JP6987086B2 - Radioactivity measuring device - Google Patents

Description

The present application relates to a radioactivity measuring device.

With the decommissioning of radioactive material handling facilities such as nuclear power plants and nuclear fuel processing facilities, these radioactive material handling facilities will be dismantled. Since structures such as concrete walls used in the buildings of facilities handling radioactive materials may be activated or contaminated with radioactivity, structural waste generated during dismantling needs to be evaluated for radioactivity intensity. In addition, even if an accident occurs at one of these radioactive material handling facilities, various radioactive materials may be released into the environment. Therefore, the radioactive intensity of environmental materials such as soil around the facility is also evaluated. Is required.

In the evaluation of the radioactivity intensity of a measurement object such as a concrete wall or soil, it is necessary not only to measure the radioactivity intensity on the surface but also to evaluate the distribution of the radioactivity intensity in the depth direction from the surface to the inside. In the evaluation of the distribution of the radioactivity intensity in the depth direction, the radioactivity intensity for each depth is usually obtained in advance by a preliminary analysis using simulation or the like. Then, in order to confirm the consistency of the analysis result by this preliminary analysis, a sample for each depth of the measurement object is collected by boring or the like. Then, the sample collected is measured offline with a Ge (germanium) semiconductor detector to evaluate the distribution of the radioactivity intensity in the depth direction of the object to be measured.

When evaluating the radioactivity intensity as described above with a Ge semiconductor detector, it takes time and pretreatment such as taking the sample of the collected object back to the test room and grinding the sample for shaping. It takes time and effort. Therefore, for the purpose of improving work efficiency, shortening the construction period, and reducing costs, the radioactivity intensity in the depth direction of the measurement target is directly measured at the site where the measurement target is located, without collecting a sample. Disclosed are various underground radioactivity measuring devices, radioactivity measuring devices, and devices for measuring the distribution of gamma-ray emitting nuclei in the depth direction.

That is, the underground radioactivity measuring device includes an inner tube in which a plurality of radiation detectors are housed in multiple stages in the depth direction, and an outer tube arranged on the outer periphery of the inner tube. By inserting the inner tube measurement window and the outer tube measurement window into the soil in an inconsistent state, each radiation detector measures only gamma rays in the soil. Next, by rotating or moving the inner tube relative to the outer tube to bring the measurement window of the inner tube and the measurement window of the outer tube into a matching state, the radioactivity existing in the vicinity of each radiation detector is achieved. Beta rays emitted from the cesium enter each radiation detector, which causes each radiation detector to measure both beta and gamma rays at its respective depth level. The calculation unit obtains the measured value of only beta rays by subtracting the measured value of only gamma rays from the measured values of beta rays and gamma rays measured by each radiation detector. Thereby, the radioactivity depth distribution of beta rays in the soil can be measured (see, for example, Patent Document 1).

That is, the radioactivity measuring device includes a radiation detection probe having a plurality of radiation receiving elements in the longitudinal direction. Each radiation receiving element acquires a radiation count in the soil. The analysis unit calculates the maximum likelihood count number obtained by subtracting the unnecessary count number from the count number acquired for each radiation receiving element. The unnecessary count number is an excessive count number acquired from the radiation of the radioactive substance at a depth position different from the depth position to be acquired by each radiation receiving element. Then, the radioactivity distribution in the soil is derived from the calculated maximum likelihood count (see, for example, Patent Document 2).

That is, the device for measuring the distribution of gamma-ray emitting nuclides in the depth direction includes a gamma-ray measuring device, for example, a Ge detector, which has a sufficient shield around it to shield gamma-rays from other than the measurement target. Measure the Ge detector at a distance ri from the concrete surface. The distance ri from the concrete surface is changed, the measurement is performed n times, and the n measured values at that time are input to the arithmetic unit. The arithmetic unit solves a multidimensional simultaneous linear equation using the detection efficiency of the detector for the energy of the gamma-ray emitting nuclide, the linear attenuation coefficient of the concrete for the energy of the gamma-ray emitting nuclide, etc. Calculate the amount (see, for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2015-49229 (paragraphs [0021] to [0031], FIG. 1). Japanese Unexamined Patent Publication No. 2017-44697 (paragraphs [0019] to [0035], FIG. 2). Japanese Unexamined Patent Publication No. 62-282288 (page 3, FIG. 1, FIG. 2)

In the underground radioactivity measuring device disclosed in Patent Document 1, by using beta rays, the influence of radioactive substances at a depth position different from the depth position to be measured by each radiation detecting element is reduced and measured. The advantage is that the distribution of radioactivity intensity in the depth direction of the object can be evaluated. However, since the measurement line type is limited to beta rays, there is a problem that the radionuclide cannot be discriminated and the radioactivity intensity of each radionuclide cannot be measured.

Further, the radioactivity measuring device disclosed in Patent Document 2 has an advantage that the energy of radiation can be identified and the radioactive nuclei can be discriminated by using gamma rays for the evaluation of the distribution of the radioactivity intensity in the depth direction. be. However, the processing is performed to remove the excessive count number acquired from the radiation of the radioactive substance at the depth position different from the depth position to be acquired from the count number detected by the radiation receiving element. Therefore, the measurement sensitivity of the radiation receiving element cannot be ensured, and the accuracy of the radioactivity intensity evaluation is lowered.

Further, the apparatus for measuring the distribution of gamma-ray emitting nuclides in the depth direction disclosed in Patent Document 3 has an advantage that the concrete to be measured can be measured non-destructively. However, in order to reduce the influence of radiation from other than concrete such as natural radiation, a shield for collimating is required, and the device cannot be made smaller or lighter. Further, radiation from a region deep inside from the concrete surface does not come out from the concrete surface due to self-absorption of the concrete itself. As described above, since there is an upper limit to the range that can be measured in the depth direction, there is a problem that it is difficult to evaluate the distribution of the radioactivity intensity in the depth direction in the measurement object having a certain thickness or more. ..

Further, although radiation is detected using a radiation detector in any of the above Patent Documents 1 to 3, the measured value of the radiation detected by the radiation detector is usually a sensitive part of the radiation detector. It is affected by the energy loss of radiation due to the interaction between radiation and radiation, or the energy resolution of the radiation detector itself. Therefore, the above-mentioned calculation method has a problem that the analysis accuracy of the calculated radioactivity intensity is lowered.

This application discloses a technique for solving the above-mentioned problems, and it is possible to accurately measure the radioactivity intensity of each radionuclide in the depth direction of the object to be measured while being lightweight. It is an object of the present invention to provide a function measuring device.

The radioactivity measuring device disclosed in the present application is
A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit that derives a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
Each of the detection areas is obtained by dividing the measurement target area into the movement direction.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated .
In the signal restoration operation
The second energy distribution in each detection region is set as an unknown number different for each detection position, and each detection position is calculated to discriminate the nuclide of the radioactive substance in each detection region.
By calculating the radioactivity intensity of the discriminated radioactive material in each of the detection regions for each detection position, the radioactivity intensity of the radioactive material in the measurement target in the movement direction is calculated.
It is a thing.
In addition, the radioactivity measuring device disclosed in the present application is
A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit that derives a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated.
Each of the detection areas is obtained by dividing the measurement target area into the movement direction.
The arithmetic unit
The second energy distribution in each detection region is calculated, and the nuclide of the radioactive substance in each detection region is discriminated.
By calculating the radioactivity intensity in each of the detection regions of the discriminated radioactive material, the radioactivity intensity of the radioactive material in the measurement target in the movement direction is calculated.
Based on the calculated radioactivity intensity of the radioactive material in each of the detection regions
The radioactivity intensity of the radioactive substance in each of the divided regions in which the measurement object is divided into a plurality of parts with respect to the moving direction is calculated.
The plurality of detection positions are provided at each set first detection interval.
The arithmetic unit
The radioactivity intensity in the moving direction is calculated based on the radiation detected for each first detection interval, and the second detection interval adjusted for the first detection interval is set based on the radioactivity intensity.
It is a thing.
In addition, the radioactivity measuring device disclosed in the present application is
A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit for deriving a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated.
The fluctuation amount of the radiation energy distribution position in the first energy distribution is measured, and the energy distribution position in the first energy distribution is adjusted based on the fluctuation amount.
It is a thing.

According to the radioactivity measuring device disclosed in the present application, it is easy to handle and more reliable because it is possible to accurately measure the radioactivity intensity of each radionucleus species in the depth direction of the object to be measured while being lightweight. High radioactivity intensity evaluation can be performed.

It is a block diagram which shows the schematic structure of the whole of the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a schematic diagram which shows the schematic structure of the radiation detection part provided in the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a schematic diagram which shows the example of the wave height distribution of the radiation derived by the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a figure regarding the explanation of the radioactivity analysis by the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a schematic diagram which shows the detection area of the radiation detection part provided in the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a schematic diagram which shows the detection area of the radiation detection part provided in the radioactivity intensity distribution measuring apparatus by Embodiment 1 and the depth area of the measurement object. It is a figure regarding the explanation of the radioactivity analysis by the radioactivity intensity distribution measuring apparatus by Embodiment 1. FIG. It is a schematic diagram which shows the detection area of the radiation detection part provided in the radioactivity intensity distribution measuring apparatus by Embodiment 1 and the depth area of the measurement object. It is a block diagram which shows the schematic structure of the whole of the radioactivity intensity distribution measuring apparatus by Embodiment 2. It is a block diagram which shows the schematic structure of the whole of the radioactivity intensity distribution measuring apparatus by Embodiment 2. It is a block diagram which shows the schematic structure of the whole of the radioactivity intensity distribution measuring apparatus according to Embodiment 3.

