KR102524464B1 - neutron DISTRIBUTION imaging system OF Spent fuel and method THEREOF - Google Patents

Abstract

The present invention generates a TTL pulse signal in which a fast neutron pulse signal and a thermal neutron pulse signal are mixed by using a He-4 detector having a built-in signal processing board and two output ports for neutrons emitted from spent nuclear fuel, A system and method for imaging a neutron distribution of spent nuclear fuel in which a generated TTL pulse signal is processed through a signal processing unit and an image processing unit to form an image. The system for imaging neutron distribution in spent nuclear fuel according to the present invention It can be configured as an image by data processing. In addition, it is possible to intuitively check the abnormal state of the spent nuclear fuel by the configured image. In addition, it can be used for soundness evaluation and soundness inspection of spent nuclear fuel.

Description

Neutron distribution imaging system of spent nuclear fuel and method thereof

The present invention relates to a neutron distribution imaging system and method of spent nuclear fuel, and more particularly, to a He-4 detector (Arktis Corporation) having a built-in signal processing board and two output ports for neutrons emitted from spent nuclear fuel. product) to generate a TTL (Transistor-Transistor Logic) pulse signal in which a fast neutron signal and a thermal neutron signal are mixed, and the generated TTL pulse signal is processed into an image through a signal processing unit and an image processing unit. It relates to a neutron distribution imaging system of spent nuclear fuel composed of and a method thereof.

In general, a nuclear fuel assembly consists of hundreds of fuel rods in which uranium powder pellets are loaded into a metal cladding and both ends are sealed, and energy generated by nuclear fission in a nuclear reactor is transferred to cooling water to generate steam to generate steam. is used as a heat source to drive

Since spent nuclear fuel burned in a nuclear reactor continuously generates decay heat for a considerable period of time due to the highly radiative nuclides present in the fuel, spent nuclear fuel is discharged from the reactor to During the period, it is stored in a temporary storage tank in the reactor with a cooling function.

Thereafter, stored using a wet storage method in which water is cooled and radiation is shielded in a separate storage tank, or stored in a thick metal or concrete cask and cooled using air or gas. Dry storage ( dry storage) method, and recently, most of the dry storage is applied. This has the aspect that dry storage has less operation management or generation of secondary waste, and safety is more emphasized.

In the case of using the dry storage method, the spent nuclear fuel cooled to a certain extent in the temporary storage tank is transferred to a dry storage facility where the spent fuel is sealed in a thick container made of metal or concrete, covered with a shield such as concrete, and cooled with air. After that, it is stored for 40 to 60 years in a dry storage facility until heat and radioactivity naturally fall to some extent, and then it is buried in the ground or moved to a facility for reprocessing.

Therefore, after sealing the spent fuel in a thick container made of metal or concrete, the state of the spent fuel cannot be determined until the container is dismantled. Therefore, a method to determine the state of the spent fuel before sealing is emerging. It became.

Korean Patent Registration No. 10-0977290 was devised for this purpose.

This prior patent discloses a radiation measuring sensor configured by integrally combining a neutron measuring sensor and a gamma ray measuring sensor that generate visible light by reacting with neutrons and gamma rays emitted from spent nuclear fuel, respectively; a pair of cables made of optical fibers and connected to the neutron measuring sensor and the gamma ray measuring sensor to respectively transmit visible light generated by the neutron measuring sensor and the gamma ray measuring sensor; a photoelectric converter for converting visible light transmitted through the pair of cables into electrical signals corresponding to the size of the visible light; and based on the electrical signal converted by the photoelectric converter, a dose ratio between neutrons and gamma rays emitted from the spent nuclear fuel is calculated, and the calculated dose ratio between neutrons and gamma rays is calculated and emitted from the spent nuclear fuel without defects. A microprocessor for determining whether or not the spent nuclear fuel is defective or the location of the defect by comparing the dose ratio of neutrons and gamma rays to be used. It is possible to prevent additional defects in the spent nuclear fuel, and to prevent workers who handle it from being exposed to radioactive materials, and to use it through the dose ratio calculated by simultaneously measuring gamma rays and neutrons emitted from the spent nuclear fuel. Since the spent nuclear fuel is defective and the location of the defect is determined, more accurate determination results can be obtained, and since the size of the sensor that measures gamma rays and neutrons is small, after inspecting the surface of the spent nuclear fuel, it is possible to determine whether or not a defect has occurred. In this case, the sensor can be inserted into the spent nuclear fuel to determine the defect more accurately.

