JP2022012968A - Radiation measurement device and radiation measurement method - Google Patents

Abstract

To provide a radiation measurement device and a radiation measurement method that can discriminate between neutrons derived from a measurement object and neutrons derived from a peripheral background.SOLUTION: A radiation measurement device 100 includes: two or more neutron detectors 101; a movement mechanism 102 for moving the neutron detectors; a coincidence counting signal measurement device 103 for simultaneously counting a plurality of neutrons emitted at the same time in one reaction, in the neutron detectors 101; a position information device 104 for acquiring positional information of the neutron detectors; a coincidence count value processing device 105 for processing a coincidence count value obtained by the coincidence counting signal measurement device 103 at a position acquired by the position information device; and a coincidence counting value curve calculation device 106 for calculating a coincidence count value derived from a measurement object, from a position dependency curve of a coincidence count value processed by the coincidence count value processing device 105.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radiation measuring device and a radiation measuring method.

Measurement using neutrons is applied as one of the means for measuring nuclear fuel in facilities handling uranium, plutonium, spent nuclear fuel, research reactors, and commercial nuclear plants. When analyzing nuclear fuel with various histories by measurement using neutrons, the characteristics are investigated offline by collecting a part of the nuclear fuel and using a dedicated analysis facility. If part of the nuclear fuel cannot be sampled and analyzed, its characteristics are being investigated offline by equipping it with dedicated equipment that can reduce the background.
The scope of application is extremely limited because the equipment and facilities required to achieve the analysis under each condition are required for the sampling of a part of nuclear fuel and the investigation by dedicated equipment. Due to the existence of the above-mentioned factors, there is a demand for a radiation measuring device and a method thereof capable of analyzing an object to be measured by measuring neutrons even in a field where nuclear fuel is stored and managed.

When measuring neutrons from the object to be measured in the field, it is necessary to consider the influence of other radiation sources located in the vicinity. Since the neutron measuring device used in the conventional analysis is not designed in consideration of the influence of peripheral radiation sources, it is difficult to apply it in the field, in-line, or online. For this reason, there is a need for a radiation measuring device and a method thereof that can measure neutrons derived from an object to be measured by reducing the influence of peripheral radiation sources.

In Patent Document 1, in the radiation measuring apparatus of the embodiment, a detector guide tube provided with an opening and a hollow portion for incident neutrons, and a neutron shielding film that covers the outer periphery of the detector guide tube in the circumferential direction and shields neutrons. And the neutron moderator arranged on the opening side of the hollow portion of the detector guide tube, and the neutron moderator arranged adjacent to the hollow portion in the tube axis direction of the detector guide tube of the neutron moderator. A neutron detector and a radiation measuring device having a neutron detector are described. The radiation measuring device described in Patent Document 1 is said to be able to absorb and block neutrons from the surroundings by using a neutron shielding film composed of cadmium or boron having a large neutron absorption cross section.

Patent Document 2 describes a neutron source device having a neutron source that emits high-speed neutrons, a collimeter having a neutron incident opening and made of a radiation shield, and a collimeter arranged in the collimeter to detect thermal neutrons. A neutron detector having a neutron detector and a data processing device for processing a signal output from the neutron detector are provided, and at least one partition member made of a radiation shield is installed in the neutron incident opening. A plurality of slits, which are partitioned by the partition member and through which the thermal neutrons incident on the neutron detector pass, are formed in the neutron incident openings and moved in front of the respective slits, and each slit is moved. A shield lid for opening and closing the neutron detector, and a shield lid provided on the collimeter in a direction orthogonal to the direction from the neutron detector toward the tip of the slit and in a direction perpendicular to the surface of the partition member. A device including a shield lid moving device to be moved is described. In the device described in Patent Document 2, the background reaching the neutron detector can be grasped by covering the slit tip with the shielding lid, and the difference from the count value when the slit tip is not covered with the shielding lid can be obtained. By measuring, the accuracy of moisture measurement is improved.

Japanese Unexamined Patent Publication No. 2016-121895 Japanese Patent No. 5350112

In the field of nuclear fuel analysis using neutrons in facilities handling uranium, plutonium, spent nuclear fuel, research reactors, and commercial nuclear plants, the influence of other radiation sources located in the vicinity can be reduced. A radiation measuring device and its method are required.
The technique of Patent Document 1 can absorb and block neutrons from the surroundings by using a neutron shielding film composed of cadmium and boron having a large neutron absorption cross section, but the neutrons to be shielded are mainly. Becomes a thermal neutron. When the neutron source dominated by fast neutrons is the background derived from the surroundings, the fast neutrons that have passed through the neutron shielding film are heated by the neutron reducer to become thermal neutrons, which are measured by the neutron detector. Therefore, it is difficult for the neutron shielding film to reduce the influence of fast neutrons derived from the surrounding background.

The technique of Patent Document 2 can grasp the background reaching the neutron detector by measuring the difference from the count value when the slit tip is covered with the shielding lid and the slit tip is not covered with the shielding lid. .. The object of measurement in Patent Document 2 is thermal neutrons, and since the thermal neutron flux incident on the neutron detector is controlled by using a slit or a shield lid, the neutron shield material in the shield lid handled in Patent Document 2 is used. The function of is required to have the ability to shield thermal neutrons. When this shield is used for a neutron source dominated by fast neutrons, fast neutrons pass through the shield as described above. Therefore, it is difficult to reduce the influence of fast neutrons derived from the surrounding background in the difference measurement of the count values using the shield cover.

If there is a radiation measuring device and its method that can perform nuclear fuel analysis using neutrons in the field in facilities that handle uranium, plutonium, spent nuclear fuel, research reactors, and commercial nuclear plants, it will be possible to monitor with high real-time performance. It is possible to grasp the properties of the object to be measured.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a radiation measuring device and a radiation measuring method capable of discriminating between neutrons derived from an object to be measured and neutrons derived from a peripheral background. ..

