• Title/Summary/Keyword: Buffer area

Search Result 522, Processing Time 0.032 seconds

Alternative Concept to Enhance the Disposal Efficiency for CANDU Spent Fuel Disposal System (CANDU 사용후핵연료 처분시스템 효율향상 개념 도출)

  • Lee, Jong-Youl;Cho, Dong-Geun;Kook, Dong-Hak;Lee, Min-Soo;Choi, Heui-Joo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
    • /
    • v.9 no.3
    • /
    • pp.169-179
    • /
    • 2011
  • There are two types of nuclear reactors in Korea and they are PWR type and CANDU type. The safe management of the spent fuels from these reactors is very important factor to maintain the sustainable energy supply with nuclear power plant. In Korea, a reference disposal system for the spent fuels has been developed through a study on the direct disposal of the PWR and CANDU spent fuel. Recently, the research on the demonstration and the efficiency analyses of the disposal system has been performed to make the disposal system safer and more economic. PWR spent fuels which include a lot of reusable material can be considered being recycled and a study on the disposal of HLW from this recycling process is being performed. CANDU spent fuels are considered being disposed of directly in deep geological formation, since they have little reusable material. In this study, based on the Korean Reference spent fuel disposal System (KRS) which was to dispose of both PWR type and CANDU type, the more effective CANDU spent fuel disposal systems were developed. To do this, the disposal canister for CANDU spent fuels was modified to hold the storage basket for 60 bundles which is used in nuclear power plant. With these modified disposal canister concepts, the disposal concepts to meet the thermal requirement that the temperature of the buffer materials should not be over $100^{\circ}C$ were developed. These disposal concepts were reviewed and analyzed in terms of disposal effective factors which were thermal effectiveness, U-density, disposal area, excavation volume, material volume etc. and the most effective concept was proposed. The results of this study will be used in the development of various wastes disposal system together with the HLW wastes from the PWR spent fuel recycling process.

A Study on the Maintenance Plan of Trees in Gwanghalluwon Garden for Representing Traditional Space (전통공간 재현을 위한 광한루원의 수목정비방안 연구)

  • Lee, Won-Ho;Kim, Dong-Hyun;Kim, Jae-Ung;Ahn, Hye-In;Kim, Dae-Yeol;Cho, Un-Yeon
    • Journal of the Korean Institute of Traditional Landscape Architecture
    • /
    • v.32 no.3
    • /
    • pp.82-95
    • /
    • 2014
  • This study aims to draw up measures to planting tree and maintain a landscape in traditional space. Preceding comprehensive theoretical consideration of selected species of trees and tree maintenance. And analysis of present condition of planting in cases of Gwanghalluwon Garden, then draw a maintenance plans of planting through species of trees and landscape of planting recorded in literature. The results were as follows. First, Analysis of selected species of trees and tree maintenance that traditional space. A dispute about the selection species of trees in traditional space has been continued until today. Because unconditional reject of foreign trees are limited. In this context, should be sublated that hasty blind faith of records and dichotomous preparation plans such as removal of foreign trees and implicitly planting of native plants. Secondly, Planted trees in Gwanghalluwon garden was investigated and found to the species of trees used in traditional space such as Pine(Pinus densiflora S. et Z.), Sawleaf Zelkova(Zelkova serrata), Ginkgo(Ginkgo biloba), Crape Myrtle(Lagerstroemia indica L.). But, present planting irrelevant to traditional space, except Gwanghallu pavilion area from the spatiality. Thirdly, A look at the records or literature that maintenance of planting through historical research are limited. Because literature was recorded Salix spp., Crape Myrtle, Bambusoideae(Pseudosasa japonica), lotus only among planted trees in Gwanghalluwon garden. Fourth, Gwanghallu zone have nature of history and sense of place. And It was going to restore the appearance on historical. Consequently maintenance plan of planting of Gwanghallu zone should be maintain the current state. Wanwol pavillion zone can be recognized as the original form because they look similar to the Gwangallu zone's buildings. Therefore, it is necessary to secure the sense of place different from Gwanghallu zone by buffer planting for composition of transition space. Wolmaejip zone and lawn zone was marketplace in outside of castle and large forest. Accordingly, this area should be symbolic restoration of the Yulrim(栗林) and representation of the marketplace in outside of castle through aggregation of facilities and administrative facilities in Gwanghalluwon garden. East lawn of the Wanwol pavilion zone is should be maintained the current state that opened place in terms of using thought linked with the Wanwol pavilion zone. Boundary zone of the Gwanghalluwon garden is difficult to associate in terms of historical research and authenticity. Therefore, application of cultural landscape that appeared in literature is be worth.