Hereinafter, the radioactivity measuring device according to each embodiment of the present application will be described below with reference to the drawings. In each figure, the same or similar components are designated by the same reference numerals, and the sizes and scales of the corresponding components are independent of each other.
Further, although the configuration of the radioactivity measuring device actually includes a plurality of members, only the parts necessary for the explanation are described and the other parts are omitted for the sake of simplicity.

Embodiment 1.
Hereinafter, the radioactivity intensity distribution measuring device 100 as the radioactivity measuring device according to the first embodiment of the present application will be described with reference to the drawings.
FIG. 1 is a block diagram showing an overall schematic configuration of the radioactivity intensity distribution measuring device 100 according to the first embodiment.
FIG. 2 is a schematic diagram showing a schematic configuration of the radiation detection unit 1 shown in FIG.
When the same component is illustrated between FIG. 1 showing the entire configuration of the radioactivity intensity distribution measuring device 100 and another figure excerpted from a part of the configuration, the size and scale of the same component are shown. Etc. may be different. This also applies to each embodiment after the first embodiment.

As shown in FIG. 1, the radioactivity intensity distribution measuring device 100 includes a sampling unit 10, a radiation analysis unit 20 as an analysis unit, and a display unit 30.
The sampling unit 10 detects radiation. The radiation analysis unit 20 analyzes the radiation detected in the sampling unit 10. The display unit 30 displays the analysis result by the radiation analysis unit 20.

The sampling unit 10 is configured to have a longitudinal shape that can be inserted into a hole T1 drilled or the like in a concrete piece T as a measurement object. The sampling unit 10 includes an expansion / contraction unit 2, a radiation detection unit 1 as a detection unit attached to the tip of the expansion / contraction unit 2, and a fixed-length pipe 3 that covers the radiation detection unit 1 and the expansion / contraction unit 2. Have.

The expansion / contraction unit 2 is configured to be expandable and contractible so as to be movable back and forth with respect to the movement direction Y from the surface T2 of the concrete piece T to the inside, and the radiation detection unit 1 can be fixed at an arbitrary position in the movement direction Y. .. Since this moving direction Y is the depth direction to the inside of the concrete piece T in the present embodiment, this moving direction Y is hereinafter referred to as the depth direction Y.
In this way, the radiation detection unit 1 has a plurality of arbitrary detection positions A (A1, A2 ... AN, where N is the detection position A) in the pipe 3 with respect to the depth direction Y of the concrete piece T by the expansion / contraction unit 2. It is fixed to the total number), and the radiation emitted from the radioactive substance 50 contained in the concrete piece T is detected at these plurality of detection positions A.

Further, the radiation detection unit 1 faces the inner wall of the hole T1 and secures a set predetermined distance F between the inner wall of the hole T1 and the set predetermined distance F. Further, in order to facilitate understanding in the figure, the radioactive material 50 in the concrete piece T is shown in a round shape.

Hereinafter, the detailed configuration of the radiation detection unit 1 will be described.
A NaI (Tl) scintillation detector is used for the radiation detection unit 1. As shown in detail in FIG. 2, the radiation detection unit 1 includes a scintillator 1a, a photodetector 1b, and a preamplifier 1c as an amplifier.

When the scintillator 1a is incident with radiation, energy is applied by the radiation to emit fluorescence having a unique wavelength. The generated fluorescence is converted into electrons on the photoelectric surface of the photodetector 1b, converted into an electric signal, for example, a pulse signal, and output. The pulse signal output from the photodetector 1b is amplified by the preamplifier 1c.
In this way, when the radiation emitted from the radioactive substance 50 contained in the concrete piece T is incident, the radiation detection unit 1 outputs a pulse signal G as a detection signal having a wave height proportional to the energy of the incident radiation. The output pulse signal G is input to the radiation analysis unit 20 in the subsequent stage.

Next, the outline of each part of the radiation analysis unit 20 will be described.
The radiation analysis unit 20 is provided to analyze the pulse signal G from the radiation detection unit 1 output from the sampling unit 10.
As shown in FIG. 1, the radiation analysis unit 20 includes a waveform shaping unit 21, a wave height analysis unit 22 as an analysis unit, a radioactivity intensity calculation unit 23 as a calculation unit, and a response function database 24 as a storage unit. , Equipped with.

The waveform shaping unit 21 amplifies and shapes the waveform of the pulse signal G from the radiation detection unit 1 output from the sampling unit 10.
The wave height analysis unit 22 derives a count for each energy value of the pulse signal G.
The response function database 24 stores the response function K of the radiation detection unit 1.
The radioactivity intensity calculation unit 23 discriminates the nuclide of the radioactive substance 50 and discriminates the radioactive material by performing a signal restoration calculation using the response function K described later with respect to the output result of the wave height analysis unit 22. Calculate the radioactivity intensity of 50.

The waveform shaping unit 21 is composed of, for example, a waveform shaping device (not shown) and an amplifier 21a. The wave height analysis unit 22 is composed of, for example, a pulse height analyzer or the like. The radioactivity intensity calculation unit 23 is composed of, for example, a single or a plurality of microprocessors. The response function database 24 is composed of, for example, a memory connected to a microprocessor or the like. The display unit 30 is composed of, for example, a liquid crystal display or the like.

Next, detailed processing in each of the above parts of the radiation analysis unit 20, which is the main part of the first embodiment, will be described.
When the waveform shaping unit 21 receives the pulse signal G from the radiation detection unit 1 output from the sampling unit 10, the waveform shaping unit 21 amplifies the pulse signal G at a preset amplification factor using the amplifier 21a. Shape the waveform into a shape suitable for later processing. The amplified and shaped pulse signal G is input to the wave height analysis unit 22 in the subsequent stage.

The wave height analysis unit 22 performs the following wave height analysis based on the output of the waveform shaping unit 21.
FIG. 3 is a schematic diagram showing an example of the radiation height distribution M derived by the wave height analysis unit 22 according to the first embodiment. The case where the radiation detection unit 1 measured the gamma ray from cesium-137 as a radioactive substance 50 is shown.

The wave height analysis unit 22 performs AD conversion (Analog to Digital conversion) of the pulse signal G having a peak value of a predetermined value or more among the pulse signals G of the radiation detection unit 1 amplified by the waveform shaping unit 21 in the previous stage. )do. The wave height analysis unit 22 adds 1 count to a channel (energy discrimination stage) having an energy discrimination range corresponding to the peak value of the AD-converted pulse signal G. By performing this operation on each pulse signal G, the wave height analysis unit 22 obtains a wave height distribution M as a first energy distribution showing a count for each energy peak value of each pulse signal G.

The wave height distribution M shown in FIG. 3 is derived for each of a plurality of detection positions A, and is derived at a certain detection position A among the plurality of wave height distributions M derived for each detection position A. The wave height distribution M is shown.
Each of the derived wave height distributions M is stored in a memory (not shown) of the wave height analysis unit 22 for each detection position A, and is input to the radioactivity intensity calculation unit 23 in the subsequent stage.

Normally, the radiation detected by the radiation detection unit 1 includes, for example, radiation from a naturally radioactive nuclide in addition to the radiation from cesium-137. Therefore, the wave height distribution M shown in FIG. 3 is the sum of the radiation from cesium-137 and the radiation from the naturally radioactive nuclide.

The radioactivity intensity calculation unit 23 carries out radioactivity analysis based on the wave height distribution M, which is the output of the wave height analysis unit 22.
FIG. 4 is a diagram relating to an explanation of radioactivity analysis by the radioactivity intensity calculation unit 23 according to the first embodiment, and is a decay diagram of cesium-137.
The data in the figure represent the case where a single energy gamma ray is emitted.

It can be discriminated from this decay diagram that the energy of gamma rays emitted from cesium-137 is about 662 keV and the emission ratio is 85%. Therefore, in the wave height distribution M, for example, when the unit of the channel is 10 keV, the radiation of the energy 662 keV emitted by cesium-137 is detected and counted in the channel of 660 keV or more and 670 keV or less. That is, the identification of cesium-137 can be carried out by using the energy discrimination range of the channel counted by the wave height distribution M (660 keV or more and 670 keV or less) and the energy value of cesium-137 (662 keV). can.
However, such a method of identifying a nuclide of a radioactive substance based directly on the wave height distribution M may have a low analysis accuracy as described below.

When the nuclide of the radioactive substance is identified directly from the wave height distribution M shown above, the minimum energy unit of the radiation that can be analyzed depends on the energy resolution of the radiation detection unit 1. When the energy resolution of the radiation detection unit 1 is low, the width of the energy peak of the radiation appearing in the wave height distribution M is widened. At this time, when radiations from a plurality of radionuclides are derived, the peaks of the plurality of radiations overlap in the wave height distribution M and are detected as one energy peak, resulting in a decrease in analysis accuracy.

