JP7085964B2 - Radiation detector - Google Patents

Description

The present application relates to a radiation detector.

Neutrons and gamma rays are mixed and generated in nuclear power plants and accelerator facilities. In order to accurately grasp the exposure dose, it is necessary to measure not only gamma rays but also neutron exposure doses. For radiation such as neutrons and gamma rays, the exposure dose is measured using the interaction between radiation and matter. Since gamma rays and neutrons interact differently with substances, measurements are generally made with different radiation detectors. In the dose rate measurement by gamma rays, a semiconductor detector or a scintillator such as sodium iodide is used. The detector output is converted to the dose rate by adjusting the energy characteristics of the sensitivity of these detectors to match the energy dependence of the dose rate due to gamma rays. _On the other hand, in neutron exposure dose measurement, it is necessary to detect neutrons in a wide energy range from the thermal neutron region to the fast neutron region. Is common. Therefore, in order to measure the dose rate for different types of radiation, there is a problem that different radiation detectors must be prepared.

In order to solve this problem, some neutron detectors are sensitive to gamma rays, and some gamma ray detectors are sensitive to neutrons. By using these, the dose rates of gamma rays and neutrons are used. A technique for measuring with one detector is being studied. For example, using a scintillator in which an inorganic scintillator that captures neutrons is uniformly mixed with an organic scintillator that is sensitive to neutrons and gamma rays, neutrons and gamma rays are used by utilizing the difference in the pulse waveform of the scintillator when neutrons and gamma rays are detected. (For example, see Patent Document 1).

In addition, the gamma ray detector is surrounded by a neutron decelerating material containing a neutron absorber, neutrons are detected by gamma rays generated by the neutron absorption reaction in the neutron absorber, and gamma rays pass through the neutron decelerating material, so gamma rays are also present. It is detectable, and the amount of neutron absorber and neutron decelerator is adjusted so that the dose rate per gamma ray bundle and the dose rate per neutron flux are the same, and the dose rate of gamma ray and neutron is one detector. (For example, see Patent Document 2).

Special Table 2014-534442A Japanese Unexamined Patent Publication No. 2007-47066

In Patent Document 1, gamma rays and neutrons can be discriminated from the difference in the waveform of the scintillation pulse. However, neutrons when two pulses are generated within a certain period of time, the scintillation pulse generated when fast neutrons are scattered by the organic scintillator and the scintillation pulse generated when the scattered neutrons are absorbed by the inorganic scintillator. Since the energy of fast neutrons incident from the pulse generated by deceleration is measured, there is a problem that the energy of incident neutrons cannot be measured when the energy of the incident neutrons is low and the scintillation pulse due to deceleration is below the detection limit. rice field. In general, the detection limit of an organic scintillator is about several hundred kev, so it is difficult to accurately evaluate the exposure dose from neutrons in the low energy region by this method.

Further, in Patent Document 2, since detection is performed only by gamma rays regardless of whether neutrons or gamma rays are incident, it is not possible to distinguish between neutrons and events caused by gamma rays, and the cause of the increase in dose rate is caused by either gamma rays or neutrons. There was a problem that it was impossible to judge. Furthermore, since the sensitivity of the central part of the gamma ray detector differs depending on the energy of gamma rays, the energy dependence of the dose rate per gamma ray bundle cannot be accurately considered, and it is difficult to accurately evaluate the exposure dose. There was a challenge.

The present application has been made to solve the above-mentioned problems, and an object thereof is to separate the dose rates of neutrons and gamma rays by one radiation detector and measure them accurately.

The radiation detector disclosed in the present application is a radiation detector that separately detects the dose rates of neutrons and gamma rays, and is a scintillator that generates scintillation light having a different pulse waveform based on the incident neutrons or gamma rays. An optical sensor that photoelectrically converts scintillation light into a pulse signal, a particle discrimination circuit that calculates pulse waveform discrimination parameters for neutrons and the gamma ray from the waveform of the pulse signal, and discriminates between neutrons and gamma rays, and a pulse signal. Based on the peak value and pulse waveform discrimination parameters of the pulse signal discriminated from the threshold value or higher by the wave height discrimination circuit that compares the threshold values, neutrons and gamma rays are separated to determine the respective dose rates. A dose calculation device for calculation and a decelerating body that slows down high-speed neutrons to thermal neutrons among neutrons are provided around the scintillator. The dose calculator is based on the count rate of the peak part of the neutron energy spectrum caused by the interaction with thermal neutrons caused by the decelerator, the physical properties of the scintillator, the neutron energy, and the structure of the decelerator. The neutron dose rate is calculated by multiplying it by a predetermined sensitivity coefficient .

