• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.654-659
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• 2018

In this study, continuous long-term observation is implemented with an ocean radar. Ocean radar conducts remote observation (combined) with ground-based radars, which enable a series of simultaneous observations of an extensive range of the coast with high frequency. An ocean radar for continuous long-term observation is operated at Samcheok on the east coast of Korea. Samcheok experienced tsunami damage in recent years and is the location of a nuclear power plant. In order to examine the reliability of the ocean radar, a pressure-type wave gauge, ultrasonic wave gauge, and ocean buoy are installed for the purpose of data comparison and verification. The ocean radar used in this study is an array-type HF-RADAR named WERA (WavE RAdar). The analysis of the data obtained from continuous long-term observations showed that the radar observations were in agreement with more than 90% of the wave data collected within a 25 km range from the center of two sites. Less than 1% of the entire observation data was unmeasured by the time series analysis. As a result of comparing the radar data with the direct observations made by the wave gauge, it was inferred that the RMS deviation is less than 20cm and the correlation coefficient was in the range of 0.84 ~ 0.87. Moreover, supported by such observations, a comprehensive monitoring system is being developed to provide the public with real-time reports on waves and currents via the internet.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.618-629
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• 2021

The Fukushima nuclear power plant (NPP) accident caused by the East Japan Earthquake in 2011 and the recent increase in the frequency of earthquakes in Korea have caused safety concerns regarding radionuclide exposure. In addition, the Tokyo Electric Power Company (TEPCO) in Japan recently decided to release radionuclide-contaminated water from Fukushima's NPP into the Pacific Ocean, raising public concerns that the possibility of radionuclide contamination through both domestic- and foreign fishery products is increasing. Although many studies have been conducted on the input of artificial radionuclides into the Pacific after the Fukushima NPP accident, studies on the distribution and accumulation of artificial radionuclides in marine products from East Asia are lacking. Therefore, in this study, we attempted to explore recent research on the distribution of artificial radionuclides (e.g., ¹³⁷Cs, ^239+240Pu, ⁹⁰Sr, and etc.) in marine products from Korean seas after the Fukushima NPP accident. In addition, we also discuss future research directions as it is necessary to prepare for likely radiation accidents in the future around Korea associated with the new nuclear facilities planned by 2030 in China and owing to the discharge of radionuclide-contaminated water from the Fukushima NPP.

• Structural Engineering and Mechanics
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• v.4 no.2
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• pp.139-148
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• 1996

Vector algorithms and the relative importance of the four basic modules (computation of element stiffness matrices, assembly of the global stiffness matrix, solution of the system of linear simultaneous equations, and calculation of stresses and strains) of a finite element computer program for inelastic analysis of reinforced concrete shells are presented. Performance of the vector program is compared with a scalar program. For a cooling tower problem, the speedup factor from the scalar to the vector program is 34 for the element stiffness matrices calculation, 25.3 for the assembly of global stiffness matrix, 27.5 for the equation solver, and 37.8 for stresses, strains and nodal forces computations on a Gray Y-MP. The overall speedup factor is 30.9. When the equation solver alone is vectorized, which is computationally the most intensive part of a finite element program, a speedup factor of only 1.9 is achieved. When the rest of the program is also vectorized, a large additional speedup factor of 15.9 is attained. Therefore, it is very important that all the modules in a nonlinear program are vectorized to gain the full potential of the supercomputers. The vector finite element computer program for inelastic analysis of RC shells with layered elements developed in the present study enabled us to perform mesh convergence studies. The vector program can be used for studying the ultimate behavior of RC shells and used as a design tool.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.275-275
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• 2022