Further, as shown in FIG. 3, a part of the wave height distribution M derived by the wave height analysis unit 22 is detected as an energy peak part Mp like a hatched part, but the rest of the wave height distribution M is low energy. It is detected as a continuous distribution portion Mc on the side. This is because the radiation incident on the radiation detection unit 1 causes energy loss in the process of causing various interactions such as Compton scattering with the radiation detection unit 1. At that time, since the radiation detection unit 1 also has radiation that goes out of the radiation detection unit 1 without dropping the total energy, the continuous energy distribution portion Mc (continuous distribution portion Mc) on the low energy side in this way. Occurs.
Normally, the radioactivity intensity is obtained only from the count in the energy peak portion Mp, and the count in the continuous distribution portion Mc portion cannot be used for nuclide identification of radiation and is not used for nuclide analysis. Therefore, the measurement sensitivity of the radiation detection unit 1 cannot be ensured, and as a result, the analysis accuracy is lowered.

Therefore, in order to secure the energy resolution of the radiation detection unit 1 and improve the radiation analysis accuracy by excluding the influence of the interaction between the radiation detection unit 1 and the radiation, the radioactivity intensity calculation unit 23 is described below. Perform the signal restoration operation described.
As an example of the signal restoration operation, there is an unfolding method which is a kind of inverse problem operation. In unfolding, the response function K with the radiation detection unit 1 is calculated in advance at a constant energy interval with respect to the radiation to be measured. Then, it is a method of performing an unfolding calculation using the calculated response function K to calculate the actual energy distribution S (energy spectrum of the radiation source) of the radiation from the radioactive substance 50.

The response function K represents the interaction between the radiation detection unit 1 and the radiation, the type of the radiation detection unit 1, the positional relationship between the radiation detection unit 1 and the measurement object, and the radiation detection unit 1 and the measurement object. It corresponds to the density of the air between, the material and density of the object to be measured, and the energy value of the radiation incident on the radiation detection unit 1.
In this way, the radioactivity intensity calculation unit 23 performs a signal restoration calculation on the wave height distribution M derived by the wave height analysis unit 22 using the response function K called from the response function database 24, and performs a signal restoration calculation from the radioactive material 50. The energy distribution S as the second energy distribution, which is the actual radiation source spectrum of radiation, is restored.

Hereinafter, the signal restoration calculation performed by the radioactivity intensity calculation unit 23 will be described in more detail using a mathematical formula.
FIG. 5 is a schematic diagram showing a detection region Re measured by the radiation detection unit 1 according to the first embodiment.
The upper side in FIG. 5 is the opening side Y2 of the hole T1 of the concrete piece T in FIG. 1, and the lower side in FIG. 5 is the bottom side Y1 of the hole T1 of the concrete piece T in FIG.

First, each detection region Re (Re1 to Re5) in which the radiation detection unit 1 detects radiation will be described.
The radiation emitted from the radioactive substance 50 contained in the concrete piece T is self-absorbed by the concrete piece T. Therefore, the radiation reaching the radiation detection unit 1 is within the effective volume in the concrete piece T centered on the radiation detection unit 1, that is, within the columnar effective volume within the effective radius x and the effective depth z shown in FIG. It is released from the radioactive substance 50 contained in.

Here, the effective volume that can be measured by the radiation detection unit 1, that is, each region in which the measurement target region in which the radiation detection unit 1 measures radiation is divided into five with respect to the depth direction Y is divided into five detection regions Re1 and Re2. , Re3, Re4, Re5. The number of divisions for dividing the effective volume is not limited to 5. Further, usually, the region width ReH of each detection region Re in the depth direction Y is set to the same length as the width J of the radiation detection unit 1 in the depth direction Y.

Next, a state in which the radiation detection unit 1 is inserted into the concrete piece T to detect radiation will be described.
FIG. 6 shows the detection regions Re (Re1 to Re5) for each detection position A (A1 to A5) in the hole T1 of the concrete piece T of the radiation detection unit 1 according to the first embodiment, and the depth direction of the concrete piece T. It is a schematic diagram which shows each depth region D (D1 to D5) of Y.

The shaded area in FIG. 6 is the radiation detection unit 1. The width J of the radiation detection unit 1 with respect to the depth direction Y is shown to be the same as the region width ReH of the detection region Re. However, the length of the detection region Re in the horizontal direction in FIG. 6 is shown shorter than that of the detection region Re shown in FIG. Further, the illustration of the hole T1 of the concrete piece T, the expansion / contraction portion 2, the pipe 3, and the radioactive material 50 is omitted.

Here, a plurality of detection positions A in which the radiation detection unit 1 is fixed in the hole T1 are set at each detection interval AH set from the bottom side Y1 of the hole T1 toward the opening side Y2. It is assumed that there are five points, A1, A2, A3, A4, and A5.
FIG. 6 shows a state in which the radiation detection unit 1 detects radiation at each detection position A5, A4, A3 while shifting its fixed position from the detection positions A5, A4, and A3.
In the figure, the radiation detection unit 1 when fixed at the detection positions A1 and A2 is not shown.

Then, in the example shown in FIG. 6, the detection interval AH of the radiation detection unit 1 is set to the same length as the region width ReH of the detection region Re (width J of the radiation detection unit 1). That is, the radiation detection unit 1 moves by the width J of the depth direction Y of the radiation detection unit 1 while shifting its fixed position with respect to the depth direction Y.

When the center of the radiation detection unit 1 with respect to the depth direction Y is fixed at the detection position A5, the radiation detection unit 1 adds the radiation incident from the measurable effective volume, that is, the detection regions Re1, Re2, and Re3. Detects the radiation. Since the detection areas Re4 and Re5 are outside the concrete piece T, no radiation is detected.

Similarly, when the radiation detection unit 1 is fixed at the position of the detection position A4, the radiation detection unit 1 detects a spectrum obtained by adding the radiation incident from the detection regions Re1, Re2, Re3, and Re4.
Similarly, when the radiation detection unit 1 is fixed at the position of the detection position A3, the radiation detection unit 1 detects a spectrum obtained by adding the radiation incident from the detection regions Re1, Re2, Re3, Re4, and Re5.

Here, each region in which the inner region of the concrete piece T is divided into five from the surface T2 of the concrete piece T in the depth direction Y is divided into five depth regions D1, D2, D3, D4, and so on. Let it be D5. The depth regions D1 to D5 are unit widths in the depth direction Y when evaluating the distribution of the radioactive material 50 in the depth direction Y in the concrete piece T, so that an evaluation result with desired accuracy can be obtained. It is divided into any number.

In the present embodiment, the region width ReH in the depth direction Y of each detection region Re that divides the effective volume in which the radiation detection unit 1 can detect radiation, and each depth region D that divides the region in the concrete piece T. It is the same as the width in the depth direction Y of, and the number of each division is also set to be the same.
That is, when the spectrum obtained by adding the radiation incident from the detection regions Re1 to Re3 is measured at the detection position A5, the result is from the radioactive substance 50 contained in the depth regions D3 to D5 in the concrete piece T. It means that the spectrum of the sum of the radiation is being measured.

Similarly, at the detection position A4, when the spectrum obtained by adding the radiation incident from the detection regions Re1 to Re4 is measured, the spectrum obtained by adding the radiations from the depth regions D2 to D5 in the concrete piece T is measured. It will be.
Similarly, when the spectrum obtained by adding the radiation incident from the detection regions Re1 to Re5 is measured at the detection position A3, the spectrum obtained by adding the radiations from the depth regions D1 to D5 in the concrete piece T is measured. You will be doing.

Ideally, the detection region Re to be measured by the radiation detection unit 1 is the detection region Re3 located at the same depth as the radiation detection unit 1. That is, the region to be measured by the radiation detection unit 1 is the depth region D5 when fixed to the detection position A5, the depth region D4 when fixed to the detection position A4, and fixed to the detection position A3. When it is done, it is the depth region D3.

However, in the case of actual measurement, as described above, the radiation detection unit 1 not only emits radiation from the radioactive substance 50 contained in the detection region Re3 to be measured, but also other detection regions Re1, 2, 4, Radiation from 5 is also measured. Therefore, the count value of the wave height distribution M derived from the radiation detection unit 1 at each detection position A is actually from the detection region Re3 (depth region D at the depth where the radiation detection unit 1 is located) of the corresponding measurement target. It becomes an excessive value compared with the count value of radiation of.
That is, the wave height distribution M obtained by the radiation detection unit 1 fixed to each detection position A is affected by the radiation from the radioactive substance 50 in the detection region Re3 to be measured and the detection region Re1 other than the detection region Re3. It is the sum of both the effects of radiation from the radioactive material 50 in 2, 4 and 5.

Further, for example, the incident radiation from the detection regions Re2 and Re1 other than the detection region Re3 incident on the radiation detection unit 1 fixed at the detection position A3 causes various interactions with the radiation detection unit 1 at the detection position A3. Energy loss is likely to occur in the process. At that time, since some radiation goes out of the radiation detection unit 1 without dropping the total energy in the radiation detection unit 1, as described above, the measurement result has a wave height distribution having a waveform as shown in FIG. It becomes M. The wave height distribution M also depends on the energy resolution of the radiation detection unit 1.