According to the radiation detector disclosed in the present application, the dose rates of neutrons and gamma rays can be separated and measured accurately by one radiation detector.

It is a block diagram of the radiation detector which concerns on Embodiment 1. FIG. It is a schematic diagram which shows the example of the difference of the pulse waveform of a neutron and a gamma ray in the scintillator provided in the radiation detector which concerns on Embodiment 1. FIG. It is a block diagram which shows an example of the hardware of a radiation detector. It is a figure explaining the processing flow from the output minute pulse signal to the calculation of a dose rate. It is a schematic diagram which shows the example of the 2D histogram created by the dose calculation apparatus which concerns on Embodiment 1. FIG. It is a schematic diagram which shows the example of the energy spectrum created by the dose calculation apparatus which concerns on Embodiment 1. FIG. It is a schematic diagram which shows the relationship between the energy of the gamma ray and the load count which concerns on Embodiment 1. FIG. It is a schematic diagram which shows the example of the neutron energy dependence of the count rate with respect to a neutron flux and the dose rate with respect to a neutron flux which concerns on Embodiment 1. FIG. It is a schematic diagram which shows the example of the neutron energy dependence of the count rate with respect to the dose rate which concerns on Embodiment 1. FIG. It is a block diagram of the radiation detector which concerns on Embodiment 2. FIG. It is a figure explaining the processing flow until the dose rate which concerns on Embodiment 2 is calculated.

Hereinafter, the radiation detector of the embodiment will be described with reference to the drawings, but the same or corresponding members and parts will be described with the same reference numerals in the drawings.

Embodiment 1.
FIG. 1 is a block diagram of the radiation detector 1 according to the first embodiment. The radiation detector 1 is located around the scintillator 4 in which the neutron 2 and the gamma ray 3 are incident, the optical sensor 5 that measures the weak scintillator light emitted by the scintillator 4 due to the interaction with the neutron 2 or the gamma ray 3, and the scintillator 4. The scintillator 6 to be installed, the amplification circuit 11 that processes the signal output from the optical sensor 5, the wave height discrimination circuit 12, the particle discrimination circuit 13, and the dose calculation device 14, and the dose rate obtained as a result of the processing are displayed. It is composed of a display 15 for recording a dose rate and a recording device 16 for recording a dose rate.

First, a scintillator 4, a speed reducer 6, and an optical sensor 5, which are radiation detection units, will be described. The scintillator 4 is sensitive to both neutrons 2 and gamma rays 3, and the constituent molecules are excited by the energy applied from the incident neutrons 2 or gamma rays 3 and differ based on the neutrons or gamma rays when returning to the ground state. Generates scintillation light, which is a pulse waveform. In addition, in order to increase the probability of interaction with thermal neutrons, substances with a high probability of interaction with thermal neutrons, such as lithium-6, which is an isotope of lithium, boron-10, which is an isotope of boron, gadolinium, and cadmium. Are mixed in the scintillator 4, which is also sensitive to gamma rays. As can be seen from the schematic diagram showing the difference between the pulse waveforms of the neutron 2 and the gamma ray 3 in the scintillator 4 of FIG. 2, the scintillator 4 has a different emission attenuation time of the scintillation light generated by the neutron 2 or the gamma ray 3. For the scintillator 4, for example, an anthracene or an organic liquid scintillator, and an inorganic scintillator such as calcium fluoride are used. Here, in order to further improve the measurement accuracy of the dose rate, a substance that increases the interaction probability with thermal neutrons is mixed with the scintillator, but even if it is not mixed, the dose rates of neutrons and gamma rays are separated. It can be measured accurately.

Of the neutrons 2, fast neutrons with high energy tend to lose energy due to scattering with light elements having a small mass number. Therefore, the reducer 6 installed for the purpose of decelerating fast neutrons is composed of a light element such as polyethylene as a main material. By providing the decelerator 6, a peak is generated in the energy spectrum of the neutron 2 due to the interaction with the decelerated fast neutron, the thermal neutron. On the other hand, since the gamma ray 3 has a high probability of interaction with an element having a large atomic number, the probability of occurrence of an interaction with a reducer 6 composed of a light element is small, and the gamma ray 3 is incident on the scintillator 4 without being attenuated.