However, there is a problem that the prior patents are still insufficient to intuitively grasp the abnormal state of spent nuclear fuel.

1. Korean Patent Registration No. 10-0977290 "Spent Nuclear Fuel Defect Determination Apparatus and Method for Defect Determination Using the Same" (registration date: 2010.08.16.)

Therefore, an object of the present invention has been made to solve the above problems, and by constructing an image of the spent fuel using neutrons emitted from the spent fuel, the use of which can intuitively grasp the abnormal state of the spent fuel. It is intended to provide a neutron distribution imaging system and method for post-nuclear fuel.

A neutron distribution imaging system for spent nuclear fuel according to the present invention includes a plurality of He-4 detectors for detecting neutrons emitted from spent nuclear fuel and generating a neutron counter value and a TTL pulse signal; a He-4 detector control module for detecting neutrons generated from the nuclear fuel for each angle by controlling the operation and position of the plurality of He-4 detectors; Connected to the He-4 detector and the He-4 detector control module, the control signal of the He-4 detector control module is converted and transmitted to the He-4 detector, and the neutron counter value of the He-4 detector is converted into the He-4 detector control module. 4 signal converter to deliver to the detector control module; Is connected to the He-4 detector, obtains an accumulated neutron count value through the plurality of TTL pulse signals received from the He-4 detector, and transmits the acquired accumulated neutron count value to an image processing unit signal processing unit; and forming a sinogram by mapping the accumulated neutron count value transmitted from the signal processing unit with respect to an angle, and integrating the formed sinogram with respect to a total radius of rotation to obtain the spent nuclear fuel An image processing unit for imaging the neutron distribution, wherein the signal processing unit receives the plurality of TTL pulse signals in which a fast neutron pulse signal and a thermal neutron pulse signal are mixed and generates a reference clock generated by a reference clock generator 654. a signal check module for detecting a rising edge and a falling edge of the TTL pulse signal based on the basis; a counter counting the number of rising edges of a reference clock between a rising edge and a falling edge of the TTL pulse signal; a comparator that compares the count value of the counter with a preset reference value; When the count value of the counter is smaller than the reference value, the TTL pulse signal is classified as a fast neutron pulse signal, and when the count value of the counter is greater than the reference value, the TTL pulse signal is classified as a thermal neutron pulse signal It includes; pulse signal classification unit to classify into.

In addition, the method for imaging the neutron distribution of the spent fuel according to the present invention images the neutron distribution of the spent fuel through a plurality of TTL pulse signals in which fast and thermal neutron pulse signals output from the He-4 detector are mixed. A neutron distribution imaging method of receiving the plurality of TTL pulse signals, based on a reference clock generated by a reference clock generator, a rising edge and a falling edge of the TTL pulse signal to a signal check module detecting by; counting the number of rising edges of a reference clock between a rising edge and a falling edge of the TTL pulse signal by a counter; comparing the count value of the counter with a preset reference value by a comparator; When the count value of the counter is smaller than the reference value, the pulse signal classification unit classifies the TTL pulse signal into a fast neutron pulse signal, and when the count value of the counter is greater than the reference value, the pulse signal classifying the TTL pulse signal into a thermal neutron pulse signal by a classification unit; accumulating the fast and thermal neutron counts; forming a sinogram by mapping the accumulated count values to angles; and imaging the neutron distribution of the spent nuclear fuel by integrating the formed sinogram with respect to the total radius of rotation.

As described above, the system and method for imaging the neutron distribution of spent nuclear fuel according to the present invention has the advantage of being able to construct an image by processing data of the spent fuel.

