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Ha S.J.,Korea Electric Power Research Institute | Park C.E.,KEPCO Engineering and Construction Company Inc. | Kim K.D.,Korea Atomic Energy Research Institute | Ban C.H.,Korea Nuclear Fuel Co.
Nuclear Engineering and Technology | Year: 2011

The Korean nuclear industry is developing a thermal-hydraulic analysis code for safety analysis of pressurized water reactors (PWRs). The new code is called the Safety and Performance Analysis Code for Nuclear Power Plants (SPACE). The SPACE code adopts advanced physical modeling of two-phase flows, mainly two-fluid three-field models which comprise gas, continuous liquid, and droplet fields and has the capability to simulate 3D effects by the use of structured and/or nonstructured meshes. The programming language for the SPACE code is C++ for object-oriented code architecture. The SPACE code will replace outdated vendor supplied codes and will be used for the safety analysis of operating PWRs and the design of advanced reactors. This paper describes the overall features of the SPACE code and shows the code assessment results for several conceptual and separate effect test problems.

Byun J.-K.,Korea University | Jeong D.-H.,KEPCO Engineering and Construction Company Inc. | Choi Y.-D.,Korea University | Shin J.-K.,Hanzhong University
Energies | Year: 2013

In the present study, a fuel cell driven ground source heat pump (GSHP) system is applied in a community building and heat pump system performance is analyzed by computational methods. Conduction heat transfer between the brine pipe and ground is analyzed by TEACH code in order to predict the performance of the heat pump system. The predicted coefficient of performance (COP) of the heat pump system and the energy cost were compared with the variation of the location of the objective building, the water saturation rate of the soil, and the driven powers of the heat pump system. Compared to the late-night electricity driven system, a significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system. This is due to the low cost of electricity production of the fuel cell system and to the application of the recovered waste heat generated during the electricity production process to the heating of the community building. © 2013 by the authors.

Mullapudi T.R.S.,MMI Engineering Inc. | Summers P.,MMI Engineering Inc. | Moon I.-H.,KEPCO Engineering and Construction Company Inc.
Structures Congress 2012 - Proceedings of the 2012 Structures Congress | Year: 2012

Impact analysis of nuclear plant structural walls composed of surface steel plates, tie-bars, shear studs and concrete are discussed utilizing a simplified model of a fictitious wall to perform the analysis using LS-DYNA. The concrete constitutive model is based on Winfrith concrete model which covers all aspects of concrete behavior including cracking. The model was used to conduct a series of numerical studies to evaluate the effect of several parameters affecting the behavior of the wall. These parameters include thickness of the wall, thickness of the steel plate and diameter of tie bars. These studies resulted in several conclusions regarding the global and local behavior of the steel plated concrete wall system. © ASCE 2012.

Lee Y.I.,Seoul National University | Yi J.,Seoul National University | Yi J.,KEPCO Engineering and Construction Company Inc. | Choi T.,Chosun University
Journal of Sedimentary Research | Year: 2015

The Sindong Group (Aptian-Albian) in southeastern Korea is a 2-3-km-thick fluvio-lacustrine sedimentary package deposited in an elongated basin (the Nakdong Trough), which was formed by extension in an active-continental-margin setting. The provenance of the Sindong Group was studied to understand spatial and temporal variation in composition in three different parts of the basin by using integrated data on petrography, quartz SEM-cathodoluminescence (CL) analysis, and zircon Zr/Hf analysis. Although Sindong Group sandstones display wide variation in the composition of framework grains, they generally have increasing amounts of feldspar and decreasing amounts of quartz up sequence. Significant amounts of volcanic rock fragments and volcanic quartz are observed in the late-stage sediments. Metamorphic quartz is predominant in all Sindong Group sandstones, indicative of the exposure of metamorphic rocks in the source terrane, mostly from Precambrian basement and Triassic granites. The occurrence of significant amounts of plutonic quartz from early-stage sediments suggests that Jurassic granites were widely exposed in the source terranes. In addition, the episodic increase in volume of plutonic quartz content in the sequence, especially in the northern part of the basin, suggests that episodic tectonic activity occurred in the catchment. The increasing feldspar content up sequence could support the occurrence of tectonic activity in the catchments. The Zr/Hf analysis of detrital zircons revealed that the majority of zircons are of continental-crust origin formed in orogenic settings, but zircons in the lowest strata in the northern part of the basin were derived largely from anorogenic magmatic rocks of mantle origin. Our results demonstrate that source terranes for the Sindong Group have heterogeneous spatial and temporal distribution and were composed mainly of Precambrian basement and Triassic to Jurassic granitic rocks, with minor (meta)sedimentary rocks and syndepositional volcanic rocks. The detritus derived from syndepositional volcanic rocks became significant in the late stage of basin filling, representing the transition from extensional tectonism to continental-arc magmatism. The differences in characteristics of quartz SEM-CL and zircon Zr/Hf ratios in different parts of the basin are best explained by deposition on different alluvial fans and river systems. Copyright © 2015, SEPM (Society for Sedimentary Geology).