THE CHANGE OF THE CONFIGURATION OF HYDROXYAPATITE CRYSTALS IN ENAMEL BY CHANGES OF PH AND DEGREE OF SATURATION OF LACTIC ACID BUFFER SOLUTION (유산 완충용액의 pH 및 포화도 변화에 따른 법랑질 내 수산화인회석 결정 형태의 변화)

  • Chon, Young-Eui;Jung, Il-Young;Roh, Bung-Duk;Lee, Chan-Young
    • Restorative Dentistry and Endodontics
    • /
    • v.32 no.6
    • /
    • pp.498-513
    • /
    • 2007
  • Since it was reported that incipient enamel caries can be recovered, previous studies have quantitatively evaluated that enamel artificial caries have been, remineralized with fluoride showing simultaneously the increase of width of surface layer and the decrease of width of the body of legion. There is, however, little report which showed that remineralization could occur without fluoride. In addition, the observations on the change of hydroxyapatite crystals also have been scarcely seen. In this study, enamel caries in intact premolars or molars was induced by using lactic acidulated buffering solutions over 2 days. Then decalcified specimens were remineralized by seven groups of solutions using different degree of saturation(0.212, 0.239, 0.301, 0.355) and different pH(5.0, 5.5, 6.0) over 10 days. A qualitative comparison to changes of hydroxyapatite crystals after fracturing teeth was made under SEM(scanning electron microscopy) and AFM(atomic force microscopy). The results were as follows: 1. The size of hydroxyapatite crystals in demineralized area was smaller than the normal ones. While the space among crystals was expanded, it was observed that crystals are arranged irregularly. 2. In remineralized enamel area, the enlarged crystals with various shape were observed when the crystals were fused and new small crystals in intercrystalline spaces were deposited. 3. Group 3 and 4 with higher degree of saturation at same pH showed the formation of large clusters by aggregation of small crystals from the surface layer to the lesion body than group 1 and 2 with relatively low degree of saturation at same pH did. Especially group 4 showed complete remineralization to the body of lesions. Group 5 and 6 with lower pH at similar degree of saturation showed remineralization to the body of lesions while group 7 didn't show it. Unlike in Group 3 and 4, Group 5 and 6 showed that each particle was densely distributed with clear appearance rather than crystals form clusters together.