In addition, there is an advantage in that the abnormal state of the spent nuclear fuel can be intuitively confirmed by the constructed image.

In addition, there is an advantage that it can be used for soundness evaluation and soundness inspection of spent nuclear fuel.

1 is a cross-sectional view of the internal structure of a dry storage vessel used in a neutron distribution imaging system for spent nuclear fuel according to the present invention.
2 is an exemplary diagram of a He-4 detector for detecting the dry storage container of FIG. 1 and spent nuclear fuel stored therein;
3a and 3b are perspective views and enlarged views of the He-4 detector of FIG. 2;
4 is an exemplary view of dedicated control software for the He-4 detector of FIG. 3;
5 is an exemplary view of a TTL pulse signal output from the He-4 detector of FIG. 2;
6 is a schematic configuration block diagram of a neutron distribution imaging system for spent nuclear fuel according to the present invention.
7 is a block diagram of the FPGA of FIG. 6;
8 is an example of signal processing by the FPGA of FIG. 6;
9A and 9B are projection views and sinogram transformation examples of spent nuclear fuel;
10 is an exemplary view of an image constructed by a neutron distribution imaging system for spent nuclear fuel according to the present invention.
11 is a flowchart of a method for imaging a neutron distribution of spent nuclear fuel according to the present invention.

Hereinafter, a neutron distribution imaging system and method of spent nuclear fuel according to the present invention will be described in more detail through detailed descriptions of embodiments with reference to the drawings.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, it should be understood that this is not intended to limit the present invention to specific embodiments, and includes all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. Terms are only used to distinguish one component from another.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

The invention can be presented as functional block structures and various processing steps. These functional blocks may be implemented with any number of hardware or/and software components that perform specific functions. For example, the present invention relates to integrated circuit components, such as memory, processing, logic, look-up tables, etc., that can perform various functions by means of the control of one or more microprocessors or other control devices. can be hired Similar to components of the present invention that may be implemented as software programming or software elements, the present invention may include various algorithms implemented as data structures, processes, routines, or combinations of other programming constructs, such as C, C++ , Java (Java), can be implemented in a programming or scripting language such as assembler (assembler). Functional aspects may be implemented in an algorithm running on one or more processors. In addition, the present invention may employ conventional techniques for electronic environment setting, signal processing, and/or data processing. Terms such as mechanism, element, means, and configuration may be used broadly and are not limited to mechanical and physical configurations. The term may include a meaning of a series of software routines in association with a processor or the like.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in the description with reference to the accompanying drawings, the same or corresponding components are assigned the same reference numerals, and overlapping descriptions thereof will be omitted. do.

1 is a cross-sectional view of the internal structure of a dry storage container used in a neutron distribution imaging system for spent nuclear fuel according to the present invention, and FIG. 2 is a dry storage container of FIG. 1 and a He-4 detector for detecting spent fuel stored therein. 3A and 3B are a perspective view and an enlarged view of the main part of the He-4 detector of FIG. 2, FIG. 4 is an example of dedicated control software for the He-4 detector of FIG. 3, and FIG. 5 is an example of the He-4 detector of FIG. 6 is a schematic configuration block diagram of a neutron distribution imaging system for spent nuclear fuel according to the present invention, FIG. 7 is a configuration block diagram of the FPGA of FIG. 6, and FIG. FIG. 6 is an example of signal processing by FPGA, FIGS. 9a and 9b are examples of projection and sinogram conversion of spent fuel, and FIG. 10 is a diagram of a neutron distribution imaging system for spent fuel according to the present invention. 11 is a flowchart of a method for imaging a neutron distribution of spent nuclear fuel according to the present invention.

Now, referring to FIG. 1 , the internal structure of the dry storage container used in the neutron imaging system for spent nuclear fuel according to the present invention will be described.

As shown in FIG. 1, the internal structure of the dry storage container used in the neutron imaging system for spent nuclear fuel according to the present invention is the dry storage container 100 used in the dry storage method and the dry storage container 100 It includes a plurality of spent nuclear fuel (110).

