JP2021113751A - Nuclear substance detection device, nuclear substance detection method, and sample analysis method - Google Patents

Abstract

To appropriately recognize a secondary neutron component and analyze a sample when both a primary neutron component and a secondary neutron component generated from the sample are detected.SOLUTION: A neutron detector 20 outputs a pulse each time it absorbs one neutron. An analyzer 30 includes a time difference calculation part 31 for calculating a time difference of a detection timing of a neutron in the neutron detector 20, and an analysis part 32 for performing the above-mentioned recognition from data of the time difference. The time difference calculation part 31 calculates a time difference Δt of a detection timing when the neutron detector 20 detects the neutron before the detection timing each time the neutron detector 20 detects the neutron, and the analysis part 32 recognizes this value, stores all the recognized Δt, and generates a histogram after end of measurement. A nuclear material in a sample S is detected from the histogram of Δt, and the content can be estimated.SELECTED DRAWING: Figure 1

Description

The present invention relates to a nuclear material detection device and a nuclear material detection method for detecting a nuclear material in a sample by detecting radiation emitted from the nuclear material. The present invention also relates to a sample analysis method for analyzing a sample by irradiating the sample with a primary signal and detecting a secondary signal generated.

A technique for detecting nuclear material by recognizing neutrons emitted from nuclear material (fissile material) is known. Since neutrons have high material permeability, they can also detect nuclear materials existing inside baggage, containers, vehicles, and the like. FIG. 8 is a diagram schematically explaining the principle of such a nuclear material detection method.

Here, the sample S to be detected for the presence or absence of the nuclear material is housed inside the container 100. The neutron beam 120 (primary neutron) emitted from the neutron source 110 passes through the container 100 and irradiates the sample S. As a result, as neutrons emitted from the sample S side, the primary neutron component (primary signal) 130, which is a component in which the primary neutron is scattered by the sample S, and the nuclear material due to the primary neutron when the nuclear material is present in the sample S. There is a secondary neutron component (secondary signal) 140 due to neutrons (secondary neutrons) generated as a result of the nuclear reaction. The neutron detector 150 outside the container 100 detects both the primary neutron component 130 and the secondary neutron component 140, and particularly when the secondary neutron component 140 is significantly recognized, it is determined that the nuclear material is present in the sample S. can do. On the other hand, the primary neutron component 130 exists regardless of the presence or absence of nuclear material in the sample S. In FIG. 11, the directions of the primary neutron component 130 and the secondary neutron component 140 are shown differently for convenience, but the directions in which they are emitted do not change in particular, and they are actually mixed.

The neutron detector 150 can detect the neutrons incident on the neutron detector 150, but it is not easy to determine whether the detected neutron is the primary neutron component 130 or the secondary neutron component 140. As a method for detecting a nuclear material by recognizing the secondary neutron component 140 as described above, for example, a DDT (Differential Die-Away Technology) method is known. In the DDT method, as the above-mentioned neutron beam 120, a neutron beam emitted in the form of a pulse (short pulse) having a short duration is used. FIG. 9 schematically shows the passage of time from the end of irradiation of the neutron beam of the count number (logarithmic display) of the neutron detector 150 in such a case. In this case, if the neutron beam 120 is emitted in the form of a controlled short pulse, the primary neutron component 130 is observed as a component of the broken line (1) that attenuates with a short time constant in FIG. On the other hand, since the nuclear reaction by the primary neutron occurs for a certain period of time after the incident of the primary neutron, the secondary neutron component 140 is detected delayed from the primary neutron component 130, and is attenuated with a long time constant in FIG. It is observed as a component of (2). Actually, the component (1) and the component (2) are detected without distinction by the neutron detector 150. Therefore, when such a component is mixed, the actual detection result is shown in FIG. The characteristics are as shown by the solid line in which both 1) and (2) are included.

Actually, since the maximum intensity of the component (1) in FIG. 9 is orders of magnitude higher than the maximum intensity of the component (2), it is generally not easy to recognize only the component (2). .. In the DDT method, the neutron beam 120 (primary neutron) is made into a short pulse shape, and considering the difference in time constant between (1) and (2), the component (1) is added after the neutron beam 120 is turned off. The component (2) that became dominant after being sufficiently attenuated is detected. As a result, the secondary neutron component 140 can be recognized. Such a technique is described in, for example, Non-Patent Document 1.

