• Nuclear Engineering and Technology
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• v.17 no.3
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• pp.193-199
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• 1985

Iodine-induced stress corrosion cracking tests of Zircaloy-4 cladding were undertaken using the modified infernal pressurization method. The effects of iodine concentration and applied stress were studied. The critical iodine concentration for SCC was found to be about 0.2 mg/$\textrm{cm}^2$ at 603$^{\circ}$K. The threshold stress was dependent on the test temperature and the mechanical properties of the specimen. The fracture surface showed that the crack propagated stepwise iron one grain to others until the material was unstable and then ruptured mechanically. The initial region showed the transgranular feature and the wedge-shaped cracks. As the crack proceeded, the transgranular and ductile-tearing mired feature appeared in the middle region.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.41-42
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• 2021

The Green New Deal policy was established to innovate the government's energy consumption structure, establish a third basic energy plan to strengthen the global competitiveness of the energy industry, and realize a carbon neutral society due to the increased need for transition to a low-carbon economy. Waterworks such as drinking water, water purification plant, and pressurization plant analyze control factors and energy consumption status by process to improve energy management efficiency and reduce energy usage through the 4th industrial revolution. Ultimately, we want to realize net-zero water purification plant.

• Journal of Environmental Health Sciences
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• v.49 no.3
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• pp.129-133
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• 2023

Background: With the rise in global mobility, aircraft indoor air quality has become a significant public health concern. This study focuses on the health implications of increased travel and bleed air-air drawn from aircraft engines for cabin pressurization and air conditioning. Objectives: This research aims to review the potential health effects related to exposure to aircraft cabin air, particularly the effects of bleed air during fume events. Methods: We conducted a literature review of existing studies on aircraft cabin air quality. We focused on both the immediate and health effects of exposure to cabin air, particularly those related to bleed air contaminants. Results: The review found a possible link between exposure to aircraft cabin air and certain health issues, especially in cabin crew and frequent flyers. There was an increased incidence of respiratory and neurological symptoms related to bleed air exposure. However, the cumulative health effects of frequent air travel remain inconclusive due to limited data. Conclusions: This study highlights the need for improving air quality in aircraft to protect public health. While further research is needed to understand the cumulative effects of frequent air travel, the reduction of exposure to bleed air contaminants should be a priority. These findings underline the need for regulatory changes and technological improvements in aircraft cabin air quality.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1513-1525
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• 2024

An improved mitigation system for thermally-induced steam generator tube rupture accidents was introduced to prevent direct environmental release of fission products bypassing the containment in the OPR1000. This involves injecting bypassed steam into the containment, cooling, and decontaminating it using a water coolant tank. To evaluate its performance, a severe accident analysis was performed using the MELCOR 2.2 code for OPR1000. Simulation results show that the proposed system sufficiently prevented the release of radioactive nuclides (RNs) into the environment via containment injection. The pool scrubbing system effectively decontaminated the injected RN and consequently reduced the aerosol mass in the containment atmosphere. However, the decay heat of the collected RNs causes re-vaporization. To restrict the re-vaporization, an external water source was considered, where the decontamination performance was significantly improved, and the RNs were effectively isolated. However, due to the continuous evaporation of the feed water caused by decay heat, a substantial amount of steam is released into the containment. Despite the slight pressurization inside the containment by the injected and evaporated steam, the steam decreased the hydrogen mole fraction, thereby reducing the possibility of ignition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.167-168
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• 2023

The government has established a zero-energy roadmap in accordance with its 2050 carbon neutrality strategy, and from 2023 onwards, residential buildings with 30 generations or more must be constructed as zero-energy structures. In response to this, measures for energy conservation through enhanced building tightness are being developed. The LH (Land and Housing Corporation) aims to achieve the first-stage building tightness performance targets by 2022 in preparation for this. Currently, South Korea has the "KS L ISO9972 - Building Tightness - Measuring the airtightness of buildings by the fan pressurization method" as the method for measuring building tightness, which was established in 2006 and revised in 2016. In practice, the airtightness is measured using the Blower Door Test method, and it is expressed as ACH50 (the number of air changes per hour at a pressure difference of 50 Pa between the indoor and outdoor environments). This study aims to measure and analyze the airtightness of Happy Homes constructed from 2020 to 2022, categorized by building type.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.319-326
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• 2012

