KR102394944B1 - Apparatus for measuring and amending activity concentration density of radioactive material and operation calibration methode thereof - Google Patents

Abstract

In regard to a method of operating a nuclide analysis system for radioactive substances in accordance with the present disclosure, the nuclide analysis system includes a detector module including a collimator and a scintillator-based detector, a detector driving module driving the detector module, a search platform housing a container to be measured, and a search platform driver driving the search platform. The method includes the steps of: in regard to a calibration for determining an effective view of the detector module and a segmentation of the container to be measured, performing a method of adjusting the effective view of the detector module based on a position of the collimator with respect to the detector and a first calibration for determining the segmentation of the container to be measured by determining a position of the detector module with respect to the container to be measured on the search platform based on the detector driving module and the search platform driver; performing a second calibration for calibrating an electric output signal and radiation measurement information of the detector module; and performing a third calibration for calculating an efficiency curve by container and density of contents by using a relational expression between a simulation and an actual measurement so as to calculate an efficiency curve by container and density of contents for quantitative analysis on a nuclide concentration. The present invention can save cost and time for calibration required always.

Description

Apparatus for measuring radionuclide concentration of radioactive materials and calibration method of the apparatus

The present disclosure relates to the correction of a system essential for the effective operation of a nuclide concentration analysis equipment for a large-capacity structured and unstructured packaging container in the treatment of a large amount of waste generated during the decommissioning process of a nuclear power plant. More specifically, the present disclosure provides 1. A method for determining the effective field of view (UFOV) of a detector that maximizes the detection efficiency of a nuclide analysis system, 2. A method for calibrating a nuclide analysis system, and 3. Obtaining an efficiency curve according to the density of the container and contents to be measured. it's about how

In the treatment of radioactive decommissioning waste generated during the nuclear power plant decommissioning process, it is classified by radiation level according to the regulatory guidelines and acceptance criteria, and packaged, transported, and disposed of. /Acceptance standards are regulated to satisfy general requirements such as nuclide and concentration analysis, size/weight, solidification requirements, and physical/chemical properties.

In particular, since the classification of nuclide and analysis of the concentration of nuclides becomes the standard for classification and self-disposal by level of decommissioned waste, accurate measurement and analysis are very important.

In Korea, up to now, 200 liters or 320 liters of standard drum containers have been used as standard for packaging containers for radioactive waste. The facility, such as the Nuclear Environment Corporation, has been built and operated very well.

However, the waste generated during the dismantling of nuclear power plants contains a large amount of concrete, soil, and metals, and depending on the characteristics of the large quantity, the 200-liter or 320-liter drum container used as the current standard has problems in terms of efficiency/economical use. will do Therefore, in general, packaging containers of various sizes and uses are used for the treatment of decommissioning wastes, and they are sometimes extended to the size of ISO containers. Therefore, a dedicated nuclide analysis system for measuring such a large-capacity container is constructed and used.

(1) Ortec Inc., Auras 3000, Free Release Waste Assay Counter, www.ortec-online.com. (2) Mirrion Technologies. WM2500, Modular Gamma Box and Container Counter. www. Canberra.com 2008. (3) Twomey, Timothy R., et al. "Radiological Performance of an Automated HPGe Assay System for Bulk Containers of Decommissioning Waste Intended for Free Release." INMM 51th Annual Meeting, Baltimore, MD. 2010. (4) Young, Brian M., Stephen Croft, and Hank Zhu. "The Influence of Source and Matrix Nonuniformity on the TMU and Bias of Large Container Gamma-Ray Assay Results." Proceedings of 47th Annual Meeting of the INMM (Institute of Nuclear Materials Management). 2006. (5) ORTEC software manual, “GammaVision®, Gamma-Ray Spectrum Analysis and MCA Emulator for Microsoft® Windows® 7, 8.1, and 10 Professional”, USA. International Organization for Standardization (2010) ISO 11929 determination of the characterisctic limit for measurement of ionizaing radiation-fundamentals and application, Geneva.

The present disclosure discloses a method for maximizing detection efficiency of a system through adjustment of an effective field of view of a detector, a method for calibrating the system, and a method for calculating an efficiency curve according to the density of contents.

In the method of operating a nuclide analysis system for a radioactive material according to an embodiment of the present disclosure, the nuclide analysis system comprises a detector module including a collimator and a scintillator-based detector, a detector driving module for driving the detector module, and a container to be measured In the calibration for determining the effective field of view of the detector module and the segmentation of the container to be measured, comprising: a search table for accommodating and a search bar driving device for driving the search bar A method of adjusting an effective field of view and performing a first correction for determining the segmentation of the measurement target container by determining the position of the detector module with respect to the measurement target container on the search target based on the detector driving module and the scanning device driving device; Performing the second correction to match the electrical output signal of the detector module with the radiation measurement information, and using the relationship between simulation and actual measurement to calculate the efficiency curve for each container and each density of the contents for quantitative analysis of nuclide concentration and performing a third correction for calculating the efficiency curve for each container and each density of the contents.

The step of performing the first calibration of the operating method of the nuclide analysis system according to an embodiment of the present disclosure includes determining an effective field of view of an optimal detector module that maximizes sensitivity and minimizes uniformity in the design of a collimator, measuring obtaining a minimum detection activity (MDA) according to a predetermined position of the detector module with respect to the target container; and determining the number of segments of the container to be measured for which the MDA is the minimum.

The step of determining the effective field of view of the detector module of the operating method of the nuclide analysis system according to an embodiment of the present disclosure is the step of determining the sensitivity by the following equation, sensitivity = Am/A0, where Am is the radiation detected by the detector module and A0 is the total amount of radiation generated from the container to be measured, and the uniformity is obtained by the following equation,

Here, max and min are the maximum and minimum of the radiation signal (activity) measured by the detector module in the measurement target container.

In the step of determining the number of segments of the measurement target container of the operating method of the nuclide analysis system according to an embodiment of the present disclosure, the detector driving module includes a plurality of presets of the detector module for the measurement target container based on the search stand driving device. determining a predetermined position; and determining the number of segmentations for which an MDA is minimized for a plurality of predetermined positions.

The calculation method of the MDA of the operating method of the nuclide analysis system according to an embodiment of the present disclosure uses the following formula defined in ISO,

은 관심 피크의 분기이고, t는 측정시간이며,

은 에너지 피크 효율이고, B 는 background 방사선량이고, background 방사선량은 측정대상 용기의 내부의 면적 및 측정대상 용기의 외부의 면적의 비율을 고려한다.

is the branch of the peak of interest, t is the measurement time,

is the energy peak efficiency, B is the background radiation dose, and the background radiation dose considers the ratio of the area inside the container to be measured and the area outside the container to be measured.

The step of performing the second correction for matching the electrical output signal of the detector module and the radiation measurement information of the operating method of the nuclide analysis system according to an embodiment of the present disclosure is to perform a measurement target container of a predetermined volume containing a radioactive material 24 dividing by the calibration volumes of , the detector generating an electrical output signal for one of the calibration volumes, obtaining third radiation measurement information stored in advance for one of the calibration volumes, and the electrical output signal to obtain a formula for converting ? into third radiation measurement information, wherein one correction volume among the correction volumes is divided into eight unit correction volumes, and a correction source is located at the center of gravity of each of the unit correction volumes, In the unit correction volume, the portion other than the correction source is filled with air, the electrical output signal and the third radiation measurement information are energy-specific efficiency, and the efficiency is the radiation dose collected from the detector/total dose of the correction source.

The calibration source of the method of operation of the nuclide analysis system according to an embodiment of the present disclosure is Am-241, Cd-109, Co-57, Ce-139, Sn-113, Cs-137, Co-60 and Y as CRM sources. -88 includes crew members.