The optical sensor 5 receives scintillation light, which is a pulse waveform emitted by the scintillator 4, performs photoelectric conversion, and outputs a minute pulse signal as an electric signal. The optical sensor 5 and the scintillator 4 are in close contact with each other via an adhesive or the like so as not to sandwich the air layer, and are optically coupled to each other. As the optical sensor 5, for example, a photomultiplier tube, a photoelectric diode, or an avalanche optical diode is used, but the optical sensor 5 is not limited thereto.

The wave height discrimination circuit 12, the particle discrimination circuit 13, and the dose calculation device 14 of the radiation detector 1 are composed of a processor 111 and a storage device 112, as shown in FIG. 3 as an example of hardware. Although not shown, the storage device 112 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Further, the auxiliary storage device of the hard disk may be provided instead of the flash memory. The processor 111 executes the program input from the storage device 112. In this case, a program is input from the auxiliary storage device to the processor 111 via the volatile storage device. Further, the processor 111 may output data such as a calculation result to the volatile storage device of the storage device 112, or may store the data in the auxiliary storage device via the volatile storage device.

Next, the operation of the radiation detector 1 will be described.
Neutrons 2 are scattered as they pass through the decelerator 6, and fast neutrons are sufficiently decelerated to the region of thermal neutrons, which are low-energy neutrons, and then incident on the scintillator 4. Thermal neutrons cause a nuclear reaction with the atomic nuclei constituting the scintillator 4, and charged particles corresponding to the Q value of the reaction, which is a mass defect before and after the nuclear reaction, are generated. The generated charged particles apply full energy to the scintillator 4 to generate scintillation light. On the other hand, the gamma ray 3 is incident on the scintillator 4 without being attenuated when passing through the decelerating body 6, and scintillation light is generated by the interaction with the scintillator 4. The scintillation light is a pulse waveform having different emission decay times between neutrons and gamma rays. The scintillation light of neutrons and gamma rays propagating inside the scintillator 4 is incident on the optical sensor 5, and the optical sensor 5 outputs a minute pulse signal to the amplifier circuit 11.

FIG. 4 is a diagram illustrating a processing flow from the output minute pulse signal to the calculation of the dose rate. The amplifier circuit 11 amplifies the input minute pulse signal and outputs it as a pulse signal that can be used in a later stage (step S11). The output pulse signal is input to the wave height discrimination circuit 12 and the particle discrimination circuit 13.

The wave height discrimination circuit 12 discriminates the input pulse signal according to the threshold value (step S12). The threshold value is determined by the noise level of the entire measurement circuit system to be a wave height that does not include the wave height of the noise level. The pulse signal is output to the dose calculation device 14 together with the logic signal (steps S13 and S14). As the logic signal, "HIGH" is output when the pulse signal is equal to or higher than the threshold value, and "LOW" is output when the pulse signal is lower than the threshold value.

The particle discrimination circuit 13 calculates a PSD parameter in order to discriminate between a neutron and a gamma ray based on the fact that the emission attenuation time of the neutron passing through the scintillator 4 is longer than the emission attenuation time of the gamma ray (step S15). PSD is a method for discriminating the type of radiation from the waveform of a pulse signal called pulse waveform discrimination, and there are two methods, time measurement and charge integration. In the case of time measurement, the PSD parameter used for discrimination is defined as (pulse waveform fall time or pulse width) / (pulse waveform rise time). In the case of charge integration, the PSD parameter is defined as (charge of the falling part of the pulse waveform or the charge of the entire pulse) / (charge of the rising part of the pulse waveform). For example, in the pulse waveform shown in FIG. 2, since the emission decay time of neutrons and gamma rays is long for neutrons and short for gamma rays, the PSD parameter of neutrons is higher than that of gamma rays regardless of whether it is calculated by time measurement or charge integration. growing. In the particle discrimination circuit 13, the PSD parameter may be calculated by any method. The particle discrimination circuit 13 outputs the calculated PSD parameters of neutrons and gamma rays to the subsequent dose calculation device 14.

The dose arithmetic unit 14 calculates the respective dose rates of neutrons and gamma rays. The calculation process will be described in order. The dose calculation device 14 first sets the peak value of the pulse signal (hereinafter referred to as the pulse height) to which the logic signal in the “HIGH” state is given for each pulse and the digitally converted value of the PSD parameter for a predetermined time. The width is saved, and a two-dimensional histogram as shown in FIG. 5 is created (step S16). The pulse signal to which "LOW" is added is regarded as noise and is not processed. Since the emission decay time of the scintillation light does not depend on the pulse wave height of the generated scintillation light, each detection event of the neutron and the gamma ray is accurately and surely separated as shown in FIG.