Han-green building is one of the modernized Korean traditional buildings developed by Korea Forest Research Institute. This building was developed to increase the competitiveness of Korean traditional building using state-of-art technologies; hence Han-green building has the inherent characteristics of traditional building such as exposed wood frame in wall. Because of discontinuity in wall by the exposed wood frame, there is a concern on heat-air leaking in terms of energy performance. In this study, air-tightness of Han-green building was evaluated to investigate the influence of gaps between frames and in-fill walls. Blower door test was carried out to evaluate the air-tightness, and air-change rate (ACH50) was evaluated by averaging four set of pressurization and depressurization test. The air-change rate of Han-green house was 5.91 $h^{-1}$. To improve energy performance of Han-green house, thermal infrared images of Han-green house were taken in winter with heating to find out where the heat loss occurred. It was found that the building lost more heat through gaps between frames and in-fill walls rather than through other parts of this building. After covering all the gaps by taping, the blower door test was performed again, and the air-change rate was improved to 5.25 $h^{-1}$. From this analysis, it was concluded that the heated air can leak through the gaps between frames and walls. Therefore, when one designs the post and beam building with exposed frame, the detail design between frame and wall needs to be carefully dealt. However, Han-green building showed relatively high air-tightness comparing with other country research results.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.26-32
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• 2020

In this study, a facility was constructed to supply liquid nitrogen to simulate combustion instability in a liquid rocket combustor. The pressurization and supply performances were predicted and verified through different experiments. The liquid nitrogen supply system was composed of a pressurized supply system, and a dome regulator was used to adjust the pressure of the pressurant. A cavitation venturi was used to control the mass flow rate of liquid nitrogen. The condition of liquid nitrogen supply was a mass flow rate of 2.55 kg/s and the venturi inlet pressure was above 100 bar. Based on the initial experiment, it was observed that the predicted amount of the pressurant was not sufficiently supplied and the target pressure was not supplied due to a drop in tank pressure. Through the modification of the established facilities, the target mass flow rate was successfully supplied and the cryogenic liquid nitrogen supply facility was verified.

• Fire Science and Engineering
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• v.30 no.2
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• pp.56-61
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• 2016

Recently, Since buildings are bigger and higher, the damage of human life can be increased by fire flame and smoke in fire. Smoke control system is necessary to decrease this damage. Therefore, Air supply pressurization smoke control system is applied to vestibule of escape stairway. NFSC requires pressure differential of above 40 Pa, but pressure differential is excessively overpressure in the field. It is known that the cause of this over pressure differential is much leakage of damper. Over pressure differential can bad effect to escaper by pressurizing the door. Analyze the real leakage of damper by increasing the number of dampers operation for identifying this problems. The result of testing, the leakage has difference between new dampers and increased the number of operation dampers. As the static preassure increase, the leakage difference increase. Comparison with preceding study, this result has similar linear tendency.

• Fire Science and Engineering
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• v.16 no.2
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• pp.59-69
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• 2002

The conventional fire extinguishing gas-agent system has a configuration in which the gas-agent comes out of a cylindrical container having vertically settled shape. However, in this study a horizontally installed container of a piping shape having a cylinder of the same shape with a cylinder valve and a discharge nozzle was used, and the relationship between orifice size of nozzle and discharge rate of gas-agent was investigated through various experiments including the measurement of discharge rate under different ambient-temperature conditions. In such experiments, HCFC Blend A was used without super-pressurization by nitrogen. From this research, it was observed that statutory discharge duration of 10 seconds can be met if the relatively large size of the valve and the nozzle orifice were properly selected.

• Journal of computational fluids engineering
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• v.9 no.3
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• pp.49-56
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• 2004

A heated and expanded helium is used to pressurize liquid propellants in propellant tanks of propulsion system of liquid propellant launch vehicles. To produce a heated and expanded helium, an hot-gas heat exchanger is used by utilizing heat source from an exhausted gas, which was generated in a gas generator to operate turbine of turbo-pump and dumped out through an exhaust duct of engine. Both experimental and numerical approaches of hot-gas heat exchanger design were conducted in the present study. Experimentally, siliconites - electrical resistance types - were used to simulate the full heat condition instead of an exhausted gas. Cryogenic heat exchangers, which were immersed in a liquid nitrogen pool, were used to feed cryogenic gaseous helium in a hot-gas heat exchanger. Numerical simulation was made using commercially utilized solver - Fluent V.6.0 - to validate experimental results. Helically coiled stainless steel pipe and stainless steel exhausted duct were consisted of tetrahedron unstructured mesh. Helium was a working fluid Inside helical heat coil and regarded as an ideal gas. Realizable k-』 turbulent modeling was adopted to take turbulent mixing effects in consideration. Comparisons between experimental results and numerical solutions are Presented. It is observed that a resulted hot-gas heat exchanger design is reliable based on the comparison of both results.