In order to solve the above problems, the radiation measuring device of the present invention is a radiation measuring device that detects neutrons, and is a radiation measuring device that detects two or more neutron detectors, a moving means for moving the neutron detectors, and one time. A coincidence counting signal measuring device that simultaneously counts a plurality of neutrons emitted simultaneously in a reaction by the neutron detector, a position information device that acquires the position information of the neutron detector, and the simultaneous counting at the position acquired by the position information device. Calculates the same clock value derived from the object to be measured from the position-dependent curve of the same clock value processed by the same clock value processing device and the same clock value processing device that processes the same clock value obtained by the counting signal measuring device. It is characterized by being provided with a numerical curve calculation device for the same clock.
Other aspects of the invention will be described in embodiments described below.

According to the present invention, it is possible to provide a radiation measuring device and a radiation measuring method capable of discriminating between neutrons derived from an object to be measured and neutrons derived from a peripheral background.

It is a figure which shows the structure of the radiation measuring apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the signal measurement of the coincidence counting signal measuring apparatus of the radiation measuring apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the comparison of the distance dependence of the count value and the clock value in the single detector when the neutron detector of the radiation measuring apparatus which concerns on 1st Embodiment of this invention is single. It is a figure which shows the measurement result processing in the clock numerical processing apparatus of the radiation measuring apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the extraction of the clock numerical curve by the measurement object in the clock numerical curve calculation apparatus of the radiation measuring apparatus which concerns on 1st Embodiment of this invention. It is a measurement flowchart of the radiation measurement method using the radiation measurement apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the signal measurement in the coincidence counting signal measuring apparatus which used the peak value of the radiation measuring apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the extraction of the clock numerical curve by the measurement object which limited the calculation range in the clock numerical curve arithmetic unit of the radiation measuring apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 4th Embodiment of this invention. It is a measurement flowchart of the radiation measurement method using the radiation measurement apparatus which concerns on 5th Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 6th Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 7th Embodiment of this invention. It is a figure which shows the structure of the neutron detector of the radiation measuring apparatus which concerns on 7th Embodiment of this invention. It is a figure which shows the structure of the neutron detector which does not surround the whole area around the radiation measuring apparatus which concerns on 7th Embodiment of this invention. It is a figure which shows the structure of the radiation measuring apparatus which concerns on 8th Embodiment of this invention. It is a figure which shows the structure of the multi-channel neutron detector of the radiation measuring apparatus which concerns on 8th Embodiment of this invention. It is a figure which shows the structure of the multi-channel neutron detector of the radiation measuring apparatus which concerns on 8th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First Embodiment)
FIG. 1 is a diagram showing a configuration of a radiation measuring device according to the first embodiment of the present invention. The radiation measuring device and the radiation measuring method of the present embodiment are a non-destructive inspection device for discriminating neutrons from the measurement target and surroundings in facilities handling uranium, plutonium, spent nuclear fuel, research reactors, and commercial nuclear plants. This is an example applied to the radiation measurement method.
[Radiation measuring device 100]
The radiation measuring device 100 includes a neutron detector 101, a moving mechanism 102 (moving means), a coincidence counting signal measuring device 103, a position information device 104, a clock numerical processing device 105, and a clock numerical curve calculation device 106. And.

The neutron detector 101 is two or more neutron detectors, which are mounted on the moving mechanism 102 and detect the neutron 109 emitted from the neutron source 108 contained in the measurement object 107.
The moving mechanism 102 places the neutron detector 101 on the stage and moves the neutron detector 101 manually or automatically.

The coincidence counting signal measuring device 103 measures the signal of the neutron detector 101 as a coincidence counting. Specifically, the coincidence counting signal measuring device 103 simultaneously counts a plurality of neutrons emitted simultaneously in one reaction by the neutron detector 101.
The position information device 104 acquires the position information of the neutron detector 101. The position calculation device 104 includes, for example, a distance measuring device that uses an optical camera, a laser, an ultrasonic wave, a radar, or the like after determining a certain initial value as a means for measuring the position coordinates.

The clock numerical value processing device 105 calculates the same clock value at each measurement position together with the position information obtained by the position information device 104. That is, the clock numerical value processing device 105 processes the clock value obtained by the coincidence counting signal measuring device 103 at the position acquired by the position information device 104. Here, the unit of the numerical value of the clock is the number, and specifically, the count number (count) is counted.

The clock numerical curve calculation device 106 calculates the clock numerical curve by the neutrons emitted from the measurement object 107. Specifically, the clock value curve calculation device 106 calculates the clock value derived from the measurement object from the position-dependent curve of the clock value processed by the clock value processing unit 105.

Although the position of the neutron source 108 is shown inside the measurement object 107 as a dotted source, this is an example, and the position of the neutron source 108 may be the inside or the surface of the measurement object 107, and further, the dotted source. It may be a surface radiation source, a surface radiation source, or a volume radiation source.

<Neutron detector 101>
The neutron detector 101 is composed of two or more units and is used in combination with the moving mechanism 102. In FIG. 1, a configuration in which two neutron detectors 101 are mounted is shown as an example, but the configuration is not limited to this. The neutron detector 101 is composed of two or more units that are positioned apart in order to simultaneously count a plurality of neutrons emitted at the same time in one reaction.

As the neutron detector 101, a detector that measures thermal neutrons and extrathermal neutrons, a detector that measures fast neutrons, or a detector that measures both of them is applied, depending on the type. Gas detectors, scintillation detectors, and semiconductor detectors are typical types of thermal neutron detectors. Lithium, boron, gadolinium, cadmium, uranium, plutonium, etc. are applied to these detectors as thermal neutron sensitive materials. A He-3 proportional counter, a BF3 proportional counter, a B-10 coated proportional counter, a fission counter, and the like are applied to the gas detector.

