• Earthquakes and Structures
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• v.14 no.5
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• pp.389-398
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• 2018

The seismic isolation system makes a structure isolated from ground motions to protect the structure from seismic events. Seismic isolation techniques have been implemented in full-scale buildings and bridges because of their simplicity, economic effectiveness, inherent stability and reliability. As for the responses of an isolated structure due to seismic events, it is well known that the most uncertain aspects are the seismic loading itself and structural properties. Due to the randomness of earthquakes and uncertainty of structures, seismic response distributions of an isolated structure are needed when evaluating the seismic fragility assessment (or probabilistic seismic safety assessment) of an isolated structure. Seismic response time histories are useful and often essential elements in its design or evaluation stage. Thus, a large number of non-linear dynamic analyses should be performed to evaluate the seismic performance of an isolated structure. However, it is a monumental task to gather the design or evaluation information of the isolated structure from too many seismic analyses, which is impractical. In this paper, a new methodology that can evaluate the seismic fragility assessment of an isolated structure is proposed by using stochastic response database, which is a device that can estimate the seismic response distributions of an isolated structure without any seismic response analyses. The seismic fragility assessment of the isolated nuclear power plant is performed using the proposed methodology. The proposed methodology is able to evaluate the seismic performance of isolated structures effectively and reduce the computational efforts tremendously.

• International Journal of Safety
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• v.11 no.2
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• pp.10-14
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• 2012

Recently, the combined power plants are refocused rapidly as a replaceable energy system of the nuclear power plant. The large turbine is revolved highly at 1800~3600 rpm. Thus, the turbine speed should be monitored with mechanical and electrical method for a safety. The electrical cutoff valve which blocks the flow channel with the electrical signal is with a built in. The aim of this study is to develop a manufacturing technology through by the localization of a solenoid actuated directional control valve. Especially the results show performances of the solenoid valve by the experiments and modeling and the reliability estimation. Applied load port pressure was changed rapidly on the form of a quadratic curve over time. And in the cases of square waveform when 0~100 V and 20~120 V input voltage, it was driven on a stable state until 13.4 Hz and 16.6 Hz, respectively. We think that this study will give useful data for the electricity safety system of the combined power plant gas turbine.

• The Korean Journal of Physiology
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• v.10 no.2
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• pp.23-28
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• 1976

Author have already reported that urinary aldosterone excretion of the Korean who usually eat high sodium diet is significantly lower comparing with the American, although the plasma aldosterone concentration is identical in the former with that of the latter. Measurement of urinary aldosterone excretion and Plasma concentration only is insufficient to establish the pressence and/or mode of evolution of the Korean. In this experiments, aldosterone secretion rate(ASR) was measured in normotensive Korean during high and low dietary sodium intake with or without additional potassium supply. Results were as follows; 1) In normal Korean, dietary sodium restriction resulted in appreciable increase in ASR, and a sustained increase in urinary aldosterone excretion with an increase in plasma level. 2) Oral potassium loading easily stimulated the adrenal cortex of the Korean who already adapted to a high sodium diet when dietary sodium is still identical with not·mal American. 3) Quantitative relationships between aldosterone secretion rate, plasma concentration and urinary excretion of aldosterone were altered by potassium loading. 4) Urinary aldosterone excretion didn't reflect concurrent increase aldosterone secretion in subjects with Potassium intake. It was discussed that the changes of tile relationships and of adrenal hyper response on Potassium Beading in the Korean will be elucidated by measuring the metabolic clearance rate.

• Journal of Welding and Joining
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• v.24 no.2
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• pp.48-56
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• 2006

The fatigue strength of the welds is affected by such factors as the weld geometry, microstructures, tensile properties and residual stresses caused by fabrication. It is very important to evaluate the structural integrity of the welds in nuclear power plant because the weldment undergoes the most of damage and failure mechanisms. In this study, the fatigue assessments for a reactor vessel outlet nozzle with the weldment to the piping system are performed considering the welding residual stresses as well as the effect of local brittle zone in the vicinity of the weld fusion line. The analytical approaches employed are the microstructure and mechanical properties prediction by semi-analytical method, the thermal and stress analysis including the welding residual stress analysis by finite element method, the fatigue life assessment by following the ASME Code rules. The calculated results of cumulative usage factors(CUF) are compared for cases of the elastic and elasto-plastic analysis, and with or without residual stress and local brittle zone effects, respectively. Finally, the fatigue life of reactor vessel outlet nozzle weld is slightly affected by the local brittle zone and welding residual stresses.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.465-474
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• 2006

A gas fueling system composed of a gas reservoir, an on-off valve, and a gas transferring tube, which is the simplest construction for the pre-programmed gas puffing, was simulated by numerically solving the time-dependent one-dimensional gas flow equation. The purpose of the simulation is to establish the relationship between the gas flow pattern (the elapsed time to the maximum flow, the maximum flow rate, the gas pulse duration) and the system parameters (the filling pressure and the volume of the gas reservoir, and the length and the diameter of the gas transferring tube).