Glass Dissolution Rates From MCC-1 and Flow-Through Tests

  • Jeong, Seung-Young
    • Proceedings of the Korean Radioactive Waste Society Conference
    • /
    • 2004.06a
    • /
    • pp.257-258
    • /
    • 2004
  • The dose from radionuclides released from high-level radioactive waste (HLW) glasses as they corrode must be taken into account when assessing the performance of a disposal system. In the performance assessment (PA) calculations conducted for the proposed Yucca Mountain, Nevada, disposal system, the release of radionuclides is conservatively assumed to occur at the same rate the glass matrix dissolves. A simple model was developed to calculate the glass dissolution rate of HLW glasses in these PA calculations [1]. For the PA calculations that were conducted for Site Recommendation, it was necessary to identify ranges of parameter values that bounded the dissolution rates of the wide range of HLW glass compositions that will be disposed. The values and ranges of the model parameters for the pH and temperature dependencies were extracted from the results of SPFT, static leach tests, and Soxhlet tests available in the literature. Static leach tests were conducted with a range of glass compositions to measure values for the glass composition parameter. The glass dissolution rate depends on temperature, pH, and the compositions of the glass and solution, The dissolution rate is calculated using Eq. 1: $rate{\;}={\;}k_{o}10^{(ph){\eta})}{\cdot}e^{(-Ea/RT)}{\cdot}(1-Q/K){\;}+{\;}k_{long}$ where $k_{0},\;{\eta}$ and Eaare the parameters for glass composition, pH, $\eta$ and temperature dependence, respectively, and R is the gas constant. The term (1-Q/K) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_{0},\;{\eta}\;and\;E_{a}$ are the parameters for glass composition, pH, and temperature dependence, respectively, and R is the gas constant. The term (1-Q/C) is the affinity term, where Q is the ion activity product of the solution and K is the pseudo-equilibrium constant for the glass. Values of the parameters $k_0$, and Ea are determined under test conditions where the value of Q is maintained near zero, so that the value of the affinity term remains near 1. The dissolution rate under conditions in which the value of the affinity term is near 1 is referred to as the forward rate. This is the highest dissolution rate that can occur at a particular pH and temperature. The value of the parameter K is determined from experiments in which the value of the ion activity product approaches the value of K. This results in a decrease in the value of the affinity term and the dissolution rate. The highly dilute solutions required to measure the forward rate and extract values for $k_0$, $\eta$, and Ea can be maintained by conducting dynamic tests in which the test solution is removed from the reaction cell and replaced with fresh solution. In the single-pass flow-through (PFT) test method, this is done by continuously pumping the test solution through the reaction cell. Alternatively, static tests can be conducted with sufficient solution volume that the solution concentrations of dissolved glass components do not increase significantly during the test. Both the SPFT and static tests can ve conducted for a wide range of pH values and temperatures. Both static and SPFt tests have short-comings. the SPFT test requires analysis of several solutions (typically 6-10) at each of several flow rates to determine the glass dissolution rate at each pH and temperature. As will be shown, the rate measured in an SPFt test depends on the solution flow rate. The solutions in static tests will eventually become concentrated enough to affect the dissolution rate. In both the SPFt and static test methods. a compromise is required between the need to minimize the effects of dissolved components on the dissolution rate and the need to attain solution concentrations that are high enough to analyze. In the paper, we compare the results of static leach tests and SPFT tests conducted with simple 5-component glass to confirm the equivalence of SPFT tests and static tests conducted with pH buffer solutions. Tests were conducted over the range pH values that are most relevant for waste glass disssolution in a disposal system. The glass and temperature used in the tests were selected to allow direct comparison with SPFT tests conducted previously. The ability to measure parameter values with more than one test method and an understanding of how the rate measured in each test is affected by various test parameters provides added confidence to the measured values. The dissolution rate of a simple 5-component glass was measured at pH values of 6.2, 8.3, and 9.6 and $70^{\circ}C$ using static tests and single-pass flow-through (SPFT) tests. Similar rates were measured with the two methods. However, the measured rates are about 10X higher than the rates measured previously for a glass having the same composition using an SPFT test method. Differences are attributed to effects of the solution flow rate on the glass dissolution reate and how the specific surface area of crushed glass is estimated. This comparison indicates the need to standardize the SPFT test procedure.