The scintillation detector is equipped with a scintillator containing elements with a large reaction cross section of thermal neutrons such as lithium 6, boron 10, and gadrinium. The types of scintillators include, for example, LiI: Eu and ZnS: Ag. Boron 10-containing plastic scintillator, lithium 6 or boron 10-containing glass scintillator, LiCaAlF ₆ , Gd ₃ Al ₂ Ga3O ₁₂ , Gd2SiO ₅ : Ce, Cs ₂ LiLaBr ₆ : Ce, Cs ₂ LiYCl ₆ : Ce, Cs ₂ LiLaCl ₆ : Ce , Cs ₂ LiLaBr ₆ -xClx: Ce, Cs ₂ LiYBr ₆ : Ce and the like. There is also a method of applying an element sensitive to thermal neutrons to the surface of the scintillator. In that case, not only the scintillator described above, but also LaBr ₃ , CsBr ₃ , LYSO, LSO, GAGG, CsI, NaI, BGO, GPS. , La-GPS, LuAG, SrI, plastic scintillators and other scintillators used as radiation detectors can be handled as neutron detectors.

Similarly, the semiconductor detector is equipped with a semiconductor containing an element having a large reaction cross-sectional area of thermal neutrons such as lithium 6, boron 10, and gadolinium, and the types of semiconductors include CdTe and CdZnTe. Furthermore, there is also a method of applying an element sensitive to thermal neutrons to the surface of a semiconductor. In that case, not only CdTe and CdZnTe, but also silicon, germanium, diamond, silicon carbide, and CsPbCl ₃ , CsPbBr ₃ , and LiTaO having a Perovskite structure. A semiconductor detector such as a semiconductor detector of ₃ or the like can be used.

The extrathermal neutron detector includes an anti-jump proton counter tube that measures energy transfer by anti-jump protons due to the reaction between neutrons and hydrogen, using hydrogen gas or methane gas as a sensitive part as a gas detector. In addition, a threshold detector is applied to the fast neutron detector. One of the main types used is a fission counter tube, and uranium-234, uranium-236, uranium-238, neptunium-237, thorium232, etc. are applied as neutron-sensitive parts. In addition, organic scintillators such as anthracene and stilbene are also used.

Hereinafter, the operation of the radiation measuring apparatus 100 configured as described above will be described.
<Signal measurement of coincidence counting signal measuring device 103>
FIG. 2 is a diagram showing signal measurement of the coincidence counting signal measuring device 103 of the radiation measuring device 100. The horizontal axis represents the detection time, and the vertical axis represents the peak value of the output signal of the coincidence counting signal measuring device 103.
The coincidence counting signal measuring device 103 measures the signal output from the neutron detector 101, and outputs the signal when the signal having the sameness is recognized. Here, the two neutron detectors 101 are referred to as a neutron detector 101a and a neutron detector 101b.

The output signal 110 by the neutron detector 101a and the output signal 111 by the neutron detector 101b are output when the neutron 109 reaches each neutron detector. Of these, the neutron source 108 may emit a plurality of neutrons in one reaction, and these neutrons may be detected by the neutron detector 101. As a case where a plurality of neutrons are emitted in one reaction, for example, there are cases where a plurality of neutrons are emitted due to nuclear fission, and cases where a plurality of neutrons are emitted by a nuclear reaction using an accelerator or the like. In such a state, when the neutron detector 101a and the neutron detector 101b determine that a signal is detected at the same time in an arbitrary detection time width 113, this signal is transmitted by the neutron detector 101a and the neutron detector 101b. Suppose that multiple neutrons emitted in one reaction are detected. The fact that the signal is detected at the same time is output as the coincidence counting signal 112.
In FIG. 2C, the coincidence counting signal 112 is an output when the output signal 110 by the neutron detector 101a and the output signal 111 by the neutron detector 101b are simultaneously detected, and two are output. ..

The clock numerical value processing device 105 combines the position information obtained by the position information device 104 and the same clock value obtained by the simultaneous counting signal measuring device 103, and calculates the same clock value at each measurement position.

<Distance dependence of the count value and the same clock value>
FIG. 3 is a diagram showing a comparison of the distance dependence of the count value and the clock value in the single detector when the neutron detector 101 is single. The horizontal axis is the distance from the object to be measured, and the vertical axis is the same clock value and count value (single detector) (Log scale).

When acquiring the count value using a single detector, assuming that the neutron source 108 (see FIG. 1) is a dotted source, the count value in the count value curve 114 (see FIG. 3) is inversely proportional to the square of the distance. It is expressed by. On the other hand, when the clock value processing device 105 (see FIG. 1) uses the clock value, the clock value curve 115 (see FIG. 3) is expressed as being inversely proportional to the fourth power of the distance under the same assumption. To.

Although the case of measuring the point radiation source has been described here, when the surface radiation source or the volume radiation source is the measurement target, each multiplier becomes small. When focusing on the rate of change of the clock value curve, the existence of the neutron source 108 because the rate of change is large compared to the count value curve obtained by a single detector by acquiring the clock value curve. It can be seen that it becomes easy to detect the presence or absence of.

<Measurement result processing of the same clock numerical processing device 105>
FIG. 4 is a diagram showing measurement result processing in the clock numerical processing device 105 of the radiation measuring device 100. The horizontal axis is the distance from the object to be measured, and the vertical axis is the same clock value (Log scale).
FIG. 4 shows the same clock value 116 at each measurement position on the drawing of the distance and the same clock value. Here, as an example, a state in which the neutron detector 101 (see FIG. 1) is placed between the measurement object 107 (see FIG. 1) and the surrounding background radiation source is set.
As shown in FIG. 4, the clock value 116 sharply decreases as the distance from the measurement object 107 increases (see the left side of FIG. 4). On the other hand, since the clock value 116 approaches the peripheral background radiation source, the clock value increases from a certain distance (see the right side of FIG. 4).