Therefore, in the present embodiment, the detection regions Re1 and 2 are different from the detection region Re3 (depth region D at the depth where the radiation detection unit 1 is located) to be measured from the wave height distribution M derived by the radiation detection unit 1. Separates the influence of radiation from the radioactive substance 50 in 4, 5 (depth region D at a depth different from the depth where the radiation detection unit 1 is located), and corrects the energy resolution of the radiation detection unit 1 in the wave height distribution M. Further, in order to remove the influence of the interaction between the radiation and the radiation detection unit 1, the signal restoration calculation using the response function K shown below is performed.
That is, the relationship between the response function K, the wave height distribution M derived from the radiation detection unit 1 fixed to each detection position A, and the actual energy distribution S of each detection region Re is determined by the following mathematical formula (using a matrix). It is represented by 1).

M5, M4, and M3 in the above mathematical formula (1) are wave height distributions M derived when the radiation detection unit 1 is fixed at the detection positions A5, A4, and A3, respectively.

The response functions K1 ... KV in the above mathematical formula (1) are the response functions of the radiation detection unit 1 due to the radiation from the detection regions Re1 ... Re5 having different distances from the radiation detection unit 1. As described above, the response function K of the radiation detection unit 1 is configured corresponding to the radiation from the radioactive substance 50 in all the divided detection regions Re1 to Re5.

The SI ... SV in the above mathematical formula (1) is the actual radiation energy distribution S in the detection regions Re1 ... Re5 when the radiation detection unit 1 is fixed at the detection position A5.
Further, SI'... SV' is the actual radiation energy distribution S in the detection regions Re1 ... Re5 when the radiation detection unit 1 is fixed at the detection position A4.
Further, SI "... SV" is the actual radiation energy distribution S in the detection regions Re1 ... Re5 when the radiation detection unit 1 is fixed at the detection position A3.
The reason for determining the actual energy distribution S of the detection region Re for each detection position A of the radiation detection unit 1 is that a measurement error occurs for each detection position A.

If each term of the above formula (1) is set as M, K, and S, respectively, it can be expressed as the following formula (2).

Therefore, when the energy distribution S in each detection region Re is obtained, the inverse transformation of the mathematical formula (2) is performed as in the following mathematical formula (3). For example, a general inverse matrix is used for the inverse transformation.

By solving the above mathematical formula (3), the energy resolution of the radiation detection unit 1 in the wave height distribution M is corrected, and the influence of the interaction between the radiation and the radiation detection unit 1 is removed. Further, from each wave height distribution M derived from the radiation detection unit 1, a detection region Re1 different from the detection region Re3 (depth region D at the depth where the radiation detection unit 1 is located) of the measurement target of the radiation detection unit 1 The influence of radiation from 2, 4 and 5 (depth region D having a depth different from the depth at which the radiation detection unit 1 is located) is removed.
In this way, the information of the energy distribution S including only the actual energy information of the radiation emitted from the radioactive substance 50 in each detection region Re is extracted by the above calculation by the radioactivity intensity calculation unit 23.

When there are L types of incident radionuclides, the derived wave height distribution M corresponds to the result of weighted integration of the radioactivity intensity of each radionuclide as shown in the following mathematical formula (4).

FIG. 7 is an energy distribution S of the radioactive material 50 restored by performing a signal restoration operation using the response function K of the present embodiment with respect to the wave height distribution M shown in FIG.
This energy distribution S is restored for each detection region Re.
As shown in FIG. 7, in the restored energy distribution S, the radiation energy (662 keV) of the cesium-137 to be measured and the radiation energy from other naturally radioactive nuclides are separately restored. It turns out.

Next, the radioactivity intensity calculation unit 23 calculates the radioactivity intensity I of the radiation emitted from cesium-137 for each detection region Re based on the energy distribution S in each restored detection region Re.
Hereinafter, the details of the calculation of the radioactivity intensity I by the radioactivity intensity calculation unit 23 will be described.

Information such as the radiation emission rate of each nuclide is recorded in the radioactivity intensity calculation unit 23.
The radioactivity intensity calculation unit 23 divides the number (count) of gamma rays of cesium-137 by the measurement time from the energy distribution S obtained by the signal restoration calculation. As a result, the number of gamma rays of cesium-137 emitted from the concrete piece T per unit time can be obtained. Further, the radioactivity intensity calculation unit 23 divides the number of obtained gamma rays by the radiation emission rate Ra, which is the ratio of emitting specific gamma rays when cesium-137 is destroyed. As a result, the radioactivity intensity I of cesium-137 is obtained.

Next, the radioactivity intensity calculation unit 23 calculates the radioactivity intensity I of each depth region D of the concrete piece T based on the calculated radioactivity intensity I in each detection region Re as follows.
As described above, the region width ReH in the depth direction Y of each detection region Re and the width in the depth direction Y of each depth region D in the concrete piece T are set to be the same as the number of each division. .. Therefore, the energy distribution S (SI to SV, SI'to SV', SI "to SV") of each detection region Re obtained by using the mathematical formula (3) for the mathematical formula (1) is the concrete piece T to be measured. The energy distributions S1 to S5 of each depth region D1 to D5 in the above are described by the following mathematical formula (5).

The energy distribution S of the same depth region D appears in each column of the matrix on the right side of the above formula 5, but usually, it includes a measurement error and the like, so the values do not match. Therefore, the average of the energy distributions S in the same depth region D is taken as the calculation result of the depth region D.
For example, the sum of the energy distributions S3 in the depth region D3 in each column is divided by the number of columns 3 in the matrix to calculate the average value of the energy distribution S3 in the depth region D3.
In this way, in order to reduce the influence of the measurement error, the radioactivity intensity calculation unit 23 has changed the radioactivity intensity I in each detection region Re for each detected detection position A to each detection region Re (each depth region). The average value of the radioactivity intensity I of D) is calculated.

In this way, the distribution evaluation of the radioactivity intensity I with respect to the depth direction Y of cesium-137 can be obtained inside the concrete piece T.
The radioactivity intensity calculation unit 23 shows the one that calculates the average value of the radioactivity intensity I in each detection region Re (each depth region D of the concrete piece T), but the average value is calculated each time. It is not limited. Using the radioactivity intensity I of each detection region Re (each depth region D) derived from the mathematical formula (5) before calculating the average value, the distribution evaluation of the radioactivity intensity in the depth direction Y is performed. May be good.

Next, the radioactivity intensity calculation unit 23 calculates the radioactivity concentration W indicating the amount of radioactivity of cesium-137 contained in the unit volume based on the calculated energy distribution S in each detection region Re. .. That is, the radioactivity intensity calculation unit 23 sets the radioactivity concentration W of cesium-137 contained in each detection region Re (each depth region D) as the volume V of each detection region Re (each depth region D). By using the radiation emission rate Ra of cesium-137, it is calculated as in the following formula (6).

In this way, the distribution evaluation of the radioactivity concentration W of cesium-137 with respect to the depth direction Y can be obtained inside the concrete piece T.
The plurality of detection positions A and the detection interval AH can be set from the outside of the radioactivity intensity distribution measuring device 100. Therefore, it is also possible for the operator to adjust the detection position A and the detection interval AH while checking the measurement result displayed on the display unit 30 near the radioactivity intensity distribution measuring device 100 at the time of measurement.

As described above, the example in which the radiation detection unit 1 moves while shifting its fixed position by the width J of the depth direction Y of the radiation detection unit 1 has been shown.
Hereinafter, an example will be shown in which the radiation detection unit 1 moves by a distance smaller than the width J in the depth direction Y of the radiation detection unit 1 while shifting its fixed position with respect to the depth direction Y.

FIG. 8 shows the detection regions Re (Re1 to Re5) for each detection position A (A1 to A9) in the hole T1 of the concrete piece T of the radiation detection unit 1 according to the first embodiment, and the depth direction of the concrete piece T. It is a schematic diagram which shows each depth region D (D1 to D10) of Y.
The radiation detection unit 1 shows a state in which the fixed position is measured while shifting the detection positions A9, A8, and A7 with respect to the depth direction Y.

The distance of the detection interval AH of the radiation detection unit 1 shown in FIG. 8 is set to half the distance of the detection interval AH shown in FIG. That is, the radiation detection unit 1 moves by a distance of half the width J of the depth direction Y of the radiation detection unit 1 while shifting its fixed position with respect to the depth direction Y.
Further, the width of the depth regions D (D1 to D10) in the depth direction Y is set to half the width of each detection region Re in the depth direction Y.

Even in this case, the radioactivity intensity calculation unit 23 extracts information on the energy distribution S including only the actual energy information of the radiation emitted from the radioactive substance 50 in each detection region Re based on the above mathematical formula (1). do.
Then, the radioactivity intensity calculation unit 23 calculates the radioactivity intensity I of each depth region D (D1 to D10) of the concrete piece T based on the calculated radioactivity intensity I in each detection region Re.
For example, when calculating the radioactivity intensity I in the depth region D9, weighting is taken in the range where the detection region Re3 in the detection position A9 and the detection region Re3 in the detection position A8 overlap (corresponding to the depth region D9). , The average of the radioactivity intensity I may be taken.