The step of performing the third correction of the operating method of the nuclide analysis system according to an embodiment of the present disclosure is to calculate a correction factor between the simulation (Simul) and the actual measurement (Exp) in a state in which the medium of the measurement target container is filled with air. obtaining an efficiency curve that is a simulation result by performing a simulation while changing the density of the medium of the container to be measured, and correcting an efficiency curve that is a simulation result based on a correction factor to obtain a measured efficiency curve for each density of the medium including the steps of

In addition, the program for implementing the operating method of the nuclide analysis system as described above may be recorded in a computer-readable recording medium.

1) Method of maximizing the detection efficiency of a radionuclide analysis system by adjusting the effective field of view of the detector

According to the effective field of view determined using the method defined in the present disclosure, a total of 24 segmentations are made for a container of 1x1x3 m3, which is a commercial system (non-patent literature (non-patent literature) It shows the effect of improving MDA than 1) and (2)).

2) Calibration method of the nuclide analysis system

When the system calibration method proposed in the present disclosure is used, the amount of radiation source required when performing the calibration method for a relatively large volume is reduced, and the time taken for calibration is shortened, thereby saving cost and time for always required calibration. have an effect

3) How to calculate the efficiency curve according to the density of the contents

By linking the experimental method and the Monte carlo simulation method to calculate the efficiency curve for each energy band according to the density, it is possible to predict the efficiency curve that is expected to be limited by the experimental method, and it has the effect of saving cost and time.

1 shows a perspective view of a nuclide analysis system according to an embodiment of the present disclosure.
2 shows a detector 22 according to an embodiment of the present disclosure.
3 is a diagram illustrating sensitivity and uniformity according to an embodiment of the present disclosure.
4 is a diagram illustrating segmentation of a measurement target container according to an embodiment of the present disclosure.
5 is a diagram illustrating a background area for each segmentation of a measurement target container according to an embodiment of the present disclosure.
6 is a diagram illustrating an experimental result according to segmentation of a measurement target container according to an embodiment of the present disclosure.
7 is a view showing a container to be analyzed according to the present disclosure.
8 is a view showing a correction volume and a unit correction volume divided by the analysis target container according to the present disclosure.
9 shows a simulation result of a unit correction volume according to an embodiment of the present disclosure.
10 is a diagram illustrating an efficiency curve according to an embodiment of the present disclosure.
11 is a diagram illustrating a correction factor according to an embodiment of the present disclosure.
12 is a diagram illustrating an efficiency curve according to a medium.

Hereinafter, a preferred embodiment of the calibration method of the apparatus for measuring the nuclide concentration of a radioactive material according to the present disclosure will be described in detail based on the accompanying drawings. Advantages and features of the disclosed embodiments, and methods of achieving them, will become apparent with reference to the embodiments described below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments allow the present disclosure to be complete, and those of ordinary skill in the art to which the present disclosure pertains. It is only provided to fully inform the person of the scope of the invention.

Terms used in this specification will be briefly described, and the disclosed embodiments will be described in detail.

Terms used in this specification have been selected as currently widely used general terms as possible while considering the functions in the present disclosure, but these may vary depending on the intention or precedent of a person skilled in the art, the emergence of new technology, and the like. In addition, in a specific case, there is a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding invention. Therefore, the terms used in the present disclosure should be defined based on the meaning of the term and the contents of the present disclosure, rather than the simple name of the term.

References in the singular herein include plural expressions unless the context clearly dictates the singular. Also, the plural expression includes the singular expression unless the context clearly dictates the plural.

In the entire specification, when a part "includes" a certain element, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

Also, as used herein, the term “unit” refers to a software or hardware component, and “unit” performs certain roles. However, "part" is not meant to be limited to software or hardware. A “unit” may be configured to reside on an addressable storage medium and may be configured to refresh one or more processors. Thus, by way of example, “part” includes components such as software components, object-oriented software components, class components and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays and variables. The functionality provided within components and “parts” may be combined into a smaller number of components and “parts” or further divided into additional components and “parts”.

According to an embodiment of the present disclosure, “unit” may be implemented with a processor and a memory. The term “processor” should be interpreted broadly to include general purpose processors, central processing units (CPUs), microprocessors, digital signal processors (DSPs), controllers, microcontrollers, state machines, and the like. In some circumstances, a “processor” may refer to an application specific semiconductor (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), or the like. The term “processor” refers to a combination of processing devices, such as, for example, a combination of a DSP and a microprocessor, a combination of a plurality of microprocessors, a combination of one or more microprocessors in combination with a DSP core, or any other such configurations. may refer to.

The term “memory” should be interpreted broadly to include any electronic component capable of storing electronic information. The term memory includes random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erase-programmable read-only memory (EPROM), electrical may refer to various types of processor-readable media, such as erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, and the like. A memory is said to be in electronic communication with the processor if the processor is capable of reading information from and/or writing information to the memory. A memory integrated in the processor is in electronic communication with the processor.

Hereinafter, with reference to the accompanying drawings, embodiments will be described in detail so that those of ordinary skill in the art to which the present disclosure pertains can easily implement them. And in order to clearly describe the present disclosure in the drawings, parts not related to the description will be omitted.

Among radioactive wastes, especially in the case of decommissioning wastes, wastes generated in large quantities are packaged in large containers that can be expanded to the size of containers or containers of various sizes for other purposes. Therefore, when the decommissioning waste generated during the decommissioning of a nuclear power plant is packaged and disposed of in various sizes, a non-destructive measuring device capable of nuclide analysis and concentration analysis is used regardless of the size of the container.

1 shows a perspective view of a nuclide analysis system according to an embodiment of the present disclosure.

The nuclide analysis system 10 of the radioactive material of FIG. 1 can non-destructively perform the nuclide concentration of the radioactive material of the large container. The nuclide analysis system 10 includes a detector device 20, an inspection table device 30 including a scanning device driving device that linearly drives the container inspection table 40 in the Z-axis direction, and a container inspection table on which a container containing a radioactive material is placed. (40) may be included.

The nuclide analysis system 10 may include one detector device 20 on either side of the container inspection table 40 . That is, the nuclide analysis system 10 may include two detector devices 20 .

The detector device 20 may include a detector module 21 and a detector 22 . The container inspection table 40 may be located at an upper end of the inspection table device 30 . A container containing a radioactive material may be located on the upper end of the container inspection table 40 . 1 illustrates a case in which the detector device 20 includes only one detector module 21, but is not limited thereto. The detector device 20 may include two detector modules 21 . The two detector modules can be arranged vertically. The distance between the centers of the detectors respectively included in the two detector modules arranged vertically may be 0.4 m to 0.6 m. For example, the distance between the centers of the detectors may be 0.5 m.

The detector device 20 included in the nuclide analysis system 10 is a 1x1x3 (HxDxL) (m^3) container and a 1x1x3 (m^3) container and a detector module 21 to be suitable for concentration analysis of structured or atypical wastes other than the container. can be moved to at least one of the x, y, and z axes. The detector device 20 may move the detector module 21 in at least one of the x and y axes by using the detector driving module. That is, the detector module 21 may be movable in at least one direction of up/down (y), in/out (left and right, x), and front/rear (z). However, the present invention is not limited thereto, and the detector module 21 may move at least one of up/down or in/out, and the examination table device 30 may move the search target container forward/backward (z-axis).

For an effective description of the present disclosure, the nuclide analysis system proposed as an example in FIG. 1 will be described by limiting the analysis of the nuclide concentration to a volume of 1x1x3 m^3.

Hereinafter, a method of maximizing the detection efficiency of the nuclide analysis system 10 by adjusting the effective field of view of the detector will be described.

2 shows a detector 22 according to an embodiment of the present disclosure.