Further, Patent Document 1 describes a method for analyzing a nuclear material by a method known as a furnace noise analysis process. Here, after a certain period of time (for example, 50 msec) has elapsed from the irradiation of pulsed neutrons, the time width (gate width) is specified and neutrons are counted, and the average value and dispersion of the counted values are used to determine the noise component (Y). The value) is calculated, and the nuclear material can be detected from the gate width dependence of this Y value. In addition, quantitative analysis of nuclear material in the sample can be performed by setting a long measurement time to reduce the statistical error of the measurement.

"Newtron diesel methods for fissile materials of fissile waste", Coop. K. L, Los Alamos National Laboratory, LA-UR-89-2124 (1989)

International Publication 2014/034743

Since the detection ability of the nuclear material is not sufficient by either of the above methods, it is difficult to detect the abundance of the nuclear material with high accuracy, for example. Further, for example, the technique described in Patent Document 1 can detect the presence of nuclear material, but the secondary neutrons detected here are after a certain period of time has elapsed after irradiation with pulsed neutrons (primary neutrons). Therefore, high-intensity prompt fission neutrons are not detected, only delayed fission neutrons. Therefore, since the number of detected neutrons is small, the detection ability is not high, and it takes a long time to detect the presence of nuclear material with sufficient accuracy.

Therefore, when both the primary neutron component (primary signal) and the secondary neutron component (secondary signal) generated from the sample are detected, the secondary neutron component can be appropriately recognized and the sample can be analyzed. Was desired.

The present invention has been made in view of such problems, and an object of the present invention is to provide an invention for solving the above problems.

The present invention has the following configurations in order to solve the above problems.
The nuclear material detection device of the present invention is a nuclear material detection device that detects the nuclear material in a sample by detecting the secondary radiation emitted by the nuclear reaction caused by the irradiation of the primary radiation, and the intensity of the nuclear material detection device. Within a certain measurement period, a radiation source that irradiates the sample with radiation that changes with time as the primary radiation, and a radiation detector that detects the radiation emitted from the side of the sample each time it is incident. , A time difference calculation unit that calculates the time difference between the detection timing of the radiation and the detection timing of the radiation detected before the radiation when the radiation detector detects the radiation, and a histogram of the time difference. It is characterized by including an analysis unit for estimating the contribution of the secondary radiation in the histogram and detecting the nuclear material.
In the nuclear material detection device of the present invention, the analysis unit is characterized in detecting or quantifying the presence of the nuclear material in the sample.
In the nuclear material detection device of the present invention, the radiation is a neutron beam, and the radiation detector detects neutrons.
In the nuclear material detection device of the present invention, the radioactive source includes a neutron source that constantly emits the radiation and a rotating body to which the neutron source is fixed, and the neutron source and the sample. The rotating body is rotationally driven so that the distance between the two is changed.
In the nuclear material detection device of the present invention, the radiation source is characterized by periodically emitting the pulsed radiation.
The nuclear material detection method of the present invention is a nuclear material that detects the nuclear material in a sample by emitting the nuclear material by a nuclear reaction caused by irradiation of the primary radiation and recognizing a secondary radiation of the same type as the primary radiation. A detection method using a radiation detector that irradiates the sample with radiation whose intensity changes with time as the primary radiation and detects the radiation emitted from the side of the sample each time it is incident. A time difference measuring step for calculating the time difference between the detection timing of the radiation and the detection timing of the radiation detected before the radiation when the radiation is detected within a certain measurement period, and the time difference. It is characterized by comprising an analysis step of creating a histogram of the above, estimating the contribution of the secondary radiation in the histogram, and detecting the nuclear material.
In the nuclear material detection method of the present invention, the radiation is a neutron beam, and the radiation detector detects neutrons.
In the sample analysis method of the present invention, when a countable secondary signal generated by irradiating a sample with a countable primary signal is measured by a detector, the primary signal is detected together with the secondary signal. In a sample analysis method in which the sample is analyzed by the secondary signal in the above, the primary signal whose intensity changes with time is applied to the sample, and the primary signal is emitted from the side of the sample. And using a detector that detects the secondary signal each time it is incident, the detection timing when the primary signal or the secondary signal is detected within a certain measurement period, and the detection timing A time difference measurement step of calculating a time difference from a previously recognized detection timing, and an analysis step of creating a histogram of the time difference, estimating the contribution of the secondary radiation in the histogram, and analyzing the sample. Equipped.

