The Effect of Grid Ratio and Material of Anti-scatter Grid on the Scatter-to-primary Ratio and the Signal-to-noise Ratio Improvement Factor in Container Scanner X-ray Imaging

Lee, Jeonghee,Lim, Chang Hwy,Park, Jong-Won,Kim, Ik-Hyun,Moon, Myung Kook,Lim, Yong-Kon The Korean Association for Radiation Protection 2017 방사선방어학회지 Vol.42 No.4

Background: X-ray imaging detectors for the nondestructive cargo container inspection using MeV-energy X-rays should accurately portray the internal structure of the irradiated container. Internal and external factors can cause noise, affecting image quality, and scattered radiation is the greatest source of noise. To obtain a high-performance transmission image, the influence of scattered radiation must be minimized, and this can be accomplished through several methods. The scatter rejection method using an anti-scatter grid is the preferred method to reduce the impact of scattered radiation. In this paper, we present an evaluation the characteristics of the signal and noise according to physical and material changes in the anti-scatter grid of the imaging detector used in cargo container scanners. Materials and Methods: We evaluated the characteristics of the signal and noise according to changes in the grid ratio and the material of the anti-scatter grid in an X-ray image detector using MCNP6. The grid was composed of iron, lead, or tungsten, and the grid ratio was set to 2.5, 12.5, 25, or 37.5. X-ray spectrum sources for simulation were generated by 6- and 9-MeV electron impacts on the tungsten target using MCNP6. The object in the simulation was designed using metallic material of various thicknesses inside the steel container. Using the results of the computational simulation, we calculated the change in the scatter-to-primary ratio and the signal-to-noise ratio improvement factor according to the grid ratio and the grid material, respectively. Results and Discussion: Changing the grid ratios of the anti-scatter grid and the grid material decreased the scatter linearly, affecting the signal-to-noise ratio. Conclusion: The grid ratio and material of the anti-scatter grid affected the response characteristics of a container scanner using high-energy X-rays, but to a minimal extent; thus, it may not be practically effective to incorporate anti-scatter grids into container scanners.

컨테이너 검색기 이송대차 추진용 선형 유도전동기의 2차측 리액션플레이트 재질에 따른 특성 연구

정재훈(Jae-Hoon Jeong),최장영(Jang-Young Choi),성소영(So-Young Sung),박종원(Jong-Won Park),임재원(Jaewon Lim) 대한전기학회 2016 전기학회논문지 Vol.65 No.1

This paper presents the analysis of the analysis of thrust characteristics of linear induction motors(LIMs) according to secondary reaction plate. LIMs are well known as high speed transport systems, which can obtain thrust directly without gears and links, or auxiliary mechanisms. A simple structure, easy maintenance, and less environmental pollution are advantages of LIMs. In transport systems using LIMs, the secondary reaction plate is an important design factor, because it has considerable impact on the cost of the railway as well as the performance of the LIMs. This paper deals analyzed the characteristics of linear induction motor used for moving the vehicle of container scanner. Thrust, efficiency and load characteristic were interpreted with FEM regarding two models whose material of secondary reaction plate was copper and aluminum. It suggested the interpretation of thrust, efficiency and power factor characteristic along slip and compared the operation ability of linear induction motor through characteristics analysis along the load.

Feasibility study of a non-destructive assay system for certifying identified isotopes and their activity concentrations for radioactive waste in a large container

Joung Jinhun,Nguyen Hung M.,Kim Yongkwon,Lee Mi-hyun,Cho Hang-rae,Park Kyung-Rok,Lee Ji-Hoon,Dho Ho-seog,Cho Chun-Hyung 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.1

We have generated a system concept for a non-destructive assay (NDA) system to certify identified isotopes and their activity concentrations for radioactive waste in a large container. Various optimization studies have evaluated the system performance in terms of the MDA (minimum detectable activity) results using the Monte Carlo simulation in conjunction with experimental studies. The proposed system consists of a total of eight HPGe (high-pressure germanium) detectors: four detectors on the top and the other four detectors on the bottom. The top and the bottom detector arrays are aligned and face each other. This detector arrangement has advantages in employing the attenuation correction as proposed by T. Chang [IEEE Trans. Nucl. Sci. NS-25, 638 (1978)]. We also found that the UFOV (useful field of view) of the detector highly influences the system efficiency, which leads to an improvement in the MDA performance. However, while the wider FOV of the detector improves the detection efficiency by allowing incoming radiation from other segmented volumes, it may suffer from nonuniform performance or increased errors in estimating an activity concentration for each segmented volume. To prevent such potential errors in employing the wider FOV, we have proposed an activity estimation algorithm, a so-called ‘fine volume reconstruction’, based on a back-projection method that estimates the activity concentration of each segmented volume. We demonstrate the feasibility of the conceptual system for use as a free release assay system for ISO containers up to a size of 2.4 × 6.0 × 1.3 m3 (W x L x H). The detector efficiency was about four times higher than those of typical commercial systems. Future studies include fine-tuning of the activity reconstruction algorithm and a validation study on various materials and non-uniform activity concentrations.