  • PDF

Isolation and Characterization of Exopolysaccharide Producing Lactic Acid Bacteria from Korean Soy Sauce and Soybean Paste (전통 장류로부터 Exopolysaccharide 생성 유산균의 분리 및 특성)

  • Yun, Hye Ju;Lee, You Jung;Yeo, Soo-Hwan;Park, Hye Young;Park, Heui-Dong;Baek, Seong Yeol
    • Microbiology and Biotechnology Letters
    • /
    • v.41 no.2
    • /
    • pp.190-197
    • /
    • 2013
  • Three slime-forming lactic acid bacteria were isolated from traditional Korean fermented soy sauce and soybean paste and shown to produce exopolysaccharides (EPS) in sucrose media. By isolating the strains, examining their morphological characteristics and determining their 16S rDNA sequences, N58-5 and K6-7 were identified as Leuconostoc mesenteroides and N45- 10 as Leuconostoc citreum. The acid and bile tolerances of these three strains were investigated. Amongst the three lactic acid bacteria, Leuc. citreum N45-10 exhibited the highest viability ($10^5-10^6$ CFU/ml) in 0.05 M sodium phosphate buffer (pH 0.3) for 2 h, in artificial gastric juice for 2 h and in 0.3%, 0.5% oxgall for 24h. Leuc. mesenteroides K6-7, N58-5 and Leuc. citreum N45- 10 were grown in sucrose liquid medium and 8.16 g/L, 3.65 g/L, 16.17 g/L of EPS was collected, respectively. The hydrolyzed EPS was analyzed by HPLC in order to determine the sugar composition of EPS. Leuc. mesenteroides K6-7 and N58-5 showed two peaks indicating glucose and fructose, thus they were determined to be hetero-type polysaccharides. Leuc. citreum N45-10 showed only the glucose polymer, indicating it to be a homo-type polysaccharide. In addition, all three lactic acid bacterial hemolysis did not demonstrate a clear zone in blood agar in the area surrounding a lactic acid bacteria colony.

Interaction Between TCP and MAC-layer to Improve TCP Flow Performance over WLANs (유무선랜 환경에서 TCP Flow의 성능향상을 위한 MAC 계층과 TCP 계층의 연동기법)

  • Kim, Jae-Hoon;Chung, Kwang-Sue
    • Journal of KIISE:Information Networking
    • /
    • v.35 no.2
    • /
    • pp.99-111
    • /
    • 2008
  • In recent years, the needs for WLANs(Wireless Local Area Networks) technology which can access to Internet anywhere have been dramatically increased particularly in SOHO(Small Office Home Office) and Hot Spot. However, unlike wired networks, there are some unique characteristics of wireless networks. These characteristics include the burst packet losses due to unreliable wireless channel. Note that burst packet losses, which occur when the distance between the wireless station and the AP(Access Point) increase or when obstacles move temporarily between the station and AP, are very frequent in 802.11 networks. Conversely, due to burst packet losses, the performance of 802.11 networks are not always as sufficient as the current application require, particularly when they use TCP at the transport layer. The high packet loss rate over wireless links can trigger unnecessary execution of TCP congestion control algorithm, resulting in performance degradation. In order to overcome the limitations of WLANs environment, MAC-layer LDA(Loss Differentiation Algorithm)has been proposed. MAC-layer LDA prevents TCP's timeout by increasing CRD(Consecutive Retry Duration) higher than burst packet loss duration. However, in the wireless channel with high packet loss rate, MAC-layer LDA does not work well because of two reason: (a) If the CRD is lower than burst packet loss duration due to the limited increase of retry limit, end-to-end performance is degraded. (b) energy of mobile device and bandwidth utilization in the wireless link are wasted unnecessarily by Reducing the drainage speed of the network buffer due to the increase of CRD. In this paper, we propose a new retransmission module based on Cross-layer approach, called BLD(Burst Loss Detection) module, to solve the limitation of previous link layer retransmission schemes. BLD module's algorithm is retransmission mechanism at IEEE 802.11 networks and performs retransmission based on the interaction between retransmission mechanisms of the MAC layer and TCP. From the simulation by using ns-2(Network Simulator), we could see more improved TCP throughput and energy efficiency with the proposed scheme than previous mechanisms.