Further, for example, when calculating the radioactivity concentration W in the depth regions D5 to D9, as shown below, the radioactivity concentration W may be averaged by weighting in the range where the detection regions Re3 overlap. ..
Specifically, as shown in FIG. 8, the radioactivity concentration W of the detection region Re3 obtained by measuring at the detection position A9 is 5 Bq / cm ³ , and the radioactivity concentration W of the detection region Re 2 is 10 Bq / cm. It is assumed that it was ^3.
Further, it is assumed that the radioactivity concentration W of the detection region Re3 obtained by measuring at the detection position A8 is 8 Bq / cm ³ and the radioactivity concentration W of the detection region Re 2 is 11 Bq / cm ³ .
Further, it is assumed that the radioactivity concentration W of the detection region Re3 obtained by measuring at the detection position A7 is 9Bq / cm ³ and the radioactivity concentration W of the detection region Re 2 is 8 Bq / cm ³ .
In this case, the radioactivity intensity calculation unit 23 derives the radioactivity concentration W in the depth regions D5 to D10 as follows.

The radioactivity intensity calculation unit 23 derives the radioactivity concentration W in the depth region D10 as 5Bq / cm ^{3 which} is the value of the radioactivity concentration W in the detection region Re3 obtained at the detection position A9.

^{The radioactivity intensity calculation unit 23 sets the radioactivity concentration W in the depth region D9 at 5 Bq / cm 3} of the radioactivity concentration W in the detection region Re3 obtained at the detection position A9 and the detection region obtained at the detection position A8. the sum of the 8Bq / cm ³ of the radioactivity concentration W of Re3 is to derive the 6.5Bq / cm ³ divided by 2.

^{The radioactivity intensity calculation unit 23 sets the radioactivity concentration W in the depth region D8 at 10 Bq / cm 3} of the radioactivity concentration W in the detection region Re2 obtained at the detection position A9 and the detection region obtained at the detection position A8. and 8Bq / cm ³ activity concentration W of Re3, deriving a 9Bq / cm ³ and 9Bq / cm ³ divided by 3 by summing the radioactivity concentration W of the detection region Re3 obtained at the detection position A7.

^{The radioactivity intensity calculation unit 23 sets the radioactivity concentration W in the depth region D7 to 10 Bq / cm 3} of the radioactivity concentration W in the detection region Re2 obtained in the detection position A9 and the detection region obtained in the detection position A8. and 11Bq / cm ³ activity concentration W of re2, deriving a 9Bq / cm ³ and 10 Bq / cm ³ divided by 3 by summing the radioactivity concentration W of the detection region Re3 obtained at the detection position A7.

^{The radioactivity intensity calculation unit 23 sets the radioactivity concentration W in the depth region D6 to 11 Bq / cm 3} of the radioactivity concentration W in the detection region Re2 obtained in the detection position A8 and the detection region obtained in the detection position A7. the sum of the 8Bq / cm ³ of the radioactivity concentration W of Re2 and to derive the 9.5Bq / cm ³ divided by 2.

The radioactivity intensity calculation unit 23 derives ^{the radioactivity concentration W in the depth region D5 as 8Bq / cm 3 which} is the value of the radioactivity concentration W in the detection region Re2 obtained at the detection position A7.

In this way, the radioactivity intensity calculation unit 23 arbitrarily changes the detection position P with respect to the depth direction Y, and obtains the radioactivity intensity I or the radioactivity concentration W in each detection region Re for each calculated detection position A. The radioactivity intensity I or the radioactivity concentration W in each depth region D can be calculated.
Therefore, it is possible to evaluate the radioactivity distribution in the depth direction Y of the concrete piece T, which does not depend on the region width ReH in the depth direction Y of the detection region Re.

The calculation of the radioactivity intensity I and the radioactivity concentration W by the radioactivity intensity calculation unit 23 is not limited to cesium-137, and can be similarly calculated for radioactive substances other than cesium-137.
Further, although the concrete piece T is mentioned as the object to be measured, it may be, for example, soil or food such as rice, and can be applied to all the objects to be measured in which the radiation detection unit can be inserted.

Further, in the above, the response function K of the radiation detection unit 1 is shown to be configured for radiation from all the detection regions Re. However, the response function K may be configured to correspond only to the radiation from the radioactive substance 50 in the detection region Re3 to be measured. Even in this case, the distribution of the radiation intensity I with respect to the depth direction Y of the concrete piece T is excluded from the influence of the interaction between the radiation detection unit 1 and the radiation while ensuring the energy resolution of the radiation detection unit 1. Evaluation can be carried out.

In the above description, the radiation detection unit 1 shows a NaI (Tl) scintillation detector that outputs a pulse signal G having a wave height corresponding to the energy of incident radiation, but the present invention is not limited thereto. The radiation detection unit 1 may output a detection signal other than the pulse signal G that corresponds to the energy of the incident radiation.

Further, the pulse height analyzer 22 is shown as a pulse height analyzer that derives the wave height distribution M based on the wave height peak value of the received pulse signal G, but the present invention is not limited to this. The wave height analysis unit 22 may have a configuration capable of deriving an energy distribution indicating a count for each energy value of the incident radiation based on a detection signal other than the pulse signal G corresponding to the energy of the incident radiation.

Although the figure shows an example in which the sampling unit 10 and the radiation analysis unit 20 are combined to form an integrated unit and only the display unit 30 is separately configured, the sampling unit 10 and the radiation analysis unit 20 are shown. And the display unit 30 may be integrally configured. Alternatively, the radiation detection unit 1, the radiation analysis unit 20, and the display unit 30 may be separately configured. Alternatively, only the radiation detection unit 1 may be separated and configured, and the radiation analysis unit 20 and the display unit 30 may be integrally configured.

Further, although the one provided with one radiation detection unit 1 is shown, the present invention is not limited to this. Even when a plurality of radiation detection units 1 are provided, the signal restoration calculation using the response function K configured as described above is performed while moving the plurality of radiation detection units 1 in the concrete piece T. , The radiation intensity distribution can be evaluated accurately in the depth direction Y.
If the number of radiation detection units 1 is one, the number of response functions K can be reduced to reduce the calculation load in the signal restoration calculation.

According to the radioactivity measuring device of the present embodiment configured as described above, the radiation detection unit is configured to be movable in the depth direction into the inside of the object to be measured. Then, the radiation emitted from the radioactive substance in the measurement object is detected at a plurality of detection positions in the depth direction.
Further, the response function of the radiation detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection area in which the measurement target area centered on the radiation detection unit is divided into a plurality of areas. Then, the radioactivity intensity calculation unit performs a signal restoration calculation using this response function for each wave height distribution M derived from the radiation detection unit at each detection position.

As a result, the radioactivity intensity calculation unit can secure the energy resolution of the radiation detection unit and derive the energy distribution S in the depth direction of the object to be measured, excluding the influence of the interaction between the radiation detection unit and the radiation. .. In this way, the radioactivity intensity calculation unit accurately identifies the radionuclide in the depth direction inside the object to be measured, and distributes the radioactivity intensity of the radioactive substance in the depth direction for each identified radionuclide. It is required with high accuracy.

Further, in the past, since a plurality of radiation detection units are fixed in the depth direction, it is not possible to adjust the detection interval and perform measurement flexibly. Therefore, the distribution interval of radiation obtained in the measurement result depends on the size (region width) of the radiation detection unit and the installation interval thereof, and is fixed. Therefore, the distribution interval of the radiation obtained in the measurement result becomes large, and the measurement accuracy may decrease.

The detection interval of the radiation detection unit of the present embodiment can be arbitrarily set so as to be shorter than the region width in the depth direction of the radiation detection unit, for example. This makes it possible to evaluate the radioactivity intensity distribution regardless of the area width of the radiation detection unit and the interval between the detection areas. Further, by shortening the detection interval and increasing the detection position, more accurate radioactivity intensity distribution evaluation becomes possible.
In addition, since the detection position can be set arbitrarily, it is possible to flexibly evaluate the radioactivity intensity distribution according to the situation of the radioactivity distribution in the measurement object.

Further, since a large number of radiation detection units are not required as in the conventional case, it is not necessary to obtain a large number of response functions for each radiation detection unit and each depth region. This improves workability. In addition, the number of response functions used can be reduced to reduce the computational load in the signal restoration calculation and improve the evaluation speed.

Further, the radioactivity intensity calculation unit does not perform processing of subtracting the count from the radiation from the depth region different from the depth region to be measured from the count of the detection signal output from the radiation detection unit. The radioactivity distribution in each detection region is restored by using all the detection signals (counting of pulse signals) output from the radiation detection unit. Since all the counts in the wave height distribution are used in this way, high measurement sensitivity of the radiation detection unit can be ensured and the measurement time can be shortened. As a result, highly efficient and highly accurate radioactivity intensity distribution evaluation can be realized.

In addition, the radiation detection unit performs radiation measurement inside the measurement object where natural radiation from the outside is shielded or attenuated. As a result, when detecting the radiation of the radioactive substance, the influence of the radiation coming from the outside can be reduced and the measurement accuracy can be improved. In addition, a shield for shielding natural radiation becomes unnecessary, and the size and weight can be reduced.
Further, since the radiation detection unit detects the radiation inside the object to be measured, it is possible to detect the radiation from a region deep inside from the surface of the object to be measured. This makes it possible to evaluate the radioactivity intensity distribution in the depth direction regardless of the thickness of the object to be measured.

