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내부 감육곡관의 손상압력에 미치는 하중조건 및 원주방향 결함폭의 영향 평가
나연수(Yeon-Soo Na),김진원(Jin-Weon Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Wall thinning defect due to flow-accelerated corrosion (FAC) is one of the degradation mechanisms of carbon steel piping components in nuclear power plant (NPP), and it results in reducing load carrying capacity and fatigue resistance of the piping components. Especially, the wall-thinning defect leads to abrupt rupture of piping components under normal operating pressure. Thus, it is important to accurately evaluate the failure pressure of piping components containing an internal wall-thinning defect for ensuring integrity of piping system of NPP. Therefore, this study performed failure tests using real-scale elbows containing simulated wall-thinning defect under internal pressure and bending moment. Based on the results of experiments, the effect of circumferential thinning angle and bending moment on the failure pressure was investigated.
자유 낙하 충격 시험을 통한 UO₂ 소결체 표면결함에 미치는 End-face 형상 영향 평가
나연수(Yeon Soo Na),최민영(Min Young Choi),임광영(Kwang Young Lim),류수필(Su Pil Ryu),이승재(Seung Jae Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
Missing pellet surface(MPS) is one of deterioration caused by pellet-clad mechanical interaction(PCMI) mechanism of cladding in nuclear power plants(NPPs) and it results in reducing the product quality and integrity of nuclear fuels. Thus, in order to increase the MPS resistance of UO₂ pellets, it is very important to improve the thoughtness and to change the shapes of UO₂ pellet end-face. Especially, changing the shape of UO₂ pellet end-face is able to effectively improve MPS resistance of UO₂ pellets. Therefore, this study was selected candidate MPS resistant UO₂ pellet end-face shape by FEM and then performed free drop impact test using fabricated UO₂ pellet end-face shape. Based on the results of experiment, the effect of end-face shape of UO₂ pellet on missing pellet surface was investigated.
실 배관시험을 통한 손상압력에 미치는 원주방향 감육형상의 영향 평가
나연수(Yeon-Soo Na),김진원(Jin-Weon Kim),박치용(Chi-Yong Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
Wall thinning defect due to flow-accelerated corrosion (FAC) is one of the degradation mechanisms of carbon steel piping components in nuclear power plant (NPP), and it results in reducing load carrying capacity and fatigue resistance of the piping components. Especially, the wall-thinning defect leads to abrupt rupture of piping components under normal operating pressure. Thus, it is important to accurately evaluate the failure pressure of piping components containing an internal wall-thinning defect for ensuring integrity of piping system of NPP. Therefore, this study performed failure tests using real-scale straight pipes and elbows containing simulated internal wall-thinning under internal pressure and investigated the effect of circumferential thinning shape on the failure pressure. Also, the results were compared to the existing failure pressure evaluation models.
수소함유량에 따른 Zr-1.0Nb 합금 피복관의 기계적 물성치 변화
나연수 ( Yeon Soo Na ),최민영 ( Min Young Choi ),고대균 ( Dae Gyun Ko ),김윤호 ( Yoon Ho Kim ),목용균 ( Yong Kyoon Mok ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.3
Hydrogen pre-charged Zr-1.0Nb alloy was prepared to study the effect of hydrogen uptake on its mechanical properties. The apparent activation energy of the Zr-1.0Nb alloy for hydriding was about 27 kcal/mol. The tensile strength of the Zr-1.0Nb alloy with a hydrogen content of up to 700 ppm was similar to that of an as-fabricated specimen, in that its elongation was drastically decreased after 400 ppm and became nearly zero above about 1200 ppm. The critical hydrogen content range needed to produce the ductile-brittle transition was above 400 ppm.
UO₂ 소결체 끝단 형상 변경에 따른 연료봉 설계 영향 평가
나연수(Yeon Soo Na),주민제(Min Jae Ju),김경태(Kyung Tae Kim),김윤호(Yoon Ho Kim),이승재(Seung Jae Lee) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Missing pellet surface(MPS) are one of the causes of Pellet-Clad Mechanical Interaction(PCMI) failure of cladding in nuclear power plants(NPPs) and it results in reducing the product quality and integrity of nuclear fuels. Thus, in order to increase the MPS resistance of UO₂ pellets, it is very important to improve the thoughtness and to change the shapes of UO₂ pellet end-face. Especially, changing the shape of UO₂ pellet end-face is able to effectively improve MPS resistance of UO₂ pellets. Therefore, this study was selected candidate MPS resistant UO₂ pellet end-face shape by FEM and then performed nuclear fuel rod design for 5-types MPS resistance UO₂ pellet by commercial ROPER code. Based on the results of nuclear fuel rod design simulation, the effect of integrity of nuclear fuel rod with UO₂ pellet’s end-face shape change was evaluated.
