• Title/Summary/Keyword: long-term deposition

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Estimating the Amounts of Long-term Cohesive Sediment Deposition in Two Tide-dominated Bays of South Korea: Numerical Study (조석으로 인한 만 내 점착성 부유사 퇴적량 추정 : 수치해석)

  • Kang, Min Goo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.1B
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    • pp.33-40
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    • 2010
  • In this study, a two-dimensional hydrodynamic and sediment transport modeling system, HSCTM-2D is employed to simulate the amounts of long-term cohesive sediment deposition in two study bays, and its applicability is evaluated. The modeling system's two modules for hydrodynamic modeling and sediment transport modeling are calibrated, comparing the simulated results and the observed tidal levels, tidal current velocities, and suspended sediment concentrations in the Asan and the Cheonsu Bays, South Korea. It is found that there are good agreements between the simulation results and the observed values. The amounts of long-term cohesive sediment deposition of the two study bays are estimated using the modeling system, taking the suspended sediment concentrations from the open ocean in the tide-dominated environment into account. And, in the case of the Asan Bay, the annual deposition rate reaches 8.1 cm/yr; the Cheonsu Bay, 14.5 cm/yr. Overall, it is concluded that the modeling system is useful to understand the physical process of cohesive suspended sediment transport and deposition in tidal water bodies and to establish the mitigation strategy.

Assessment of Radionuclide Deposition on Korean Urban Residential Area

  • Lee, Joeun;Han, Moon Hee;Kim, Eun Han;Lee, Cheol Woo;Jeong, Hae Sun
    • Journal of Radiation Protection and Research
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    • v.45 no.3
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    • pp.101-107
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    • 2020
  • Background: An important lesson learned from the Fukushima accident is that the transition to the mid- and long-term phases from the emergency-response phase requires less than a year, which is not very long. It is necessary to know how much radioactive material has been deposited in an urban area to establish mid- and long-term countermeasures after a radioactive accident. Therefore, an urban deposition model that can indicate the site-specific characteristics must be developed. Materials and Methods: In this study, the generalized urban deposition velocity and the subsequent variation in radionuclide contamination were estimated based on the characteristics of the Korean urban environment. Furthermore, the application of the obtained generalized deposition velocity in a hypothetical scenario was investigated. Results and Discussion: The generalized deposition velocities of 137Cs, 106Ru, and 131I for each residence type were obtained using three-dimensional (3D) modeling. For all residence types, the deposition velocities of 131I are greater than those of 106Ru and 137Cs. In addition, we calculated the generalized deposition velocities for each residential types. Iodine was the most deposited nuclide during initial deposition. However, the concentration of iodine in urban environment drastically decreases owing to its relatively shorter half-life than 106Ru and 137Cs. Furthermore, the amount of radioactive material deposited in nonresidential areas, especially in parks and schools, is more than that deposited in residential areas. Conclusion: In this study, the generalized urban deposition velocities and the subsequent deposition changes were estimated for the Korean urban environment. The 3D modeling was performed for each type of urban residential area, and the average deposition velocity was obtained and applied to a hypothetical accident. Based on the estimated deposition velocities, the decision-making systems can be improved for responding to radioactive contamination in urban areas. Furthermore, this study can be useful to predict the radiological dose in case of large-scale urban contamination and can support decision-making for long-term measurement after nuclear accident.

Sensitivity Analysis of Input Parameters for a Dynamic Food-Chain Model DYNACON (동적섭식경로모델 DYNACON에 대한 입력변수의 민감도분석)

  • Hwang, Won-Tae;Lee, Geun-Chang;Han, Moon-Hee;Cho, Gyu-Seong
    • Journal of Radiation Protection and Research
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    • v.25 no.1
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    • pp.11-19
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    • 2000
  • The sensitivity analysis of input parameters for a dynamic food chain model DYNACON was conducted as a function of deposition date for the long-lived radionuclides $(^{137}Cs,\;^{90}Sr)$. Also, the influence of input parameters for the short and long-terms contamination of selected foodstuffs (cereals, leafy vegetables, milk) was investigated. The input parameters were sampled using the LHS technique, and their sensitivity indices represented as PRCC. The sensitivity index was strongly dependent on contamination period as well as deposition date. In case of deposition during the growing stages of plants, the input parameters associated with contamination by foliar absorption were relatively important in long-term contamination as well as short-term contamination. They were also important in short-term contamination in case of deposition during the non-growing stages. In long-term contamination, the influence of input parameters associated with foliar absorption decreased, while the influence of input parameters associated with root uptake increased. These phenomena were more remarkable in case of the deposition of non-growing stages than growing stages, and in case of $^{90}Sr$ deposition than $^{137}Cs$ deposition. In case of deposition during growing stages of pasture, the input parameters associated with the characteristics of cattle such as feed-milk transfer factor and daily intake rate of cattle were relatively important in contamination of milk.