<Extraction of numerical curve of the same clock>
FIG. 5 is a diagram showing extraction of the clock numerical curve by the measurement object in the clock numerical curve calculation device 106 of the radiation measuring device 100. The horizontal axis is the distance from the object to be measured, and the vertical axis is the same clock value (Log scale).
The clock value curve calculation device 106 (see FIG. 1) utilizes the distance dependence of the clock value to measure the clock value curve 117 (see FIG. 5) due to neutrons derived from the object to be measured 107 (see FIG. 1). And the same clock numerical curve 118 (see FIG. 5) due to neutrons derived from peripheral background radiation sources are separated.

By this extraction operation, the same clock numerical curve 117 by the neutron emitted from the measurement object 107 is calculated. By acquiring the clock numerical curve 117, it is possible to evaluate the presence or absence of neutrons derived from the measurement target 107 and their intensities even when a peripheral background radiation source is present.

<Measurement flow chart>
FIG. 6 is a measurement flowchart of a radiation measurement method using the radiation measurement device 100.
First, the radiation measuring device 100 is set up and measurement is started.
In step S1001, the moving mechanism 102 (see FIG. 1) places the neutron detector 101 (see FIG. 1) at the measurement position.
In step S1002, the position information device 104 acquires the position information of the neutron detector 102.
In step S1003, the coincidence counting signal measuring device 103 simultaneously counts neutrons.
In step S1004, it is determined that the measurement is completed. If the measurement is not completed (S1004: No), the process returns to step S1001.

When the measurement is completed (S1004: Yes), in step S1005, the clock value processing device 105 calculates the clock value acquired at each measurement position.
In step S1006, the clock value curve calculation device 106 calculates the clock value value curve.
In step S1007, the clock value processing device 105 calculates the clock value according to the measurement target.
In step S1008, the radiation measuring device 100 determines that the calculation is completed. If the calculation is not completed (S1008: No), the process returns to step S1007. When the calculation is completed (S1008: Yes), the radiation measuring device 100 completes all the measurements and the calculation.

In the radiation measurement method shown here, the procedure of acquiring the position information of the neutron detector (step S1002) and simultaneously counting the neutrons (step S1003) has been described, but the procedure is not limited to this. For example, the step of acquiring the position information of the neutron detector (step S1002) can be inserted between the step of simultaneously counting neutrons (step S1003) and the step of determining the measurement completion (step S1004).

As described above, the radiation measuring device 100 according to the present embodiment has two or more neutron detectors 101, a moving mechanism 102 for moving the neutron detectors, and a plurality of neutrons emitted simultaneously in one reaction. The coincidence counting signal measuring device 103 that simultaneously counts with the neutron detector 101, the position information device 104 that acquires the position information of the neutron detector, and the coincidence counting signal measuring device 103 at the position acquired by the position information device. The same clock numerical value processing device 105 that processes the clock numerical value and the same clock numerical curve calculation device 106 that calculates the same clock numerical value derived from the measurement object from the position dependence curve of the same clock numerical value processed by the same clock numerical processing device 105. And.

With this configuration, it is possible to discriminate between neutrons derived from the object to be measured and neutrons derived from the surrounding background. For example, even in an environment where the influence of the background radiation source is strong around the object to be measured, it is possible to discriminate between the neutrons derived from the object to be measured and the neutrons derived from the surrounding background. By using this calculation result, it is possible to reduce the size of the device and grasp the properties of the object to be measured with high accuracy and high speed, and it is possible to map the information. As a result, nuclear fuel analysis using neutrons can be performed in the field, and even in facilities that handle uranium, plutonium, spent nuclear fuel, research reactors, and commercial nuclear plants, highly real-time monitoring and measurement objects can be performed. It is possible to grasp the properties.

(Second embodiment)
In the second embodiment, the detection time and the peak value of the signal of the neutron detector generated by one neutron are recorded, and the signals detected in the arbitrary detection time region and the arbitrary peak value region are counted as the same clock value. It is equipped with a simultaneous counting signal measuring device that uses the peak value.
FIG. 7 is a diagram showing a configuration of a radiation measuring device according to a second embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 7, the radiation measuring device 200 includes a neutron detector 101, a moving mechanism 102, a position information device 104, a clock numerical processing device 105, and a clock numerical curve calculation device 106 of the radiation measuring device 100 of FIG. In addition, a peak value utilization simultaneous counting signal measuring device 119 is provided.

The coincidence counting signal measuring device 119 using the crest value measures the detection time and the crest value of the signal output from the neutron detector 101, and outputs the signal when both the detection time and the crest value are detected in an arbitrary range. Here, as shown in FIG. 7, the two neutron detectors 101 are referred to as a neutron detector 101a and a neutron detector 101b. The output signal 120 by the neutron detector 101a and the output signal 121 by the neutron detector 101b are output when the neutron 109 reaches each neutron detector.
If there is a background radiation source around the object to be measured and it emits radiation of other radiation types such as gamma rays, the radiation of these other radiation types may be detected by a neutron detector. Since the output signal from other line types is a noise component, it is necessary to reduce the noise component in order to realize highly accurate neutron measurement.

FIG. 8 is a diagram showing signal measurement in the radiation measuring device 200 at the coincidence counting signal measuring device 119 using the peak value. The horizontal axis represents the detection time, and the vertical axis represents the peak value of the output signal of the neutron detector 101a.
In the radiation measuring device 200, the coincidence counting signal measuring device 119 using the peak value measures not only the arbitrary detection time width 123a and the detection time width 123b but also the peak value of the output signal of each neutron detector, and the neutron detector 101a. The output signal detected within the range of the detected peak value width 124a and the detected peak value width 124b of the neutron detector 101b is output as the coincidence counting signal 122.