Yang B.J.,Korea Advanced Institute of Science and Technology | Kim B.R.,KEPCO Engineering and Construction Company Inc. | Lee H.K.,Korea Advanced Institute of Science and Technology
Acta Mechanica | Year: 2012

The objective of this study is to develop a micromechanics-based viscoelastic damage model that can predict the overall viscoelastic behavior of particle-reinforced polymeric composites undergoing damage. The emphasis here is that the present model successfully combines a rate-dependent viscoelastic constitutive model and a damage model. The Laplace transform based on the Boltzmann superposition principle and the ensemble-volume averaged method suggested by Ju and Chen (Acta Mech 103:103-121, 1994a; Acta Mech 103:123-144, 1994b) are extended toward effective viscoelastic properties. Further, the probability of the distribution function of Weibull (J Appl Mech 18:293-297, 1951) is adopted to describe a damage model that is dependent on damage parameters. A series of numerical simulations including parametric studies, and experimental comparisons are carried out to give insight into the potential capacity of the present micromechanics-based viscoelastic damage framework. © 2012 Springer-Verlag.

Jung J.,Seoul National University | Jeong Y.S.,Seoul National University | Lim Y.,Seoul National University | Lee C.S.,KEPCO Engineering and Construction Company Inc. | Han C.,Seoul National University
Energy Procedia | Year: 2013

CO2 capture process using aqueous Monoethanolamine (MEA) scrubbing is a well-proven and commercially-ready technology for reducing CO2 emission to the atmosphere. Although the MEA scrubbing is the one of the most suitable technologies for post-combustion CO2 capture, the MEA process has a critical problem which is high consumption of reboiler heat energy for solvent regeneration. In order to reduce the reboiler heat requirement, this paper suggests an advanced configuration of MEA process which consists of split flow and a phase separation heat exchanger. The split flow permits to reduce the reflux ratio in the stripper and the phase separation heat exchanger permits to alleviate preheating duty loss. As a result, the regeneration energy of the advanced process is reduced by 2.84GJ/ton CO 2, which is lower than one of the reference process by 27%. © 2013 The Author.

Oh K.,Kyung Hee University | Kang M.-S.,Kyung Hee University | Heo G.,Kyung Hee University | Lee Y.-S.,National Fusion Research Institute | And 2 more authors.
Fusion Engineering and Design | Year: 2013

The purpose of this study is to review the strategy for radiation barriers in the fusion power plants and to produce simulation data for the conceptual design of safety features to maintain the integrity of such barriers as a part of R&D program through the National Fusion Research Institute of Korea. Even though the amount of radioactive source term in fusion power plants should be much less than that of fission power plants, internal as well as external events can result in damage to facilities such that public can be critically exposed by radiation. In the first part of this study, we reviewed and compared the multiple defenses to protect radioactive hazard in fission and fusion power plants. Containment was characterized as an indispensable physical barrier and the integrity of containment particularly enveloping a fuel cycle which is a major radioactive source term, tritium, should be secured. Since water is assumed as one of the coolant options in the Korean fusion DEMO plant, the thermo-hydraulic analysis was carried out using computer simulations to produce key parameters related with the integrity of containment in the second part. The performance of both of active and passive safety features to control the key parameters was compared to take recent fission technologies into account. © 2013 Elsevier B.V. All rights reserved.

