• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.888-895
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• 2022

Lately, ocean nuclear power plants have attracted attention as one of diverse uses of nuclear power plants. Because ocean nuclear power plants are movable or transportable, it is necessary to analyze the thermal hydraulics in a moving frame of reference, and computer codes have been developed to predict thermal hydraulics in large moving systems. The purpose of this study is to incorporate a three dimensional dynamic motion model into the SPACE code (Safety and Performance Analysis CodE) so that the code is able to analyze thermal hydraulics in an ocean nuclear power plant. A rotation system that describes three-dimensional rotations about an arbitrary axis was implemented, and modifications were made to the one-dimensional momentum equations to reflect the rectilinear and rotational acceleration effects. To demonstrate the code's ability to solve a problem utilizing a rotational frame of reference, code calculations were conducted on various conceptual problems in the two-dimensional and three-dimensional pipeline loops. In particular, the code results for the three-dimensional pipeline loop with a tilted rotation axis agreed well with the multi-dimensional CFD results.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3732-3744
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• 2022

To investigate the effects of ocean conditions on the thermal stress and deformation caused by thermal stratification of a pressurizer surge line in a floating nuclear power plant (FNPP), the finite element simulation platform ANSYS Workbench is utilized to conduct the fluid-solid-thermal coupling transient analysis of the surge line under normal "wave-out" condition (no motion) and under ocean conditions (rolling and pitching), generating the transient response characteristics of temperature distribution, thermal stress and thermal deformation inside the surge line. By comparing the calculated results for the three motion conditions, it is found that ocean conditions can significantly improve the thermal stratification phenomenon within the surge line, but may also result in periodic oscillations in the temperature, thermal stress, and thermal deformation of the surge line. Parts of the surge line that are more susceptible to thermal fatigue damage or failure are determined. According to calculation results, the improvements are recommended for pipeline structure to reduce the effects of thermal oscillation caused by ocean conditions. The analysis method used in this study is beneficial for designing and optimizing the pipeline structure of a floating nuclear power plant, as well as for increasing its safety.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.356-360
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• 2016

Recently, the lifetime extension of nuclear power plants has been considered. Thus, it is necessary to consider facility safety management and economic management. However, when the bolts in nuclear power plants are replaced and the turbines of nuclear power plant are disassembled, numerous problems are found in relation to stuck bolts in clamping parts. In order to solve these problems, a hybrid vacuum chamber was first designed and manufactured. It can perform arc ion plating and sputtering, which were used to deposit Ti/TiN on an A913 B7 bolt. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to determine the composition and characteristics of the bolt, and tests were conducted to determine how long the bolt could endure under various conditions in a nuclear power plant. The SEM and XRD results clearly showed a continual and even coating layer. When this TiN-coated bolt is used in a nuclear power plant, the lifetime can be extended compared to a conventional bolt, but it is necessary to determine what additional properties are required.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.69-78
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• 2021

Venturi meter is frequently used in feed water flow control system in a nuclear power plant. Its accurate measurement plays a vital role in the safe operation of the plant. This paper firstly investigates the influence of the length of each section of pipeline, the throat inner diameter of Venturi and the flow characteristics in a single-phase flow on the accuracy of Venturi measurement by numerical calculation. Then the flow and the accuracy are discussed in a multi-phase flow. Numerical results show that the geometrical parameters and the characteristics of complex turbulent flow in the single-phase flow have little impact on the accuracy of Venturi flow rate measurement. In the multi-phase flow, the calculated flow rate of Venturi deviated from the actual flow rate and this deviation value is closely related to the amount of steam in the pipeline and increases sharply with the increase of the amount of steam. The over-reading of Venturi flow rate is present.

• Ocean and Polar Research
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• v.35 no.4
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• pp.299-312
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• 2013

This study analyzed the species composition and density of a macrobenthic community according to variations in the thermal discharge volumes of a nuclear power plant before, during, and after the shutdown of the nuclear power plant during two periods. In this study, 369 macrobenthic fauna species were collected, and their mean density was 1,712 ind. $m^{-2}$. The number of species and diversity of macrobenthic fauna decreased with distance from the thermal discharge area, regardless of whether the nuclear plant shutdown or not. Many macrobenthic taxa appeared near the thermal discharge area, but polychaetes species were more prominent in outer areas than at the discharge area. The density of macrobenthic fauna decreased with distance from the thermal discharge area during a plant shutdown in the fall of 2011, but increased, except at two sites, near the discharge area in the winter of 2012. Cluster analysis indicated that the spatial distribution of the macrobenthic community changed in areas near the nuclear power plant after a shutdown period; that is, the station group I, in areas near the nuclear power plant, became narrower after the shutdown, but it recovered to previously occupied areas after the nuclear power plant began operating again. Opportunistic species, such as the polychaetes Lumbrineris longifolia (= Scoletoma longifolia) and Mediomastus californiensis, which were present in high densities near thermal discharge areas, decreased after the shutdown but recovered after the plant re-opened. The number of species and diversity of the macrofauna and the density of dominant species showed a significant correlation with temperature, except in winter periods. The results of this study revealed that changes in the amount of thermal discharge before and after the shutdown of a nuclear power plant could exert an influence on the structure of macrobenthic community within the thermal discharge areas depending on the season.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.1-7
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• 2002

