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RISS 인기검색어
- 검색키워드
- 저자 : Sungho Yoon (검색결과 269 건)
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Yoon Sungho,Son Hyeongwook,Kim Jeongtae,Kim Donguk 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4
In this study, experiments and theoretical analyses were performed on the partial discharge initiation voltage of the electrode–bound void according to various electrode materials, including the semi-conductive rubber in the joint box of the high voltage power cable. Electrode–bound void specimens using Brass, Al, Cu, SUS and EPDM semiconducting rubber were prepared, and PDIV (partial discharge inception voltage) was measured and analyzed at 25, 60 and 90 °C. As a result, it was found that the PDIV of the electrode–bound void is dependent on the work function of the electrode. It was possible to interpret the measurement results through the calculation of the discharge voltage using Paschen’s law in combination with the thermionic emission of the electrode and thermal expansion of materials. In addition, in the case of the EPDM semiconducting rubber electrode, it was analyzed that the measured PDIV was lower than the calculated value because the void thickness was reduced due to elasticity.
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A Study on Improving the National Safeguards Seals for the Wolsong Spent Fuel Dry Storage Facility
Sungho Yoon 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
A seal is one of the primary means of safeguards along with surveillance. The International Atomic Energy Agency (IAEA) uses various types of seals to verify the diversion of nuclear materials and is developing new seals according to the development of technology. Independent of the IAEA, ROK uses national safeguards seals for state-level regulation. A national safeguards inspector binds the nuclear material storage by combining a seal with a metal wire and checks the serial number of the RFID chip inserted in the seal with a reader. The Wolsong spent fuel dry storage facility has 14 modules, each with 24 seals, and thus a maximum of 336 national seals will be installed. Although dependent on the sealing method, it takes about 5 minutes to verify one seal. As such, a considerable workforce is required for verification, and both the IAEA and the ROK are currently conducting random inspections. In addition, there are cases where verification is impossible because old seals are damaged due to harsh environments and long exchange periods. Therefore, in this study, we analyzed cases in areas where sealing technology has been developed to improve the problems of the existing national safeguards seals. And we proposed a method for improving national seals by finding requirements of seals considering spent fuel dry storage facility characteristics. In international logistics, sealing is essential in product transport verification, terrorism prevention, and tariff imposition. Accordingly, the field of container sealing has been extensively developed, and the International Organization for Standardization (ISO) has regulated the mechanical requirements of the seal as ISO 17712 and the electronic requirements as ISO 18185. Mechanical seals include metal and plastic seals and metal seals include bolt seals, ball seals, and cable seals. In addition, there are various electronic seals, such as radio frequency identification (RFID), near field communication (NFC), infrared (IR). Recently, there has been a trend to use active seals that have a built-in battery and can implement various additional functions. Among the various seals, the main requirements for selecting seals suitable for dry storage facilities are as follows. First, use of a sealing tube longer than 10m should be possible. Second, it should have corrosion resistance so that it can be used for more than five years in the coastal area. Third, it must be a passive seal without a power supply. Fourth, it should not be overly costly. Finally, the seal verification time should be short. As a seal that satisfies these requirements, an electronic seal with application of the passive RFID method to the mechanical form of a metal cable seal is suitable. Since it is not an active seal, it is difficult to determine the time of breakage. Therefore, designing the seal such that the RFID is also damaged when the metal seal is broken will be helpful for verification. In this study, the requirements for national safeguards seals in dry storage facilities were defined, and measures to improve the existing national seals were studied. Field applicability will be evaluated through future sealing device design and demonstration tests.
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Facility Safeguardability Assessment for the Light Water Reactor Spent Fuel Dry Storage Facility
Sungho Yoon 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
Owing to the increase in saturation rate of the spent fuel storage pond in the Kori nuclear power plant, the interim spent fuel dry storage facility is scheduled to be constructed at the Kori site. To implement safeguards in the new dry storage facility effectively, the concept of “Safeguards-by- Design” (SBD) should be applied to reflect nuclear safeguard provisions in the earliest design stages. Detailed design information pertaining to dry storage facilities has not been determined; however, the design information related to safeguards have been inferred using case studies and interviews with nuclear power plant operators worldwide. On the basis of the results of the case studies on spent fuel dry storage facilities for light water reactors, most countries apply the metal cask method in containment buildings considering safety. Furthermore, Korean operators are also considering the same method owing to tight licensing schedules and safety issues. Using the Facility Safeguardability Assessment (FSA) methodology (one of the safeguard evaluation methodologies), the difference in design between the heavy water reactor spent fuel dry storage facility, an established IAEA safeguards approach reference nuclear facility, and the light water reactor spent fuel dry storage facility (the new nuclear facility) were analyzed. Two major differences were noted as issues pertaining to potential safeguards. First, the difference in design and transport method in terms of the difference in size and weight of the spent nuclear fuel is important; light water reactor fuel is 20 times heavier than heavy water reactor that needs partial defect inspection in assemblies. Second, the difference in safeguard approach owing to the difference between the modular storage method in heavy water reactor and the container type storage method in light water reactor must be considered; movable storage cask renders the IAEA surveillance approach difficult. The results of this study can be used to identify the safeguards requirements in advance, enabling the operator to design new dry storage facilities resulting in timely and cost-effective implementation.