Tsunamis triggered by undersea earthquakes have the characteristic of longer wavelengths and can propagate a very long distance. Although the occurrence frequency of tsunami is low, it can cause casualties and properties. Historically, tsunamis that occurred on the western coast of Japan attacked the eastern coast of the Korean Peninsula and damaged the property and the loss of human life in 1983 and 1993. By tsunami in 1983 especially, 2 people were killed, and more than 200 casualties occurred. In addition, it caused 2 million dollars in property damage at Imwon Port. In 2011, The eastern cities of Japan: Iwate, Miyagi, Ibaraki, and Fukushima were damaged by a tsunami that occurred near onshore along the Pacific ocean and caused more than 300 billion dollars in property damage, and 20,000 casualties occurred. Moreover, those provoked nuclear power plant meltdown at Fukushima. In this study, it was carried out a relationship between maximum tsunami heights and fault parameters of earthquake: strike angle, dip angle, and slip angle at Imwon port. Those fault parameters are known that it does not relate to the magnitude of earthquake directly. Virtual tsunamis, which could be triggered by probable undersea earthquakes in the future, were investigated and mutual information based on probability and information theory was introduced to figure out the relationship between maximum tsunami height and fault parameters. Fault parameters were evaluated according to the strong relationship with maximum tsunami heights finally.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.134-139
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• 2002

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. However, effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study, we investigated failure modes of locally wall thinned pipes and AE signals by bending test. From test results, we could be divided four types of failure modes of ovalization, crack initiation after ovalization, local buckling and crack initiation after local buckling. And fracture behaviors such as elastic region, yielding range, plastic deformation range and crack progress could be evaluated by AE counts, accumulative counts and time-frequency analysis during bending test. It is expected to be basic data that can protect a risk according to local wall thinning of pipes, as a real time test of AE.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.245-259
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• 1994

This paper is concerned with the development of a three-dimensional numerical model for coastal circulation and heat transport with improved prediction ability. The model uses fully nonlinear, time-dependent three-dimensional, $\sigma$-transformed equations of motion and equation of heat transport The model was verified with experimental data for wind-driven current in a one-dimensional channel and thermal jets flowing into stagnant waters and applied for unsteady flow induced by tide and thermal jets in coastal waters around Kori nuclear power plant. The model results were in good agreements with experimental data sets for wind-driven current and thermal jet, and field observed data sets in coastal waters. This study has shown that the $\kappa$-$\varepsilon$ turbulence model is applicable to various coastal conditions without any modification of turbulence constants.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.46-66
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• 2002

High-resolution multichannel seismic data were collected in the coastal area near the Gori nuclear power plant to investigate Quaternary fault pattern and timing. A 12 channel streamer, a sparker, and a portable recorder were used for data acquisition. Because the group interval of the streamer was 6.25 m and the sparker can generate acoustic waves with the frequency content of up to 500 Hz, the data show a significant improvement both in horizontal and vertical resolution. The area surveyed is covered with 30-40 m thick Holocene sediments that constitute the mud belt along the southeastern coast of Korea. The survey area is characterized by the well discriminated Pleistocene and Holocene boundary and shallow gas-charged zones. A number of Quaternary faults were found in the sediment column, that are nearly vertical and extend north-south. The Quaternary faults, arranged at a spacing of a few hundred meters, suggest that they were formed in response to compression, although some of them reveal extensional characteristics. Locally, faults disrupt Incised-channel fills that are interpreted to have formed in the early stage of transgression after the beginning of the Holocene. Seismic sections suggest that shallow gas in the mud belt sediments made its way upward through the fractured fault planes. The tectonism responsible for the opening of the East Sea has not persisted since the late Miocene, but vigorous Quaternary faulting activity in the vicinity of the southeastern Korean Peninsula indicates that tectonic stability has yet to be achieved in this region underlain by the hotter than normal mantle.