김도형(Do-Hyung Kim),나연수(Yeon-Soo Na),김진원(Jin-Weon Kim),박치용(Chi-Yong Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The objective of this study is to investigate the applicability of local failure criteria developed by simulated specimen tests in the evaluation of failure pressure of elbow with wall-thinning defect. For this purpose, the failure tests were performed on the elbow containing internal wall-thinning defect at intrados and extrados under internal pressure. Also, elastic-plastic finite element simulation was performed on the failure test to predict failure pressure by applying local failure criterion. The failure pressure was predicted using failure criterion which is local stress criterion based on the maximum load estimation. By comparing the predicted failure pressure with the measured failure pressure, the accuracy and applicability of failure criterion was investigated.
UO₂ 소결체 형상 변경을 통한 chipping에 미치는 기계적 특성 영향 평가
최민영(Min Young Choi),나연수(Yeon soo Na),정태식(Tae Sik Jung),류수필(Su pil Ryu),이승재(Seung Jae Lee) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
In pressurized water reactor (PWR), nuclear fuel rod comprises a pile of fuel pellet surrounded by a cladding. Sintered extensively uranium oxide and mixed oxide pellets are used as a nuclear reactor fuel. More advanced fuels are recently required for the more severe operating condition such as higher burn-up and increased fuel cycle. Among the advanced fuel pellet, Missing Pellet Surface (MPS) reduction pellet is considered recently. MPS predominantly extended to the pellet end. The fragment of fuel materials produced by such chipping may become trapped in the gap between the peripheral wall of the pellets and the cladding and increase the mechanical stress on the cladding, which can lead to local cladding failure due to pellet clad mechanical interaction (PCMI). To solve this problem, research is conducted on the modification of the fuel pellet shape such as dish and chamfer. In this study, the changed dish and chamfer of the nuclear fuel pellet are first simulated using Finite Element Method (FEM). From the simulated samples, the mechanical testing is performed to find the lowest percent defective of fuel pellets. Especially, the loadability test is performed to evaluate the chipping reduction performance of stacked fuel pellet behavior in the fuel rod.
김진원(Jin-Weon Kim),나연수(Yeon-Soo Na) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The purpose of this study is to investigate the effect of bend angle on the collapse behavior of locally wall thinned elbows. For this purpose, the present study performs three-dimensional finite element analysis on the 30-, 60-, and 90-degree elbows with local wall thinning at intrados, extrados, and crown, and evaluates the collapse moment under various thinning shapes and loading conditions. Combined internal pressure and in-plane bending load are considered. The results showed that the reduction in collapse moment by local wall thinning increases with decrease in bend angle of elbow. This tendency was more significant for a wall thinned elbow with higher bend radius under opening mode bending with internal pressure, and the effect of bend angle increased with increasing depth, length, and circumferential angle of wall thinning.
김도형(Do-Hyung Kim),나연수(Yeon-Soo Na),김진원(Jin-Weon Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.3
The objective of this study is to investigate the applicability of local failure criteria developed by simulated specimen tests in the evaluation of failure pressure of pipe with wall-thinning defect. For this purpose, the failure tests were performed on the straight pipe containing internal wall-thinning defect under internal pressure. Also, elastic-plastic finite element simulation was performed on the failure test to predict failure pressure by applying local failure criteria. The failure pressure was predicted using two types local failure criteria which are based on the maximum load and final failure estimation. By comparing the predicted pressure with the measured pressures, the accuracy and applicability of local failure criteria were investigated.
김진원(Jin-weon Kim),나연수(Yeon-soo Na),박치용(Chi-yong Park) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8
Wall thinning defect due to flow-accelerated corrosion (FAC) is one of the degradation mechanisms of carbon steel piping components in nuclear power plant (NPP), and it results in reducing load carrying capacity and fatigue resistance of the piping components. Especially, the wall-thinning defect leads to abrupt rupture of piping components under normal operating pressure. It is important to accurately evaluate the failure pressure of piping components containing an internal wall-thinning defect for ensuring integrity of piping system of NPP. Therefore, this study set up a system for failure test of wall-thinned elbow and performed preliminary failure tests using two real-scale elbows containing simulated internal wall-thinning under internal pressure. Also, the finite element was performed on the failure tests and the results were compared to the measured data. From these results, the performance of testing system and finite element analysis model were verified.