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Kim, Jinsu,Yoon, Jeong Whan,Kim, Hyochan,Lee, Sung-Uk Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10
In this study, a multi-physics modeling method was developed to analyze a nuclear fuel rod's thermo-mechanical behavior especially for high temperature anisotropic creep deformation during ballooning and burst occurring in Loss of Coolant Accident (LOCA). Based on transient heat transfer and nonlinear mechanical analysis, the present work newly incorporated the nuclear fuel rod's special characteristics which include gap heat transfer, temperature and burnup dependent material properties, and especially for high temperature creep with material anisotropy. The proposed method was tested through various benchmark analyses and showed good agreements with analytical solutions. From the validation study with a cladding burst experiment which postulates the LOCA scenario, it was shown that the present development could predict the ballooning and burst behaviors accurately and showed the capability to predict anisotropic creep behavior during the LOCA. Moreover, in order to verify the anisotropic creep methodology proposed in this study, the comparison between modeling and experiment was made with isotropic material assumption. It was found that the present methodology with anisotropic creep could predict ballooning and burst more accurately and showed more realistic behavior of the cladding.
김효찬(Hyochan Kim),김동현(Dong-hyun Kim),이성욱(Sung-uk Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
원자력발전소 핵연료는 금속 튜브 형태의 지르코늄 합금 피복재와 이산화우라늄(UO2) 소결체로 구성되어 있다. 핵연료 피복재는 정상 상태에서는 핵분열에 의해 발생하는 열을 냉각재로 전달하는 기능을 하며, 사고조건에서는 핵분열 생성 물질이 냉각재로 누출되지 않도록 하는 방어막 역할을 수행한다. 사고 조건에서 핵연료 피복재는 온도 및 내부 압력이 상승하여 금속 튜브 형태인 핵연료 피복재는 대변형이 발생한다. 핵연료 대변형은 피복재 건전성 및 원자로 안전성에 영향을 미치므로 이에 대한 상세한 모델 개발 및 검증 연구가 필요하다. 핵연료 피복재 대변형 실시간 다차원 측정을 수행하기 위해 3 차원 DIC(Digital Image Correlation) 기법을 적용하였다[1]. 시편 표면의 스페클 패턴을 인식하여 패턴의 이동에 의한 변형률을 측정하는 DIC (Mercury RT) 기법은 다양한 분야에서 널리 활용 중에 있다. 그러나, 측정되는 3 차원 DIC 변위 또는 변형률 데이터에 대한 검증 연구는 거의 진행된 바 없다. 본 연구에서는 3 차원 DIC 측정 데이터 신뢰성 검증을 위해 정적 및 동적 측정 데이터 검증 방법론을 제안하여 수행하였다. 정적 측정 데이터 검증 연구에서는 핵연료 팽창 형상과 유사한 3 차원 형상을 가지는 별도 시편을 제작하여 정적 조건에서 측정된 시편 제원과 제작된 시편 제원의 차이를 비교하여 형상 오차를 확인하였다. 동적 측정 데이터 검증 연구에서는 이동 가능한 3 축 stage에 추적점을 설치한다. 추적점의 각 방향 이동 값을 설정 후 DIC 장치를 활용하여 측정 후 입력된 값과 측정 오차값을 확인하였다. 정적 측정 데이터 검증 결과 측정 범위 10 mm에서 -0.425 mm ~ +0.082 mm의 작은 오차를 가짐을 확인하였다. 동적 측정 데이터 검증 결과 5 mm 변위 이동시에는 DIC 측정 평면인 X, Z 면에서는 0.5 % 이하의 작은 오차를 가지나, 측정 평면의 수직 방향인 Y 축으로는 1% 정도의 상대적으로 큰 오차를 가짐을 확인하였다. Nuclear fuel rod consists of uranium dioxide pellet and zirconium alloy cladding tube which plays an important role in retaining all radioactive gases and fission products to coolant. The cladding tube experiences large deformation as well as rupture in accident conditions. To measure multidimensional behavior of the cladding, 3D DIC (Digital image correlation) technology was employed. In this work, measured data by 3D-DIC were validated against static measurement data and kinetic measurement data. The specimen that is similar with shape of deformed cladding was measured by 3D-DIC in static methodology. Amount of displacement on 3- axis stage along each direction was measured by 3D-DIC in kinetic methodology. The measurement data were compared with fabricated dimension and programmed displacement. As a result, error bound of -0.425 mm ~ +0.082 mm was obtained in static methodology. In kinetic methodology, the below 0.5% error along X direction and Z direction were obtained. Approximately 1.0 % error along Y direction which is perpendicular to measurement plane of DIC camera was obtained.
A Method for Developing 3D Based Nuclear Power Plant Decommissioning System
Youngung Kang,Hyochan Park,Kwangsoo Park,Changgyu Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1
Considering the characteristics of nuclear power plants in order to decommission nuclear power plants safely and economically, this thesis provides a methodology for optimizing the technology for developing decommissioning characteristic evaluation system using simulation technology for core facilities of the plants based on 3D that reflects various factors. The results of pollution assessment and radiation assessment for the Kori Unit 1 reactor building, auxiliary building, and each major device are displayed in 3D drawings and viewer, and the radiation dose rate and radiation assessment results are displayed separately for each major location. Furthermore, this D/B development method which includes inserting result values of characteristic evaluation and the quantity of waste is one of the main technology to optimize the system which enables users to select decommissioning processes and predict the quantity of waste. (Refer to the presented 3D models of the containment building, D/B, tag search module, the scale calculation result of models after visualizing the result value of 3D based decommissioning characteristic evaluation) The methodology for optimizing decommissioning characteristic evaluation result value DB development system using 3D models of the first major nuclear power plant allows the display of decommissioning characteristic values in virtual reality, the selection of decommissioning process, the establishment of the decommissioning procedure. Hence, this study is expected to provide reliable guidelines for managing a decommission business efficiently in the near future and can be used in the related field if needed.