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A Study on the Establishment of Integrated Database for Safeguards and Nuclear Export Control
Sungho Yoon 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Korea Institute of Nuclear Non-proliferation and Control (KINAC) Safeguards division and Export control division operate regulation management system each other according to their work scope and characteristics. Korea Safeguards Information System (KSIS) of Safeguards division handles information for nuclear material accounting and control. Especially, accounting and declaration reports submitted to International Atomic Energy Agency (IAEA) are important information in this system. And Nuclear Import and Export Control System (NEPS) of Export control division deals with import and export information of nuclear materials and nuclear weapon trigger list items. Establishing and operating the integrated database as sharing information between KSIS and NEPS derive merits as follows. First, the full cycle of nuclear material transfer records can be managed by collecting information on the nuclear materials from import to export or disposal. In addition, regulatory body can verify inconsistency between transfer records and account records in date, location, element, mass etc. Especially, small quantity nuclear materials are major loop hole in nuclear material accountancy system. The accumulated material transfer data will give an evidence to catch loss nuclear material. Second, sharing the information on nuclear fuel cycle related research and development activities in both divisions can utilize the information to outreach on facility subject to nuclear technology transfer for Nuclear Suppliers Group (NSG) and additional protocol declaration for Safeguards Agreement with IAEA. Third, regulatory body is easily able to manage entire import and IAEA report procedure for items subject to the Nuclear Cooperation Agreement (NCA). In present, KINAC regulation on NCA is divided to Export control and Safeguards. Export control division conducts classification imported items subject to NCA and acquires prior consent or notifies to other country. And Safeguards division report inventory list for each NCA country to the ROK government once a year. Imported NCA inventory list will be generated automatically by merging database. Then, it can be easily verified without any additional process by both divisions.
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The Effect of Moisture on the Creepage Discharge of Transformer Pressboard
Yoon Sungho,Son Hyeongwook,Kim Woobin,Lee Dongzoon,Kim Jeongtae 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5
This paper addresses the creepage discharge process in moisture-absorbed pressboard under the AC voltage stress. The measurement for partial discharges, dissolved gases and furan compounds have been performed for various types of specimens such as the normal dry specimen, dry pressboard with much moisture in oil and the wet pressboard. The result showed that partial discharge inception voltage, discharge number and accumulated charge quantity increased and the discharge magnitude per pulse decreased in case of specimen with moisture. The partial discharge patterns at the initial stage in the trend with time showed different according to the types of specimens, but after the initial stage the discharge trend in all cases became similar with recurrence pattern of large/small discharges and then small discharges. In case of dry pressboard with much moisture in oil, the generation of gases was less than compared with normal dry specimen, but a lot of furans generated. On the contrary, in case of wet pressboard, large amount of gas generated almost without furan generation. Results indicated a mechanism of creepage discharge in which moisture aggregated in the amorphous region of the pressboard attracted discharges owing to the electric field enhancement, and the degradation and carbonization of pressboards would be accelerated by these discharges.
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Mass Transfer Enhancement by a Single Emulsion Droplet
Sungho Yoon,Yong Tae Kang 대한설비공학회 2016 International Journal of Air-Conditioning and Refr Vol.24 No.1
The mass transfer enhancement (MTE) by a single emulsion droplet subjected to a Poiseuille °ow is studied by using h-adaptive ¯nite element approximation. The Navier–Stokes equations with the surface tension force at a droplet–°uid phase for the °uid °ows are considered. The mass transfer is modeled by convection–di®usion equation. The interface capturing method with a conservative level set approach is employed to track the interface of a droplet. This is also incorporated with a mesh adaptivity for increasing the resolution in vicinity of the interface of the droplet. We numerically investigate the e®ect of hydrodynamic interactions of the droplet with the °uid on the mass transfer in varying physical parameters of the °uid °ows and the suspended droplet in order to ¯nd the optimum conditions to invoke the enhanced MTE. It is found that Pe is an important factor to enhance the mass transfer transported by the convective current with di®usion. It is also found that Ca is an important factor for MTE considering disturbances and deformability of the droplet during the mass transfer process. It is found that the MTE decreases with increasing Ca in a high concentration region (C ¼ 0:9) while MTE does not depend much on Ca in a low concentration region (C ¼ 0:1).
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