Here, since the dry storage container 100 and the spent nuclear fuel 110 stored in the dry storage container 100 are well known, a detailed description thereof will be omitted.

Hereinafter, with reference to FIG. 2, an example of the He-4 detector for detecting the dry storage container of FIG. 1 and the spent nuclear fuel stored therein will be reviewed.

As shown in FIG. 2, the spent nuclear fuel 110 stored in the dry storage container 100 is stored in a plurality of He-4 detectors 200 (eg Arktis' 670e He-4 detector, hereinafter referred to as "He -4 detector") is used to detect it.

Here, the plurality of He-4 detectors 200 are arranged in a line outside the dry storage container 100, and are operated and operated by a control signal from the He-4 detector control module 630 (see FIG. 6) to be described later. position is controlled. In addition, the plurality of He-4 detectors 200 each have two output ports 1 and 2 (see FIG. 3B), and the output port 1 is an RS465 port and controls the He-4 detector to be transmitted to the RS465 port. The operation and position control signal from the module 630 is received, and the neutron counter value obtained from the signal processing board (not shown) built in the He-4 detector 200 operated by the received control signal is He-4. 4 is a port that transmits to the detector control module 630, and the output port 2 is an MCX port that outputs a Transistor-Transistor Logic (TTL) pulse signal in which a fast neutron pulse signal and a thermal neutron pulse signal are mixed. However, since the He-4 detector 200 is widely known, a detailed description thereof will be omitted.

Meanwhile, a plurality of TTL pulse signals output from the He-4 detector 200 are acquired using dedicated control software as shown in FIG. 4 .

Also, a plurality of TTL pulse signals sent out through the output port 2 are as shown in FIG. 5 .

Hereinafter, with reference to FIG. 6, a system for imaging a neutron distribution of spent nuclear fuel according to the present invention will be described in more detail.

As shown in FIG. 6, the neutron distribution imaging system of spent nuclear fuel according to the present invention includes a He-4 detector 200, a signal converter 620 connected to the He-4 detector 200 and a power supply 610, The He-4 detector control module 630 connected to the signal converter 620, the He-4 detector 200 and the signal processor 650 connected to the power supply 610, the signal processor 650 and the power supply 610 A connected image processing unit 670 is included.

Here, since the power supply 610 is widely known, a detailed description thereof will be omitted.

In addition, the signal converter 620 converts the control signal transmitted from the He-4 detector control module 630 to the He-4 detector 200 into a signal suitable for the He-4 detector 200 so that the He-4 detector 200 ) to control the operation and position of the He-4 detector 200 and to transfer the neutron count value from the operated He-4 detector 200 to the He-4 detector control module 630, which is widely Since it is well known, detailed descriptions are omitted.

In addition, the He-4 detector control module 630 is a means for controlling the He-4 detector 200, and since this is widely known, a detailed description thereof will be omitted.

In addition, the signal processing unit 650 is composed of a Field Programmable Gate Array (FPGA) & System on Chip (SoC), and the FPGA is a mixture of the high-speed neutron pulse signal and the thermal neutron pulse signal output from the He-4 detector 200. It receives the TTL pulse signal, classifies the received TTL pulse signal into count signals corresponding to fast neutrons and thermal neutrons, accumulates them, generates accumulated count values, and transmits the generated accumulated count values to the SoC. The SoC converts the format of the accumulated count value transmitted from the FPGA and transmits the converted count value to the image processing unit 670 .

In addition, the signal processing unit 650 includes a storage unit 660 for storing accumulated count values, and DRAM is generally used as the storage unit 660 .

In addition, the image processing unit 670 rotates the He-4 detector 200 by 360 ° and projects the spent nuclear fuel 110 at a constant angle, respectively, and maps the converted count value to an angle to obtain a sinogram ( Sinogram) is formed, and by integrating the formed sinogram with respect to the total radius of rotation, an image (see FIG. 10) of the neutron distribution of the spent nuclear fuel 110 is generated.