For example, the crest values (two) in the detection time width 123a and the detection time width 123b of the output signal 120 by the neutron detector 101a shown in FIG. 8A are both the detection crest value width 124a shown in FIG. 8A. It is in. On the other hand, only one of the crest values (two) in the detection time width 123a and the detection time width 123b of the output signal 121 by the neutron detector 101b shown in FIG. 8B is the detection crest height shown in FIG. 8B. It is in the price range 124b. Therefore, among the output signals 121 of the neutron detector 101b, the output signal peak value having a detection time width of 123a can be regarded as noise.

In this way, in the radiation measuring device 200, the coincidence counting signal measuring device 103 records the detection time and the crest value (see the crest value in FIG. 8) of the signal of the neutron detector generated by one neutron, and the arbitrary detection time. The signals detected in the region and any peak value region are counted as the same clock value. That is, not only the arbitrary detection time width 123a and the detection time width 123b, but also the peak value of the output signal of each neutron detector is measured, and the detection peak value width 124a in the neutron detector 101a and the detection peak value width 124b in the neutron detector 101b are measured. The output signal detected within the range of is output as the coincidence counting signal 122 (FIG. 8 (c)).
The pulse output by the coincidence counting signal 122 in FIG. 8C is the case where the peak value of both the detection peak value width 124a of the neutron detector 101a and the detection peak value width 124b of the neutron detector 101b is equal to or higher than a predetermined value. Only one of the combinations is shown.

As a result, even in an environment where a background radiation source exists around the object to be measured and there are many noise components, neutrons derived from the object to be measured and neutrons derived from the surrounding background can be discriminated (FIG. 8). reference). Then, by using this calculation result, the properties of the object to be measured can be grasped with high accuracy.

(Third embodiment)
FIG. 9 is a diagram showing a configuration of a radiation measuring device according to a third embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 9, the radiation measuring device 300 is attached to the neutron detector 101, the moving mechanism 102, the coincidence counting signal measuring device 103, the position information device 104, and the clock numerical processing device 105 of the radiation measuring device 100 of FIG. In addition, the same clock numerical curve calculation device 125 having a function of limiting the same clock numerical value to be calculated is provided.

FIG. 10 is a diagram showing extraction of the clock value curve by a measurement object having a limited calculation range in the clock value curve calculation device 125 of the radiation measurement device 300. The horizontal axis is the distance from the object to be measured, and the vertical axis is the same clock value (Log scale).
As shown in FIG. 10, the distance width 126 is set for the same clock value 116 at each measurement position. As a concept of the setting range of the distance width 126, as shown in FIG. 3, the clock value decreases as the distance from the measurement object 117 (see FIG. 5) increases, so that the clock value can be obtained at a measurement position close to the measurement object 117. It is desirable to use the same clock value. By using the same clock value 116 (see FIG. 10) at each measurement position in the distance width 126 (see FIG. 10), the neutron 109 (see FIG. 1) emitted from the measurement object 107 (see FIG. 1) is used. The clock value curve 127 (see FIG. 10) is calculated.

By acquiring the same clock numerical curve 127 (see FIG. 10) based on the distance width 126 (see FIG. 10), the use of the same clock numerical value at a distance susceptible to the same clock numerical curve by peripheral background radiation sources can be used. Can be avoided.

As described above, in the radiation measuring device 300, the clock value curve calculation device 106 is in an arbitrary distance region from the measurement target in the position dependence curve of the clock value processed by the clock value processing device 105. The same clock value derived from the object to be measured is calculated using the same clock value.

This makes it possible to avoid the use of the same clock value at a distance that is easily affected by the same clock value curve by the peripheral background radiation source, even in an environment where the background radiation source has a strong influence around the object to be measured. , It is possible to discriminate between neutrons derived from the object to be measured and neutrons derived from the surrounding background. Then, by using this calculation result, the properties of the object to be measured can be grasped with high accuracy.

(Fourth Embodiment)
FIG. 11 is a diagram showing a configuration of a radiation measuring device according to a fourth embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 11, the radiation measuring device 400 includes a neutron detector 101, a moving means 102, a coincidence counting signal measuring device 103, a position information device 104, a clock numerical processing device 105, and a clock numerical processing device 105 of the radiation measuring device 100 of FIG. In addition to the clock numerical curve calculation device 106, a calculation information storage device 128 is provided. The radiation measuring device 500 of the fifth embodiment also has the same configuration.

The arithmetic information storage device 128 stores analytical information analyzed in advance by an arithmetic expression or radiation transport calculation as arithmetic information for extracting the same clock numerical curve by the measurement object or the peripheral background radiation source. For the above arithmetic expression, a linear function, a polynomial function, an exponential function, a logarithmic function, a power function, or a mathematical expression combining these functions is used.

As shown in FIG. 3, when the neutron source of the object to be measured is a point source, it is inversely proportional to the fourth power of the distance, but when it is a surface source or a volume source, a function with a smaller multiplier is used. Easy to fit. From this, a function suitable for the state of the radiation source of the object to be measured is applied.

When analyzing in advance by radiation transport calculation, the behavior of neutrons from the object to be measured or the peripheral background radiation source to the radiation measuring device 400 is analyzed three-dimensionally. Further, the radiation measuring device 400 incorporates the composition and distribution of the object to be measured and the surrounding background radiation source, and the three-dimensional shape and composition of the substance in the measurement environment as parameters for the preliminary analysis, and makes each state. Perform the corresponding radiation transport calculation. The analysis information obtained by these analyzes is stored in the arithmetic information storage device 128.