Since the present invention is configured as described above, when both the primary neutron component (primary signal) and the secondary neutron component (secondary signal) generated from the sample are detected, the secondary neutron is appropriately used. It is possible to recognize the components and analyze the sample.

It is a figure which shows the structure of the nuclear material detection apparatus which concerns on embodiment of this invention. It is a figure explaining the operation of measuring Δt in the nuclear material detection apparatus which concerns on embodiment of this invention. This is an example of a time series of pulse output in a neutron detector in the nuclear material detection device according to the embodiment of the present invention. It is a figure which shows typically the histogram of Δt obtained in the nuclear material detection apparatus which concerns on embodiment of this invention. It is an example of the histogram of Δt obtained by the Example of the nuclear material detection apparatus which concerns on embodiment of this invention. This is an example of a histogram obtained by the DDT method obtained by a conventional nuclear material detection device. The flowchart of the nuclear material detection method or the sample analysis method which concerns on embodiment of this invention is shown. It is a figure explaining the conventional nuclear material detection method. It is a figure which shows typically the time change of the detection intensity of the neutron detected by the conventional nuclear material detection method.

FIG. 1 shows the configuration of the nuclear material detection device 1 according to the embodiment of the present invention. Here, as in the case of the DDT method, a neutron source (radiation source) 10 that emits periodic pulsed neutrons is used, and the neutron beam 200 emitted from this is housed in the sample S in the container 100. Is irradiated against. Further, a neutron detector (radiation detector: detector) 20 that detects neutrons emitted from the sample S side is used. Since the neutron detector 20 outputs a pulse each time it absorbs one neutron, it is possible to count each neutron and recognize the incident timing (detection timing) of the neutron.

The neutrons detected by the neutron detector 20 are generated by the nuclear reaction in the sample S by the primary neutron component 210 in which the neutron beam 200 is scattered in the sample S and the primary neutron in the sample S, as in the configuration of FIG. It is one of the secondary neutron components 220, which are detected by the neutron detector 20 without distinction. Although the sample S is housed inside the container 100 here, the container 100 may not be used.

In FIG. 1, an analyzer 30 is connected to the neutron detector 20. The analyzer 30 performs signal processing according to the output of the neutron detector 20 according to the state of pulse generation of the neutron beam 200 in the neutron source 10, thereby determining the presence or absence of nuclear material in the sample S or the nuclear material. Recognize the abundance of. This operation will be described below. The analysis device 30 includes a time difference calculation unit 31 that calculates the time difference of the neutron detection timing in the neutron detector 20, and an analysis unit 32 that performs the above recognition from the data of the time difference.

FIG. 2 is a diagram for explaining the state of neutron detection by the neutron detector 20 and the operation of the analysis device 30 according to the situation. FIG. 2 shows a case where the neutron detector 20 detects neutrons four times, and the detection times are t1, t2, t3, and t4. Here, each time the neutron detector 20 detects a neutron, the time difference calculation unit 31 calculates the time difference Δt from the detection timing in which the neutron is detected before the detection timing, and the analysis unit 32 recognizes this value. do.

In FIG. 2, since the output at time t1 precedes the output first, there is no output to be different with respect to this output, and Δt is not calculated. After that, for the output at time t2, one of Δt = t2-t1 is obtained, and for the output at time t3, Δt = t3-t1 and Δt = t3-t2 are obtained, and time t4 For the output of, Δt = t4-t1, Δt = t4-t2, and Δt = t4-t1 are obtained. In this way, it is necessary to calculate a large amount of Δt for the later output, but if the time difference calculation unit 31 or the analysis unit 32 stores t1 to t4 in this way, the time difference detection unit 31 will be able to calculate this. Can be calculated.

