• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1001-1008
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• 1996

Staphylococcal food poisoning is the major cause of bacterial food poisoning occurring in this country. Therefore government regulates commercial foods through Official Dictionary of Food that there should be free of enterotoxigenic Staphylococcus aureus in Korean rice cakes, bread, and a box lunch. Since at least 5 days are required to identify the S. aureus by the official method in the Dictionary it is difficult to prevent the food poisoning and the investigation of the outbreaks. In this report an improved determination method of the S. aureus has been developed using polymerase chain reaction (PCR) technique. Sense and antisense primers for specific amplification of genes encoding staphylococcal enterotoxins were designed and synthesized for the PCR. Rapid chromosomal DNA isolation method was also developed from S. aureus using lysostaphin. The PCR condition was developed as follows. Reaction solution $(50\;{\mu}l)$ consisted of target DNA $2\;{\mu}l$ (about 20ng), 10X buffer $5\;{\mu}l$, primer 100pmole, dNTP (10 mM) $4\;{\mu}l$ and Taq DNA polymerase 2.5 unit in a thin-wall tube. Operation condition of the PCR was 5 min pre-denaturation at $94^{\circ}C$, 15 sec denaturation at $94^{\circ}C$, 15 sec annealing at $50^{\circ}C$, 20 sec extension at $72^{\circ}C$, and 5 min post-extension at $72^{\circ}C$, and 30 cycles of denaturation-annealing- extension. Using the PCR with Perkin Elmer GeneAmp PCR system 2400, types of enterotoxigenic S. aureus could be identified from Ddok or bread in a day.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.420-427
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• 2006

The structural and leakage integrity of steam generator tubes should be sustained against all postulated loads even if a crack is present. During the past three decades, most of the efforts with respect to integrity evaluation of steam generator tubes have been focused on limit load solutions but, recently, the applicability of elastic-plastic fracture mechanics was examined cautiously due to its effectiveness. The purpose of this paper is to introduce a testing method to estimate fracture resistance characteristics of steam generator tubes with a through-wall crack. Due to limited thickness and diameter, inevitably, the steam generator tubes themselves were tested instead of standard specimen or alternative ones. Also, a series of three dimensional elastic-plastic finite element analyses were carried out to derive closed-form estimation equations with respect to J-integral and crack extension for direct current potential drop method. Since the effectiveness of $J_{IC}$ as well as J-R curves was proven through comparison with those of standard specimens taken from pipes, it is believed that the proposed scheme can be utilized as an efficient tool for integrity evaluation of cracked steam generator tubes.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.129-132
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• 2008

Combustion characteristics of a gas generator for a 30 ton-class liquid rocket engine were studied. At the early stage of development, the combustion tests of the gas generator were performed by only using the nozzle which substitute for a turbine manifold exit. Then, the extension tube was applied between the gas generator and the nozzle for imitating the resonant mode of gas generator and turbine manifold. Finally, the hot-firing tests were performed on the condition of connecting the gas generator with the turbine manifold. In the paper, the step-by-step results such as temperature distribution and pressure fluctuations were analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.930-937
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• 2003

The extension of design life among power plants is increasingly becoming a world-wide trend. Kori #1 unit in Korea is operating two cycle. It has two man-ways for tube inspection in a steam generator which is one of the important components in a nuclear power plant. Especially, stud bolts fur man-way cover have damaged by disassembly and assembly several times and degradation for bolt materials for long term operation. It should be evaluated and compared by ASME Code criteria for integrity evaluation. Integrity evaluation criteria which has been made by the manufacturer is not applied on the stud bolts of nuclear pressure vessels directly because it is controlled by the yield stress of ASME Code. It can apply evaluation criteria through FEM analysis to damaged female threads and to evaluated safety fer helical-coil method which is used according to Code Case-N-496-1. From analysis results, we found .that it is the same results between stress intensity which got from FEM analysis on damaged female threads over 10％ by manufacture integrity criteria and 2／3 yield strength criteria on ASME Code. It was also confirmed that the helical-coil repair method would be safe.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.43-49
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• 2010

In the present study, optimization of throttle margin for high pressure turbine to be retrofitted or partially modified for power uprating or life extension in nuclear power plant, has been performed to increase the electrical output. Throttle margin for high pressure turbine is required to maintain all the time the rated power by opening more of governor valves whenever inlet pressure is decreased due to the tube plugging of steam generator. If throttle margin of high pressure turbine is too much compared to remaining lifetime, loss of electrical output due to pressure drop of governor valves is inevitable. On the contrary, if it is too little, the rated power operation can not be accomplished when inlet pressure of high pressure turbine is dropped after many years operation. So, throttle margin for high pressure turbine in nuclear power plant is compromised considering for the degradation of steam generator, governor valve capacity, manufacturing tolerance of high pressure turbine, future plan of power uprating, and remaining lifetime of power plant.

