• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.489-494
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• 1997

A comparative transient analyses were performed for oxide and nitride cores or a large (3000 MWt), pool-type, liquid-metal-cooled reactor (LMR). The study was focused on three representative accident initiators with failure to scram : the unprotected loss-of-flow (ULOF), the unprotected transient overpower (UTOP), and the unprotected fast transient overpower (UFTOP). The margins to fuel melting and sodium boiling have been evaluated for these representative transients. The results show that there is an increase in safety margin with nitride core which maintains the physical dimensions of the oxide core.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.232-237
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• 1994

An extended study of optimal thruster combination for simultaneous attitude and orbital maneuvers of a jet-controled spacecraft is conducted. In this case, the spacecraft has not enough number of thrusters to control the rotation and translation separately. Therefore, thrusters are employed by combining to eliminate their coupling effects. The combinations are determined to minimize the fuel consumption. The redundancy study for some thruster failure cases is also presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.204-205
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• 2012

• Journal of Energy Engineering
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• v.27 no.2
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• pp.1-13
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• 2018

The proportion of natural gas-fueled power generation is expanding due to the change of domestic energy policy pursuing reduction of dust and increasing clean energy consumption. Natural gas fuels used for the combined-cycle power plants and the district-heating power plants are operated at high temperature and high pressure in the fuel supply system. Accidents due to leakage of the gas such as fire and explosion should be prevented by applying risk management techniques. In this study, risk assessment was performed on the natural gas fuel supply system of a combined power plant based on the API RP 581 RBI code. For the application of the API RBI code, lines and segments of the evaluation target system were identified. Operational data and input information were analyzed for the calculations of probability of failure and consequence of failure. The results of the risk assessment were analyzed over time from the initial installation time. In the code-based evaluation, the gas fuel supply system was mainly affected by thinning, external damage, and mechanical fatigue damage mechanisms. As the operating time passes, the risk is expected to increase due to the external damage caused by the CUI(Corrosion Under Insulation).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3736-3741
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• 2015

Crash impact test is conducted to verify the crashworthiness of fuel tank. Success of the crash impact test means the improvement of survivability of crews by preventing post-crash fire. But, there is a big risk of failure due to huge external load in the crash impact test. The failure of crash impact test can result in serious delay of a entire rotorcraft development because of the design complement and re-production of the test specimens requiring a long-term preparation. Thus, the numerical simulations of the crash impact test has been required at the early design stage to minimize the possibility of trial-and-error in the real test. Present study conducts on the numerical simulation of phase I crash impact test using SPH supported by crash simulation software, LS-DYNA. Test condition of MIL-DTL-27422 is reflected on analysis and material data is acquired by specimen test of fuel cell material. As a result, the crash load on the skin material, overlap area and metal fitting is estimated to confirm the possibility of acquisition of the design load for the determination of the overlap area and adhesive strength.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.2
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• pp.1-13
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• 2020

The characterization of aging of the pyrotechnic device is conducted thermally, chemically, and spectroscopically. The device is comprised of two parts: (i) igniter composed of Zr and (ii) pyrotechnic delay composed of ZrNi alloy. The thermally induced chemical reaction is identified through Differential Scanning Calorimetry (DSC) and Thermogravimetry Analysis (TGA). The peak deconvolution of the themo-chemical data is used to estimate the enthalpy change of each metallic fuel component. Laser Induced Breakdown Spectroscopy (LIBS) and X-ray Photoelectron Spectroscopy (XPS) are used for chemical species analysis. The decomposition of oxidants by moisture significantly affected the fuel aging, and the formation of oxide film and metal oxide on the fuel surface gave rise to the thermal energy decrease.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.46-51
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• 2000

It is required that fuel gas accidents should be managed carefully along with the increase of fuel gas consumption. Factors to cause accidents were investigated through a systematic analysis of gas accidents during recent 4 years, which could be applied to prepare countermeasures to reduce gas accidents. The thawing season is found to be weak to gas accidents, showing a slightly higher rate of accident occurring than average. During this term although the number of LPG accident is similar to that of yearly average, countermeasures are required for LPG facilities since the portion of accident is large; in detail, user's carelessness, defective facility, or instrument failure are major causes. The number of city gas accident facility is larger than that of yearly average; particularly, defective facilities, third-party work, and appliance failure are major causes. As a result, countermeasures have been suggested for the accident of large portion or above yearly average.

• Journal of the Korean Institute of Gas
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• v.23 no.6
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• pp.33-38
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• 2019

In order to invigoration the hydrogen economy, production of hydrogen needed for hydrogen charging stations and hydrogen fuel cells is needed. Generally, it is reforming used to coal fuel or natural gas. Other technologies include water electrolysis using pure water. Among these water electrolysis technologies, development is mainly carried out using PEM(Polymer Electrolyte Membrane electrolysis). In this study, the company aims to identify potential harmful hazards to PEM electrolysis hydrogen stations in the development stage among hydrogen charging stations. In order to find the hazardous factors in the facilities of the electrolysis and hydrogen charging stations, we were analyzed by Failure Mode & Effect Analysis(FMEA).

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1236-1249
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• 2021

Although there are still controversial opinions and uncertainty on application of SiC_f/SiC composite cladding as next-generation cladding material for its great oxidation resistance in high temperature steam environment and other outstanding advantages, it cannot deny that SiC_f/SiC cladding is a potential accident tolerant fuel (ATF) cladding with high research priority and still in the engineering design stage for now. However, considering its disadvantages, such as low irradiated thermal conductivity, ductility that barely not exist, further evaluations of its in-pile behaviors are still necessary. Based on the self-developed code we recently updated, relevant thermohydraulic and mechanical models in FROBA-ATF were applied to simulate the cladding behaviors under normal and accident conditions in this paper. Even through steady-state performance analysis revealed that this kind of cladding material could greatly reduce the oxidation thickness, the thermal performance of UO₂-SiC was poor due to its low inpile thermal conductivity and creep rate. Besides, the risk of failure exists when reactor power decreased. With geometry optimization and dopant addition in pellets, the steady-state performance of UO₂-SiC was enhanced and the failure risk was reduced. The thermal and mechanical performance of the improved UO₂-SiC was further evaluated under Loss of coolant accident (LOCA) and Reactivity Initiated Accident (RIA) conditions. Transient results showed that the optimized ATF had better thermal performance, lower cladding hoop stress, and could provide more coping time under accident conditions.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.110-115
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• 2007

Solid oxide fuel cell(SOFC) has high fuel flexibility due to its high operating temperatures. Hydrocarbonaceous fuels such as diesel has several advantages such as high energy density and established infrastructure for fuel cell applications. However diesel reforming has technical problems like coke formation in a reactor, which results in catastrophic failure of whole system. Performance degradation of diesel autothermal reforming (ATR) leads to increase of undesirable hydrocarbons at reformed gases and subsequently degrades SOFC performance. In this study, we investigate the degradation of SOFC performance(OCV, open circuit voltage) under hydrocarbon(n-Butane) feeds and characteristics of diesel performing under various ratios of reactants($H_2O/C,\;O_2/C$ molar ratios) for improvement of SOFC performance. Especially we achieved relatively high performance of diesel ATR under $H_2O/C=0.8,\;O_2/C=3$ condition.