuring unit 10 stores the acquisition time of the reflected wave W2 in the data storage unit 11.

In the next step S27, the counting circuit 13 adds 1 to the counting value of the radiation R. That is, the number of incidents of the radiation R is counted.

In the next step S28, the position specifying unit 14 identifies the incident position P of the radiation R based on the difference D between the acquisition times of the initial wave W1 and the reflected wave W2.

In the next step S29, the timekeeping unit 9 starts counting the temporary stop timer that temporarily stops the acquisition of the pulse signal, and ends the process. A predetermined count value is set in the stop timer. Then, the stop timer ends counting after a certain period of time has elapsed.

(Second Embodiment)
Next, the radiation measuring device 1 of the second embodiment will be described with reference to FIGS. 7 to 8. The same components as those shown in the above-described embodiment are designated by the same reference numerals, and duplicate description will be omitted.

As shown in FIG. 7, in the radiation detection unit 3 of the second embodiment, three radiation detection units 5 are connected. A terminating device 23 (terminating resistor) is attached to the second terminal 22B of the radiation detection unit 5B at the end. By attaching this terminator 23, the state of impedance mismatch changes. Therefore, when the pulse signal is reflected by the second terminal 22B which is the termination, the reflected wave W2 having the opposite polarity is electrically generated (see FIG. 8).

By doing so, the reflected wave W2 of the pulse signal reflected by the second terminal 22B at the end has the opposite polarity to the initial wave W1, so that the reflected wave W2 can be specified. That is, it becomes easy for the waveform identification unit 15 (see FIG. 1) to discriminate between the reflected wave W2 and other waveforms.

Although the radiation measuring apparatus according to the present embodiment has been described from the first embodiment to the second embodiment, the configuration applied in any one embodiment may be applied to other embodiments, or each of them may be applied. The configurations applied in the embodiments may be combined.

Although the flowchart of the present embodiment illustrates a mode in which each step is executed in series, the context of each step is not necessarily fixed, and even if the context of some steps is exchanged. good. Also, some steps may be executed in parallel with other steps.

The system of this embodiment includes a control device in which a dedicated chip, a controller such as an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), or a CPU (Central Processing Unit) is highly integrated, and a ROM (Read Only). Storage devices such as Memory) or RAM (Random Access Memory), external storage devices such as HDD (Hard Disk Drive) or SSD (Solid State Drive), display devices such as displays, and input devices such as mice or keyboards. , With a communication interface. This system can be realized with a hardware configuration using a normal computer.

The program executed by the system of the present embodiment is provided by incorporating it into a ROM or the like in advance. Alternatively, the program may be a non-transient storage medium that is a computer-readable file such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD) in an installable or executable format. It may be stored in the computer and provided.

Further, the program executed by this system may be stored on a computer connected to a network such as the Internet, and may be downloaded and provided via the network. The system can also be configured by connecting and combining separate modules that independently exert the functions of the components to each other via a network or a dedicated line.

In this embodiment, the neutron beam is exemplified as the radiation to be measured, but other embodiments may be used. For example, the radiation to be measured may be gamma rays, muons, or proton rays.

In the present embodiment, the neutron emitting substance is the object Q, but the object Q may be in another embodiment. For example, the nuclear fuel may be the object Q, or the human body may be the object Q. The present embodiment may be applied in order to adjust the size of the whole body counter used for the internal exposure inspection of the nuclear power plant worker.

In this embodiment, the radiation detection unit 5 having the cylindrical portion 17 extending linearly is illustrated, but the tubular portion 17 may be bent. Further, the tubular portion 17 is not limited to having a cylindrical shape, but may have a prismatic shape.

In the present embodiment, a plurality of radiation detection units 5 are arranged side by side in one direction (vertical direction on the paper surface in FIG. 3), and the radiation detection units 5 for expansion are also arranged so as to be arranged in one direction. , Other expansion forms may be used. For example, the radiation detection units 5 for expansion may be arranged not only in one direction but also in the other direction. For example, as shown in the modified example of FIG. 9, when five radiation detection units 5 are lined up in one direction, the sixth radiation detection unit 5 for expansion is placed in the other direction (left-right direction on the paper in FIG. 9). You may arrange them in. That is, it is orthogonal to the longitudinal direction of the tubular portion 17 of the five radiation detection units 5 arranged side by side, and is adjacent to one side of a rectangle formed by integrating these five radiation detection units 5. The sixth radiation detection unit 5 is added to.