In FIG. 2, it is assumed that the neutrons were detected four times, but the period during which such data collection is performed (measurement period) is usually sufficiently longer than the pulse period of the neutron beam 200. Therefore, more neutrons are actually detected within this measurement period. FIG. 3 shows an example of the time series of the pulse output in such a neutron detector 20, and here, the output immediately after the end of the period in which the neutron in the pulse is turned on is shown. Here, as in the case of the DDT method, when the primary neutron component 210 has a periodic pulse shape, the change over time in the count number of neutrons detected by the neutron detector 20 immediately after the irradiation of neutrons is , As shown in FIG. That is, the neutrons detected by the neutron detector 20 are similar in that primary neutrons and secondary neutrons coexist. Here, the primary neutrons include those that have reached the neutron detector 20 with a delay due to being scattered by the sample S.

The analysis unit 32 stores all of the Δt recognized as described above within the measurement period, and generates a histogram (frequency distribution) thereof after the measurement is completed. If the operation of sample S and the neutron source 10 is stable, the situation does not change from cycle to cycle, so ideally the same result can be obtained, but in reality, neutrons are obtained within one detection time zone. The number of detections is small, and the statistical variation is large. However, when the above measurement is performed to calculate Δt and a histogram of all Δt is obtained, statistical variation can be reduced and highly accurate results can be obtained.

The result of the histogram obtained in this way and its physical meaning will be described. The characteristic of FIG. 4 is a diagram schematically showing a histogram of Δt thus obtained. From the results of FIGS. 9 and 3, the characteristic of FIG. 4 also decreases as Δt increases, and is similar to the characteristic of FIG. 9 described above, except that the horizontal axis is Δt.
Since the neutrons detected here include the primary neutron and the secondary neutron as described above, the combination of the two outputs used for the calculation of Δt as described above (the latter output and the earlier output). Includes the one in which the secondary neutron is the later output when the earlier output is the primary neutron. From the characteristics of FIG. 9, the larger the Δt, the higher the probability that the combination of outputs used in the calculation of Δt is due to the secondary neutron and the primary neutron. On the contrary, if Δt is small, the probability that the combination corresponding to this Δt is due to the secondary neutron and the primary neutron is low, and the possibility that this combination is due to the primary neutrons is high.

Therefore, in FIG. 4, the contribution of the primary neutron is large in the region A where Δt is small, and the contribution of the secondary neutron is large in the region B where Δt is large. .. Similarly, the spread in the horizontal axis (Δt) direction in the characteristics of FIG. 4 corresponds to the time when the secondary neutrons are emitted after the primary neutrons are absorbed by the nuclear material. That is, the characteristics of FIG. 4 and the characteristics of FIG. 9 are similar, and the contributions of the primary neutron and the secondary neutron to each characteristic are the same. Therefore, in FIG. 4, when the nuclear material content is high (broken line) as compared with the case where the nuclear material content is low (solid line), the value becomes larger in the region where Δt is large, and the histogram of Δt shows the sample S in the sample S. It is possible to detect nuclear material and estimate its content.

However, while the vertical axis in the characteristics of FIG. 9 is the count number at which neutrons were detected, the vertical axis in FIG. 4 is the number for which Δt was calculated, which is clear from the simple example of FIG. As such, the number is higher than the count in which neutrons were detected. Therefore, in the histogram of FIG. 4, even when the neutron source 10 and the neutron detector 20 are the same, the number of samples used for the histogram can be increased as compared with the case of creating the histogram of FIG. The statistical accuracy can be improved.

FIG. 5 shows a histogram (Example) obtained as a result of measuring the sample S actually containing plutonium (Pu) and the sample S not containing plutonium with the configuration of FIG. Here, the amount of Pu in the sample S was 0 g (none), 100 mg, and 300 mg, the pulse period of the neutron beam was 10 msec, and the measurement period was 10 sec. From this result, the difference between these three measurement results, especially in the region where Δt is large, is clear. Therefore, for example, if the analysis unit 32 stores the measurement result for a standard sample in which the abundance of Pu is known in advance, the analysis unit 32 recognizes the abundance of Pu from the histogram obtained by the measurement. be able to.