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Effects of Interlayer Formation and Thermal Treatment on Field-emission Properties of Carbon Nanotube Micro-tips (계면층 형성 및 열처리가 탄소 나노튜브 미세팁의 전계방출 특성에 미치는 영향)

  • Kim, Bu-Jong;Park, Jin-Seok
    • Journal of the Semiconductor & Display Technology
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    • v.12 no.2
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    • pp.1-6
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    • 2013
  • The effects of interlayer formation and thermal treatment on the field-emission properties of carbon nanotubes (CNTs) were investigated. The CNTs were prepared on tungsten (W) micro-tip substrates using the electrophoretic deposition (EPD) method. The interlayers, such as aluminum (Al) and hafnium (Hf) were coated on the W-tips prior to CNT deposition and after the deposition of CNTs all the species were thermally treated at $700^{\circ}C$ for 30 min. The field-emission properties of CNTs were significantly improved by thermal treatment. The threshold electric field for igniting the electron emission was decreased and the emission current was increased. The Raman spectroscopy results indicated that this was attributed mainly to the enhancement of CNTs by thermal treatment. Also, the CNTs deposited on the interlayers showed the remarkably improved results in the long-term emission stability, especially when they were thermally treated. The X-ray photoelectron spectroscopy (XPS) measurement confirmed that this was resulted from the formation of the additional cohesive forces between the CNTs and the underlying interlayers.

Prediction of radioactivity releases for a Long-Term Station Blackout event in the VVER-1200 nuclear reactor of Bangladesh

  • Shafiqul Islam Faisal ;Md Shafiqul Islam;Md Abdul Malek Soner
    • Nuclear Engineering and Technology
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    • v.55 no.2
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    • pp.696-706
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    • 2023
  • Consequences of an anticipated Beyond Design Basis Accident (BDBA) Long-Term Station Blackout (LTSBO) event with complete loss of grid power in the VVER-1200 reactor of Rooppur Nuclear Power Plant (NPP) of Unit-1 are assessed using the RASCAL 4.3 code. This study estimated the released radionuclides, received public radiological dose, and ground surface concentration considering 3 accident scenarios of International Nuclear and Radiological Event Scale (INES) level 7 and two meteorological conditions. Atmospheric transport, dispersion, and deposition processes of released radionuclides are simulated using a straight-line trajectory Gaussian plume model for short distances and a Gaussian puff model for long distances. Total Effective Dose Equivalent (TEDE) to the public within 40 km and radionuclides contribution for three-dose pathways of inhalation, cloudshine, and groundshine owing to airborne releases are evaluated considering with and without passive safety Emergency Core Cooling System (ECCS) in dry (winter) and wet (monsoon) seasons. Source term and their release rates are varied with the functional duration of passive safety ECCS. In three accident scenarios, the TEDE of 10 mSv and above are confined to 8 km and 2 km for the wet and dry seasons, respectively in the downwind direction. The groundshine dose is the most dominating in the wet season while the inhalation dose is in the dry season. Total received doses and surface concentration in the wet season near the plant are higher than those in the dry season due to the deposition effect of rain on the radioactive substances.

Field emission properties of carbon nanotubes grown on micro-tip substrates using an electrophoretic deposition method (미세 팁 기판 위에 전기영동법으로 성장시킨 탄소 나노튜브의 전계방출 특성)

  • Chang, Han-Beet;Noh, Young-Rok;Kim, Jong-Pil;Park, Jin-Seok
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.4
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    • pp.7-12
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    • 2010
  • Field-emission characteristics of carbon nanotubes(CNTs), which were grown on conical-type tungsten micro-tips by using an electrophoretic deposition(EPD) method, were examined. The EPD method proved to be convenient to manipulate and arrange CNTs from well dispersed suspensions onto such tip-type substrates. The growth rate of CNTs was proportional to the applied d.c. bias voltage and the process time. It was observed from the Raman study that the EPDproduced CNTs showed better crystal qualities with the Raman intensity ratio( $I_D$/$I_G$) of 0.41-0.42 than the CVD-produced CNTs and their crystal qualities could be further improved by thermal annealing. The electron emitters based on the EPDCNTs showed excellent field emission properties, such as the threshold voltage for electron emission of about 620 V and the maximum emission current of about 345 ${\mu}A$. In addition, the EPD-CNTs exhibited the stable long-term(up to 40 h) emission capability and the emission stability was enhanced by thermal annealing.