Oh Y.G.,KEPCO Engineering and Construction Company Inc. | Lee S.J.,Chungnam National University
IEEE Transactions on Nuclear Science | Year: 2010

The advanced design features of NSSS (Nuclear Steam Supply System) Integrity Monitoring System for Shin-Kori Nuclear Units 3 and 4 are summarized herein. During the overall system design and detailed component design processes, many design improvements have been made for the system. The major design changes are: 1) the application of a common software platform for all subsystems, 2) the implementation of remote access, control and monitoring capabilities, and 3) the equipment redesign and rearrangement that has simplified the system architecture. Changes give an effect on cabinet size, number of cables, cyber-security, graphic user interfaces, and interfaces with other monitoring systems. The system installation and operation for Shin-Kori Nuclear Units 3 and 4 will be more convenient than those for previous Korean nuclear units in view of its remote control capability, automated test functions, improved user interface functions, and much less cabling. © 2010 IEEE.

Fullmer W.D.,Purdue University | Lee S.Y.,KEPCO Engineering and Construction Company Inc. | Lopez De Bertodano M.A.,Purdue University
Nuclear Technology | Year: 2014

Methods to remedy the ill-posedness of the basic one-dimensional two-fluid model, which is widely used in nuclear reactor safety codes, have been the subject of considerable study. Both of the two prevalent methods have drawbacks. Unconditional hyperbolization uses nonphysical constitutive relations to create a well-posed two-fluid model that is hyperbolic over all flow conditions. However, when the model is hyperbolized, it is also stabilized, which is not a universal property of two-phase flows. The second method, the preferred method of the U.S. Nuclear Regulatory Commission safety codes, is to simply use a first-order upwind numerical method that relies on numerical viscosity to regularize the ill-posedness of the model by damping the short-wavelength instabilities. Unfortunately, the scale of the "short wavelength" is related to a particular numerical grid or discretization. Because of the consistency of the numerical method, in the limit of an infinitely resolved grid, i.e., Δx, Δt→0, the numerical viscosity vanishes, as does its regularization effect. This results in a somewhat heuristic user guideline that suggests a lower limit on the grid size based on a cross-sectional dimension Δx≥DH that is a combination of the long-wavelength assumption and experience. However, a cutoff wavelength achieved by numerical viscosity is not set by the grid size alone but also depends on the time step, the material, and the flow properties, as demonstrated with a von Neumann stability analysis. This can create poor resolution in areas where numerical stability may not be a substantial problem, unless the guideline is intentionally violated. Additionally, strict observance of this limit makes verification by convergence difficult or impossible. Therefore, it is proposed that an artificial viscosity be prescribed explicitly, i.e., independently of any particular numerical method or grid. An artificial viscosity model is derived that prescribes exactly a cutoff in the linear stability growth rate at a specified wavelength, e.g., λ0 = 2DH, consistent with the aforementioned user guideline. It is shown, using the water faucet problem, that the proposed artificial viscosity model can be used to remove the high-frequency component of the solution without limiting the resolution of the grid. Furthermore, the solution also converges, which was not the case without the artificial viscosity.

Yang B.J.,Korea Advanced Institute of Science and Technology | Kim B.R.,KEPCO Engineering and Construction Company Inc. | Lee H.K.,Korea Advanced Institute of Science and Technology
Composite Structures | Year: 2012

A viscoelastic damage model for aligned and 3D randomly oriented discontinuous fiber-reinforced polymeric composites is proposed. The model, which predicts the effective viscoelastic stress-strain behavior of the composites, is based on a combination of the Laplace-transformed superposition principle and the ensemble-averaged micromechanics. The Weibull's damage function is incorporated into the model for the modeling of the evolution of damaged fibers. An inverse analysis based on experimental data is adopted to simulate the strain rate sensitivity of the model. A series of numerical simulations based on the proposed model are performed to examine the influence of damage parameters, fiber orientations, strain rates, and the aspect ratio of discontinuous fibers on the behavior of the composites. In addition, experimental comparisons are made to illustrate and assess the predictive capability of the proposed model. © 2011 Elsevier Ltd.

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