The clock value curve calculation device 106 fits these calculation formulas and analysis information with the clock value 116 at each measurement position, so that the clock value curve 127 due to the neutron 109 emitted from the measurement object 107 (FIG. 10). See).

As described above, the radiation measuring device 400 includes a calculation information storage device 128 that stores the calculation information calculated by the clock numerical curve calculation device 106. The clock numerical curve calculation device 106 uses the neutron 109 emitted from the measurement object 107 by fitting the calculation formula and analysis information stored in the calculation information storage device 128 to the clock numerical value 116 at each measurement position. Calculate the clock value curve 127.

This makes it possible to discriminate between neutrons derived from the object to be measured and neutrons derived from the surrounding background with high accuracy. Then, by using this calculation result, the properties of the object to be measured can be grasped with high accuracy.

(Fifth Embodiment)
A fifth embodiment describes a radiation measuring method of the radiation measuring device.
FIG. 12 is a measurement flowchart of a radiation measuring method using the radiation measuring device 500 (see FIG. 11). The same processing step as the flow of FIG. 6 is designated by the same reference numeral, and the description of the overlapping portion will be omitted.
When the clock value processing device 105 calculates the clock value according to the measurement target in step S1006, the calculation area (distance width) is set in step S2001. That is, in step S2001, a distance region with the measurement target is set as a calculation region in the position dependence curve of the same clock value.
In step S2002, the calculation information is fitted. That is, in step S2002, the operation information calculated in the clock value curve calculation step and stored in the operation information storage device and the position dependence curve of the clock value are fitted.

In step S2003, it is determined that the fitting is completed. If it is not completed, the process returns to step S2001. When the fitting is completed, the process proceeds to step S7, and in step S1007, the same clock value according to the measurement target is calculated.

As described above, the radiation measuring apparatus 500 (see FIG. 11) according to the present embodiment further includes step S2001 for setting a distance region to the measurement object as a calculation region in the position dependence curve of the clock value, and calculation information. Step S2002 for fitting the position-dependent curve of the same clock value with the calculation information stored in the storage device 128 (see FIG. 11), step S2003 for determining the fitting completion, and step S7 for extracting the same clock value curve according to the measurement target. And prepare.

As a result, even in an environment where the influence of the background radiation source is strong around the object to be measured, the radiation measuring device and the radiation measuring device capable of discriminating between the neutrons derived from the object to be measured and the neutrons derived from the surrounding background with high accuracy. We can provide that method. Then, by using this calculation result, the properties of the object to be measured can be grasped with high accuracy.

(Sixth Embodiment)
FIG. 13 is a diagram showing a configuration of a radiation measuring device according to a sixth embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 13, the radiation measuring device 600 includes a neutron detector 101, a moving means 102, a simultaneous counting signal measuring device 103, a position information device 104, a clock numerical processing device 105, and a clock numerical processing device 105 of the radiation measuring device 100 of FIG. In addition to the clock numerical curve calculation device 106, a neutron flux conversion coefficient storage unit 129 for storing the neutron flux conversion coefficient 129a and a neutron flux calculation device 130 are provided.

The neutron flux conversion coefficient storage unit 129 stores the neutron flux conversion coefficient 129a that converts the measured value of the same clock into a thermal neutron flux, an extrathermal neutron flux, or a high-speed neutron flux.
Here, the convertible neutron flux depends on the type of neutron detector used and the measurement configuration. As the neutron conversion coefficient 129a at a distance x from the measurement object, a thermal neutron flux conversion coefficient Athermal (x), an extrathermal neutron flux conversion coefficient Aepi (x), and a fast neutron conversion coefficient Afast (x) are provided. For these conversion coefficients, those obtained in advance by experiments and analyzes are used.

In the same clock numerical curve obtained by the same clock numerical curve calculation device 106, the same clock numerical value NCOIN (x) at a distance x from the measurement object is used.

The neutron flux calculation device 130 calculates the neutron flux of each energy by multiplying the numerical value NCOIN (x) of the same clock and the neutron conversion coefficient of each energy stored in the neutron flux conversion coefficient 129a. Formulas (1) to (3) are used as the calculation formula.

F _thermal (x) = A _thermal (x) × N _COIN (x)… (1)
F _epi (x) = A _epi (x) × N _COIN (x)… (2)
F _fast (x) = A _fast (x) × N _COIN (x)… (3)

As mentioned above, the convertible neutron flux depends on the type of neutron detector used and the measurement configuration. By using the formulas (1) to (3), the neutron flux at the energy to be measured can be calculated.

As described above, the radiation measuring device 600 (see FIG. 13) according to the present embodiment includes the neutron flux conversion coefficient storage unit 129 that stores the neutron flux conversion coefficient 129a that converts the clock value derived from the measurement object into a neutron flux. The neutron flux calculation device 130 for calculating the neutron flux at the measurement position from the same clock value derived from the measurement object and the neutron flux conversion coefficient 129a is provided. Further, using the result of calculating the same clock value curve by the measurement target, the step of calculating the neutron flux from the same clock value by the measurement target and the neutron flux conversion coefficient 129a is executed.

This makes it possible to provide a radiation measuring device capable of measuring a neutron flux derived from a measurement object and a method thereof. Then, by using this calculation result, it is possible to grasp the properties of the object to be measured.

(7th Embodiment)
FIG. 14 is a diagram showing a configuration of a radiation measuring device according to a seventh embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 14, the radiation measuring device 700 includes a neutron detector 101, a moving means 102, a coincidence counting signal measuring device 103, a position information device 104, a clock numerical processing device 105, and a radiation measuring device 100 of the radiation measuring device 100 of FIG. In addition to the clock numerical curve calculation device 106, a neutron detector 131 is provided.