In addition, unlike the conventional method, a sample of the object to be measured is taken by boring, taken back to the laboratory, and pretreated for measurement, but the intensity of radioactivity can be measured directly at the site where the object is to be measured. Therefore, workability is improved.

Further, the radioactivity intensity calculation unit calculates the radioactivity intensity in each detection region as the distribution of the radioactivity intensity in the depth direction of the radiation detection unit. In this way, by obtaining the radioactivity intensity in each detection region, the distribution of radioactive substances in the depth direction can be clearly grasped. Further, since the radioactivity intensity in each detection region is calculated, the radioactivity concentration for each unit volume can be accurately calculated by using the effective volume in each detection region.

Further, the radioactivity intensity calculation unit calculates the radioactivity intensity of the radioactive substance in each depth region based on the calculated radioactivity intensity of the radioactive substance in each detection region.
In this way, it is possible to calculate the radioactivity intensity for each depth region in which the measurement object is divided into a desired number in the depth direction, and it is possible to evaluate the radioactivity intensity distribution with a desired accuracy.

In addition, the radioactivity intensity calculation unit calculates the radioactivity intensity in each detection area for each detection position, and from the calculated radioactivity intensity in each detection area for each detection position, the radioactivity intensity in each detection area is calculated. Calculate the average value. As a result, it is possible to reduce the measurement error of the radioactivity intensity in each detection region that occurs at each detection position, and it is possible to evaluate the radioactivity intensity distribution with higher accuracy.
Further, the calculation unit may calculate the average value of the radioactivity intensity in each depth region from the radioactivity intensity in each detection region for each calculated detection position. Even in this case, it is possible to reduce the measurement error of the radioactivity intensity in each detection region that occurs at each detection position.

Further, the response function of the radiation detection unit is configured to correspond to radiation from radioactive substances in all detection areas. The wave height distribution derived from the radiation detection unit is affected by radiation other than the detection area to be measured. In this way, the response function of the radiation detection unit is derived from radioactive substances from all detection areas. By configuring it to correspond to the radiation of, it is possible to separate the influence of radiation other than the detection area of the measurement target of the radiation detection unit from the energy distribution restored in the signal restoration calculation. As a result, the radioactivity intensity in each detection region can be calculated with high accuracy, and the radioactivity intensity distribution can be evaluated with high reliability.

Further, the radioactivity intensity calculation unit uses the energy distribution S in each detection region as a matrix using the wave height distribution M of the radiation detection unit at each detection position and the response function K configured corresponding to each detection region. It is represented by, and the signal restoration operation is performed based on this matrix.
With such a configuration, the radioactivity distribution in the depth direction can be calculated by using a simple solution method using an inverse matrix. In this way, even when the amount of calculation in the signal restoration calculation increases, the calculation speed can be secured.

Further, as the radiation detector, a NaI (Tl) scintillation detector that outputs a pulse signal having a wave height proportional to the energy of the incident radiation may be used. Then, as the wave height analysis unit, a pulse height analyzer that derives a wave height distribution M indicating a count for each wave height peak value of this pulse signal may be used.
As described above, since the commonly used NaI (Tl) scintillation detector and pulse height analyzer can be used, the cost can be reduced. Further, the NaI (Tl) scintillation detector does not need to be cooled by a cooler or the like such as a Ge semiconductor detector. Therefore, maintenance of the cooler becomes unnecessary, and the operation and maintenance of the device can be simplified.

Further, the radiation detector is installed so as to face the object to be measured at a predetermined distance set.
In order to perform the signal restoration calculation with high accuracy, it is desirable that the positional relationship between the radiation detection unit and the object to be measured, the density of the substance between them, and the like do not change when calculating the response function. Therefore, by drilling a hole having a predetermined diameter and depth in the object to be measured, the positional relationship between the radiation detection unit and the object to be measured is fixed at a set distance. As a result, the positional relationship between the radiation detector and the object to be measured and the density of air between them are unlikely to fluctuate, and are therefore considered to be unchanged. As described above, the radiation intensity distribution measuring device of the present embodiment is suitable as a device for applying and analyzing the signal restoration calculation.

Embodiment 2.
Hereinafter, the second embodiment of the present application will be described with reference to the parts different from the first embodiment.
FIG. 9 is a block diagram showing an overall schematic configuration of the radioactivity intensity distribution measuring device 200a according to the first embodiment.
In the radioactivity intensity distribution measuring device 100 shown in the first embodiment, the operator confirms the measurement data near the device at the time of measurement and adjusts the detection position A of the radiation detection unit 1. Therefore, in the present embodiment, in order to save labor, the detection position A is automatically adjusted by the radioactivity intensity distribution measuring device 200a itself according to the distribution state of the radioactive substance of the measurement target. In the automatic adjustment of the detection position A, the radioactivity intensity distribution measuring device 200a sets the movement range Q of the radiation detection unit 1, and within the set movement range Q, the detection provided at each set detection interval. Radiation detection is performed at position A.

The radiation analysis unit 220a further includes a determination unit 228 as a calculation unit and a change unit 229 as a calculation unit with respect to the radiation analysis unit 20 shown in the first embodiment.
Hereinafter, the automatic adjustment of the detection position A by the determination unit 228 and the change unit 229 will be described.
First, the radioactivity intensity calculation unit 23 emits radiation in the depth direction Y based on the radiation detected at a plurality of detection positions A provided for each set first detection interval AH1, as in the first embodiment. Calculate the intensity I. The radioactivity intensity calculation unit 23 outputs this calculation result to the determination unit 228.

The determination unit 228 determines whether or not the first detection interval AH1 needs to be changed based on the calculation result of the radioactivity intensity I in the depth direction Y. For example, when the determination unit 228 detects that the radioactivity intensity I in the depth region D at a certain depth exceeds the first predetermined value TH1, the determination unit 228 has a higher accuracy in the vicinity of the depth region D. It is determined that it is necessary to change the first detection interval AH1 for distribution evaluation. In this case, the determination unit 228 indicates the setting of the movement range Q of the radiation detection unit 1 for moving the radiation detection unit 1 only in the vicinity of the depth region D where the radioactivity intensity I is high, and the first detection interval AH1. The adjustment instruction and the adjustment instruction are given to the change unit 229.

The changing unit 229 sets the moving range Q of the radiation detecting unit 1 with the depth region D having the radioactivity intensity I of the first predetermined value TH1 or more as the moving center according to the instruction from the determination unit 228. Further, the changing unit 229 sets the second detection interval AH2 in which the first detection interval AH1 is adjusted to be short.
Then, the radiation detection unit 1 measures radiation while shifting its fixed position for each set second detection interval AH2 within the set movement range Q.

For example, as shown in FIG. 9, when the radioactivity intensity I of the bottom side Y1 of the hole T1 is high in the hole T1 of the concrete piece T, the radiation detection unit 1 moves set to the bottom side Y1 of the hole T1. Within the range Q, radiation is detected at each second detection interval AH2 with a short detection interval. As a result, highly accurate radiation distribution evaluation can be performed in the depth region D where the radioactivity intensity I is high.

In the above, after the radiation detection unit 1 obtains the radioactivity intensity I in the depth direction Y at the first detection interval AH1, the radiation detection unit 1 moves to the vicinity of the depth region D where the radioactivity intensity I is high. An example of moving only within the set movement range Q and not moving outside the set movement range Q is shown.
However, the present invention is not limited to this, and the radiation detection unit 1 may move outside the movement range Q to perform radiation detection after obtaining the radioactivity intensity I in the depth direction Y at the first detection interval AH1. good. In this case, it is preferable to perform radiation detection at the second detection interval AH2 with a short detection interval only within the movement range Q, and perform radiation detection at the first detection interval AH1 with a long detection interval outside the movement range Q.

Further, in the above, the second detection interval AH2 is configured to be shorter than the first detection interval AH1, but the present invention is not limited to this. For example, when the radioactivity intensity I of the radioactive substance 50 is lower than the predetermined value of the set lower limit and a rough evaluation is sufficient, the second detection interval AH2 may be set larger than the first detection interval AH1. ..

Next, a radioactivity intensity distribution measuring device 200b having a configuration different from that of the radioactivity intensity distribution measuring device 200a shown above will be described.
The radioactivity intensity distribution measuring device 200b uses the beta rays emitted from the radioactive substance 50 to determine whether or not the first detection interval AH1 needs to be changed and to set the movement range Q of the radiation detection unit 1. Then, after that, the nuclide of the radioactive substance 50 is discriminated by using the gamma rays emitted from the radioactive substance 50, and the radioactivity intensity of the discriminated radioactive substance 50 is calculated.
Hereinafter, the details of the radiation distribution evaluation of the radioactivity intensity distribution measuring device 200b will be described.

The radioactivity intensity distribution measuring device 200b further includes a radiation detecting unit 1β for detecting beta rays in addition to the radiation detecting unit 1 for detecting gamma rays.
Further, the radiation analysis unit 220b further includes a beta ray waveform shaping unit 221a and a beta ray measurement unit 221b as a calculation unit in addition to the radiation analysis unit 220b shown in FIG.