On the other hand, the characteristic of FIG. 9 by the above-mentioned DDT method is a total of the results obtained in each cycle only during the period from the time when the neutron beam is turned off to the time when the neutron beam is turned off in the pulsed neutron beam. can get. Therefore, the characteristics of FIG. 9 can be obtained as a comparative example from the same measurement results as the measurement results of the neutron detector 20 when the results of FIG. 5 are obtained. FIG. 6A shows this result. In this case, the difference between the case where Pu is 0 g and the case where Pu is 100 mg is not clear. Further, since the absolute value of the vertical axis (count number) is significantly different from that in FIG. 5, the statistical error is larger than that in FIG.

Therefore, FIG. 6 (b) shows the results of examining the same characteristics as in FIG. 6 (a) by setting the total measurement time as long as 120 sec under the same conditions and sufficiently increasing the total number of detected counts. In this result, the difference between the case where Pu is 0 g and the case where Pu is 100 mg appears.

On the other hand, in the result of FIG. 5, even when the total measurement time is 10 sec, the difference in characteristics when Pu is 0 g and 100 mg is clear. That is, by the above method, the abundance of Pu in the sample S can be recognized with higher accuracy than the DDT method if the measurement time is the same.

Further, in the technique described in Patent Document 1, in order to reduce the primary neutron component detected by the neutron detector, the measurement result after a lapse of a certain time from the end of the irradiation of the pulsed neutron was used. Therefore, the only secondary neutrons that contributed to this measurement result were delayed fission neutrons, and a larger number of prompt fission neutrons did not contribute to the measurement results. On the other hand, in the above method, since the measurement is performed immediately after the end of the pulsed neutron irradiation, the prompt fission neutron also contributes to the measurement result. Therefore, according to the above method, it is possible to detect the nuclear material with high accuracy in a shorter measurement time.

FIG. 7 is a flowchart showing the operation (nuclear material detection method) of the analysis device 30. Here, it is assumed that the measurement period, which is the time for performing this measurement, is usually sufficiently long, and this total measurement time includes a large number of cycles of neutron rays 200 that change periodically. In the following, it is assumed that this operation is performed every time the neutron detector 20 detects a neutron once. For example, if the time series data of the neutron detection is stored as shown in FIG. 3, this operation is performed after the measurement. The series data can be read out and the analysis device 30 can perform the same operation.

This operation is performed every time the neutron detector 20 detects a neutron (S1) within the measurement period. When the output from the neutron detector 20 is obtained (S1), the analysis unit 32 stores the detection timing (t1 to t4 in FIG. 2) (S2). Next, the analysis unit 32 determines from the detection timing data stored in this way whether or not there was an output from the neutron detector 20 before this within the measurement period (S3). When the output is not recognized before this (S3: No), the next output is recognized (S1) and the detection timing is stored (S2) corresponding to the case of the time t1 in FIG.

When the output is recognized before this (S3: Yes), it corresponds to the case of t2 to t4 in FIG. 2, and the analysis unit 32 calculates all the Δt corresponding to the time difference calculation unit 31 (S4). , All the results are memorized (S5). After that, the operation starting from the detection of neutrons (S1) is repeated until the measurement period ends (S6: Yes). As a result, the data of Δt is accumulated in the analysis unit 32 within the measurement period. The above processes S1 to S5 are time difference measurement steps for accumulating Δt data within the measurement period.

After that, when the measurement period ends (S6: Yes), the analysis unit 32 creates a histogram of all the stored Δt (S7). After that, the analysis unit 32 estimates the abundance of nuclear material in the sample S from the contribution of the secondary neutrons as shown in FIG. 4 in this histogram (S8). That is, the processing of S7 and S8 is an analysis step of analyzing the nuclear material from the data of Δt. As described above, this enables detection of the presence of nuclear material or quantitative analysis thereof.