As the detector 22 of the nuclide analysis system 10, a detector using a HPGe scintillator having excellent energy resolution may be used. The detector 22 may be equipped with a collimator 23 to limit a basic effective field of view of the detector 22 . The basic effective field of view may be the field of view of the detector 22 to which the collimator 23 is not mounted. The collimator 23 may be mounted on the detector 22 to shield background radiation. In the present disclosure, a field of view of the detector 22 limited by the collimator 23 is defined as an effective field of view of the detector. In general, the collimator 23 may be made of tungsten or lead to maximize the effect of radiation shielding.

The position of the collimator 23 and the relative position of the measurement target vessel of the detector 22 may determine the effective field of view (UFOV) of the nuclide analysis system 10 . For example, if the collimator 23 advances forward with respect to the detector 22 , the viewing angle 24 of the detector 22 may be narrowed. Accordingly, the effective field of view of the nuclide analysis system 10 may be narrowed. Also, when the collimator 23 is retracted back with respect to the detector 22 , the viewing angle 24 of the detector 22 can be widened. Accordingly, the effective field of view of the nuclide analysis system 10 may be widened. In the present disclosure, the viewing angle 24 of the detector 22 determined by the position of the collimator 23 is referred to as an effective field of view of the detector.

In addition, even if the position between the collimator 23 and the detector 22 is fixed, if the detector 22 is far from the measurement target container, it is possible to detect a wide area, so the effective field of view of the nuclide analysis system 10 will be widened. can In addition, even if the position between the collimator 23 and the detector 22 is fixed, if the detector 22 is close to the measurement target container, detection is possible in a narrow area, so the effective field of view of the nuclide analysis system 10 will be narrowed. can In the present disclosure, a viewing angle determined by a position between the collimator 23 and the detector 22 may be referred to as an effective field of view of the detector. The effective field of view of the nuclide analysis system 10 may be adjusted by adjusting the relative distance between the measurement target container and the detector 22 by moving the detector module 21 in the x-axis and the y-axis.

The effective field of view of the nuclide analysis system 10 may limit the detection efficiency of the nuclide analysis system 10 . Here, the detection efficiency of the nuclide analysis system 10 may be determined by a ratio of a signal to a noise. For example, the detection efficiency may represent a ratio of a signal to a noise.

In the present disclosure, the nuclide analysis system 10 may determine an effective field of view of the nuclide analysis system 10 using the relationship between sensitivity and uniformity. That is, the relationship between sensitivity and uniformity may be a figure of merit (FOM) for determining the effective field of view (UFOV) of the nuclide analysis system 10 .

The detection efficiency of the nuclide analysis system using UFOV determined using the sensitivity and uniformity can be verified through the calculation of the minimum detection activity (MDA).

As described above, the field of view 24 of the detector 22 determined by the position of the collimator 23 is referred to as an effective field of view of the detector. According to the present disclosure, the detection efficiency of the nuclide analysis system 10 can be maximized by adjusting the effective field of view of the detector.

The detection efficiency of the nuclide analysis system 10 may be expressed as a ratio between a signal and a noise (that is, a signal-to-noise ratio; SNR). That is, the detection efficiency of the nuclide analysis system 10 may mean a ratio of the amount of radiation received in the area of the measurement target container among the radiation detected by the nuclide analysis system 10 . The detection efficiency of the nuclide analysis system 10 may mean a ratio of the amount of radiation excluding the amount of radiation received from the external region of the measurement target container among the radiation detected by the nuclide analysis system 10 . In the present disclosure, detection efficiency may have the same meaning as sensitivity.

In particular, the detection efficiency of the radiation measuring device included in the nuclide analysis system 10 can be generally expressed as MDA (minimum detectable activity) by the correlation between the measurement target radiation and the background radiation.

MDA is defined as follows.

(Equation 1)

Here, B is the background radiation dose, K is the abscissas of Gaussian distribution, and Equation 1 can be simplified as Equation 2 below.

(Equation 2)

is denoted branching of interested peak,

is denoted branching of interested peak,

t is measurement time

is energy peak efficiency(=검출기의 효율)

is energy peak efficiency (= the efficiency of the detector)

)을 결정할 수 있다. 검출기의 효율은 측정대상 용기가 발산하는 방사선 중 검출기(22)가 수신하는 방사선의 양을 의미할 수 있다. 검출기(22)의 시야각이 넓을 수록 많은 방사선을 받을 것이므로 검출기의 효율은 시야각이 넓어질 수록 커질 수 있다. 또한 많은 방사선을 받아 측정대상 용기가 발산하는 방사선에 민감하게 반응할 것이므로 본 개시에서 검출기의 효율은 민감도와 동일한 의미를 나타낼 수 있다. 민감도는 검출기가 수집하는 방사선량에 비례할 수 있다. 민감도는 Am/A0와 같이 결정될 수 있다. 여기에서 Am 은 검출기 모듈이 검출하는 방사선량이며 A0는 상기 측정대상 용기에서 발생되는 방사선 총량일 수 있다.The position between the detector 22 and the collimator 23 and the position between the detector 22 and the measurement target container may determine an area in which the detector 22 receives a signal from the measurement target container. That is, the position between the detector 22 and the collimator 23 and the position between the detector 22 and the measurement target container can determine an effective field of view (UFOV). In addition, the position between the detector 22 and the collimator 23 and the position between the detector 22 and the container to be measured are the efficiency (

) can be determined. The efficiency of the detector may mean the amount of radiation received by the detector 22 among the radiation emitted by the measurement target container. The wider the viewing angle of the detector 22, the more radiation it will receive, so the efficiency of the detector can be increased as the viewing angle is widened. In addition, since it will receive a lot of radiation and react sensitively to the radiation emitted by the measurement target container, the efficiency of the detector in the present disclosure may have the same meaning as the sensitivity. The sensitivity may be proportional to the amount of radiation the detector collects. The sensitivity may be determined as Am/A0. Here, Am may be the amount of radiation detected by the detector module, and A0 may be the total amount of radiation generated by the measurement target container.

Measurement accuracy may correspond to intrinsic uniformity (IU). If the analyte vessel is too large, the nuclide analysis system 10 cannot analyze the analyte vessel at once. Therefore, the nuclide analysis system 10 can measure the analysis target container by dividing it into a plurality of calibration volumes. It can be assumed that the radiation inside the analysis target vessel is uniformly distributed. The uniformity may indicate a degree to which a radiation signal measured for each of the plurality of correction volumes is uniform. As already described, since the radiation inside the analysis target container is assumed to be uniformly distributed, the fact that the detector 22 uniformly measured the radiation signal for all the correction volumes means that the detection accuracy of the detector 22 is high. can do.

The uniformity (IU) may be defined as in Equation 3.

(Equation 3)

Here, max and min may be the maximum and minimum of the radiation signal (activity) measured in the measurement target vessel or calibration volumes. Activity may be related to a radioactive signal or a concentration of a radioactive material. The detector 22 may measure a radiation signal for the same radioactive object several times or measure a radiation signal for several parts of the same radioactive object to obtain max and min values among them. Here, the radioactive object may be a measurement target container. The first uniformity and the second uniformity, which will be described below, may be obtained by Equation 3.

There can be a trade-off between maximizing the sensitivity corresponding to the efficiency of the detector and measuring accuracy. This is because the high efficiency of the detector means that the viewing angle is large, and the detector 22 receives a lot of radiation from the outside of the measurement target container. That is, the detector 22 measures even the radiation that is not emitted from the measurement target container.