FIG. 15 is a diagram showing the configuration of the neutron detector 131.
As shown in FIG. 15, the neutron detector 131 includes a thermal neutron shield 134, a neutron moderator 133, and a thermal neutron detector 132.
When the fast neutron 135 is emitted from the neutron source 108 included in the measurement object 107, the neutron may be heated by the interaction with the measurement object itself to become a thermal neutron 136. Since the thermalization is caused by scattering with a substance, the solid angle information of the neutron source 108 and the neutron detector 131 is lost. Therefore, when the neutron (thermal neutron 136) heated by the measurement object 107 is measured by the neutron detector 101, it becomes a noise component.

In the seventh embodiment, the thermal neutron shielding material 134 is provided in order to reduce the influence of the neutrons (thermal neutrons 136) heated by the measurement object 107. The thermal neutron shielding material 134 shields neutrons (thermal neutrons 136) heated by the measurement object 107.

Further, in the seventh embodiment, the neutron moderator 133 is provided in order to heat the fast neutron 135 that was not heated by the measurement object 107 and obtain the thermal neutron 137. The neutron moderator 133 is provided around the thermal neutron detector 132.

Here, it is desirable to use a material containing an element having a large absorption cross section of thermal neutrons such as boron, lithium, cadmium, and gadolinium for the thermal neutron shielding material 134. For the neutron moderator 133, it is desirable to use a material containing a high density of hydrogen such as water or polyethylene.

FIG. 15 shows a configuration in which the neutron moderator 133 and the thermal neutron shielding material 134 are provided in the entire surrounding area of the thermal neutron detector 132, but a configuration that does not enclose the entire surrounding area can also be applied.

FIG. 16 is a diagram showing the configuration of the neutron detector 131 that does not surround the entire surrounding area. As an example, the configuration of one neutron detector is shown.
As shown in FIG. 16, the thermal neutron detector 131 has a configuration in which the thermal neutron detector 132 and the half-split neutron moderator 138 are entirely surrounded by the thermal neutron shielding material 139.
The neutrons (thermal neutrons 136) heated by the measurement object 107 are shielded by the thermal neutron shielding material 139.

The fast neutrons 135 that have passed through the thermal neutron shield 139 are heated to obtain thermal neutrons 137, which are measured by the thermal neutron detector 132.

As described above, in the radiation measuring device 700, the neutron detector 131 includes the thermal neutron shielding material 134, 139, the neutron moderator 133, and the thermal neutron detector 132.

As a result, the radiation measuring device 700 is advantageous for miniaturization of the device because the configuration of the neutron detector 131 shown in FIG. 16 has a smaller capacity than the configuration of the neutron detector 131 shown in FIG.
By using the radiation measuring device 700, it is possible to reduce the noise component caused by the object to be measured, and to discriminate between the neutrons derived from the object to be measured and the neutrons derived from the surrounding background with high accuracy. Can be done. As a result, it is possible to reduce the size of the device and grasp the properties of the measurement object with high accuracy.

(8th Embodiment)
FIG. 17 is a diagram showing a configuration of a radiation measuring device according to an eighth embodiment of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping portions will be omitted.

As shown in FIG. 17, the radiation measuring device 800 includes a neutron detector 101, a moving means 102, a coincidence counting signal measuring device 103, a position information device 104, a clock numerical processing device 105, and a radiation measuring device 100 of the radiation measuring device 100 of FIG. In addition to the clock numerical curve calculation device 106, a multi-channel neutron detector 140 and a multi-channel coincidence counting signal measurement device 141 are provided.

FIG. 18 is a diagram showing the configuration of the multi-channel neutron detector 140 (linear arrangement).
As the multi-channel neutron detector 140, the configuration in which the neutron detectors are linearly arranged is shown here. The linearly arranged neutron detector 142 arranges a plurality of neutron detectors in a one-dimensional direction and is connected to a multi-channel compatible simultaneous counting signal measuring device 141.

In FIG. 18, the moving mechanism 102 (see FIG. 1) is not shown for the sake of simplification of display, but it is actually mounted on the moving mechanism 102 and used.

FIG. 19 is a diagram showing the configuration of the multi-channel neutron detector 140 (array arrangement).
As the multi-channel neutron detector 140, a configuration diagram in which the neutron detector is arranged two-dimensionally is shown here. The array-arranged neutron detector 143 arranges a plurality of neutron detectors in a two-dimensional direction and is connected to a multi-channel compatible simultaneous counting signal measuring device 141.
Similar to FIG. 18, FIG. 18 omits the illustration of the moving mechanism 102.

As described above, the radiation measuring device 800 includes a multi-channel neutron detector 140 arranged linearly or in an array.

This makes it possible to provide a radiation measuring device and a method thereof capable of simultaneously performing neutron measurement in a region of one dimension or more. By using this device, it is possible to realize high-speed measurement and mapping of measurement objects.

[Modification example]
The radiation measuring apparatus and the radiation measuring method of the first to eighth embodiments are combined and integrated.
By integrating the radiation measuring device and the radiation measuring method according to each of the above embodiments, the radiation measuring device is derived from the measurement target even in an environment where the influence of the background radiation source is strong around the measurement target according to various execution environments. It is possible to discriminate between neutrons from the surrounding background and neutrons from the surrounding background.

The present invention is not limited to the configuration described in each of the above embodiments, and the configuration can be appropriately changed as long as it does not deviate from the gist of the present invention described in the claims.

