• Title/Summary/Keyword: Medium reactor

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A Bioreactor for the Effective Removal of the Hydrogen Sulfide from Biogas (바이오가스에 포함된 고농도 황화수소의 효율적 제거를 위한 미생물반응기)

  • Namgung, Hyeong-Kyu;Yoon, Chang No;Song, JiHyeon
    • Journal of Korean Society for Atmospheric Environment
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    • v.29 no.6
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    • pp.811-817
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    • 2013
  • A two-stage bioreactor system using sulfur-oxidizing bacteria was studied to abate high strength hydrogen sulfide ($H_2S$) from biogas. The two-stage bioreactor consisted of a $H_2S$ absorption column (0.5 L) and a microbial oxidation column (1 L) in series, and the liquid medium was continuously recirculated through the columns. The objectives of this study were to determine the feasibility of the bioreactor for biogas desulfurization and to investigate the effect of the medium circulation rate on the system performance. An averaged concentration of $H_2S$ introduced to the bioreactor was 530 ppm, corresponding to an overall loading rate of $44.4g/m^3/hr$. During the initial 20 days period at the medium recirculation rate of 8 reactor volumes per hour (12 L/hr), the dissolved oxygen (DO) concentration in the oxidation column was 6 mg/L, while the DO in the absorption column was 0.5 mg/L showing that the oxygen contents of the biogas stream was not altered. Because of the biological oxidation of $H_2S$ in the oxidation column, the sulfate concentration increased from 200 mg/L to 5,600 mg/L in the liquid medium. The removal efficiency of $H_2S$ was greater than 99% in the initial operation period. After the initial period, the medium recirculation rate between the two columns was stepwise changed eight times from 1.0 to 40 vol/hr (1.5~60 L/hr). At the recirculation rate of faster than 4 vol/hr, the $H_2S$ removal efficiencies were found to be high, but the efficiency declined at the lower recirculation rates than the threshold.

Optimized Flooding Analysis Method for Compartment for Nuclear Power Plant (원전 격실에 대한 최적 침수분석 방법)

  • Song, Dong-Soo;Kim, Sang-Yeol
    • Journal of Energy Engineering
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    • v.21 no.1
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    • pp.75-80
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    • 2012
  • In this paper a realistic bounding method for flooding analysis following rupture of large size of thanks and piping is defined. Mass and energy release during main feedwater line break accident is analyzed with RETRAN code. It is modeled that the main feed water control valve is closed in 5.0 seconds after reactor trip. In result of the analysis, largest mass and energy is discharged at 70% reactor power. The flood sources for main feedwater room are calculated when piping failure occurs in the high energy line and medium energy line. Based on the result of flood level (1.43m), it is investigated that all of the safety-related environmental qualification equipments are well located above the flood level.

CO Fermentation of Eubacterium limosum KIST612

  • Chang, In-Seop;Kim, Do-Hee;Kim, Byung-Hong;Shin, Pyong-Kyun;Sung, Ha-Chin;Lovitt, Robert W.
    • Journal of Microbiology and Biotechnology
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    • v.8 no.2
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    • pp.134-140
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    • 1998
  • Eubacterium limosum KIST612 was cultured on phosphate-buffered basal medium (PBBM) with carbon monoxide (CO) as the sole energy and carbon source. The initial growth rate of this strain was approximately 0.17~0.25 $h^-1$/ and the $K_s$ value for dissolved substrate was 0.14 mM. CO was limiting during the growth of the bacterium when the CO partial pressure was less than 0.6 atm (0.5 mM dissolved CO). The bacterial growth rate was reduced in the presence of acetate. When sufficient CO was supplied using a gas-lift reactor, the acetate concentration went up to 90 mM in 116 h. Based on these findings, it is suggested that a pressurized reactor be used to develop a process to convert CO-rich gases into multi-carbon compounds.