Meanwhile, the power supply 610, the signal converter 620, the He-4 detector control module 630, the signal processing unit 650, and the image processing unit 670 are collectively referred to as a DAQ board (Data Acquisition Board).

Now, with reference to FIGS. 7 and 8 , the configuration and signal processing of the signal processing unit according to the present invention will be described in more detail.

7 and 8, the signal processing unit 650 according to the present invention includes a signal check module 651, a counter 652, a flip-flop 653, a reference clock generator 654, and a comparator 655. , a pulse signal classification unit 656, a high-speed counter 657, and a column counter 658.

Here, the signal check module 651 is connected to the He-4 detector 200, receives the TTL pulse signal in which the fast neutron pulse signal and the thermal neutron pulse signal output from the He-4 detector 200 are mixed, and receives Rising edge and TTL at which the TTL pulse signal of the He-4 detector 200 changes from “0” to “1” based on the TTL pulse signal generated by the reference clock generator 654 A falling edge is detected when the pulse signal changes from “1” to “0”.

In addition, the counter 652 starts counting the number of rising edges of the reference clock that rises after the signal check module 651 detects the rising edge of the TTL pulse, and the signal check module 651 determines the number of rising edges of the TTL pulse signal It stops counting when it detects a falling edge. That is, the counter 652 counts the number of rising edges of the reference clock between the rising edge and the falling edge of the TTL pulse signal.

In addition, the flip-flop 653 temporarily stores the counted number of rising edges of the reference clock as a count value until the counter 652 stops counting.

Also, the comparator 655 compares the count value temporarily stored in the flip-flop 653 with a preset reference value.

In addition, the pulse signal classification unit 656 classifies the TTL pulse signal as a fast neutron pulse signal when the temporarily stored count value of the counter 652 is smaller than the reference value, and the temporarily stored count value of the counter When greater than the reference value, the TTL pulse signal is classified as a thermal neutron pulse signal.

In addition, the high-speed counter 657 counts the number of high-speed neutron pulse signals classified through the pulse signal classification unit 656, and temporarily stores the count value of the counted high-speed neutron pulse signals in a high-speed flip-flop (not shown) do.

In addition, the thermal counter 657 counts the number of thermal neutron pulse signals classified through the pulse signal classification unit 656, and temporarily stores the count value of the counted thermal neutron pulse signals in a thermal flip-flop (not shown) do.

On the other hand, by repeatedly working for a preset time in this way, the fast neutron count value and thermal neutron count value for the TTL pulse signal are accumulated, and the accumulated fast neutron count value and thermal neutron count value are stored in the storage unit 660.

In addition, the accumulated fast neutron count value and thermal neutron count value stored in the storage unit 660 of the signal processing unit 650 are fetched and read, and converted into count values suitable for the Windows protocol through dedicated control software LINUX.

Hereinafter, with reference to FIGS. 9A and 9B , an example of an image configuration by a system for imaging a neutron distribution of spent nuclear fuel according to the present invention will be described.

9A is a count value obtained by controlling the position of the He-4 detector 200 by the He-4 detector control module 630, rotating 360 ° for each angle, and projecting the spent nuclear fuel 110 at a set angle, respectively. , and FIG. 9B shows an example of a sinogram formed by mapping the acquired count values to angles.

Meanwhile, an image generated by imaging the neutron distribution of the spent nuclear fuel 110 by integrating the formed sinogram with respect to the total radius of rotation is shown in FIG. 10 .

Hereinafter, with reference to FIG. 11, a method for imaging a neutron distribution of spent nuclear fuel according to the present invention will be described in more detail.

As shown in FIG. 11, the method for imaging the neutron distribution of spent nuclear fuel according to the present invention uses a plurality of TTL pulse signals in which fast and thermal neutron pulse signals output from the He-4 detector 200 are mixed, A neutron distribution imaging method of spent nuclear fuel for imaging the neutron distribution of

In step S1110, a plurality of TTL pulse signals are received and based on the reference clock generated by the reference clock generator 654, a rising edge and a falling edge of the TTL pulse signal are determined by the signal check module ( 651) is detected. Here, the rising edge is when the TTL pulse signal changes from “0” to “1”, and the falling edge is when the TTL pulse signal changes from “1” to “0”.