In FIG. 9, a gap is provided between the tubular portion 17 of the sixth radiation detection unit 5 for expansion and the terminals 21 and 22 of the other radiation detection unit 5 to help understanding. However, by arranging the tubular portion 17 of the sixth radiation detection unit 5 for expansion on the terminals 21 and 22 of the other radiation detection unit 5 and the connecting cable 20, a gap is not formed. Is also good. Further, the 7th and 8th radiation detection units 5 may be added side by side in other directions.

According to at least one embodiment described above, radiation measurement is provided by providing a connecting cable connected to a second terminal at the other end of the radiation detection unit and connecting the radiation detection unit to another radiation detection unit. The area can be changed.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1 ... Radiation measuring device, 2 ... Sample stand, 3 ... Radiation detection unit, 4 ... Signal processing unit, 5 (5A, 5B) ... Radiation detection unit, 6 ... Signal acquisition unit, 7 ... Amplifier circuit, 8 ... Setting storage unit , 9 ... measuring unit, 10 ... measuring unit, 11 ... data storage unit, 12 ... data display unit, 13 ... counting circuit, 14 ... position specifying unit, 15 ... waveform identification unit, 16 ... noise removing unit, 17 ... tubular Unit, 18 ... Wire, 19 ... Base cable, 20 ... Connecting cable, 21 (21A) ... 1st terminal, 22 (22B) ... 2nd terminal, 23 ... Terminator, C1 ... 1st direction, C2 ... 2nd direction , D ... time difference, P ... incident position, Q ... object, R ... radiation, W1 ... initial wave, W2 ... reflected wave.

Claims (6)

A radiation detection unit having a tubular portion filled with a rare gas and a wire stretched inside the tubular portion, and a radiation detection unit.
A signal acquisition unit connected to a first terminal at one end of the radiation detection unit and acquiring a pulse signal based on a current flowing between the cylindrical portion and the wire due to radiation incident.
A connecting cable that is connected to the second terminal at the other end of the radiation detection unit and connects this radiation detection unit to the other radiation detection unit.
A measuring unit that measures the incident of radiation based on the pulse signal acquired by the signal acquisition unit, and a measuring unit.
Equipped with
A plurality of the radiation detection units are arranged side by side so as to form a rectangle, and the plurality of the radiation detection units arranged side by side are orthogonal to the longitudinal direction of the tubular portion, and one side of the rectangle is formed. The additional radiation detection unit is arranged adjacent to the
Radiation measuring device. The radiation measuring device according to claim 1, wherein a plurality of the radiation detection units are connected in series by the connecting cable. The incident position of the radiation is determined based on the difference between the acquisition time of the initial wave of the pulse signal first acquired by the signal acquisition unit and the acquisition time of the reflected wave of the pulse signal reflected by the second terminal at the end. The radiation measuring device according to claim 1 or 2 , further comprising a position specifying unit to be specified. The radiation measuring apparatus according to claim 3 , further comprising a terminator attached to the second terminal to be terminated. The radiation measuring apparatus according to claim 3 or 4 , further comprising a noise removing unit that stops the acquisition of the pulse signal for a certain period of time after the signal acquisition unit acquires the reflected wave. A step of connecting a signal acquisition unit to a first terminal at one end of a radiation detection unit having a cylindrical portion filled with a rare gas and a wire stretched inside the tubular portion.
A step of connecting this radiation detection unit to another radiation detection unit by a connecting cable connected to a second terminal at the other end of the radiation detection unit.
A step of acquiring a pulse signal based on a current flowing between the tubular portion and the wire due to the incident of radiation by the signal acquisition unit, and a step of acquiring the pulse signal.
A step of measuring the incident of the radiation based on the pulse signal acquired by the signal acquisition unit, and
Including
A plurality of the radiation detection units are arranged side by side so as to form a rectangle, and the plurality of the radiation detection units arranged side by side are orthogonal to the longitudinal direction of the tubular portion, and one side of the rectangle is formed. Using a radiation measuring device in which the additional radiation detection unit is arranged adjacent to the
Radiation measurement method.

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