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A new approach for calculation of the neutron noise of power reactor based on Telegrapher's theory: Theoretical and comparison study between Telegrapher's and diffusion noise

  • Bahrami, Mona;Vosoughi, Naser
    • Nuclear Engineering and Technology
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    • v.52 no.4
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    • pp.681-688
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    • 2020
  • The telegrapher's theory was used to develop a new formulation for the neutron noise equation. Telegrapher's equation is supposed to demonstrate a more realistic approximation for neutron transport phenomena, especially in comparison to the diffusion theory. The physics behind such equation implies that the signal propagation speed is finite, instead of the infinite as in the case of ordinary diffusion. This paper presents the theory and results of the development of a new method for calculation of the neutron noise using the telegrapher's equation as its basis. In order to investigate the differences and strengths of the new method against the diffusion based neutron noise, a comparison was done between the behaviors of two methods. The neutron noise based on SN transport considered as a precision measuring point. The Green's function technique was used to calculate the neutron noise based on telegrapher's and diffusion methods as well as the transport. The amplitude and phase of Green's function associated with the properties of the medium and frequency of the noise source were obtained and their behavior was compared to the results of the transport. It was observed, the differences in some cases might be considerable. The effective speed of propagation for the noise perturbations were evaluated accordingly, resulting in considerable deviations in some cases.

The characteristic change of water using the wet-plasma (습식 플라즈마에 의한 물의 특성 변화)

  • Lee, Jae-Dong;Park, Hong-Jae;Lee, Dong-Hun;Kim, Young-Ju;Park, Jae-Yoon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07b
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    • pp.1151-1154
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    • 2003
  • Ultraviolet rays, OH H O radical and $O_3$ produced by the streamer discharge in water are widely used to deactivate microorganisms and remove organic contaminants in water and the dominant factor of these decomposition is the oxidized reaction of hydrogen peroxide and dissolved $O_3$ in water. In this paper, the barrier discharge was used to create plasma in a gas, liquid and solid medium and the electrode with the reactor combined barrier with packed type(BPR) was made as noncontact way against water so that the effect of water characteristic change by the erosion of electrodes exposing in water should be minimized. The active radical and $O_3$ gas generated in plasma region were reacted into the water as electrode so that at the same time a dissolved $O_3$ and hydrogen peroxide were formed in water and The change of pH and conductivity were measured.

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Thermal Characteristics of an N2O Catalytic Ignitor with Packed-bed Geometry (팩 베드 형상을 가지는 N2O 촉매 점화기의 열적현상)

  • You, Woo-Jun;Kim, Jin-Kon;Moon, Hee-Jang;Jang, Seok-Pil
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.4
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    • pp.398-404
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    • 2007
  • In this paper, thermal characteristics of a nitrous oxide ($N_2O$) catalytic reactor with packed-bed geometry are theoretically and numerically investigated. Several researchers experimentally presented that catalytic decomposition of $N_2O$ in a packed bed generates about 82kJ/mole in the exothermic reaction. Based on the results they have studied the catalytic decomposition of $N_2O$ in a packed bed to use it not only as a mono-propellant thrust for small satellites but also as an igniter system for hybrid rockets. So we aim to identify important parameters existing in an $N_2O$ packed-bed geometry, and to clarify its critical effect on thermal characteristics of the catalytic igniter using a porous medium approach.

Development of an Oxide Reduction Process for the Treatment of PWR Spent Fuel (PWR 사용후핵연료 처리를 위한 금속전환공정 개발)

  • Hur, Jin-Mok;Hong, Sun-Seok;Jeong, Sang-Mun;Lee, Han-Soo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.8 no.1
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    • pp.77-84
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    • 2010
  • Reduction of oxides has been investigated for the volume reduction and recycling of the spent oxide fuel from commercial nuclear power plants. Various oxide reduction methods were proposed and KAERI (Korea Atomic Energy Research Institute) is currently developing an electrochemical reduction process using a LiCl-$Li_2O$ molten salt as a reaction medium. The electrochemical reduction process, the front end of the pyroprocessing, can connect the PWR (Pressurized Water Reactor) oxide fuel cycle to a metal fuel cycle of the sodium cooled fast reactor. This paper summarizes KAERI efforts on the development, improvement, and scale-up of the oxide reduction process.