In step S1120, after the signal check module 651 detects the rising edge of each of the TTL pulse signals, the counter 652 starts counting the number of rising edges of the reference clock. Here, when the signal check module 651 detects a falling edge at which the TTL pulse signal of the He-4 detector 200 changes from “1” to “0”, the counter 652 stops counting. That is, the number of rising edges of the reference clock between the rising edge and the falling edge of the TTL pulse signal is counted by the counter 652 .

In step S1130, the number of rising edges of the reference clock counted until the counter 652 stops counting is compared with a preset reference value by the comparator 655. Here, the number of rising edges of the reference clock counted until the counter 652 stops counting is temporarily stored in the flip-flop 653 as a count value.

In step S1140, based on the result compared by the comparator 655, when the count value of the counter 652 is smaller than the reference value, the TTL pulse signal is converted into a high-speed neutron pulse by the pulse signal classification unit 658. When the count value of the counter 652 is greater than the reference value, the TTL pulse signal is classified as a thermal neutron pulse signal by the pulse signal classification unit 658. Here, the number of high-speed neutron pulse signals classified through the pulse signal classification unit 656 is counted by the high-speed counter 657, the count value of the counted high-speed neutron pulse signal is temporarily stored in a high-speed flip-flop, and the pulse signal The number of thermal neutron pulse signals classified through the classification unit 656 is counted by the thermal counter 658, and the count value of the counted thermal neutron pulse signals is temporarily stored in the thermal flip-flop.

In step S1150, steps S1110 to S1140 are repeatedly performed to accumulate the added fast and thermal neutron count values.

In step S1160, a sinogram is formed by mapping the accumulated count values with respect to angles.

In step S1170, the formed sinogram is integrated with respect to the total radius of rotation to generate an image of the neutron distribution of the spent nuclear fuel 110. Here, the imaged image is formed by applying an Inverse Radon Transform or Filtered Back Projection image construction algorithm to the formed sinogram. In addition, the Inverse Radon Transform or Filtered Back Projection image construction algorithm is implemented in Matlab (Matrix Laboratory) or C++ coding.

Meanwhile, the present invention can be implemented as computer readable codes on a computer readable recording medium. A computer-readable recording medium includes all types of recording devices in which data readable by a computer system is stored.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, etc., and implementation in the form of a carrier wave (for example, transmission over the Internet) include In addition, the computer-readable recording medium may be distributed to computer systems connected through a network, so that computer-readable codes may be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the technical field to which the present invention belongs.

As described above, the neutron distribution imaging system and method of the spent nuclear fuel according to the present invention can be configured as an image by processing data of the spent fuel. In addition, it is possible to intuitively check the abnormal state of the spent nuclear fuel by the configured image. In addition, it can be used for soundness evaluation and soundness inspection of spent nuclear fuel.

As described above, the present invention has been described based on preferred embodiments, but these embodiments are intended to illustrate rather than limit the present invention. Various changes or alterations or adjustments to the examples will be possible. Therefore, the protection scope of the present invention should be construed as including all examples of changes, changes, or adjustments belonging to the gist of the technical idea of the present invention.

100: dry storage container 200: He-4 detector
610: power supply 620: signal converter
630: He-4 detector control module 650: signal processing unit
651: signal check module 652: counter
653: flip-flop 654: reference clock generator
655: comparator 656: pulse signal classification unit
657 High-speed counter 658 Thermal counter
660: storage unit 670: image processing unit

Claims (8)