• Nuclear Engineering and Technology
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• v.34 no.5
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• pp.502-516
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• 2002

Wolsong NPP are CANDU6 type reactors and there are 4 CANDU6 type reactors in commercial operation. CANDU type reactors require on-power refuelling by two remote controlled F/Ms (Fuelling Machines). Most of channels, fuel bundles are float by channel coolant flow and move toward downstream, however in about 30% of channels the coolant flow are not sufficient enough to carry fuel bundles to downstream. For those channels a special device, FARE (Flow Assist Ram Extension) device, is used to create additional force to push fuel bundles. It has been showing that during fuelling operation of some channels the channel coolant flow rate is reduced below specified limit (80% of normal), and consequently trip alarm signal turns on. This phenomenon occurs on selected channels that are instrumented for the channel flow and required to use the FARE device for refuelling. Hence it is believed that the FARE device causes the problem. It is also suspected that other channels that do not use the FARE device for refuelling might also go into channel flow low state. The analysis revealed that the channel How low occurs as the FARE device is introduced into the core and disappears as the FARE device is removed from the core. This paper presented the FARE device behavior, detailed fuelling operation sequence with the FARE device and effect on channel flow low phenomena. The FARE device components design changes are also suggested, such as increasing the number or now holes in the tube and flow slots in the ring orifice.

• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.811-820
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• 2013

SiC has been under investigation as a potential cladding for LWR fuel, due to its high melting point and drastically reduced chemical reactivity with liquid water, and steam at high temperatures. As SiC is a brittle material its behavior during the reflood phase of a Loss of Coolant Accident (LOCA) is another important aspect of SiC that must be examined as part of the feasibility assessment for its application to LWR fuel rods. In this study, an experimental assessment of thermal shock performance of a monolithic alpha phase SiC tube was conducted by quenching the material from high temperature (up to $1200^{\circ}C$) into room temperature water. Post-quenching assessment was carried out by a Scanning Electron Microscopy (SEM) image analysis to characterize fractures in the material. This paper assesses the effects of pre-existing pores on SiC cladding brittle fracture and crack development/propagation during the reflood phase. Proper extension of these guidelines to an SiC/SiC ceramic matrix composite (CMC) cladding design is discussed.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.373-378
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• 2000

An experimental investigation on the incipience of nucleate boiling in forced flow of water is performed as a verification and extension of previous analysis. The effects of the subcooling, Reynolds number and surface curvature on the onset of nucleate boiling(ONB) in a concentric annulus flow channel with smooth inner heating surface is investigated experimentaly. Through flow visualization, the boiling phenomenon was observed directly and the experimental results were examined to find ONB heat flux. The results show that the variation of heat flux at ONB is increased linearly as the Reynolds number and subcooling are increased. The effect of surface curvature is very great specially for a small radius when radius of the inner heating tube is increased, the heat flux at ONB is almost inversely increased for the range of this investigation. It is found that the effect of convex surface curvature on ONB heat flux is very significant for a small radius.

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.247-254
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• 2014

A study on the superconducting RF linac is underway in order to increase the beam energy up to 1 GeV by extending the Proton Engineering Frontier Project (PEFP) 100-MeV linac. The operating frequency of the PEFP superconducting linac (SCL) is 700 MHz, which is determined by the fact that the frequency of the existing normal conducting linac is 350 MHz. A preliminary study on the beam dynamics showed that two types of cavities with geometrical betas of 0.50 and 0.74 could cover the entire energy range from 100 MeV to 1 GeV. An inductive output tube (IOT) based RF system is under consideration as a high-power RF source for the SCL due to its low operating voltage and high efficiency. As a prototyping activity for a reduced beta cavity, a five-cell cavity with a geometrical beta of 0.42 was designed and fabricated. A vertical test of the prototype cavity at low temperatures was performed to check the performance of the cavity. The design study and the prototyping activity for the PEFP SCL will be presented in this paper.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.158-165
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• 2006

In order to provide the database for designing microcombustors, the combustion characteristics of premixed methane and propane air microflames at normal and elevated temperatures and atmospheric pressure generated on a microtube were studied experimentally and computationally. The stability limits of premixed microflames and the propensity of the microflames near the stability limits were experimentally determined, while the structure of the microflame at the fuel-leanest limit was obtained using a two-dimensional CFD simulation with a reduced kinetic mechanism. For all the microflames, the stability limits were observed only in the fuel-rich region. Results also show substantial extension of stability limits with elevated temperature that is realistic condition for micro fuel processing and significant fuel dilution immediately near the tube exit due to a low Peclet number times Lewis number effect.