컨테이너 검사 효율 극대화를 위한 화질 향상 기법 연구

이창호(Chang-Ho Lee),신지혜(Ji-Hye Shin),김장오(Jang-Oh Kim),정영진(Young-Jin Jung),민병인(Byung-In Min) 대한방사선과학회(구 대한방사선기술학회) 2017 방사선기술과학 Vol.40 No.4

본 연구에서는 컨테이너 엑스선 검색기의 노후화, 검출 감지기(Sensor) 불량으로 발생되는 검색영상의 잡음 (Noise)을 줄이기 위한 알고리즘을 제시고 MATLAB 툴박스에 이를 적용하여 컨테이너 검색영상의 화질(Image Quality)을 개선하고자 하였다. 검색영상은 일반적인 컨테이너 검색기 작동 점검을 위한 일일 점검영상을 활용하였으며 일일점검영상의 수평 영상과 수직 영상을 기준으로 잡음(Noise)을 디지털 방사선 영상에서 가장 기본으로 사용되는 잡음평가 방법인 제곱평균제곱근(Root Mean Square; RMS)으로 평가하였다. 또한 개선된 알고리즘을 실제 컨테이너검색영상에 적용하여 일일 점검영상과 실제 컨테이너 검색영상의 화질을 평가하였다. 그 결과 제곱평균제곱근이 일일 점검영상에서는 수평 영상에서 원본 영상 대비 평균 13.5%, 수직 영상에서는 원본 영상 대비 평균 18.2% 가 낮은 결과치를 나타내었다. 또한 실제 컨테이너 검색영상에서는 수평 영상에서 원본 영상 대비 평균 13.4%, 수직 영상에서는 원본 영상 대비 19.1%가 낮은 결과치를 나타내었다. 이는 영상의 화질개선을 객관적, 시각적으로 확인할 수 있었으며 관세청의 컨테이너 검색영상 판독 업무에 큰 도움이 될 것이라 사료된다. The purpose of this study is to present the algorithm to minimize the image noise caused by deterio-ration of high X-ray container inspection equipment and the faulty detection sensors, and to improvement quality of the container inspection images using MATLAB Toolbox. The daily checking images for the con-tainer inspection were used with the subject images and the noise caused by the horizontal and vertical images was evaluated with Root Mean Square (RMS) method, which is the most basic evaluation method of digital radiation image. Also, quality of the improved images was evaluated compared to quality of the orignal images. As a result, all RMS value of the improved images was lower then the original images by a mean of 13.5% in the horizontal images and 18.2% in the vertical images respectively. Also so did RMS value of the improved container images, by a mean of 13.4% in the horizontal images and 19.1% in the vertical images respectively. These findings can be verified objectively and visually and they would help the reading process of the container images be effective in Korea Customs Service.

Development of Diode Based High Energy X-ray Spatial Dose Distribution Measuring Device

Jeonghee Lee,Ikhyun Kim,Jong-Won Park,Yong-Kon Lim,Myungkook Moon,Sangheon Lee,Chang Hwy Lim 대한방사선방어학회 2018 방사선방어학회지 Vol.43 No.3

3D 스캐너를 활용한 CNTR선 해치커버 사전 탑재 시뮬레이션

이정혁,진형국,이동주 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11

3D 스캐닝 기술은 3D 스캐너의 레이저, 가시광선, 적외선, 초음파 등을 다양한 대상물에 투사하여 형상 정보를 점군(Cloud Data) 형태로 취득하는 기술이다. 최근 휴대성이 향상되고 고정밀도의 데이터 획득 시간이 개선된 스캐너 장비가 계속적으로 개발됨에 따라 역설계, 품질관리, 특수효과, 의학, CG 등 여러 산업군에서 3D 스캐너의 활용도가 증대되는 추세이다. 이에 본 연구에서는 3D스캐닝 기술을 컨테이너선 해치커버 탑재 공정에 적용하여, 탑재전 시뮬레이션을 통해 기존 시험 탑재하는 비효율성을 제거하고 탑재 공정을 단축할 수 있는 새로운 공정을 제안하였다. 종래에는 컨테이너선 건조 시, 개방형 화물창을 개폐하는 장치인 해치커버를 본선 상부 갑판에 정확히 탑재하기 위하여 먼저 해치커버를 본선 상부에 1차 탑재한 후, 갭조절 패드의 적정 두께와 용접/절단 수정량을 파악하고 해치커버를 하선한다. 이 후, 갭조절 패드의 재조정 및 용접/절단 수정 작업 완료후 최종적으로 해치커버를 탑재함으로써, 총 2회 탑재 공정이 필요하였다. 하지만 본 연구에서 제안된 3D 스캐너 적용 방식은 비접촉식 광대역 3D 스캐너를 활용하여 추출된 본선과 야드 내 적치된 해치커버의 계측 데이터를 기반으로 시뮬레이션을 통해 중점 관리부들의 치수 산출이 가능하여 추가 탑재 공정이 필요가 없다. 따라서 본 공정을 적용하게 되면 해치커버 탑재 시 공정 단순화, 공수 절감, 공간 활용 극대화 등의 효과에 기여 할 수 있을 것으로 기대된다.

Validation Analysis of X-ray Scan Images Through Nuclear Related Item Models

Hansol Ko 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.11