FIG. 6 is a schematic diagram showing an example of an energy spectrum created by mapping each of the neutron event and the gamma ray event separated in FIG. 5 on the energy axis. The counting rate on the vertical axis indicates the counting value of neutrons and gamma rays incident on each unit time. As shown in FIG. 6, neutrons and gamma rays are separated to create an energy spectrum (step S17). The dose rates of neutrons and gamma rays are calculated using the respective energy spectra (steps S18 and S19).

First, the calculation of the neutron dose rate will be described. Since the energy of the charged particles generated as a result of the nuclear reaction between the thermal neutron and the scintillator 4 almost matches the Q value of the reaction, a peak corresponding to the Q value appears in the energy spectrum as shown in FIG. The count rate of this peak portion is the count rate of neutrons detected by the scintillator 4. The neutron dose rate is calculated by multiplying this counting rate by a predetermined sensitivity coefficient (step S18). The method for determining the sensitivity coefficient will be described later.

Next, the calculation of the gamma ray dose rate will be described. For gamma rays, the dose rate can be easily calculated by applying any of the following methods (step S19).

First, the application of the G (E) function method will be described. The G (E) function method is a method of calculating the dose rate using the G (E) function. FIG. 7 is a schematic diagram of the G (E) function showing the relationship between the energy of gamma rays and the load count. The dose rate can be calculated by loading the energy spectrum created as shown in FIG. 6 with the G (E) function, which is a predetermined energy conversion count. Next, the inverse problem solving method will be described. Using the response function of the scintillator 4 for the gamma ray 3 obtained in advance for the energy spectrum of the gamma ray, the energy spectrum of the gamma ray is calculated by an inverse problem calculation such as unfolding or deconvolution, and the dose rate conversion coefficient for the gamma ray bundle is calculated. Can be multiplied to calculate the dose rate.

The respective dose rates of the neutron and the gamma ray calculated by the dose calculation device 14 are output to the display 15 and the recording device 16. The display 15 displays each dose rate, and the recording device 16 records each dose rate.

Here, a method for determining the sensitivity coefficient will be described. FIG. 8 is a schematic diagram showing an example of the neutron energy dependence of the counting rate on the neutron flux and the dose rate on the neutron flux, and FIG. 9 is a schematic diagram showing an example of the neutron energy dependence of the counting rate on the dose rate. The ratio of neutron 2 detected by the scintillator 4 after being decelerated to the thermal neutron region by the decelerator 6 (hereinafter referred to as the sensitivity of the scintillator 4 to the neutron 2) is the physical characteristics of the scintillator 4, the energy of the neutron 2, and the decelerator 6. It is determined by the structure of. Since the sensitivity of the scintillator 4 to the neutron 2 changes depending on the energy of the neutron, the counting rate for the neutron flux depends on the physical properties of the scintillator 4, the energy of the neutron 2 and the structure of the decelerator 6, for example, as shown by the solid line in FIG. Shown in. This characteristic is determined in the design of the radiation detector 1. On the other hand, since the dose rate to the neutron flux also changes depending on the energy of the neutron, the dose rate to the neutron flux is, for example, the broken line in FIG. Is shown. At this time, if the ratio of the solid line and the broken line is constant as shown in FIG. 8 for the energy values of all neutrons, the ratio of the count rate and the dose rate is constant as shown in FIG. By adjusting the structure such as the thickness of the speed reducer 6, the ratio of the count rate to the dose rate can be made constant. In this way, the sensitivity coefficient, which is a proportional count between the count rate and the dose rate, is determined.

As described above, in this radiation detector 1, neutrons and gamma rays are separated and their energy spectra are created based on the fact that the emission decay time of the pulse waveform of neutrons is longer than the emission decay time of gamma rays. Can determine the dose rate from the peak appearing in the energy spectrum, and the gamma ray can be calculated by the G (E) function method or the inverse problem solving method. The dose rates can be separated and measured accurately. Further, since the sensitivity coefficient is determined by adjusting the structure of the decelerating body 6 to keep the ratio of the counting rate and the dose rate constant, no matter what energy the neutron is incident on, it does not depend on the energy of the neutron 2. The dose rate can be calculated accurately from the counting rate.