The nuclide analysis system 10 uses sensitivity (efficiency of the detector) and uniformity (IU) to determine the effective field of view of the detector. Sensitivity (efficiency of the detector) and uniformity (IU) may be a figure of merit (FOM) for determining an effective field of view. In addition, the method of determining the effective field of view of the detector in which the FOM is optimized is used for the nuclide analysis system 10 . As already described, the effective field of view (UFOV) of the nuclide analysis system 10 may be determined by the effective field of view of the detector.

In order to set the effective field of view (UFOV) of the nuclide analysis system 10 in which the detection efficiency of the nuclide analysis system 10 is maximized, the nuclide analysis system 10 may perform the following procedure. The detection efficiency of the nuclide analysis system 10 can be achieved by minimizing the MDA.

The viewing angle 24 of the detector 22 is an angle limiting the measurement range of the detector 22 , and may be determined based on the degree of protrusion of the collimator 23 .

3 is a diagram illustrating sensitivity and uniformity according to an embodiment of the present disclosure.

The nuclide analysis system 10 may include a detector 22 having a viewing angle determined by the collimator 23 and detecting radiation using a scintillator. In addition, the nuclide analysis system 10 may include a main module for controlling the nuclide analysis system 10 .

The main module may include a processor and memory. The processor may execute instructions included in the memory.

The main module controls the collimator 23 to change the viewing angle 24 of the detector 22 from 40 degrees or more to 160 degrees or less, and calculates the efficiency (sensitivity) and uniformity (IU) of the detector. 3 shows the sensitivity and uniformity. The horizontal axis in FIG. 3 represents the viewing angle 24 of the detector 22 . The left vertical axis of FIG. 3 represents the efficiency (sensitivity) of the detector. In addition, the right vertical axis of FIG. 3 represents the uniformity of the detector.

As already described, sensitivity and uniformity may have a conflicting relationship with each other. Accordingly, it can be seen from the graph of FIG. 3 that as the viewing angle 24 increases, the sensitivity increases and the uniformity decreases. The nuclide analysis system may perform a step of determining the effective field of view of an optimal detector module that maximizes sensitivity and minimizes uniformity in the design of the collimator. The nuclide analysis system according to an embodiment of the present disclosure may use the graph of FIG. 3 to determine an effective field of view of an optimal detector module that maximizes sensitivity and minimizes uniformity.

The main module may match the sensitivity of 1.0*e^(-6) with the uniformity of 0 to obtain the graph of FIG. 3 . Also, the main module may match the sensitivity of 1.0 with the uniformity of 25 to obtain the graph of FIG. 3 . Accordingly, the main module may acquire the graph of FIG. 3 . The main module may define a field of view 24 at a point where sensitivity and uniformity meet as an effective field of view of the optimal detector module.

3 is a graph showing the sensitivity and uniformity performed for a container of 1x1x3 (m^3). Referring to FIG. 3 , the main module may determine 140 degrees as the effective field of view of the optimal detector module.

4 is a diagram illustrating segmentation of a measurement target container according to an embodiment of the present disclosure.

The main module may segment the vessel to be measured. The main module can know the size and location of the container to be measured in advance. In addition, the nuclide analysis system 10 may know the size and location of the measurement target container using the sensor. The nuclide analysis system 10 may segment the measurement target container based on the size and location of the measurement target container.

4 shows a part of the measurement target container 50 . For example, in the measurement target container 50 , only the unit volume measured by the detector module 21 at a time may be illustrated. Segmentation is a step of defining a unit volume with respect to the volume of the entire measurement target container, and the unit volume may be a basic unit measured by the detector module 21 at once. In case of various types of segmentation, follow the procedure below. In the present disclosure, three realistically possible segmentation types for the total volume of the measurement target container 50 of 1x1x1 m^3 will be described. The nuclide analysis system 10 may derive the optimal segmentation after obtaining the detection efficiency (MDA) for each of the three segmentation types.

For example, the nuclide analysis system 10 may determine the segmentation in which the MDA is minimized for each of the three segmentation types. In order to implement the segmentation of the three cases shown in FIG. 4 , the detector module may be located at a predetermined measurement position with respect to the measurement target container. The detector driving module may perform the step of determining the plurality of predetermined positions of the detector module with respect to the measurement target container based on the search table driving device. The plurality of predetermined positions may be candidate positions. The nuclide analysis system 10 may store a plurality of predetermined positions of the detector module with respect to the measurement target container for each segmentation of the three cases. The nuclide analysis system 10 may acquire the MDA according to a plurality of predetermined positions of the detector module with respect to the vessel to be measured.

The nuclide analysis system 10 may perform a step of determining the number of segmentations in which the MDA is the minimum for a plurality of predetermined positions. The nuclide analysis system 10 may select the segmentation of the measurement target container in the case where the MDA is the minimum. The nuclide analysis system 10 may determine the size of the unit volume based on the selected segmentation. In addition, the number of segments may be determined by dividing the measurement target container 50 into unit volumes.

)을 계산할 수 있다. 보다 구체적으로 검출기 모듈(21)은 한개의 검출기(22)를 포함할 수 있다. 핵종분석 시스템(10)은 case 1과 같이 검출기(22)를 측정대상 용기(50)의 양측에 하나씩 두고 검출기의 효율을 계산할 수 있다. 또한 검출기 모듈(21)은 두 개의 검출기(22)를 포함할 수 있다. 핵종분석 시스템(10)은 case 2와 같이 검출기(22)를 측정대상 용기(50)의 양측에 두개씩 두고 검출기의 효율을 계산할 수 있다. 또한 검출기 모듈(21)은 4 개의 검출기(22)를 포함할 수 있다. 핵종분석 시스템(10)은 case 3과 같이 검출기(22)를 측정대상 용기(50)의 양측에 4개씩 두고 검출기의 효율을 계산할 수 있다. 하지만 이에 한정되는 것은 아니다. 핵종분석 시스템(10)은 case 3과 같이 검출기(22)를 측정대상 용기(50)의 양측에 2개씩 두고 검출기를 z축으로 이동시키거나 측정대상 용기를 z축으로 움직이면서 검출기의 효율 및 MDA를 계산할 수 있다.As already described, the nuclide analysis system 10 may determine the effective field of view 211 of the detector. In FIG. 4 , the measurement target container 50 may be divided into unit volumes such as case 1 , case 2 , and case 3 . The unit volume may be 1x0.5x1 m^3 (case 1), 0.5x0.5x1 m^3 (case 2), and 0.5x0.5x0.5 m^3 (case 3). The unit volume of case 3 may be the same as the correction volume of the present disclosure. The nuclide analysis system 10 determines the efficiency (

) can be calculated. More specifically, the detector module 21 may include one detector 22 . The nuclide analysis system 10 may calculate the efficiency of the detector by placing the detector 22 one at each side of the measurement target container 50 as in case 1. Also, the detector module 21 may include two detectors 22 . The nuclide analysis system 10 can calculate the efficiency of the detector by placing two detectors 22 on both sides of the measurement target container 50 as in case 2 . Also, the detector module 21 may include four detectors 22 . The nuclide analysis system 10 can calculate the efficiency of the detector by placing four detectors 22 on each side of the measurement target container 50 as in case 3 . However, the present invention is not limited thereto. The nuclide analysis system 10 places two detectors 22 on both sides of the measurement target container 50 as in case 3, and moves the detector in the z-axis or moves the measurement target container in the z-axis to increase the efficiency and MDA of the detector. can be calculated

The area (red rectangle; 201) of the container to be measured that can be measured in case 1 to case 2 at once may be the same. The region 201 may have a width of 1 m and a length of 1 m. In case 1, since one detector 22 has to cover the area 201 , the detector module 21 may be far from the measurement target container 50 . In case 2, since the two detectors 22 have to cover the area 201, the distance between the detector module 21 and the measurement target container 50 may be shorter than in the case of case 1. In case 3, since the four detectors 22 have to cover the area 201, the distance between the detector module 21 and the measurement target container 50 may be shorter than in case 2, respectively. Alternatively, in case 3, since the two detectors 22 have to cover half of the area 201, the distance between the detector module 21 and the measurement target container 50 may be shorter than in case 2, respectively.