• Transactions on Control, Automation and Systems Engineering
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• v.1 no.2
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• pp.141-146
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• 1999

This paper describes the communication method of an auto-startup system. The Auto-Startup system is designed to operate a nuclear power plant automatically during the startup operation . In general , the operations during startup in existing plant have only been manually controlled by the operator. The manual operation caused to the operator mistake. The Auto-Startup system consists of the Distributed Control System(DCS) and G2 (Expert System). Also, Functional Test Facility(FTF) provides the plant's real-data for an Auto-Startup system. So, it is necessary to develop the communication method between these systems. We developed two methods ; one is a network and the other is a hardwire line. To communicate between these systems (DCS-G2 and DCS-FTF) , we developed the communication program. In case of DCS-FTF, we used the TCP/IP and VXI. BUt, in case of DCS-G2 , we , what it called , developed the bridge program using the GSI(G2 Standard Interface). We test to check the function of the important parameter, in time, for analysis of the developed communication method. The results are a good performance when we check the communication time of important parameter. We conclude that Auto-startup system could save heat-up time about at least 5 hours and reduced the change of the reactor operation and trip.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.3
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• pp.83-86
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• 1998

The results from the Individual Plant Examination of External Event of Yonggwyang nuclear power plants, unit 3 & 4, in Korea have shown that the high degree of diversities of the experts' opinions on seismicity and attenuation models is su, pp.sed to be generic cause of uncertainty of APEs(annual exceedance probability) in the PAHA(probabilistic seismic hazard analysis). This study investigated the sensitivity of the focal depth, which is one of the most uncertain seismicity parameters in Korea, Significant differences in resultant values of annual exceedance probabilities and much more symmetrical shape of the resultant PDFs(probability density functions), in case of consideration of focal depth, are found. These two results suggest that, even for the same seismic input data set including the seismicity models and ground motion attenuation models, to consider focal depth additionally for probabilistic seismic hazard analysis evaluation makes significant influence on the distributions of uncertainties and probabilities of exceedance per year for the whole ranges of seismic hazard levels. These facts suggest that it is necessary to derive focal depth parameter more effectively from the historical and instrumental documents on earthquake phenomena in Koran Peninsula for the future study of PSHA.

• Korean Journal of Materials Research
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• v.16 no.5
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• pp.318-322
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• 2006

Short-term high temperature degradation test was conducted on Hastelloy X, a candidate tube material for high temperature gas-cooled reactors (HTGR), to evaluate the variation of microstructure and mechanical property in air at $1050^{\circ}C$ during 2000 h. The dominant oxide layer was Cr-oxide and a very shallow Cr-depleted region was observed below the oxide layer. At the beginning of degradation, the island shape $M_6C$ precipitate (M=Mo-rich, Fe, Ni, Cr) was observed in matrix region. After 2000 h degradation, precipitate shape was changed to the chain shape and increased amount of precipitate. These results influenced mechanical property of the specimen which exposed in high temperature. Yield strength was decreased from 115MPa to 89 MPa after 24 h and 2000 h exposure, respectively.

• Progress in Medical Physics
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• v.15 no.3
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• pp.140-148
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• 2004

The absorbed dose for proton beam in water was calculated using the PTRAN code system. The proton interactions with water and the description on absorbed dose calculations are discussed, and the file structure and an execution example of the PTRAN codes are described. For 60, 100, 150, 200, and 250 MeV proton beams it is demonstrated that the absorbed dose is determined from the sum of Coulomb interactions and nuclear reactions, and that the Bragg peak feature depends On the energy straggling and multiple scattering. The PTRAN code was useful for studying the fundamental mechanism of the absorbed dose to water for clinical proton beams.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.177-181
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• 1999

Cold Neutron Source(CNS) facility comprises moderator circulation system, helium cooling system, neutron guide and auxiliary sistems. To increase the amount of cold neutron, the thermal neutron should pass cold moderator at cryogenic temperature. As cold moderator in Hanaro, the liquid hydrogen or liquid deuterium will be used and the temperature in operation will be used and the temperature in operation will be maintained to be $250^{\circ}C$ below zero. To maintain the moderator at this cryogenic temperature. He refrigerator is used to cool it down in thermosiphon having natural circulation. As a part of the conceptual design of Hanaro CNS, study on the characteristics of moderators, design of moderator chanmber and cooling method were done through the collaboration of Korea Atomic Energy Research Institute and Petersburg Nuclear Physics Institute. During the collaboration, a program for the design of moderator cooling system design concept through the parametric study using this program. In the parametric study, the effect of the moderator type on the design parameters was investigated. Also, the requirements on the performance test for the cooling system, which will be made before the basic design, were investigated.