Embodiment 2.
The radiation detector 1 according to the second embodiment will be described. FIG. 10 is a block diagram of the radiation detector 1. In the first embodiment, the decelerating body 6 surrounding the scintillator 4 is provided, but in the second embodiment, the decelerating body 6 surrounding the scintillator 4 is not provided. Since the other configurations are the same as those described in the first embodiment, the same reference numerals are given and the description thereof will be omitted. Further, the dose rate measurement of the gamma ray 3 is the same as that of the first embodiment, and the description thereof will be omitted.

FIG. 11 is a diagram illustrating a processing flow until the dose rate is calculated. In the processing flow, the processing up to step S17 for creating the energy spectrum and the gamma ray dose rate calculation (step S19) are the same as those in the first embodiment, and thus the description thereof will be omitted.

First, the case of fast neutrons having high energy among neutrons 2 will be described. As shown in FIG. 10, since the radiation detector 1 is not provided with the reducer 6, the fast neutrons are incident on the scintillator 4 without being decelerated to the energy of the thermal neutron region. In thermal neutrons, as shown in FIG. 4, a peak due to the interaction of thermal neutrons appears in the energy spectrum, but in fast neutrons, a peak does not appear in the energy spectrum. The dose calculation device 14 performs an inverse problem calculation such as unfolding or deconvolution on the energy spectrum by using the response function of the scintillator 4 for fast neutrons obtained in advance (step S21), and is incident on the scintillator 4. Create an energy spectrum of the resulting neutron 2. Then, the energy spectrum of the obtained neutron 2 is multiplied by the dose rate conversion coefficient per neutron flux (step S22) to calculate the dose rate (step S24).

Next, the case of a neutron having a low energy among the neutrons 2 will be described. When the energy becomes low, the energy of the rebound ion generated by the scattering of the neutron and the scintillator 4 also becomes low, so that the output of the scintillator 4 becomes lower than the peak value determined as noise in the wave height discrimination circuit 12, and the reverse shown above. The energy spectrum of neutrons cannot be obtained by problem calculation. However, some of the neutrons incident on the scintillator 4 repeatedly scatter inside the scintillator 4 and slow down to the thermal neutron region. Since the scintillator 4 contains a substance having a high probability of interaction with thermal neutrons, the thermal neutrons generated by deceleration cause a nuclear reaction with the scintillator 4. In the amplified pulse signal for this, a peak due to a nuclear reaction with a thermal neutron appears in the energy spectrum created in step S17. The count rate of this peak portion is the count rate of neutrons detected by the scintillator 4. The dose rate can be calculated by multiplying this count rate by a predetermined sensitivity coefficient (step S23).

Here, a method for determining the sensitivity coefficient will be described. In the radiation detector 1 not provided with the decelerator 6, the probability that relatively low-energy neutrons incident on the scintillator 4 are decelerated inside the scintillator 4 to cause a nuclear reaction and are detected is the neutron energy and the scintillator 4. It is determined by the physical properties of the scintillator 4 and the size of the scintillator 4. Therefore, by providing a scintillator 4 whose dimensions are adjusted so that the energy characteristics detected by decelerating neutrons inside the scintillator 4 and causing a nuclear reaction and the energy dependence of the dose rate per neutron flux match, counting is performed. The sensitivity coefficient , which is a proportional count of the rate and the dose rate, is determined.

As described above, since the radiation detector 1 does not have the decelerator 6 surrounding the scintillator 4, when the neutron energy is high, the neutron energy spectrum is calculated by the inverse problem calculation to obtain the dose rate. When the neutron energy is low, the dose rate can be obtained from the neutron count rate, so the neutron dose rate can be separated from the gamma ray dose rate and measured accurately. Further, since the decelerating body 6 is not provided, the configuration of the radiation detection unit can be simplified and the design can be easily performed. In addition, by adjusting the dimensions of the scintillator 4, the sensitivity coefficient was determined by keeping the ratio of the count rate and the dose rate constant, so it counts regardless of the energy of the neutrons, regardless of the energy of the neutrons. The dose rate can be calculated accurately from the rate.