Each of the above-described embodiments has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. .. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

100,200,300,400,500,600,700,800 Radiation measuring device 101,101a, 101b, 131 Neutron detector 102 Moving mechanism (moving means)
103 Simultaneous counting signal measuring device 104 Position information device 105 Same clock numerical processing device 106, 125 Same clock numerical curve calculation device 107 Measurement target 108 Neutron source 109 Neutron 110, 120, Output signal by neutron detector 101a 111, 121 Neutron detection Output signal by device 101b 112, 122 Simultaneous counting signal 113, 123a, 123b Detection time width 114 Counting value curve 115 Same clock numerical curve 116 Same clock numerical value at each measurement position 117, 127 Same clock numerical curve by neutrons derived from the object to be measured 118 Same clock numerical curve by neutrons derived from peripheral background radiation source 119 Simultaneous counting signal measuring device using peak value 124a Detection peak width in neutron detector 101a 124b Detection peak width in neutron detector 101b 126 Distance width 128 Calculation information storage device 129 Neutron flux conversion coefficient storage 129a Neutron flux conversion coefficient 130 Neutron flux calculator 132 Thermal neutron detector 133 Neutron deceleration material 134,139 Thermal neutron shield 135 High-speed neutron 136 137 Thermal neutron 138 Half-split neutron deceleration material 140 Multi-channel neutron Detector 141 Multi-channel simultaneous counting signal measuring device 142 Linearly-arranged neutron detector 143 Array-arranged neutron detector S1001 Moving step to move neutron detector S1002 Position information acquisition step to acquire position information of neutron detector S1003 1 Simultaneous counting signal measurement step that simultaneously counts multiple neutrons emitted simultaneously in one reaction with a neutron detector S1005 Same clock value that processes the same clock value obtained in the simultaneous counting signal measurement step at the position acquired in the information acquisition step. Processing step S1006, S1007 In the same clock numerical curve calculation step S2001 in the positional dependence curve of the same clock numerical value, which calculates the same clock numerical value derived from the measurement object from the position dependence curve of the same clock numerical value processed in the same clock numerical processing step. Step to set the distance area to the object to be measured as the calculation area S2002 Numerical curve of the same clock Step to fit the position dependence curve of the numerical value of the same clock with the arithmetic information calculated in the calculation step and stored in the arithmetic information storage device S2003 Measurement target Steps to extract the same clock value curve by

Claims (13)

A radiation measuring device that detects neutrons
With two or more neutron detectors
The means of moving the neutron detector and
A coincidence counting signal measuring device that simultaneously counts multiple neutrons emitted simultaneously in one reaction with the neutron detector, and
A position information device that acquires the position information of the neutron detector, and
The same clock numerical processing device that processes the same clock numerical value obtained by the coincidence counting signal measuring device at the position acquired by the position information device, and the same clock numerical processing device.
A radiation measuring device comprising the same clock numerical curve calculation device for calculating the same clock numerical value derived from a measurement object from the position-dependent curve of the same clock numerical value processed by the same clock numerical processing device. The coincidence counting signal measuring device records the detection time and peak value of the signal of the neutron detector generated by one neutron, and the signal detected in an arbitrary detection time region and an arbitrary peak value region is used as the same clock value. The radiation measuring apparatus according to claim 1, wherein counting is performed. The clock value curve calculation device is derived from the measurement target by using the clock value in an arbitrary distance region from the measurement object among the position-dependent curves of the clock value processed by the clock value processing device. The radiation measuring apparatus according to claim 1, wherein the same clock value is calculated. The radiation measuring device according to claim 1, wherein the clock numerical curve calculation device includes a calculation information storage device for storing the calculated calculation information. A neutron flux conversion coefficient storage unit that stores a neutron flux conversion coefficient that converts the same clock value derived from the measurement object into a neutron flux, and a neutron flux conversion coefficient storage unit.
The radiation measuring device according to claim 1, further comprising a neutron flux calculation device that calculates a neutron flux at a measurement position from the same clock value derived from the measurement object and the neutron flux conversion coefficient. The radiation measuring apparatus according to claim 1, wherein the neutron detector includes a thermal neutron shield, a neutron moderator, and a thermal neutron detector. The radiation measuring device according to claim 1, wherein the neutron detector detects thermal neutrons or fast neutrons. The radiation measuring device according to claim 1, wherein the neutron detector is linearly or arrayally arranged. The position information device is characterized in that it is at least one of a laser distance measuring means, a camera image measuring means, an ultrasonic distance measuring means, and a radio wave distance measuring means that acquire position information with the measurement object. The radio wave measuring device according to claim 1. It is a radiation measurement method of a radiation measurement device that detects neutrons.
Equipped with two or more neutron detectors
The movement step to move the neutron detector and
A coincidence counting signal measurement step in which a plurality of neutrons emitted simultaneously in one reaction are simultaneously counted by the neutron detector, and
The position information acquisition step for acquiring the position information of the neutron detector, and
A clock value processing step for processing the clock value obtained in the coincidence counting signal measurement step at the position acquired in the position information acquisition step, and a clock value processing step.
A radiation measurement method characterized by executing the same clock numerical curve calculation step for calculating the same clock numerical value derived from a measurement object from the position-dependent curve of the same clock numerical value processed in the same clock numerical processing step. In the same clock numerical curve calculation step,
The step of setting the distance region to the measurement target as the calculation region in the position dependence curve of the same clock value, and
A step of fitting the calculation information calculated in the same clock numerical curve calculation step and stored in the calculation information storage device and the position dependence curve of the same clock numerical value.
The step of determining the completion of the fitting and
The radiation measurement method according to claim 10, further comprising a step of extracting a numerical curve of the same clock according to a measurement target. A claim characterized by having a neutron flux calculation step for calculating a neutron flux at a measurement position from the same clock value derived from the measurement target and the neutron flux conversion coefficient using the result of calculating the same clock numerical curve by the measurement target. Item 10. The radiation measurement method according to Item 10. The radiation measurement method according to claim 10, wherein the execution timing of the numerical measurement of the clock by the neutron detector or the position information is acquired in advance.

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