In the past, safety assessment on the site of Ulchin Nuclear Power Plants against tsunamis was carried out with probable maximum earthquake magnitude and related tsunamigenic fault parameters. Recently, however, based on the seismic gap theory, some seismologists warned about earthquakes of larger magnitudes than had been expected. In this study, we revaluated tsunami risk with a finite difference model based on linear and nonlinear shallow water equations. Firstly, we simulated the\`83 tsunami and compared the calculated water surface profile with the observed wave heights. Secondly, we evaluated the rise and drop of sea water level at the site of Ulchin Nuclear Power Plant with fault parameters of the past '83, '93 tsunamis and some dangerous faults. Finally, we showed that the cooling water intake facility of Ulchin Nuclear Power Plants would be safely operated in disastrous tsunamis.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.360-364
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• 2004

The objective of this study is to estimate the feasibility of acoustic emission method Jar the internal leak from the valves in nuclear power plants. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. From the comparison of background noise data with the experimental results as to relation between leak flow and acoustic signal, the minimum leak flow rates that am be detected by acoustic signal was suggested. When the background noise level are higher than the acoustic signal, the method described below was considered that the analysis the remainder among the background noise frequency spectrum and the acoustic signal spectrum.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.961-968
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• 2013

The Arabian Gulf region has one of the highest ocean temperatures, reaching above 35 degrees and ambient temperatures over 50 degrees in the summer. Two nuclear power plants (NPP) are being introduced in the region for the first time, one at Bushehr (1,000 MWe PWR plant from Russia), and a much larger one at Barakah (4X1,400 MWe PWR from Korea). Both plants take seawater from the Gulf for condenser cooling, having to modify the secondary/tertiary side cooling systems design by increasing the heat transfer surface area from the country of origin. This paper analyses the secondary side of a typical PWR plant operating under the Rankine cycle with a simplified thermal-hydraulic model. Parametric study of ocean cooling temperatures is conducted to estimate thermal efficiency variations and its associated design changes for the secondary side. Operational safety is reviewed to deliver rated power output with acceptable safety margins in line with technical specifications, mainly in the auxiliary systems together with the cooling water temperature. Impact on the Gulf seawater as the ultimate heat sink is considered negligible, affecting only the adjacent water near the NPP site, when compared to the solar radiation on the sea surface.

• Ocean and Polar Research
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• v.39 no.2
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• pp.125-148
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• 2017

This study analyzed the community structure of macrobenthic organisms in the subtidal area suffering under the influence of thermal discharge from the Uljin nuclear power plant during 2012-2013 and reviewed the temporal change in the faunal composition of the macrobenthic community using data from previous studies since the start of the plant operation in 1989. A total of 319 species were collected in 2012-2013, with a mean density of $3,330ind./m^2$ and a mean biomass of $131.96g/m^2$. These results were similar to those obtained in 2006-2007. The dominant species were not different from each other before and after the power plant operations began, but the faunal density near the power plant drainage port was significantly higher compared to those densities obtained from other stations. Spiophanes bombyx and Polydora sp., which is known as a pollution indicator species, was dominant only in the drainage port area. The study area consisted of two subregions with different macrobenthic communities depending on the water depth, which was similar to the results of the 2006-2007 survey. The macrobenthic community structures before and after the operation of the power plant in the coastal area were not changed, but there were seasonal differences in the long-term macrobenthic community structure which were strongly related to the thermal discharge from the power plant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.7
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• pp.591-597
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• 2012

For the past few years, the concern for clean energy has been greatly increased. Ocean thermal Energy Conversion(OTEC) power plants are studied as a viable option for the supply of clean energy. In this study, we examined the thermodynamic performance of the OTEC power system for the production of electric power. Computer simulation programs were developed under the same condition and various working fluids for closed Rankine cycle, regenerative cycle, Kalina cycle, open cycle, and hybrid cycle. The results show that the regenerative cycle showed the best system efficiency. And then we examined the thermodynamic performance of regenerative cycle OTEC power system using the condenser effluent from Uljin nuclear power plant instead of the surface water. The highest system efficiency of the condition was 4.55% and the highest net power was 181 MW.