The effective field of view of the nuclide analysis system 10 by at least one detector module may be as follows. In case 1, the nuclide analysis system 10 may have an effective field of view 211 . In case 2, the nuclide analysis system 10 may have an effective field of view 212 . In case 3, the nuclide analysis system 10 may have an effective field of view 213 . The nuclide analysis system 10 may select case 3 in which the MDA is the minimum. The nuclide analysis system 10 may determine the size of the unit volume based on the selected segmentation. In addition, the number of segments may be determined by dividing the measurement target container 50 into unit volumes.

5 is a diagram illustrating segmentation of a measurement target container according to an embodiment of the present disclosure.

Referring to FIG. 5 , when calculating the MDA, the nuclide analysis system 10 may set the background (B) in Equation 1 as the background (221, 222, 223) as the radiation introduced from outside the unit volume (220). That is, the nuclide analysis system 10 may acquire the background radiation dose in consideration of the ratio of the area inside the container to be measured and the area outside the container to be measured. In addition, the ratio of the area of the backgrounds 221 , 222 , 223 to the unit volume 220 may be used as a weighting factor of the background (B). Referring to FIG. 5 , case 3 may have the smallest ratio of the areas of the backgrounds 221 , 222 , and 223 to the area of the unit volume 220 . In addition, the nuclide analysis system 10 may calculate the MDA in consideration of the background radiation dose. For example, in case 3, the background radiation dose may be obtained based on the size of the area of the unit volume 220 and the size of the area of the background 223 among the total radiation doses received by the detector module. The background radiation dose may be the total radiation dose * the size of the area of the background 223 / (the size of the area of the unit volume 220 + the size of the area of the background 223 ).

6 is a diagram illustrating an experimental result according to segmentation of a measurement target container according to an embodiment of the present disclosure.

6 is an example of calculating the MDA for each case obtained by the above procedure as a function of time. Monte Carlo simulation was performed, and the density of the medium was defined as 1.5 g/cc. As can be seen from the results, case 3 shows the optimal MDA characteristics. Therefore, the nuclide analysis system 10 can be segmented into a total of 24 units of 1x1x3 m^3 according to case 3. The nuclide analysis system 10 may segment the measurement target container 50 into a cube of 0.5x0.5x0.5 m^3. In the present disclosure, the unit volume may have the same meaning as the correction volume.

Hereinafter, the operation of the nuclide analysis system according to various embodiments of the present disclosure will be described. In the following description, the content already described with reference to FIGS. 1 to 6 is omitted, and the shortcomings below may be explained by the description of FIGS. 1 to 6 .

The main module may perform the step of performing the first correction for adjusting the position of the collimator with respect to the scintillator. In addition, the main module may perform the step of performing the second correction for matching the electrical output signal of the detector and the radiation measurement information. In addition, the main module may perform a step of performing a third correction for correcting a third efficiency curve obtained by simulation.

The first correction may be a correction for determining the effective field of view of the detector module and the segmentation of the measurement target container. The first calibration may include a method of adjusting the effective field of view of the detector module by the position of the collimator with respect to the detector. In addition, the first correction may include a method of determining the segmentation of the measurement object container by determining the position of the detector module with respect to the measurement object container of the search object based on the detector driving module and the detection platform driving device.

The main module may perform the following process to perform the first correction. The main module may control the collimator to determine the viewing angle of the detector module 21 as the first viewing angle. The main module may perform a step of acquiring the first radiation measurement information measured by the detector 22 for the measurement target container. The detector 22 may measure the measurement target container for a predetermined time.

The main module may control the collimator to determine the viewing angle of the detector module 21 as the second viewing angle. The second viewing angle may be greater than the first viewing angle. For example, the first viewing angle may be 40 degrees and the second viewing angle may be 160 degrees.

The main module may perform the step of acquiring the second radiation measurement information measured by the detector 22 for the measurement target container. The detector 22 may measure the measurement target container for a predetermined time.

The main module may perform a step of acquiring a first sensitivity and a first uniformity based on the first radiation measurement information. The main module may perform the step of acquiring the second sensitivity and the second uniformity based on the second radiation measurement information. The main module may use Equation 1 or Equation 2 to obtain the first sensitivity and the second sensitivity. Also, the main module may use Equation 3 to obtain the first uniformity and the second uniformity.

The main module may perform the step of determining an optimal field of view of the detector module of the detector based on the first sensitivity, the first uniformity, the second sensitivity, and the second uniformity. The main module may determine the effective field of view of the optimal detector module as described with reference to FIG. 3 . Briefly, the main module may perform the step of generating a coordinate plane in which the horizontal axis represents the viewing angle, the left vertical axis represents the sensitivity, and the right vertical axis represents the uniformity, as shown in FIG. 3 . The main module may perform the steps of matching a sensitivity of 1.0*e^(-6) to a uniformity of 0 and a sensitivity of 1.0 to a uniformity of 25. The main module may perform a step of displaying a sensitivity line based on the first sensitivity and the second sensitivity on the coordinate plane. The main module may perform a step of displaying a uniformity line based on the first uniformity and the second uniformity on the coordinate plane. The main module may perform a step of determining an effective field of view of the detector module that is optimal for a viewing angle at a point where the sensitivity line and the uniformity line meet.

According to another embodiment of the present disclosure, the main module may perform the following process to perform the first correction. The main module may perform a step of dividing the measurement target container 50 of a predetermined volume containing the radioactive material into the first number of correction volumes. A container of a predetermined volume may have a size of 1x1x3 m^3. The first number may be 24. The main module can divide the container to be measured into a cube with a side of 0.5m. In addition, a cube with a side of 0.5 m is divided into 8 cubes again, and a CRM source can be included in the center.

The main module may perform the step of determining the first plurality of measurement positions corresponding to the calibration volumes. For example, one of the correction volumes may be the same as the unit volume 501 of FIG. 7 . As in case 3, the main module may measure one correction volume 501 by using one of the four detectors 22 . The plurality of first measurement positions may be determined based on the size and position of the measurement target container 50 . As shown in FIG. 5 , the main module may determine the first plurality of measurement positions so that one surface of the unit volume 220 is in contact with the inside of the four radiation detection areas of the detector 22 . The first plurality of measurement positions may be 24. This is because the measurement target container 50 is divided into 24 pieces.

The main module may control the collimator to determine the viewing angle of the detector module 21 as the first viewing angle. In addition, the detector module 21 may perform the step of acquiring the first radiation measurement information measured at the plurality of first measurement positions. The detector 22 may perform measurement for a predetermined time at each of the first plurality of measurement positions.

The main module may control the collimator to determine the viewing angle of the detector module 21 as the second viewing angle. The second viewing angle may be greater than the first viewing angle. For example, the first viewing angle may be 40 degrees and the second viewing angle may be 160 degrees. The detector may perform the step of acquiring the second radiation measurement information measured at the first plurality of measurement positions. The detector 22 may perform measurement for a predetermined time at each of the first plurality of measurement positions.

The main module may perform a step of acquiring a first sensitivity and a first uniformity based on the first radiation measurement information. The main module may perform the step of acquiring the second sensitivity and the second uniformity based on the second radiation measurement information. The main module may use Equation 1 or Equation 2 to obtain the first sensitivity and the second sensitivity. Also, the main module may use Equation 3 to obtain the first uniformity and the second uniformity.