Similar to the radiation detection unit 1, the radiation detection unit 1β detects beta rays emitted from the radioactive substance 50 contained in the concrete piece T at each detection interval AH in the depth direction Y. Then, the radiation detection unit 1β outputs a detection signal corresponding to the incident radiation to the beta ray waveform shaping unit 221a.

The beta ray waveform shaping unit 221a amplifies the input detection signal and shapes the waveform, and outputs the output to the beta ray measuring unit 221b. The beta ray measuring unit 221b calculates the radioactivity intensity I in the depth direction Y based on the input detection signal. The calculated radiation intensity I of the beta ray with respect to the depth direction Y is output to the determination unit 228.

The determination unit 228 determines whether or not the first detection interval AH1 needs to be changed based on the calculation result of the radiation intensity I of the beta ray in the depth direction Y. When the radioactivity intensity I of the beta ray in the depth region D of a certain depth is higher than the first predetermined value TH1 for the beta ray, the determination unit 228 needs to change the first detection interval AH1. Is determined. Then, the determination unit 228 gives a change instruction for adjusting the first detection interval AH1 and an instruction for setting the movement range Q with respect to the depth direction Y of the radiation detection unit 1 to the change unit 229.
In addition, when the radioactive intensity I of the radioactive substance 50 is lower than the predetermined value of the lower limit for the set beta ray and a rough evaluation is sufficient, the second detection interval AH2 is set to be larger than the first detection interval AH1. May be done.

The change unit 229 sets the second detection interval AH2 and sets the movement range Q according to the instruction from the determination unit 228.
Then, the radiation detection unit 1 and the radiation detection unit 1β measure the radiation while shifting their fixed positions at the detection positions A provided for each set second detection interval AH2 within the set movement range Q.

Since beta rays have a short range and self-absorption occurs in the measurement target, the radiation detection unit 1β, which is a detection element for beta rays, is only beta rays from the radioactive substance 50 near each fixed detection position A. Is detected. Therefore, if the beta rays are measured by the radiation detection unit 1β, which is a detection element for beta rays, the magnitude of the radioactivity intensity I in each depth region D can be determined.
As described above, by using the radiation detection unit 1β which is a beta ray detection element and the radiation detection unit 1 which is a gamma ray detection element in combination, it is possible to discriminate the depth region D having a high radioactivity intensity I. Beta rays can be used, and gamma rays can be used for the discrimination of radiation nuclei.

According to the radioactivity intensity distribution measuring device of the present embodiment configured as described above, the same effect as that of the first embodiment is obtained, and the radioactivity intensity calculation unit is a radiation detection unit inside the measurement object. It is possible to accurately identify the radionuclide in the depth direction and accurately determine the distribution of the radioactivity intensity of the radioactive substance in the above-mentioned arrangement direction for each identified radionuclide.

Further, the determination unit and the change unit set the second detection interval in which the first detection interval is adjusted based on the radioactivity intensity with respect to the depth direction Y, which is calculated based on the radiation detected for each first detection interval. do.
Thereby, for example, radiation detection with a small detection interval can be performed in the vicinity of a depth region where the radioactivity intensity is high, and radiation detection with a large detection interval can be automatically performed in a depth region where the radioactivity intensity is low. In this way, it is possible to evaluate the radiation intensity distribution according to the distribution state of the radioactive substance of the measurement target while shortening the time required for radiation detection.
In addition, since no worker is required, labor saving of the measurement worker can be realized.

Further, the determination unit and the change unit may set the movement range of the radiation detection unit in the depth direction based on the radioactivity intensity in the depth direction.
For example, the time required for radiation detection is shortened by performing radiation detection only in the vicinity of the depth region determined to have high radioactivity intensity and not performing radiation detection in the depth region determined to have low radioactivity intensity. At the same time, it is possible to evaluate the radioactivity intensity distribution according to the distribution state of the radioactivity intensity of the object to be measured.
In addition, the determination unit and the change unit set the movement range with the depth region where the radioactivity intensity is the first predetermined value or more as the movement center, so that the radioactivity intensity distribution evaluation in the vicinity of the region where the radioactivity intensity is high can be surely performed. You can.

Further, a radiation detection unit for measuring beta rays is provided to evaluate the radiation intensity in the depth direction using beta rays, and the moving range in which the radiation detection unit performs radiation detection is determined by the beta rays in this depth direction. It may be set based on the radioactivity intensity of. Normally, since the signal restoration calculation is not used for the calculation of the radioactivity intensity of beta rays, the calculation load for determining the magnitude of the radioactivity intensity in the depth direction can be reduced, and the time required for evaluation can be shortened.

Embodiment 3.
Hereinafter, the third embodiment of the present application will be described with reference to the parts different from the third embodiment.
FIG. 11 is a block diagram showing an overall schematic configuration of the radioactivity intensity distribution measuring device 300 according to the third embodiment.

In the present embodiment, the radiation analysis unit 320 further includes an output fluctuation detection unit 325 as a calculation unit and a compensation coefficient calculation unit 327 as a calculation unit for the radiation analysis unit 20 shown in the first embodiment. To prepare for.
In order to realize more accurate radiation analysis of radioactive substances, it is possible to make a difference between the measured wave height distribution M in the radiation detection unit 1 and the response function K in the radiation detection unit 1 stored in the response function database 24. It needs to be as small as possible.
The radiation detection unit 1 generally has a temperature characteristic. Therefore, the output of the radiation detection unit 1 is affected by the temperature of the installation location, and the output of the radiation detection unit 1 fluctuates. Further, the radiation detection unit 1 is affected by deterioration over time, and the output may fluctuate after long-term use. When the output of the radiation detection unit 1 fluctuates in this way, a difference occurs between the actually measured peak height distribution M and the response function K stored in the response function database 24, which affects the measurement accuracy. May affect.

The fluctuation of the output of the radiation detection unit 1 as described above can be determined by the fluctuation of the energy distribution position of the wave height distribution M with respect to the radiation detection unit 1 obtained by the wave height analysis unit 22, that is, the deviation of the energy peak position. Therefore, the output fluctuation detection unit 325 monitors the energy value (first energy value) at the characteristic peak in the wave height distribution M, for example, the peak of the radiation emitted from potassium 40 or the like, in a predetermined measurement environment, and uses it as a reference. Record as peak position P0. Here, the predetermined measurement environment refers to an environment or state as a reference for measurement, such as a reference temperature or a usage state in which the performance of the radiation detection unit 1 has not deteriorated.

Then, the output fluctuation detection unit 325 records the energy value (first energy value) at the peak of potassium-40 monitored after the reference peak position P0 is recorded as the measurement peak position P1.
Then, the output fluctuation detection unit 325 detects the fluctuation amount of the output of the radiation detection unit 1 from the reference peak position P0 and the measurement peak position P1. When the output fluctuation detection unit 325 detects a deviation from the peak position that should be originally, the output fluctuation detection unit 325 inputs the information of the reference peak position P0 that should be originally and the information of the current measurement peak position P1 to the compensation coefficient calculation unit 327. The compensation coefficient calculation unit 327 calculates the compensation coefficient Z as a function of the peak position ratio (variation amount) P0 / P1 by the following mathematical formula (7).

If the relationship between the channel of the wave height analysis unit 22 and the energy of the measured radiation is a linear function, its linearity is good, and the error is extremely small, the above equation (7) may be set to the compensation coefficient Z = P0 / P1. There is no problem.

The compensation coefficient Z calculated by the compensation coefficient calculation unit 327 is input to the wave height analysis unit 22. Then, the wave height analysis unit 22 adjusts the distribution position of the wave height distribution M by multiplying the energy value of each peak position of the count of the AD-converted pulse signal G by the compensation coefficient Z, and obtains the shape of the wave height distribution M. Compensate for the original shape.

According to the radioactivity intensity distribution measuring device of the present embodiment configured as described above, the same effect as that of the first embodiment is obtained, and the radioactivity intensity calculation unit is inside the measurement object with respect to the depth direction. It is possible to accurately identify the radionuclides and accurately determine the distribution of the radioactivity intensity of the radioactive substance in the depth direction for each of the identified radionuclides.
Further, the compensation coefficient calculation unit calculates a compensation coefficient for adjusting the distribution position in the wave height distribution, and the wave height analysis unit automatically adjusts the distribution position of the wave height distribution according to this compensation coefficient. As a result, highly accurate radiation analysis can be maintained regardless of the usage state of the equipment of the radioactivity intensity distribution measuring device and the surrounding environmental state.
Further, since the compensation for the fluctuation of the distribution position of the wave height distribution is performed by directly multiplying the peak position of the wave height distribution by the compensation coefficient, the adjustment accuracy of the distribution position of the wave height distribution can be improved.

Further, the output fluctuation detection unit records the characteristic peak position (first energy value) of the radiation from the radioactive substance other than cesium-137 of the radioactive substance to be measured as the reference peak position P0. That is, the output fluctuation detection unit originally exists in the natural world such as potassium 40, other than cesium-137 diffused due to an accident at a facility handling radioactive substances, and is based on a radioactive substance having a large absolute amount. Therefore, a stable reference peak position P0 can be set regardless of the presence or absence of detection of cesium-137.
As the conditions for determining the characteristic peak other than cesium-137, for example, the energy value is known and the count of the pulse signal G exceeds the set second predetermined value. It may be a characteristic peak.