Study on the Consequence Effect Analysis & Process Hazard Review at Gas Release from Hydrogen Fluoride Storage Tank (최근 불산 저장탱크에서의 가스 누출시 공정위험 및 결과영향 분석)

  • Ko, JaeSun
    • Journal of the Society of Disaster Information
    • /
    • v.9 no.4
    • /
    • pp.449-461
    • /
    • 2013
  • As the hydrofluoric acid leak in Gumi-si, Gyeongsangbuk-do or hydrochloric acid leak in Ulsan, Gyeongsangnam-do demonstrated, chemical related accidents are mostly caused by large amounts of volatile toxic substances leaking due to the damages of storage tank or pipe lines of transporter. Safety assessment is the most important concern because such toxic material accidents cause human and material damages to the environment and atmosphere of the surrounding area. Therefore, in this study, a hydrofluoric acid leaked from a storage tank was selected as the study example to simulate the leaked substance diffusing into the atmosphere and result analysis was performed through the numerical Analysis and diffusion simulation of ALOHA(Areal Location of Hazardous Atmospheres). the results of a qualitative evaluation of HAZOP (Hazard Operability)was looked at to find that the flange leak, operation delay due to leakage of the valve and the hose, and toxic gas leak were danger factors. Possibility of fire from temperature, pressure and corrosion, nitrogen supply overpressure and toxic leak from internal corrosion of tank or pipe joints were also found to be high. ALOHA resulting effects were a little different depending on the input data of Dense Gas Model, however, the wind direction and speed, rather than atmospheric stability, played bigger role. Higher wind speed affected the diffusion of contaminant. In term of the diffusion concentration, both liquid and gas leaks resulted in almost the same $LC_{50}$ and ALOHA AEGL-3(Acute Exposure Guidline Level) values. Each scenarios showed almost identical results in ALOHA model. Therefore, a buffer distance of toxic gas can be determined by comparing the numerical analysis and the diffusion concentration to the IDLH(Immediately Dangerous to Life and Health). Such study will help perform the risk assessment of toxic leak more efficiently and be utilized in establishing community emergency response system properly.

Mineralogy and the Behavior of Heavy Metals at Different Depths in Tailing Impoundment of the Samsanjeil mine (삼산제일광산 광미 매립지의 매립 심도에 따른 광물 변화 및 중금속의 거동)

  • Kim, Heong-Jung;Kim, Yeong-Kyoo;Choo, Chang-Oh
    • Journal of the Mineralogical Society of Korea
    • /
    • v.22 no.3
    • /
    • pp.229-240
    • /
    • 2009
  • In Gosung, the symptoms similar to itai-itai disease from neighboring residents of the Samsanjeil mine have been social issues. Therefore, various researches on the behavior of heavy metals of the tailings impoundment of 280,000 ton in the Samsanjeil mine are required. In this paper, mineralogical and geochemical studies on the tailings at different depths in the Samsanjeil mine were investigated and the factors on the behavior of heavy metals were also studied. At two sampling sites (NN and SN), samples were collected at different depths down to 1 m. At NN sites, pH values decreased with depth, while those at SN sites did not show significant changes. XRD analysis showed that the main minerals in the tailings were quartz, microcline, muscovite, and chlorite with minor amount of gypsum. There were no noticeable changes in the mineral composition with depth. At NN sites, the amount of calcite was negligible, and jarosite, which usually occurs at acid soil or acid mine drainage at pH lower than 4, was identified. However, the samples at SN site contained relatively high contents of calcite with pyrite. Therefore, calcite seemed to buffer the acid and control pH at SN site. The contents of heavy metals in tailings were in the order of Cu > As > Zn > Pb > Co > Cr > Ni > Cd. The heavy metal concentrations in the tailings were closely related with pH changes. The concentrations of Cd and Co were much lower at NN site at which pH values are low than those at SN sites. Contrary to that, Cr and As which exist as oxyanions showed higher concentrations at SN sites. This result showed that the behaviors of heavy metals in our study area were controlled by pH which is influenced by the contents of calcite.

