• Nuclear Engineering and Technology
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• v.40 no.6
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.65-72
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• 2021

700 W class laboratory model Hall thruster, which can be used for the orbit control or station keeping of small satellites, was developed. The size of the discharge channel was determined using a scaling law, and the magnetic field was designed to be symmetric with respect to the midline of the discharge channel and to be maximized outside the discharge channel. Base pressure of a vacuum chamber was maintained below 2.0×10^-5 Torr during experiments, and the thrust was measured by a thrust stand. The anode flow rate and coil current were varied with the fixed anode voltage at 300 V. Under the operation condition at 2.36 mg/s anode flow rate and 2.4 A coil current, performance was optimized as 38 mN thrust, 1,540 s total specific impulse, and 50 % anode efficiency at 620 W anode power.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.186-194
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• 1998

Species composition and biomass of intertidal benthic algae were studied at the coast of Yonggwang Nuclear Power Plant area and its adjacent stations over 4 seasons (October 1995-August 1996), Of 68 species identified, 7 were Cyanophyta, 12 were Chlorophyta, 14 were Phaeophyta and 35 were Rhodophyta. The largest number of algal species (44) was found at Sangnok, the northernmost station of the study area, whereas the smallest number of species (15) was found from Tongho, ca. 13 km north of the power plant site. Number of species showed highest during the spring (44) and minimum was recorded in autumn (28). Biomass per unit area showed maximum in spring ($189.5\;g\;dry\;wt{\cdot}m^{-2}$ in average) and minimum in winter ($107.9\;g\;dry\;wt{\cdot}m^{-2}$ in average). Biomass values exhibited a wide range of variation among the stations, ranging from a low of $22.0\;g\;dry\;wt{\cdot}m^{-2}$ in annual average at Tongho to a high of $295.7g\;dry\;wt{\cdot}m^{-2}$ in average at Sangnok. Dominant species in biomass were Corallina pilulifera, Sargassum thunbergii, Gymnogongrus flabelliformis and Enteromorpha compressa. There have been little variation in the dominant algal species around the power plant site during the past 10 years and also these algae appeared throughout the west coast of Korea with higher frequency.

• Nuclear Engineering and Technology
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• v.27 no.5
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• pp.767-774
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• 1995

Behavior of radionuclides such $^{60}$ Co, $^{54}$ Mn and $^{137}$ Cs in the incineration Process was Studied by trial burns of simulated wastes with radio-isotope tracers. Behavior of nonvolatiles, $^{60}$ Co and $^{54}$ Mn, was similar to that of particulate matters in the process. Decontamination factors(DFs) for $^{60}$ Co and $^{54}$ Mn were 4.7$\times$10$^{5}$ and 6.2$\times$10$^{5}$ , respectively. Behavior of semivolatile radio-isotope, $^{137}$ Cs, was temperature dependent. DFs for $^{l37}$Cs at In different incineration temperature of 85$0^{\circ}C$ and $700^{\circ}C$ were 2.8$\times$10$^3$ and 2.6$\times$10$^4$, respectively. Trial bums of dry active waste(DAW) transported from nuclear power station(NPS) Kori 3,4 were also performed. DF for gross $\beta$/${\gamma}$ radioactivity in DAW was 1.1$\times$10$^{5}$ . This was a little higher than the estimated value, which was calculated from the tracer test results and nuclides distribution in the DAW. Average emission concentration was 0.019 Bq/N $m^3$, which could meet the maximal permissible concentration(MPC) in stack emission.n.

• Progress in Medical Physics
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• v.2 no.2
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• pp.129-139
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• 1991

The method of etching tracks in PN-3 dosimeter has been applied to tracks of recoil protons from a neutron source. Both the etch and the detection response of PN-3 has been studied as a function of etched-track diameters against various parameters. We could obtain very useful informations about charge, energy, and mass of particles and the relationship between the track etching rate and the track forming procedure in order to analyze the particle recorded in the solid state track detector. The best etching condition could be found by means of changing the etching circumstances for various energies and particles in order to detect the charged particle accurately. It could be influenced widely that the polymer plastic detector could develep the detecting technique for the low energy level neutron and could be used as a neutron dosimeter in the radiation field such as the nuclear power station, the medical institute and the nondtructive testing institute.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.104-108
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• 2014