In the above nuclear material detection method, in order to distinguish the secondary neutron component and the primary neutron component in the characteristics of FIG. 4, a periodic pulse shape in which the period during which the neutron is emitted in the neutron beam 200 is limited is limited. It was said. However, the above-mentioned neutron detection (S1) can be performed within a certain measurement period regardless of such a periodic state and without recognizing the start timing of the period. Therefore, as compared with the case of the DDT method, it is not necessary to recognize the generation timing of the pulsed neutron at the time of neutron detection, and the measurement becomes easy. However, the above measurement may be performed for each cycle, and the measurement may be performed only during a specific period within the cycle (for example, only during the period when neutrons are off) as in the DDT method. As for the measurement period, it is generally preferable that the measurement period is longer than the pulse period because the number of samples is large. However, since the intensity of the detected neutrons is strong, the characteristics of FIG. 4 can be sufficiently recognized even if the measurement period is short. In some cases, the measurement period may be shorter than the pulse period.

Further, the neutron beam 200 does not have to be in the form of a pulse, and it is sufficient that the neutron beam changes with time as long as the primary neutron and the secondary neutron can be distinguished as described above in the characteristics of FIG. For example, when the intensity of the neutron beam changes not in a steep pulse shape but in a gradual change, the degree of contribution of the secondary neutron to the contribution of the primary neutron in the characteristics of FIG. 4 is that of the neutron beam in this periodic change. Although it changes according to the fluctuation rate of intensity, contrast, etc., the same principle holds. In particular, according to the above method, a result with high statistical accuracy can be obtained as shown in FIG. 5. Therefore, even in such a case, the distinction between the contribution of the secondary neutron and the contribution of the primary neutron in the histogram can be made. It is easier than the conventional method.

Therefore, the neutron beam does not have to be in the form of a pulse, and its intensity may change periodically. Therefore, for example, as a neutron source, "Conceptual Study on a Novel Method for Defecting Nuclear Material Use a Neutron Source", Masao Komeda and Technology Rotate a neutron source (radioisotope) that constantly emits neutrons, as described in 135 (2020), 106993 (http://www.sciencedirect.com/science/article/pii/S306454919304955). It is also possible to use a neutron source fixed to a disk (rotating body) and configured so that the distance between the neutron source and the sample changes periodically as the disk rotates. In general, it is not easy to obtain a neutron source that emits neutrons in an accurate pulse shape, but by using a neutron source in this way, it is possible to easily obtain a neutron source whose intensity fluctuates periodically. Alternatively, as long as the primary neutron and the secondary neutron can be distinguished as described above, the temporal intensity change of the neutron does not have to be periodic. From the above, in the above configuration, it is not necessary to achieve at least precise synchronization between the analyzer 30 and the neutron source 10.

In addition, in the above method, nuclear material was detected by detecting neutrons (primary neutrons, secondary neutrons) with a neutron detector (radiation detector), but it is a reaction by absorbing radiation (primary radiation). When the presence or absence of radioactive substances (nuclear substances) that emit other radiation (secondary radiation) is detected using a radiation detector, the secondary radiation and the primary radiation are detected in the same way by the radiation detector without distinction. The above configuration can be used in the same manner. That is, the above configuration is also effective in the case of detecting other radiation (γ-rays, etc.) instead of the above-mentioned primary neutrons and secondary neutrons to detect a nuclear substance that emits radiation. At this time, the types of the primary radiation and the secondary radiation may be different as long as the primary radiation and the secondary radiation are similarly detected by the radiation detector. In this case, even if the primary radiation and the secondary radiation can be discriminated by the radiation detector, according to the above configuration, it is not necessary to discriminate between the primary radiation and the secondary radiation, so that signal processing becomes easy.

Further, as described above, the analysis using the histogram of the detection time difference Δt is generally performed when the sample is irradiated with a countable primary signal and the sample is analyzed based on the secondary signal generated thereby. Can be applied as a target. In such a case, when the secondary signal is detected (counted) by a single detector, the underlying primary signal is also detected in the same manner, and it may be difficult to distinguish between the two and count them. be. For example, in sonar, it is conceivable that a sound wave is used as such a primary signal, and a sound wave emitted by reverberation of this sound wave from a sample is used as a secondary signal. In this case, when the detector detects the secondary signal, the primary signal is also detected at the same time.