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 herein. 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 Radiation detector, 2 Neutron, 3 Gamma ray, 4 Scintillator, 5 Optical sensor, 6 Decelerator, 11 Amplifier circuit, 12 Wave height discrimination circuit, 13 Particle discrimination circuit, 14 Dose calculator, 15 Display, 16 Recording device

Claims (7)

A radiation detector that separates and detects the dose rates of neutrons and gamma rays.
A scintillator that generates scintillation light with different pulse waveforms based on incident neutrons or gamma rays,
An optical sensor that photoelectrically converts the scintillation light into a pulse signal,
A particle discrimination circuit that calculates pulse waveform discrimination parameters for neutrons and gamma rays from the pulse signal waveform and discriminates between neutrons and gamma rays.
A wave height discrimination circuit that compares the pulse signal with a predetermined threshold value,
A dose calculation device that separates the neutron and the gamma ray and calculates the respective dose rates based on the peak value of the pulse signal discriminated from the threshold value or higher by the wave height discrimination circuit and the pulse waveform discrimination parameter .
Around the scintillator, a decelerating body that slows down fast neutrons to thermal neutrons among the neutrons is provided .
The scintillator is a mixture of a substance constituting the scintillator and a substance that increases the probability of interaction with the thermal neutron.
In the dose calculation device, the physical properties of the scintillator, the energy of the neutron, and the reducer are added to the count rate of the peak portion of the energy spectrum of the neutron caused by the interaction with the thermal neutron generated by the reducer. A radiation detector characterized in that the dose rate of the neutron is calculated by multiplying by a predetermined sensitivity coefficient according to the structure of the above . The radiation detector according to claim 1 , wherein the dose calculation device applies a G (E) function to an energy spectrum of gamma rays to calculate a dose rate of gamma rays. The dose calculation device performs an inverse problem calculation on the gamma ray energy spectrum using the response function of the scintillator, calculates the energy spectrum of the gamma ray incident on the scintillator, and converts the dose rate into the calculated energy spectrum. The radiation detector according to claim 1 , wherein the dose rate of gamma rays is calculated by multiplying by a coefficient. A radiation detector that separates and detects the dose rates of neutrons and gamma rays.
A scintillator that generates scintillation light with different pulse waveforms based on incident neutrons or gamma rays,
An optical sensor that photoelectrically converts the scintillation light into a pulse signal,
A particle discrimination circuit that calculates pulse waveform discrimination parameters for neutrons and gamma rays from the pulse signal waveform and discriminates between neutrons and gamma rays.
A wave height discrimination circuit that compares the pulse signal with a predetermined threshold value,
A dose calculation device that separates the neutron and the gamma ray and calculates the respective dose rates based on the peak value of the pulse signal discriminated from the threshold value or higher by the wave height discrimination circuit and the pulse waveform discrimination parameter . Equipped with
The scintillator is a mixture of a substance constituting the scintillator and a substance that increases the probability of interaction with thermal neutrons.
The dose calculation device performs an inverse problem calculation on the neutron energy spectrum using the response function of the scintillator, calculates the energy spectrum of the neutron incident on the scintillator, and converts the dose rate into the calculated energy spectrum. A radiation detector characterized in calculating the dose rate of neutrons by multiplying by a coefficient. A radiation detector that separates and detects the dose rates of neutrons and gamma rays.
A scintillator that generates scintillation light with different pulse waveforms based on incident neutrons or gamma rays,
An optical sensor that photoelectrically converts the scintillation light into a pulse signal,
A particle discrimination circuit that calculates pulse waveform discrimination parameters for neutrons and gamma rays from the pulse signal waveform and discriminates between neutrons and gamma rays.
A wave height discrimination circuit that compares the pulse signal with a predetermined threshold value,
A dose calculation device that separates the neutron and the gamma ray and calculates the respective dose rates based on the peak value of the pulse signal discriminated from the threshold value or higher by the wave height discrimination circuit and the pulse waveform discrimination parameter . Equipped with
The scintillator is a mixture of a substance constituting the scintillator and a substance that increases the probability of interaction with thermal neutrons.
The dose calculation device is predetermined for the count rate of the peak portion of the energy spectrum of the neutron due to the interaction with the thermal neutron, according to the physical properties of the scintillator, the energy of the neutron, and the size of the scintillator. A radiation detector characterized in that the dose rate of the neutron is calculated by multiplying the sensitivity coefficient . The radiation detector according to claim 4 or 5, wherein the dose calculation device applies a G (E) function to an energy spectrum of gamma rays to calculate a dose rate of gamma rays. The dose calculation device performs an inverse problem calculation on the gamma ray energy spectrum using the response function of the scintillator, calculates the energy spectrum of the gamma ray incident on the scintillator, and converts the dose rate into the calculated energy spectrum. The radiation detector according to claim 4 or 5, wherein the dose rate of gamma rays is calculated by multiplying by a coefficient.

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