The main module may perform the step of determining an optimal field of view of the detector module of the detector based on the first sensitivity, the first uniformity, the second sensitivity, and the second uniformity. The main module may determine the effective field of view of the optimal detector module as described with reference to FIG. 3 . Briefly, in FIG. 3 , the main module displays the first sensitivity for the first viewing angle as a first point 301 on the graph and the second sensitivity for the second viewing angle as the second point 302 on the graph. can Also, the main module may draw a first line connecting the first point and the second point. Also, the main module may display the first uniformity with respect to the first viewing angle as the third point 303 on the graph. The main module may display the second uniformity with respect to the second viewing angle as a fourth point 304 on the graph. Also, the main module may draw a second line connecting the third and fourth points. The main module may determine a viewing angle of a point where the first line and the second line meet as an effective field of view of the optimal detector module.

The configuration in which the main module acquires sensitivity and uniformity with respect to the first viewing angle and the second viewing angle has been described above, but the present invention is not limited thereto. The main module may obtain a graph as shown in FIG. 3 by acquiring sensitivity and uniformity for more various viewing angles. For example, the detector may measure or simulate at least one of 40, 60, 80, 100, 120, 140, and 160 degrees to obtain a graph as shown in FIG. 3 . Also, the main module may determine an effective field of view of the optimal detector module.

Hereinafter, a calibration method of the nuclide analysis system 10 according to the present disclosure will be described.

7 is a view showing a container to be analyzed according to the present disclosure. 8 is a view showing a correction volume and a unit correction volume divided by the analysis target container according to the present disclosure.

The calibration of the nuclide analysis system 10 is a factor that converts the unit concentration (Bq/g) of radiation according to the electrical output signal of the detector 22 . In particular, the nuclide analysis system 10 proposed as an example in the present disclosure has a prerequisite that wastes of similar density are packaged. Therefore, a correction method specialized for this is proposed. Referring to FIG. 7 , the volume of the measurement target container 50 may be, for example, 1x1x3 m^3. The nuclide analysis system 10 may perform a correction on the correction volume 501 corresponding to about 1/24 of the total volume, and perform a method of magnifying the correction on the entire volume based on this correction. The nuclide analysis system 10 according to the present disclosure can minimize the effort and time required for calibration.

Calibration of the nuclide analysis system 10 is to determine the correlation between the electrical output signal of the detector 22 and the concentration of the radioactive material actually present. Using this correction value, the electrical output signal of the detector can be converted into a unit concentration (Bq/g) of the radioactive material.

Since the nuclide analysis system 10 in which the correction method of the present disclosure is used has a relatively large volume, it takes a lot of effort and time to obtain a correction value for the entire volume. Therefore, the nuclide analysis system 10 according to the present disclosure performs the best correction method according to this by using the prerequisite that the contents of a similar density are packaged during the classification and packaging of the decommissioning waste.

Taking the 1x1x3 m^3 container as an example, first, considering the symmetry of the position of the detector 22 and the segmentation unit volume compared to the total volume of the measurement target container 50, the correction volume that is about 1/24 of the total volume ( 501) can be performed and applied to the entire volume.

Referring to FIG. 8 , the correction volume 501 may be divided into eight unit correction volumes 502 again. The unit correction volume 502 may be a cube. A certified radiation material (CRM) 503 that already knows a radiation signal (activity; third radiation measurement information) may be positioned in the center of the unit correction volume 502 . After measuring the signal of each detector 22, it is possible to predict the radiation concentration compared to the signal by using the correlation thereof.

The nuclide analysis system 10 may perform Monte Carlo simulation in order to check whether the calibration method by the 8-compartment method using the calibration volume 501 as the unit calibration volume 502 can be a sample representing the whole.

The sample used at this time is a CRM (certified radiation material) source and contains the radioactive material defined in Table 1 below. The nuclide analysis system 10 may secure a sample capable of calculating the correction factor for the entire energy band by one measurement using the CRM source.

The table below defines the energy band according to the isotope included in the CRM source. CRM sources may include Am-241, Cd-109, Co-57, Ce-139, Sn-113, Cs-137, Co-60 and Y-88.

Table 1. Isotopes and Energy Domains Included in CRM Sources

In the calibration of the nuclide analysis system 10, especially in the case of decommissioning waste, since it is possible to uniformly distribute the waste of a similar density, it is actively used to correct the partial volume, not the whole volume, and then expand it to the entire volume Interpretation methods can be effective.

Referring to FIGS. 7 and 8 , the nuclide analysis system 100 may select a volume for performing calibration. More specifically, the correction volume 501 corresponding to 1/24 of the total area may be selected based on the segmentation described with reference to FIGS. 4 and 5 .

The nuclide analysis system 10 may perform the following process in order to calibrate the calibration volume. The nuclide analysis system 10 may perform segmentation on the calibration volume 501 to obtain the final eight unit calibration volumes 502 . A CRM source may be located in the center of each unit correction volume 502 . In this case, the medium of the correction volume 501 may be set as the first material. The first material may be, for example, air.

In order to determine whether the eight unit correction volumes 502 are appropriate, a simulation is performed for the case where the CRM source is uniformly distributed throughout the correction volume 501, and the eight unit correction volumes with the CRM source in the center are performed. Decide whether you can represent the whole.

9 shows a simulation result of a unit correction volume according to an embodiment of the present disclosure.

The horizontal axis of FIG. 9 may be the value of energy, and the vertical axis may be the efficiency of the detector. A blue line in FIG. 9 represents a simulation result for a case in which the CRM source is uniformly distributed throughout the correction volume 501 . The red line in FIG. 9 is a simulation result for a case where the CRM source is located in the center of each of the eight unit correction volumes 502 . Referring to FIG. 9 , it can be seen that the detector efficiencies are similar in both cases. That is, it can be seen that there is no problem at all even if the correction is performed using the case where the CRM source is located in the center of each of the unit correction volumes 502 .

According to various embodiments of the present disclosure, the nuclide analysis system 10 may perform the following process. In the description below, the content already described with reference to FIGS. 1 to 9 is omitted, and deficiencies in the description below may be explained by the description of FIGS. 1 to 9 .

The second calibration may include a method of matching the electrical output signal of the detector module with the radiation measurement information.

The step of the main module performing the second correction according to an embodiment of the present disclosure may include the following process. The main module may perform the step of dividing the measurement target container of a predetermined volume containing the radioactive material into the first number of calibration volumes. The first number may be 24. If the measurement target container has a size of 1x1x3 m^3, the correction volumes may have a size of 0.5x0.5x0.5 m^3. The main module may perform the step of determining the first plurality of measurement positions corresponding to the calibration volumes. The measurement position may be a position where one detector module 21 can acquire radiation measurement information for a correction volume having a size of 0.5x0.5x0.5 m^3 as in case 3 of FIG. 4 .

For example, the detector device 20 may include two detector modules 21 . The two detector modules can be arranged vertically. The distance between the centers of the detectors respectively included in the two detector modules arranged vertically may be 0.5 m. The nuclide analysis system 10 may include one detector device 20 on either side of the container inspection table 40 . That is, the nuclide analysis system 10 may include two detector devices 20 and may include four detector modules 21 . Referring to case 3 of FIG. 4 and FIG. 7 , one detector module 21 may acquire radiation measurement information for a correction volume having a size of 0.5x0.5x0.5 m^3. Accordingly, the radionuclide analysis system 10 including the four detector modules 21 may simultaneously acquire radiation measurement information for four calibration volumes at one measurement location. The radionuclide analysis system 10 may simultaneously acquire radiation measurement information for four calibration volumes again after moving the measurement target vessel by 0.5 m along the z-axis. The nuclide analysis system 10 may move the measurement target container in the z-axis by 0.5 m 6 times to acquire radiation measurement information for the entire measurement target container having a size of 1x1x3 m^3.