In such a case, if both the primary signal and the secondary signal can be counted and the detection timing of each detection temple can be recognized, the same method can be applied. In this case, it is preferable that the primary signal is in the form of a pulse as in the above case, but the point that analysis is possible even if the primary signal is not in the form of a pulse is the same as in the above case. In this case, the detector is appropriately set according to the types of the primary signal and the secondary signal. Further, as long as both the primary signal and the secondary signal can be detected by the same detector, the types of the primary signal and the secondary signal may be different as in the case of the radiation described above.

Alternatively, for example, even when the detector for detecting the primary signal and the detector for detecting the secondary signal can be individually provided by changing the arrangement, according to the above configuration, a single detector for detecting both is provided. Can be used to analyze a sample using a secondary signal. That is, the sample analysis method including the same time difference measurement step and analysis step as described above is effective other than the detection of nuclear material.

1 Nuclear material detector 10,110 Neutron source (radioactive source)
20,150 Neutron detector (radiation detector: detector)
30 Analytical device 31 Time difference calculation unit 32 Analytical unit 100 Container 120, 200 Neutron beam (radiation)
130, 210 Primary neutron component 140, 220 Secondary neutron component S sample

Claims (8)

A nuclear material detection device that detects the nuclear material in a sample by detecting the secondary radiation emitted by the nuclear reaction caused by the irradiation of the primary radiation.
A radiation source that irradiates the sample with radiation whose intensity changes with time as the primary radiation,
A radiation detector that detects the radiation emitted from the side of the sample each time it is incident, and
Time difference calculation unit that calculates the time difference between the detection timing of the radiation and the detection timing of the radiation detected before the radiation when the radiation detector detects the radiation within a certain measurement period. When,
An analysis unit that creates a histogram of the time difference, estimates the contribution of the secondary radiation to the histogram, and detects the nuclear material.
A nuclear material detection device characterized by comprising. The nuclear material detection device according to claim 1, wherein the analysis unit detects or quantifies the presence of the nuclear material in the sample. The nuclear material detection device according to claim 1 or 2, wherein the radiation is a neutron beam, and the radiation detector detects neutrons. The radiation source is
A neutron source that constantly emits the radiation,
A rotating body with a fixed neutron source is provided.
The nuclear material detection device according to claim 3, wherein the rotating body is rotationally driven so that the distance between the neutron source and the sample changes. The nuclear material detection device according to claim 3, wherein the radiation source periodically emits the pulsed radiation. It is a nuclear material detection method that detects the nuclear material in a sample by recognizing the secondary radiation of the same type as the primary radiation, which is emitted by the nuclear reaction caused by the irradiation of the primary radiation.
The sample is irradiated with radiation whose intensity changes with time as the primary radiation.
Using a radiation detector that detects the radiation emitted from the side of the sample each time it is incident, when the radiation is detected within a certain measurement period, the detection timing of the radiation and the radiation The time difference measurement step of calculating the time difference of the detection timing of the radiation detected before, and
An analysis step of creating a histogram of the time difference, estimating the contribution of the secondary radiation to the histogram, and detecting the nuclear material.
A nuclear material detection method characterized by comprising. The nuclear material detection method according to claim 6, wherein the radiation is a neutron beam, and the radiation detector detects neutrons. When a countable secondary signal generated by irradiating a sample with a countable primary signal is measured by a detector, the primary signal is detected together with the secondary signal. This is a sample analysis method for analyzing samples.
The sample is irradiated with the primary signal whose intensity changes with time, and the sample is irradiated with the primary signal.
Using a detector that detects the primary signal and the secondary signal emitted from the side of the sample each time it is incident.
A time difference measurement step of calculating the time difference between the detection timing when the primary signal or the secondary signal is detected within a certain measurement period and the detection timing recognized before the detection timing.
An analysis step of creating a histogram of the time difference, estimating the contribution of the secondary radiation to the histogram, and analyzing the sample.
A sample analysis method comprising.

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