The recent Fukushima nuclear power plant accidents shows that the core make up at high RCS pressure condition is very important to prevent core melting. The core make up flow at high pressure condition should be driven by gravity force or passive forces because the AC-powered safety features are not available during a Station Black Out (SBO) accident. The reactor Coolant System (RCS) mass inventory is continuously decreased by releasing steam through the pressurizer safety valves after reactor trip during a SBO accident. The core will be melted down within 2~3 hours without core make up action by active or passive mode. In the new design concept of a Hybrid Safety Injection Tank (Hybrid SIT) both for low and high RCS pressure conditions, the low pressure nitrogen gas serves as a charging pressure for a LBLOCA injection mode, while the PZR high pressure steam provides an equalizing pressure for a high pressure injection mode such as a SBO accident. After the pressure equalizing process by battery driven initiation valve at a high pressure SBO condition, the Hybrid SIT injection water will be passively injected into the reactor downcomer by gravity head. The SBO simulation by MARS code show that the core makeup injection flow through the Hybrid SIT continued up to the SIT empty condition, and the core heatup is delayed as much.

• Journal of Radiation Protection and Research
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• v.21 no.1
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• pp.9-16
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• 1996

For the determination of radiostrontium, $^{89}Sr\;and\;^{90}Sr$ in environmental soil sample, a solvent extraction method for the separation of Ca and Sr from matrix using crown ether was investigated. In comparison with the existing fuming nitric acid method, the extraction method showed high chemical yield of strontium and provided simple and rapid analytical steps. The new analytical method applied to the determination of radiostrontium in some soil sample around a nuclear power station to show that the analytical procedure is readily applicable to the practical radioactivity monitoring.

• Strategy21
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• s.44
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• pp.142-176
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• 2018

So far, the main threat to South Korea was North Korea. That is why South Korea established a strategy based on the threat of North Korea and most of the budget on defense was used to deter North Korea. Even though the neighboring countries(China, Japan, and Russia) are growing as a real threat with abilities and intentions based on their powerful naval forces, South Korea has not yet been able to establish a strategy that regards neighboring countries as a threat. But the decades-old structural mechanism of the Korean security environment is undergoing a radical change on April 27, 2018, through the South-North summit and the Panmunjom Declaration. Under the changing security environment, South Korea was placed in a complicated dilemma that had to deal with threats of two axes(China), three axes(China, Japan), and four axes(Japan, Russia). If the one axis threat(North Korea) is dominated by land threats, the second, third and fourth axis threats are threats from the sea. This paper analyzed the maritime strategy of Korea within the framework of maritime-geopolitics, in other words recognition and expansion of the sphere of maritime. I have designed that the maritime defense space that we can deny from threats is divided into three lines of defense: 1 line (radius 3,000km), 2 lines (2,000km), and 3 lines (1,000km). The three defense zones of the three lines were defined as an active defense(1 line), defensive offense(2 line), active offense(3 line). The three defense zones of the three lines were defined as the sphere of core maritime, As a power to deny the sphere of core maritime, it was analyzed as a maneuvering unit, a nuclear-powered submarine, the establishment of missile strategy, and the fortification of islands station. The marine strategy of South Korea with these concepts and means was defined as 'Offensive Maritime Denial Strategy'.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.97-102
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• 2012

Alternate alternating current (AAC) is used in nuclear power plants (NPPs) in order to cope with station black outs (SBOs). AAC has been provided using diesel engine drive types in Korea's NPPs. The structure of gas turbine generators (GTGs) is simpler than that of diesel generators (DGs), and GTGs have the advantage of longer maintenance intervals. However, GTG-AAC was not used in NPPs in Korea because of the lack of operation/maintenance experience. The purpose of this paper is to analyze the safety of APR+ considering a diversity of AAC types. This paper analyzes reliability data, mechanical specifications of DGs and GTGs, and the sensitivity of core damage frequency to the ACC type.

• Journal of Energy Engineering
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• v.28 no.1
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• pp.22-29
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• 2019

A heat pump system using wasted heat from thermal effluent to supply the heating energy can reduce energy consumption and emissions of greenhouse gases by greenhouse facilities nearby. The Jeju National University consortium constructed a heat pump system using the thermal effluent from the Jeju thermal power plant of KOMIPO to provide with cool or hot water to greenhouse facilities located 3 km from the power station. In this paper, the system configuration of the heat pump system was summarized, and the results of operations for demonstration of a heating performance carried out during the winter season in 2018 were investigated. The preoperational tests proved that the water temperature drop through the pipeline transporting extracted heat was less than $2^{\circ}C$. The COP (coefficient of performance) of the heat pump was higher than 4.0, and hot water with the maximum temperature of $50^{\circ}C$ could be supplied to greenhouse facilities by utilizing wasted heat from thermal effluent.