However, as already described, it may be inefficient to obtain radiation measurement information for the entire volume and perform the second correction. Accordingly, the main module may perform the step of controlling the detector to generate an electrical output signal for one of the calibration volumes. That is, the nuclide analysis system 10 may perform the step of generating an electrical output signal for one of the calibration volumes at one of the first plurality of measurement positions by the detector having the effective field of view of the optimal detector module. The main module may perform the step of acquiring the third radiation measurement information stored in advance for one of the calibration volumes. The electrical output signal and the third radiation measurement information are energy-specific efficiency, and the efficiency may be the radiation dose collected by the detector/total dose of the corrected radiation source. The main module may perform a step of matching the electrical output signal with the third radiation measurement information. More specifically, the nuclide analysis system 10 may perform the step of obtaining a formula for converting the electrical output signal into the third radiation measurement information. The main module may generate a table or a function indicating how much the electrical output signal means a unit concentration (Bq/g) of radiation.

One of the correction volumes is divided into a second number of unit correction volumes, and a correction source may be located at the center of gravity of each of the unit correction volumes. The second number may be eight. The calibration source may be the CRM source already described above. A portion of the unit calibration volume other than the calibration source may be filled with air. As described above, since a calibration source with a known radiation dose is used, the nuclide analysis system 10 may pre-store the third radiation measurement information for the calibration volume.

According to another embodiment of the present disclosure, according to FIGS. 1 to 6 , the detector 22 having an optimal field of view of the detector module may generate an electrical output signal with respect to one of the correction volumes. The electrical output signal may include radiation related information. The electrical output signal may be a signal related to a unit concentration of radiation according to energy.

The main module may perform the step of acquiring the third radiation measurement information stored in advance for one of the calibration volumes. As already described, one correction volume 501 among the correction volumes is divided into a second number of unit correction volumes 502, and the CRM source 503 is located at the center of gravity of the unit correction volumes 502, respectively. can do. The main module may store the third radiation measurement information in advance when the CRM source 503 is respectively located at the center of gravity of the unit correction volumes 502 and the medium is the first material. This is because the radiation measurement information for the CRM source 503 is already known information or information that can be known through simulation. The third radiation measurement information may mean a unit concentration (Bq/g) of radiation.

The main module may perform a step of matching the electrical output signal of the detector 22 with the third radiation measurement information. More specifically, the main module may generate a table or a function indicating how much the electrical output signal means a unit concentration (Bq/g) of radiation.

Also, the meaning of the electrical output signal according to energy may be different. For example, an electrical output signal for radiation having an energy of 1 keV and an electrical output signal for radiation having an energy of 2 keV may be different from each other. The main module may generate a table or a function indicating how much an electrical output signal according to energy means a unit concentration (Bq/g) of radiation.

According to the present disclosure, the above correction is performed using the CRM source, and since the CRM source emits radiation having various energies, the meaning of the electrical output signal according to various energies can be confirmed even if the above process is performed only once.

Hereinafter, a method for calculating the efficiency curve of the nuclide analysis system according to the density of the medium will be described.

10 is a diagram illustrating an efficiency curve according to an embodiment of the present disclosure. 11 is a diagram illustrating a correction factor according to an embodiment of the present disclosure. 12 is a diagram illustrating an efficiency curve according to a medium.

Hereinafter, the nuclide analysis system 10 will be described along with FIGS. 10 to 12 .

The efficiency curve of the nuclide analysis system 10 is a function representing the ratio of radiation substantially detected by the nuclide analysis system 10 to the total radiation included in the object. The efficiency curve is an important factor in analyzing the concentration of radionuclides along with the correction factor. Therefore, the nuclide analysis system 10 should store all the efficiency curves according to the density of the contents in advance. The present disclosure proposes a method of predicting/calculating efficiency curves for various densities using actual measurement experiments and simulations.

The nuclide analysis system 10 may perform the following process to calculate an efficiency curve according to the density of the contents.

The efficiency curve of the detector 22 is an essential factor in interpreting the activity actually measured in each energy band by applying the attenuation according to the medium as a function of the density and energy of the medium. Activity may be related to a radioactive signal or a concentration of a radioactive material.

This is a complex function of the density of the medium, the dimensions of the container, the energy band of the radioactive material, and the FOV of the detector, and it is practically impossible to obtain the efficiency curve for all cases through experimentation. Therefore, the present disclosure proposes a method of calculating the efficiency curves according to the specifications of different types of media or containers based on Monte Carlo Simulation after conducting the experiment on the air medium and Monte Calro simulation in parallel and finding the correlation therebetween. do.

The dismantling waste generates wastes of various densities such as concrete, soil, metal, and solids. Therefore, the efficiency curve equation of the detector according to the density is an essential factor in the quantitative analysis of nuclides contained in waste.

However, in reality, it is very difficult to experimentally grasp the efficiency curve of the detector for wastes of various types of densities.

In the present disclosure, by using the medium in the air state as a reference, the experiment and Monte Carlo Simulation are performed in parallel to formulate the difference in the two analyses, and Monte Carlo Simulatoin for the medium of different density is used for each. After predicting the efficiency curve for , we propose a method of predicting the final efficiency curve using the formulation as a correction factor.

The nuclide analysis system 10 calculates the correction factor between the simulation (Simul) and the actual measurement (Exp) in a state in which the medium of the measurement target container is filled with air.

can be done The main module can obtain an efficiency curve in the case of air as the medium through simulation. The medium is a material inside the container to be measured, and may refer to a material other than a radiation source (correction source). A blue line 1010 of FIG. 10 may represent a first efficiency curve according to a simulation result. The simulation may be a Monte Carlo Simulation. The main module may obtain an efficiency curve in the case of air, which is the same medium, through an experiment using the detector 22 . The red line 1020 of FIG. 10 may represent the second efficiency curve according to the experimental result. The main module can formulate the error between simulation and experiment. The error between simulation and experiment can be determined by Equation 4. ratio may be an error (correction factor).

(Equation 4)

simuEff may mean an efficiency curve through simulation, and expEff may mean an efficiency curve through experiment.

The line in FIG. 11 may represent an error (correction factor). The vertical axis of FIG. 11 may represent Ratio. Ratio may be Simu/Exp. Simus of FIG. 11 may correspond to SimuEff of Equation 4. Also, Exp of FIG. 11 may correspond to ExpEff of Equation 4. Also, the main module may formulate the error (correction factor) to obtain Equation 1120 . The formula may be a function of an error (correction factor) according to energy. Through this process, the main module can acquire a correction factor (error) in the entire energy band as shown in Equation 1120. The main module may obtain a correction factor according to energy using Equation 1120.

The nuclide analysis system 10 may perform a simulation while changing the density of the medium of the measurement target container to obtain an efficiency curve that is a simulation result. The main module can perform simulations using materials other than air as a medium. Other materials may have different densities than air. When the main module performs simulations using a material other than air as a medium, it may mean that the main module performs simulations on densities of various media. The main ㅁ module can obtain an efficiency curve as a simulation result for the density of various media.

The nuclide analysis system 10 may perform a step of correcting an efficiency curve, which is a simulation result, based on a correction factor to obtain a measured efficiency curve for each density of the medium. The main module may perform correction by applying Equation 1120 to an efficiency curve that is a simulation result for various densities. For example, the main module may multiply the efficiency curve, which is the simulation result, by the reciprocal of the value according to Equation 1120. Because Equation 4 is equal to ratio=simuEff/expEff. Here, simuEff may mean an efficiency curve through simulation, and expEff may mean an efficiency curve through experiment. The main module may correct an efficiency curve that is a simulation result by acquiring a correction factor for each energy. The main module can acquire the final efficiency curve for all media through this process. The final efficiency curve may be similar to the experimental efficiency curve. Therefore, the user can acquire the efficiency curve according to the medium only through simulation without a separate experiment. For example, FIG. 12 may show an efficiency curve according to density/energy. The horizontal axis of FIG. 12 may indicate energy and the new axis may indicate the efficiency of the detector.