• Ocean and Polar Research
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• v.28 no.4
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• pp.385-393
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• 2006

Screening performance of the existing intake screens (drum and travelling screen) on mass impingement of marine animals, a euphausiid, Euphausia pacifica and a scyphozoan medusae, Aurelia aurita that have often clogged intake screens of the Uljin Nuclear Power Plant, was tested. The maximum tolerable densities of marine animals in the inflowing seawater upon the screen were estimated with two different approaches. First the maximum density of jellyfish was calculated from (1) passing amount of seawater per unit time through the screens and (2) the covered area of animals on the screens clogged. The maximum density of krill tolerable in the drum screen was cited from a simulated record of Uljin NPP, then those in the travelling screens were also calculated using the data of drum screen and ratio of seawater amount passing through the screens under the condition of 0.5m water column (W.C.) of the differential pressure (AP) produced by screens, an established permissible limit of ${\Delta}P$. Secondly, the screening performances were also tested by hydrodynamic measurements with various screen models in a circulating water channel equipped with a speed-controlling pump and a differential pressure gauge. From the first approach, the maximum tolerable densities of drum and travelling screen were calculated as 2.0 and $1.5ind/m^3$ for the Jellyfish and 900 and $680ind./m^3$ for the euphausiid, respectively. These densities estimated from the second approach were 2.1 and $0.8ind/m^3$ for the jellyfish and 1059 and $504ind/m^3$ for the euphausiid, respectively. These estimates were compared with the data from historic clogging events to evaluate the practical performance of these intake screens. The comparisons suggest a newly improved intake-screen of which performance should be at least seven times (approximately) better than the existing ones ior the krill and 3.2 times for the jellyfish, respectively, for preventing mass impingement, and for maintaining the condition of the differential pressure between the screens below 0.3 m W.C.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.183-192
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• 1998

The long-term observation of temperature in the coastal waters adjacent to the Wolsung Nuclear Power Plant has been carried out from November 10, 1996 to August 22, 1997, for approximately 280 days using a real-time temperature measurement buoy system. The sea-surface temperature was measured at every 10 minute using 10 buoys. The vertical structure of temperature was investigated near the outlet of the plant with two thermistor chains equipped with 10 sensors at 1 m interval The monthly averaged temperature was the lowest with spatial average of $12.8^{\circ}C$ in February and was the highest in August with spatial average of $19.6^{\circ}C$. The extremely low temperature was frequently observed between June and August, which seems to be the consequence of the intrusion of cold water near the southeastern coast of Korea. Distributions of the daily and hourly averaged temperature show that the highest temperature always occurred near the outlet of the plant and the warm-water patch moved along the north-south direction with the semidiurnal period. The semidiurnal fluctuation of temperature was also observed near the surface of the vertical profiles. The spectral analysis of temperature between February and April 1997 shows that the semidiurnal components prevailed near the outlet. It is likely that the semidiurnal components were due to the prevailing semidiurnal tide in this region. In August 1997, the diurnal components were dominant at the surface water of all stations except Station 12, which suggests that the warm water from the outlet of the plant has less effects in summer on the surrounding waters than the strong solar radiation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.5
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• pp.387-395
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• 2024

In 2011, the Fukushima nuclear power plant accident in Japan resulted in more than 1.3 million tons of radioactive contaminated water, and the Japanese government has been releasing large amounts of contaminated water into the ocean since 2023. This accident has raised concerns about marine pollution and seafood consumption, as well as the effects on highly radiosensitive children and fetuses. Radiation protection materials are being researched to better prepare for various radiation accidents, including marine radioactive contamination incidents. Natural radioprotectors have fewer side effects and are more easily commercialized than chemical radioprotectors. This study aimed to confirm the function of a mixture of folic acid and α-tocopherol, natural antioxidants, in protecting living organisms from radiation. In the experiment, Spraque-Dawley rats (SD rats) were used to induce pregnancy to target fetuses with high radiation sensitivity, and the second generation's skeletal system, blood analysis, body weight, spleen, brain, and small intestine were examined after birth. After administering a mixture of folic acid and α-tocopherol, the irradiated group showed significant recovery (p<0.05) in blood analysis, small intestinal villus length, and cerebral cortex thickness measurements compared to the comparison group (irradiated group), suggesting that the mixture of folic acid and α-tocopherol is effective for in vivo radioprotection in a radioactive contaminated environment.