An Actual Condition and Management Plan of Historical Cultural Forest in Joseon Royal Tombs Seolleung and Jeongneung (조선왕릉 선릉·정릉의 역사문화경관림 실태와 관리 방안)

  • Choi, Jong-Hee
    • Journal of the Korean Institute of Traditional Landscape Architecture
    • /
    • v.37 no.3
    • /
    • pp.13-21
    • /
    • 2019
  • The purpose of this study is to understand the actual conditions of Seolleung and Jeongneung historical cultural landscape forests of Joseon Royal Tombs and to prepare systematic preservation and management plans, and the results of the study are as follows. First, in the current situation, vegetation is dominated by Quercus aliena and Pinus densiflora, and it is distributed as Quercus aliena community 21.22%, Pinus densiflora community 21.22% and Pinus densiflora afforestation 3.69%. The main vegetation communities are Pinus densiflora community, Quercus aliena community, Alnus japonica community, Pinus densiflora afforestation, and Pinus koraiensis afforestation. Second, in the measuring of Diameter of Basal Height in eight quadrat, the main species were Pinus densiflora, Quercus aliena and Alnus japonica and the maximum Distribution of Diameter of Basal Height was 20-25cm of Pinus densiflora, 25-30cm of Quercus aliena, and 25-30cm of Alnus japonica. Third, the forest is located between King and Queen's royal tombs in Seolleung, which is not suitable for the form of the tombs. In Jeongneung, the narrow space of the ceremony area shows an unfavorable environment for the formation of pine forests, and the pine forests on the left and right have a different heights that hinders the visual landscape. Fourth, as a management plan for the forests, stray pine trees, which are exotic species, are removed and pine forests are formed along the ridges. After removing the forest between the King and Queen's royal tombs of Seolleung, grass is formed, and the height of the pine forest on the left and right of Jeongneung is adjusted, and pines near the Gokjang are continuously monitored. Visually heterogeneous trees are arranged boldly, the boundary is adjusted to harmonize with the surrounding deciduous trees and maintains a buffer space of about 10m. This study is expected to provide important implications for Joseon Royal Tombs and in the future, the actual conditions of each Joseon Royal Tombs should be understood and appropriate management plans should be prepared.

Macroporous Thick Tin Foil Negative Electrode via Chemical Etching for Lithium-ion Batteries (화학적 식각을 통해 제조한 리튬이온 이차전지용 고용량 다공성 주석후막 음극)

  • Kim, Hae Been;Lee, Pyung Woo;Lee, Dong Geun;Oh, Ji Seon;Ryu, Ji Heon
    • Journal of the Korean Electrochemical Society
    • /
    • v.22 no.1
    • /
    • pp.36-42
    • /
    • 2019
  • A macroporous Sn thick film as a high capacity negative electrode for a lithium ion secondary battery was prepared by using a chemical etching method using nitric acid for a Sn film having a thickness of $52{\mu}m$. The porous Sn thick film greatly reduced the over-voltage for the alloying reaction with lithium by the increased reaction area. At the same time. The porous structure of active Sn film plays a part in the buffer and reduces the damage by the volume change during cycles. Since the porous Sn thick film electrode does not require the use of the binder and the conductive carbon black, it has substantially larger energy density. As the concentration of nitric acid in etching solution increased, the degree of the etching increased. The etching of the Sn film effectively proceeded with nitric acid of 3 M concentration or more. The porous Sn film could not be recovered because the most of Sn was eluted within 60 seconds by the rapid etching rate in the 5 M nitric acid. In the case of etching with 4 M nitric acid for 60 seconds, the appropriate porous Sn film was formed with 48.9% of weight loss and 40.3% of thickness change during chemical acid etching process. As the degree of etching of Sn film increased, the electrochemical activity and the reversible capacity for the lithium storage of the Sn film electrode were increased. The highest reversible specific capacity of 650 mAh/g was achieved at the etching condition with 4 M nitric acid. The porous Sn film electrode showed better cycle performance than the conventional electrode using a Sn powder.