According to various embodiments of the present disclosure, the main module may perform the following process. In the description below, the content already described with reference to FIGS. 1 to 12 is omitted, and deficiencies in the description below may be explained with reference to FIGS. 1 to 12 .

The third correction may include a method of calculating the efficiency curve for each container and each density of the contents by using the relational expression between simulation and actual measurement to calculate the efficiency curve for each container and for each density of the contents for quantitative analysis of the nuclide concentration. there is.

The main module may perform the following process to perform the third correction. The main module may perform a step of simulating one of the correction volumes including the CRM source and filling the periphery of the CRM source with the first material with a predetermined algorithm to obtain a first efficiency curve. As already described, the CRM source may be located at the center of the unit correction volume included in one of the correction volumes. The efficiency curve may mean the efficiency of the detector according to energy. The predetermined algorithm may be a Monte Carlo Simulation. The first material may be air. A blue line 1010 of FIG. 10 may represent a first efficiency curve according to a simulation result. The horizontal axis of FIG. 10 means the energy level. Also, the vertical axis of FIG. 10 represents the efficiency of the detector.

The main module may perform the step of obtaining the fourth radiation measurement information for one of the calibration volumes by using the detector 22 . As already described, the CRM source may be located at the center of the unit correction volume included in one of the correction volumes. Also, the periphery of the CRM source may be filled with the first material.

The main module may perform the step of obtaining a second efficiency curve based on the fourth radiation measurement information. A red line 1020 of FIG. 10 may represent a second efficiency curve according to the simulation result.

The main module may perform the step of obtaining an error function based on the first efficiency curve and the second efficiency curve. The error can be determined by Equation 4. In Equation 4, ratio may be an error (correction factor). The error function may be as shown in FIG. 11 .

The line in FIG. 11 may represent an error (correction factor). Also, the main module may formulate the error (correction factor) to obtain Equation 1120 . The formula may be a function of an error (correction factor) according to energy. Through this process, the main module can acquire a correction factor (error) in the entire energy band as shown in Equation 1120. The main module may obtain a correction factor according to energy using Equation 1120.

The main module may perform a step of simulating one of the correction volumes including the CRM source and filling the periphery of the CRM source with the second material with a predetermined algorithm to obtain a third efficiency curve. The second material may be different from the first material. The second material may be concrete, iron, or the like.

The main module may perform a step of obtaining a corrected third efficiency curve by correcting based on the third efficiency curve and the error function. The main module may perform correction by applying Equation 1120 to the third efficiency curve. For example, the main module may multiply the third efficiency curve by the reciprocal of the value according to Equation 1120. This is because in Equation 4, the efficiency curve through the experiment is in the denominator like ratio=simuEff/expEff. The main module may correct the third efficiency curve by acquiring a correction factor for each energy. The corrected third efficiency curve may be almost matched with an efficiency curve through an actual experiment for a container filled with the second material.

The main module can acquire the final efficiency curve for all media through this process. The final efficiency curve may be similar to the experimental efficiency curve. Therefore, the user can simulate the efficiency curve through the experiment by acquiring the efficiency curve according to the medium only through simulation without a separate experiment. For example, Figure 12 shows efficiency curves for a plurality of media. The plurality of media may have different densities. That is, FIG. 12 may show an efficiency curve according to a plurality of densities/energies. The horizontal axis of FIG. 12 may indicate energy and the new axis may indicate the efficiency of the detector.

The present disclosure described above is not limited by the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible without departing from the technical spirit of the present disclosure. It will be clear to those of ordinary skill in the art.

10: nuclide analysis system 20: detector device
21: detector module 22: detector
23: collimator 24: collimator effective field of view
30: inspection table device 40: container inspection table
50: measurement target container 501: calibration volume
502: unit correction volume 503: CRM source

Claims (8)

In the method of operating a nuclide analysis system for a radioactive material,
The nuclide analysis system includes a detector module including a collimator and a scintillator-based detector, a detector driving module for driving the detector module, a search table accommodating a measurement target container, and a search table driving device for driving the search table,
In the correction for determining the effective field of view of the detector module and the segmentation of the measurement target container, the method of adjusting the effective field of view of the detector module according to the position of the collimator with respect to the detector and the detector driving module; performing a first correction of determining the segmentation of the measurement target container by determining a position of the detector module with respect to the measurement target container on the search target based on the search station driving device;
performing a second correction to match the electrical output signal of the detector module with the radiation measurement information; and
Performing a third correction for calculating the efficiency curve for each container and for each density of the contents by using the relational expression between simulation and actual measurement to calculate the efficiency curve for each container and for each density of the contents for quantitative analysis of the nuclide concentration including,
The step of performing the first correction is,
determining an effective field of view of an optimal detector module that maximizes sensitivity and minimizes uniformity in designing a collimator;
acquiring a minimum detection activity (MDA) according to a predetermined position of the detector module with respect to the measurement target container; and
The method of operating a nuclide analysis system comprising the step of determining the number of segments of the measurement target container at which the MDA is the minimum.
delete The method of claim 1,
The step of determining the effective field of view of the detector module,
determining the sensitivity by the following equation;
Sensitivity = Am/A0,
where Am is the amount of radiation detected by the detector module, A0 is the total amount of radiation generated by the measurement target container,
The uniformity is obtained by the following equation,

where max and min are the maximum and minimum of the radiation signal (activity) measured by the detector module in the measurement target container,
How a nuclide analysis system works.
The method of claim 1,
In the step of determining the number of segmentation of the measurement target container,
determining, by the detector driving module, a plurality of predetermined positions of the detector module with respect to the measurement target container based on the search table driving device; and
Method of operation of a nuclide analysis system comprising the step of determining the number of segments for which the MDA is the minimum for the plurality of predetermined positions.
5. The method of claim 4,
The calculation method of MDA uses the following formula defined by ISO,

is the branch of the peak of interest, t is the measurement time,

is an energy peak efficiency, B is a background radiation dose, and the background radiation dose is an operating method of a nuclide analysis system in consideration of the ratio of the area inside the measurement target container and the outside area of the measurement target container.
The method of claim 1,
The step of performing a second correction to match the electrical output signal of the detector module and the radiation measurement information,
dividing the vessel to be measured of a predetermined volume containing a radioactive material into 24 calibration volumes;
the detector generating an electrical output signal for one of the calibration volumes;
obtaining third radiation measurement information stored in advance for one of the correction volumes; and
obtaining a formula for converting the electrical output signal into the third radiation measurement information,
One of the correction volumes is divided into eight unit correction volumes, a correction source is located at the center of gravity of each of the unit correction volumes, and a portion of the unit correction volume other than the correction source is filled with air. , The electrical output signal and the third radiation measurement information are energy-specific efficiency, and the efficiency is the total dose of the radiation dose/correction radiation source collected by the detector,
How a nuclide analysis system works.
7. The method of claim 6,
The correction source is
Method of operation of a nuclide analysis system comprising Am-241, Cd-109, Co-57, Ce-139, Sn-113, Cs-137, Co-60 and Y-88 sources as CRM sources.
The method of claim 1,
The step of performing the third correction is,
calculating a correction factor between the simulation (Simul) and the actual measurement (Exp) in a state in which the medium of the measurement target container is filled with air;
obtaining an efficiency curve, which is a simulation result, by performing a simulation while changing the density of the medium of the measurement target container; and
and obtaining a measured efficiency curve for each density of a medium by correcting the efficiency curve, which is the simulation result, based on the correction factor.

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