The output fluctuation detection unit 325 and the compensation coefficient calculation unit 327 may be provided in the radioactivity intensity distribution measuring devices 200a and 200b shown in the second embodiment.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not exemplified are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1,1β radiation detection unit (detection unit), 22 wave height analysis unit (analysis unit),
23 Radioactivity intensity calculation unit (calculation unit), 24 Response function database (storage unit),
221b Beta ray measurement unit (calculation unit), 228 judgment unit (calculation unit),
229 Change unit (calculation unit), 325 Output fluctuation detection unit (calculation unit),
100,200a, 200b, 300 Radioactivity intensity distribution measuring device (radioactivity measuring device).

Claims (25)

A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit that derives a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
Each of the detection areas is obtained by dividing the measurement target area into the movement direction.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated .
In the signal restoration operation
The second energy distribution in each detection region is set as an unknown number different for each detection position, and each detection position is calculated to discriminate the nuclide of the radioactive substance in each detection region.
By calculating the radioactivity intensity of the discriminated radioactive material in each of the detection regions for each detection position, the radioactivity intensity of the radioactive material in the measurement target in the movement direction is calculated.
Radioactivity measuring device. The arithmetic unit
Based on the calculated radioactivity intensity of the radioactive material in each of the detection regions
The radioactivity intensity of the radioactive substance in each of the divided regions in which the measurement object is divided into a plurality of parts with respect to the moving direction is calculated.
The radioactivity measuring device according to claim 1. The arithmetic unit,
From the radioactivity intensity at each of said detection region for each arithmetic been the detected position, and calculates the average value of radioactivity intensity in each of said detection regions,
The radioactivity measuring device according to claim 2. The arithmetic unit
From the calculated radioactivity intensity in each detection area for each detection position, the average value of the radioactivity intensity in each division area is calculated.
The radioactivity measuring device according to claim 3. The plurality of detection positions are provided at each set first detection interval.
The arithmetic unit
The radioactivity intensity in the moving direction is calculated based on the radiation detected for each first detection interval, and the second detection interval adjusted for the first detection interval is set based on the radioactivity intensity.
The radioactivity measuring device according to any one of claims 2 to 4. The arithmetic unit
The radioactivity intensity in the moving direction is calculated based on the radiation detected at each first detection interval, and the moving range in which the detection unit moves in the moving direction is set based on the radioactivity intensity.
The radioactivity measuring device according to claim 5. The detection unit is configured to be able to detect radiation including beta rays emitted from the radioactive substance.
The arithmetic unit
The radioactivity intensity of the beta ray with respect to the moving direction in the measurement object is calculated.
The moving range is set based on the radioactivity intensity of the beta rays with respect to the moving direction.
The radioactivity measuring device according to claim 6. The arithmetic unit
Among the divided regions whose radioactivity intensity is calculated by the radiation detected at each first detection interval, the movement is centered on the divided region whose radioactivity intensity is equal to or higher than the first predetermined value. Set the range and
Within the movement range, the second detection interval is set to be smaller than the first detection interval.
The radioactivity measuring device according to claim 6 or 7. The response function of the detector is
Configured to cover all said detection areas,
The radioactivity measuring device according to any one of claims 1 to 8. The arithmetic unit
The second energy distribution of the radiation of the radioactive substance in each detection region is represented by a matrix using the first energy distribution at each detection position and the response function of the detection unit, and is based on the matrix. Calculate
The radioactivity measuring device according to any one of claims 1 to 9. The detection unit outputs a pulse signal having a wave height corresponding to the energy of the incident radiation as the detection signal.
The analysis unit derives a wave height distribution indicating the count of the pulse signal for each peak value of the pulse signal as the first energy distribution.
The radioactivity measuring device according to any one of claims 1 to 10. The response function is set based on the positional relationship between the measurement object and the detection unit and the density of gas between the measurement object and the detection unit.
The radioactivity measuring device according to any one of claims 1 to 11. The response function was set based on the material and density of the object to be measured.
The radioactivity measuring apparatus according to any one of claims 1 to 12. The calculation unit measures the fluctuation amount of the radiation energy distribution position in the first energy distribution, and adjusts the energy distribution position in the first energy distribution based on the fluctuation amount.
The radioactivity measuring device according to any one of claims 1 to 13. The arithmetic unit
In the first energy distribution derived in a predetermined measurement environment, the first energy value, which is the peak position of the count of the detection signal whose count exceeds the second predetermined value, is recorded as the reference peak position, and the reference peak position is recorded. The first energy value derived after recording is recorded as the measurement peak position, and
The amount of fluctuation is derived from the reference peak position and the measurement peak position, and the energy of radiation in the first energy distribution is derived so that the measurement peak position is located at the reference peak position based on the fluctuation amount. Adjust the distribution position of
The radioactivity measuring device according to claim 14. The calculation unit calculates a correction coefficient based on the fluctuation amount, and obtains a correction coefficient.
The analysis unit adjusts the distribution position of the radiation energy in the first energy distribution by multiplying the correction coefficient by the energy value of each peak position of the count in the first energy distribution.
The radioactivity measuring device according to claim 14 or 15. A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit that derives a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated.
Each of the detection areas is obtained by dividing the measurement target area into the movement direction.
The arithmetic unit
The second energy distribution in each detection region is calculated, and the nuclide of the radioactive substance in each detection region is discriminated.
By calculating the radioactivity intensity in each of the detection regions of the discriminated radioactive material, the radioactivity intensity of the radioactive material in the measurement target in the movement direction is calculated.
Based on the calculated radioactivity intensity of the radioactive material in each of the detection regions
The radioactivity intensity of the radioactive substance in each of the divided regions in which the measurement object is divided into a plurality of parts with respect to the moving direction is calculated.
The plurality of detection positions are provided at each set first detection interval.
The arithmetic unit
The radioactivity intensity in the moving direction is calculated based on the radiation detected for each first detection interval, and the second detection interval adjusted for the first detection interval is set based on the radioactivity intensity.
Radioactivity measuring device. The arithmetic unit
The radioactivity intensity in each of the detection areas was calculated for each detection position.
From the calculated radioactivity intensity in each detection area for each detection position, the average value of the radioactivity intensity in each detection area is calculated.
The radioactivity measuring device according to claim 17. The arithmetic unit
From the calculated radioactivity intensity in each detection area for each detection position, the average value of the radioactivity intensity in each division area is calculated.
The radioactivity measuring device according to claim 18. The arithmetic unit
The radioactivity intensity in the moving direction is calculated based on the radiation detected at each first detection interval, and the moving range in which the detection unit moves in the moving direction is set based on the radioactivity intensity.
The radioactivity measuring device according to claim 18 or 19. The detection unit is configured to be able to detect radiation including beta rays emitted from the radioactive substance.
The arithmetic unit
The radioactivity intensity of the beta ray with respect to the moving direction in the measurement object is calculated.
The moving range is set based on the radioactivity intensity of the beta rays with respect to the moving direction.
The radioactivity measuring device according to claim 20. The arithmetic unit
Among the divided regions whose radioactivity intensity is calculated by the radiation detected at each first detection interval, the movement is centered on the divided region whose radioactivity intensity is equal to or higher than the first predetermined value. Set the range and
Within the movement range, the second detection interval is set to be smaller than the first detection interval.
The radioactivity measuring device according to claim 20 or 21. A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident,
An analysis unit that derives a first energy distribution, which is an energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A storage unit that stores the response function of the detection unit, and a storage unit.
The second energy distribution, which is the radiation energy distribution of the radioactive material, is calculated by performing a signal restoration calculation using the response function for the first energy distribution, and the nuclear species of the radioactive material are discriminated. , A calculation unit for calculating the radioactivity intensity of the discriminated radioactive substance,
The detection unit is configured to be movable in the direction of movement toward the inside of the object to be measured, and detects radiation emitted from the radioactive substance in the object to be measured at a plurality of detection positions with respect to the direction of movement.
The response function of the detection unit is configured to correspond to the radiation emitted from the radioactive substance in each detection region in which the measurement target region centered on the detection unit is divided into a plurality of areas.
The arithmetic unit
By performing the signal restoration calculation using the response function, the radioactivity intensity of the discriminated radioactive material in the measurement target in the moving direction is calculated.
The fluctuation amount of the radiation energy distribution position in the first energy distribution is measured, and the energy distribution position in the first energy distribution is adjusted based on the fluctuation amount.
Radioactivity measuring device. The arithmetic unit
In the first energy distribution derived in a predetermined measurement environment, the first energy value, which is the peak position of the count of the detection signal whose count exceeds the second predetermined value, is recorded as the reference peak position, and the reference peak position is recorded. The first energy value derived after recording is recorded as the measurement peak position, and
The amount of fluctuation is derived from the reference peak position and the measurement peak position, and the energy of radiation in the first energy distribution is derived so that the measurement peak position is located at the reference peak position based on the fluctuation amount. Adjust the distribution position of
The radioactivity measuring device according to claim 23. The calculation unit calculates a correction coefficient based on the fluctuation amount, and obtains a correction coefficient.
The analysis unit adjusts the distribution position of the radiation energy in the first energy distribution by multiplying the correction coefficient by the energy value of each peak position of the count in the first energy distribution.
The radioactivity measuring device according to claim 23 or 24.

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