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Monitoring of Fuel and Cladding Elongation in a Nuclear Fuel Rod
홍진태(Jintae Hong),양태호(Tae-Ho Yang),안성호(Sung-Ho Ahn),정창용(Chang-Young Joung) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.7
To evaluate the performance of nuclear fuel, it is necessary to measure the fission gas release, fuel temperature, fuel stack elongation, cladding elongation, fuel rod inner pressure, coolant temperature, and neutron flux during irradiation tests. Linear variable differential transformer (LVDT) is applied to the in-pile instruments for measuring the fuel rod inner pressure. In this study, design modification of LVDT was carried out to measure the fuel elongation and cladding elongation, without changing the structural soundness of the conventional nuclear fuel test rig used in HANARO. The magnetic core was directly connected to the fuel stack or cladding using a supporter, and it moved through the guide rail of LVDT sensor according to the deformation of fuel pellets or cladding. The performance verification and data calibration of the modified LVDT were verified by the deformation simulation system, where displacement was induced using a micrometer.
홍진태(Jintae Hong),김가혜(Ka-Hye Kim),정황영(Hwang-Young Jeong),안성호(Sung-Ho Ahn),정창용(Chang-Young Joung) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.1
To develop a new nuclear fuel, it needs to make a test fuel rod and carry out burn-up test in the test loop of a research reactor to check the irradiation characteristics of the nuclear fuel. At that time, several sensors such as thermocouples, LVDTs and SPNDs are needed to be attached in and out of the fuel rod and connect them with instrumentation cables. Then, the instrumentation cables deliver the signals measured by the sensors to the measuring device located outside of the reactor pool. In particular, to install a thermocouple in a fuel rod, it needs to drill off holes on the alumina blocks and sintered UO2 pellets. However, because the hardness of a sintered UO2 pellet is 700 Hv (or HRC 61) and that of an alumina block is 1480 Hv, a special drilling machine which adapts a diamond coated drill bit had developed. In this study, several case experiments have been carried out to find an optimal drilling condition of the drilling machine. And, using the optimal drilling condition, minimum numbers of the holes that a drill bit can drill off are verified.
Study on the Thermal Design of Nuclear Battery for Lunar Mission
홍진태(Jintae Hong),손광재(Kwang-Jae Son),김종범(Jong-Bum Kim),박종한(Jong-Han Park),안동규(Dong-Gyu Ahn),양동열(Dong-Yol Yang) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.4
For a stable electric power supply in the space, nuclear batteries have been used as the main power source in a spacecraft owing to their long lifetime and high reliability. In accordance with the plan for lunar mission in Korea, nuclear batteries will supply electricity to the rover that needs to be developed. According to the information about the estimated payload, Korea Atomic Energy Research Institute started with the conceptual design based on the previous studies in USA and Russia. Because a nuclear battery converts the decay heat of the radioisotope into electricity, thermal design, radiation shield, and shock protection need to be considered. In this study, two types of nuclear batteries, radial type and axial type, were designed according to the alignment of the thermoelectric module. Heat transfer analyses were performed to compare their thermoelectric efficiency, and test mockups were fabricated to evaluate their performances.
홍진태(Jintae Hong),정황영(Hwang-Young Jeong),안성호(Sung-Ho Ahn),정창용(Chang-Young Joung) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.2
When a new nuclear fuel is developed, an irradiation test needs to be carried out in the research reactor to analyze the performance of the new nuclear fuel. In order to check the performance of a nuclear fuel during the irradiation test in the test loop of a research reactor, sensors need to be attached in and out of the fuel rod and connect them with instrumentation cables to the measuring device located outside of the reactor pool. In particular, to check the temporary temperature change at the center of a nuclear fuel during the irradiation test, a thermocouple should be instrumented at the center of the fuel rod. Therefore, a hole needs to be made at the center of fuel pellet to put in the thermocouple. However, because the hardness and the density of a sintered UO<SUB>2</SUB> pellet are very high, it is difficult to make a small fine hole on a sintered UO2 pellet using a simple drilling machine even though we use a diamond drill bit made by electro deposition. In this study, an automated drilling mach ne using a CVD diamond drill has been developed to make a fine hole in a fuel pellet without changing tools or breakage of workpiece. A sintered alumina (Al<SUB>2</SUB>O<SUB>3</SUB>) block which has a higher hardness than a sintered UO<SUB>2</SUB> pellet is used as a test specimen. Then, it is verified that a precise hole can be drilled off without breakage of the drill bit in a short time.