STATUS AND PERSPECTIVE OF TWO-PHASE FLOW MODELLING IN THE NEPTUNE MULTISCALE THERMAL-HYDRAULIC PLATFORM FOR NUCLEAR REACTOR SIMULATION

  • BESTION DOMINIQUE;GUELFI ANTOINE;DEN/EER/SSTH CEA-GRENOBLE,
    • Nuclear Engineering and Technology
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    • v.37 no.6
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    • pp.511-524
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    • 2005
  • Thermalhydraulic reactor simulation of tomorrow will require a new generation of codes combining at least three scales, the CFD scale in open medium, the component scale and the system scale. DNS will be used as a support for modelling more macroscopic models. NEPTUNE is such a new generation multi-scale platform developed jointly by CEA-DEN and EDF-R&D and also supported by IRSN and FRAMATOME-ANP. The major steps towards the next generation lie in new physical models and improved numerical methods. This paper presents the advances obtained so far in physical modelling for each scale. Macroscopic models of system and component scales include multi-field modelling, transport of interfacial area, and turbulence modelling. Two-phase CFD or CMFD was first applied to boiling bubbly flow for departure from nucleate boiling investigations and to stratified flow for pressurised thermal shock investigations. The main challenges of the project are presented, some selected results are shown for each scale, and the perspectives for future are also drawn. Direct Numerical Simulation tools with Interface Tracking Techniques are also developed for even smaller scale investigations leading to a better understanding of basic physical processes and allowing the development of closure relations for macroscopic and CFD models.

INTEGRAL EFFECT TESTS IN THE PKL FACILITY WITH INTERNATIONAL PARTICIPATION

  • Umminger, Klaus;Mull, Thomas;Brand, Bernhard
    • Nuclear Engineering and Technology
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    • v.41 no.6
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    • pp.765-774
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    • 2009
  • For over 30 years, investigations of the thermohydraulic behavior of pressurized-water reactors under accident conditions have been carried out in the PKL test facility at AREVA NP in Erlangen, Germany. The PKL facility models the entire primary side and significant parts of the secondary side of a of pressurized water reactor at a height scale of 1:1. Volumes, power ratings and mass flows are scaled with a ratio of 1:145. The experimental facility consists of four primary loops with circulation pumps and steam generators (SGs) arranged symmetrically around the reactor pressure vessel (RPV). The investigations carried out encompass a very broad spectrum from accident scenario simulations with large, medium, and small breaks, over the investigation of shutdown procedures after a wide variety of accidents, to the systematic investigation of complex thermohydraulic phenomena. The PKL tests began in the mid 1970s with the support of the German Research Ministry. Since the mid 1980s, the project has also been significantly supported by the German PWR operators. Since 2001, 25 partner organizations from 15 countries have taken part in the PKL investigations with the support and mediation of the OECD/ NEA (Nuclear Energy Agency). After an overview of PKL history and a short description of the facility, this paper focuses on the investigations carried out since the beginning of the international cooperation, and shows, by means of some examples, what insights can be derived from the tests.

Comparison of Cariogenicity of Bovine Milk and Low-fat Milk on Streptococcus mutans Biofilm (국내 시판 우유와 저지방 우유의 Streptococcus mutans 세균막에 대한 우식원성 비교)

  • Hwang, Minseon;Park, Howon;Lee, Juhyun;Seo, Hyunwoo;Lee, Siyoung
    • Journal of the korean academy of Pediatric Dentistry
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    • v.44 no.2
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    • pp.170-179
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    • 2017
  • The purpose of this study was to compare the cariogenicity of commercially available bovine milk and low-fat milk in a biofilm model using the CDC Biofilm Reactor. Streptococcus mutans ATCC 25175 biofilms were formed on saliva coated bovine enamel slabs in a CDC Biofilm Reactor. Biofilms were exposed three times per day to one of the following materials: commercial whole milk (fat content: 3.4%), low-fat milk (fat content: 1%), or 0.9% NaCl. Medium pH was measured at different time points. After 5 days, biofilms were separated from slabs to evaluate the CFUs. The biofilm thickness was observed by confocal laser-scanning microscopy (CLSM). Enamel slab's demineralization was assessed by measuring surface microhardness before and after the experiment. For microhardness and CFUs assessment, no significant difference was found among the three groups. All groups showed similar pattern of medium pH change and biofilm thickness. Our results showed that there was no difference in the cariogenicity between whole milk and low-fat milk. Both milks were relatively non-cariogenic compared to the control group.