As a neutron distribution imaging system for spent nuclear fuel,
a plurality of He-4 detectors 200 that detect neutrons emitted from spent nuclear fuel and generate a neutron counter value and a TTL pulse signal;
a He-4 detector control module 630 for detecting neutrons generated from the nuclear fuel for each angle by controlling the operation and position of the plurality of He-4 detectors 200;
Connected to the He-4 detector and the He-4 detector control module, the control signal of the He-4 detector control module is converted and transmitted to the He-4 detector, and the neutron counter value of the He-4 detector is converted into the He-4 detector control module. 4 Signal converter 620 to deliver to the detector control module;
Connected to the He-4 detector 200, obtaining an accumulated neutron count value through the plurality of TTL pulse signals received from the He-4 detector 200, and the obtained accumulated neutron count value a signal processing unit 650 that transmits to the image processing unit 670; and
A sinogram is formed by mapping the accumulated neutron count value transmitted from the signal processing unit with respect to an angle, and the formed sinogram is integrated with respect to a total radius of rotation to obtain neutrons of the spent nuclear fuel Including; image processing unit for imaging the distribution;
The signal processing unit 650,
A rising edge and a falling edge of the TTL pulse signal based on the reference clock generated by the reference clock generator 654 by receiving the plurality of TTL pulse signals in which the fast neutron pulse signal and the thermal neutron pulse signal are mixed a signal check module 651 that detects a falling edge;
a counter 652 counting the number of rising edges of a reference clock between a rising edge and a falling edge of the TTL pulse signal;
a comparator 655 for comparing the count value of the counter 652 with a preset reference value;
When the count value of the counter 652 is smaller than the reference value, the TTL pulse signal is classified as a fast neutron pulse signal, and when the count value of the counter 652 is greater than the reference value, the TTL pulse signal A neutron distribution imaging system for spent nuclear fuel comprising a pulse signal classification unit 658 for classifying a signal into a thermal neutron pulse signal.
delete The method of claim 1,
A flip-flop 653 counts the number of rising edges of the reference clock until the counter 652 stops counting and temporarily stores the number as a count value;
The neutron distribution imaging system of the spent nuclear fuel in which the count value temporarily stored in the flip-flop 653 is compared with the preset reference value.
The method of claim 1,
The He-4 detector control module 630 controls the positions of the plurality of He-4 detectors 200 to rotate the plurality of He-4 detectors 200 for each angle.
A neutron distribution imaging method of spent nuclear fuel for imaging the neutron distribution of the spent nuclear fuel through a plurality of TTL pulse signals in which fast and thermal neutron pulse signals output from the He-4 detector 200 are mixed,
The plurality of TTL pulse signals are received and based on the reference clock generated by the reference clock generator 654, a rising edge and a falling edge of the TTL pulse signal are determined by the signal check module 651 Detecting (S1110);
counting the number of rising edges of the reference clock between the rising and falling edges of the TTL pulse signal by a counter 652 (S1120);
comparing the count value of the counter 652 with a reference value preset by the comparator 655 (S1130);
When the count value of the counter 652 is smaller than the reference value, the TTL pulse signal is classified as a fast neutron pulse signal by the pulse signal classification unit 658, and the count value of the counter 652 is the reference value If it is greater than , classifying the TTL pulse signal into a thermal neutron pulse signal by the pulse signal classification unit 658 (S1140);
Steps S1110 to S1140 are repeatedly performed to accumulate fast and thermal neutron count values (S1150);
forming a sinogram by mapping the accumulated count values with respect to angles (S1160); and
Imaging the neutron distribution of the spent nuclear fuel by integrating the formed sinogram with respect to the total radius of rotation (S1170).
The method of claim 5,
In step S1120, the number of rising edges of the reference clock is counted by the counter 652 in association with the rising edge of the reference clock, and polling of the plurality of TTL pulse signals by the signal check module 651 A method for imaging the neutron distribution of spent nuclear fuel in which the count is stopped when an edge is detected. The method of claim 5,
In the step S1170, the neutron distribution of the imaged spent nuclear fuel is formed by applying an Inverse Radon Transform or Filtered Back Projection image construction algorithm to the formed sinogram.
The method of claim 7,
The Inverse Radon Transform or Filtered Back Projection image composition algorithm is a neutron distribution imaging method of spent nuclear fuel implemented by Matlab (Matrix Laboratory) or C++ coding.

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