홍진태(Jintae Hong),허성호(Sung-Ho Heo),김가혜(Ka-Hye Kim),박승재(Sung-Jae Park),정창용(Chang-Young Joung) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.4
조사시험 도중 핵연료의 특성변화를 확인하기 위하여 원자로 수조내에 위치한 조사리그로부터 핵연료봉을 분리한 후 핫셀로 이송하여 중간검사를 진행한다. 또한 중간검사를 마친 핵연료봉은 원자로의 작업 수조로 이동시켜 조사리그에 재장착을 하게 되며, 재조립된 조사리그는 원자로 노심의 조사리그에 장착시켜 조사시험을 계속 진행한다. 그러나 중성자 조사가 진행된 핵연료봉은 높은 에너지의 방사선을 방출하기 때문에 작업자가 방사선에 피폭되지 않게 하기 위하여 핵연료봉 장탈착 공정은 원자로 작업수조수 내에서 이루어져야 한다. 특히 조사리그의 길이가 5.4 미터이고, 핵연료봉의 장탈착 작업이 이루어질 하나로 작업수조수의 깊이는 6 미터로 매우 깊어 장탈착 작업을위한 특수한 장치가 필요하다. 본 연구에서는 중간검사가 가능한 새로운 핵연료봉 조립체를 설계하고, 조사 핵연료봉 조립체의 장탈착용 툴을 개발하여 노외 성능시험을 통해 그 성능을 검증하였다. To check the characteristics of nuclear fuels during an irradiation test, the nuclear fuel rod needs to be disassembled from the test rig located in the pool of the research reactor. Then, the disassembled fuel rod is delivered to the hot cell for intermediate examination. A fuel rod that passes the intermediate examination is delivered to the reactor pool to be reassembled into the test rig. The irradiation test is resumed with the reassembled test rig. Because nuclear fuel rods irradiated by neutrons are highly radioactive, all the disassembly and reassembly processes should be carried out in the pool of the research reactor to prevent operators being exposed to radiation. In particular, because a test rig is 5.4-m long and the reactor pool of HANARO is 6-m deep, special tools need to be developed for performing the disassembly and reassembly processes. In this study, a new assembly design of nuclear fuel rods for intermediate examination is introduced. Furthermore, tools for treating the irradiated fuel rod assembly are introduced, and their performance is verified by an out pile test.
홍진태(Jintae Hong),정창용(Chang-Young Joung),허성호(Sung-Ho Heo),김가혜(Ka-Hye Kim) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.1
핵연료 연소시험 도중 핵연료봉에서 발생하는 열을 효과적으로 제거하기 위해서는 핵연료의 발열량을 정확하게 계산하고 충분한 유속을 갖는 냉각수를 순환시켜야 한다. 하나로는 개방형 수조 형태로서 핵연료 연소시험을 위한 별도의 냉각수 순환 루프를 갖추고 있는데, 여기에 핵연료 조사리그를 장착하고 냉각수를 순환시킴으로써 조사중인 핵연료봉의 온도를 일정온도 이하로 유지시킨다. 특히 순환되는 냉각수의 유속이 매우 높은 상태에서 조사리그 내에 부착된 부품이나 센서들이 유체유발 진동에 의해 파손되거나 기능을 상실하는 경우 매우 큰 기회비용을 야기한다. 본 연구에서는 조사리그 부품의 건전성 사전 검토 및 고속 유동에서의 센서 동작 특성에 대한 사전검토를 위해 냉각수 모의 순환장치를 개발하였다. To remove heat generated during a burn-up test of nuclear fuels, the heat generation rate of nuclear fuels should be calculated accurately, and a coolant should be circulated in the test loop at an adequate flow rate. HANARO is an open pool?type reactor with an independent test loop for the burn-up test of nuclear fuels. A test rig is installed in the test loop, and a coolant is circulated through the test loop to maintain the temperature of the nuclear fuel rods within a desired temperature during an irradiation test. The components and sensors in the test rig can be broken or malfunction owing to the flow-induced vibration. In this study, a coolant flow simulation system was developed to verify and confirm the soundness of components and sensors assembled in the test rig with a high flow rate of the coolant.