Development and testing of multicomponent fuel cladding with enhanced accidental performance

  • Krejci, Jakub;Kabatova, Jitka;Manoch, Frantisek;Koci, Jan;Cvrcek, Ladislav;Malek, Jaroslav;Krum, Stanislav;Sutta, Pavel;Bublikova, Petra;Halodova, Patricie;Namburi, Hygreeva Kiran;Sevecek, Martin
    • Nuclear Engineering and Technology
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    • v.52 no.3
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    • pp.597-609
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    • 2020
  • Accident Tolerant Fuels have been widely studied since the Fukushima-Daiichi accident in 2011 as one of the options on how to further enhance the safety of nuclear power plants. Deposition of protective coatings on nuclear fuel claddings has been considered as a near-term concept that will reduce the high-temperature oxidation rate and enhance accidental tolerance of the cladding while providing additional benefits during normal operation and transients. This study focuses on experimental testing of Zr-based alloys coated with Cr-based coatings using Physical Vapour Deposition. The results of long-term corrosion tests, as well as tests simulating postulated accidents, are presented. Zr-1%Nb alloy used as nuclear fuel cladding serves as a substrate and Cr, CrN, CrxNy layers are deposited by unbalanced magnetron sputtering and reactive magnetron sputtering. The deposition procedures are optimized in order to improve coating properties. Coated as well as reference uncoated samples were experimentally tested. The presented results include standard long-term corrosion tests at 360℃ in WWER water chemistry, burst (creep) tests and mainly single and double-sided high-temperature steam oxidation tests between 1000 and 1400℃ related to postulated Loss-of-coolant accident and Design extension conditions. Coated and reference samples were characterized pre- and post-testing using mechanical testing (microhardness, ring compression test), Thermal Evolved Gas Analysis analysis (hydrogen, oxygen concentration), optical microscopy, scanning electron microscopy (EDS, WDS, EBSD) and X-ray diffraction.

Characteristics of long-term operated Electrostatic airclean filter for air-conditioner (장시간사용(長時間使用)한 공조용(空調用) 전기집진(電氣集塵)필터의 특성(特性))

  • Hong, Young-Ki;Kang, Kwang-Ok;Lee, Sung-Hwa;Son, Sang-Cheol
    • Proceedings of the KIEE Conference
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    • 1995.11a
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    • pp.453-455
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    • 1995
  • In electrostatic airclean filter, the collection efficiency defends on particle charge in the ionizer section. The effect of electrostatic airclean filter condition (deposition of dust, variation of corona discharge current) on corona discharge characteristics was well studied. However, it seems not to be studied on corona discharge characteristics of electrostatic airclean filter respect to contaminated electrode which is caused by practical use. In this paper, Long-term(60days) effects are studied experimentally by two methods. The one is ozone concentration, the other is collection efficiency. Generation of ozone level was increased but collection efficiency was slightly reduced in long-term used electrostatic airclean filter.

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Effects of Selective Growth on Electron-emission Properties of Conical-type Carbon Nanotube Field-emitters (원추형 기판 위에 탄소 나노튜브의 선택적 성장이 전계방출 특성에 미치는 영향)

  • Kim, Bu-Jong;Noh, Young-Rok;Park, Jin-Seok
    • Journal of the Semiconductor & Display Technology
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    • v.11 no.1
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    • pp.61-65
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    • 2012
  • In this study, for use of carbon nanotubes (CNTs) as a cold cathode of x-ray tubes, we examine the effects of selective growth of CNTs on their field emission properties and long-term stability. The selective growth of CNTs was performed by selectively etching the catalyst layer which was used for CNTs' nucleation. CNTs were grown on conical-type tungsten substrates using an inductively-coupled plasma chemical vapor deposition system. For all the grown CNTs, their morphologies and microstructures were analyzed by field-emission scanning electron microscope and Raman spectroscopy. The electron-emission properties of CNTs and the long-term stability of emission currents were measured and characterized according to the CNTs' growth position on the substrate.