• Journal of Radiation Protection and Research
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• v.29 no.3
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• pp.157-163
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• 2004

Atmospheric dispersion modelling has been widely used to predict the fate and transport of radioactive or toxic materials released from nuclear facilities which is an unlikely accidental event. To improve the forecasting performance of the dispersion model, it is required that source rate and dispersion characteristics must be defined appropriately. Generally, source term of the radioactive materials is much uncertain at the early phase of an accidental event. In this study, we computed the source rate with the experimental field data monitored at the Yeoung-Kwang nuclear site and obtained the optimal source rate to minimize the errors between the measured concentrations and the computed ones by the Gaussian plume model. Computed source term showed a good result within 24% of the artificially released source rate.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.32-38
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• 2018

The purpose of this study is to assess quantitatively the amount of leaks and the extent of dispersion in case of a leak at a hydrogen fluoride tank container unloading station, and to suggest a safety improvement plan to prevent recurrence of similar accidents. In 2012, Company H leaks 8 tonnes of tank containers with a maximum storage capacity of 18 Ton, causing it to become a social issue. As a result of calculation using Gaussian plume model, the concentration was estimated to be more than 20ppm from the leak point to 1,321 m radius. The leakage of hydrogen fluoride from the company R in 2014 was estimated to be 11.02 kg, of which 2.9 kg was treated by the scrubber. As a result of calculation using Gaussian plum model, the damage range with a concentration of 20ppm or more from the leak source was estimated to be 69 m in radius. As a result of comparing the above two accidents, it was found that the leakage amount was about 987 times different and the damaged site was more than 19 times different. Therefore, it was concluded that it was necessary to control the wearing of the protective equipment, the enclosure of the unloading site, the installation of the scrubber, and the emergency training to avoid the accidental leakage of a hydrogen fluoride from the unloading site.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.5
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• pp.529-540
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• 1996

Dispersion experiment using SF$_{6}$ tracer was performed in the flat field of Chunchon Basin during four nights from August 29 to September 2, 1991. The purpose of this study is to analyze toe horizontal distribution of tracer concentration under the strong stable conditions and to evaluate the results calculated by INPUFF model. Incase of high wind speed, plume spread of SF$_{6}$ concentration appeared in narrow area of the downwind and the standard deviation of the horizontal wind angle (.sigma.$_{a}$) was amall. However, the SF$_{6}$ was spread widely in cases of low wind speed because of the large .sigma.$_{a}$. The result of the INPUFF model was similar to the observed distribution of the SF$_{6}$ concentration. It is proved that the Gaussian puff model is useful when wind direction varies significantly.tly.tly.tly.

• Nuclear Engineering and Technology
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• v.19 no.2
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• pp.99-106
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• 1987

Comparison study on the radiological effects by radionuclides from hypothetical 1,000MWe coal-fired power station and nuclear power plant is made. This paper describes the radiological effects only for gaseous effluents released in normal operation. Source terms for coal-fired Power station are quoted from foreign data and those for nuclear power plant are calculated for reference power plant. Gaussian plume model is used to assess atmospheric dispersion of radioactive effluents based on one year meteorological data of Kori site and individual doses are calculated at the maximum X/Q point. Doses from nuclear power plant are slightly more than those from coal-fred power plant. In the case of coal-fired power plant, doses by ingestion of contaminated vegetation are 73.5% of total doses.

• Journal of the Korean Society of Safety
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• v.9 no.1
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• pp.89-94
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• 1994

Two methods, the numerical method of CPQRA and the manual method of IAEA, were used to estimate the effect distance from release and dispersion of toxic materials. The Gaussian plume model which has a weather stability class D with wind velocity of 5m/s was applied to calculate dispersion of toxic materials. Also, probit function were employed to evaluate the human fatality as a result of exposure to toxic gases. Furthermore, concentration of toxic materials corresponding to LC$_{50}$ for 30 min could be determined by setting Pr as 5.0 and solving the probit function. Calculations were conducted by employing chlorine and ammonia as toxic materials because they are not only most commonly used In chemical plants but also very harmful to humans. Calculated results by employing toxic materials indicated that the effect distance from the CPQRA method was between the minimum and maximum distance from the method proposed by IAEA.A.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.4
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• pp.263-271
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• 2000

To investigate the distribution of air pollutants dispersion in the horizontal wind fields, a chaff release experiment was carried out by an airplane. The temporal and spatial variations of a chaff plume from an elevated point source using the WSR-88D(NEXRAD) radar. The observed profiles of radar reflectivity were compared with the Gaussian diffusion model at slightly unstable atmospheric condition. The present study shows that the distributions of radar reflectivity from chaffs and their concentration by the model are in general agreement with time variation. The dispersion coefficients in downwind($\sigma$(sub)x) and crosswind($\sigma$(sub)y) spread data exceeded what has generally been found at Pasquill and Brigg\`s estimates. As a result, it was clearly shown that horizontal and vertical diffusion coefficients are more accurately determined as compared with theoretical coefficients. At longer diffusion distances(than 10km), a radar observation provided the determination of maximum range and diffusion height more qualitatively, too.

• Journal of the Korean Society of Safety
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• v.10 no.1
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• pp.56-63
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• 1995

Two methods of the numerical method of CPQRA(Chemical Process Quantitative Risk Analysis) and the manual method of IAEA(International Atomic Energy Agency) were used to estimate the individual risk and societal risk around the chemical plant. Where, the CPQRA is introduced to verify the theoritical background of the manual of international atomic energy agency. The Gaussian plume model which has a weather stability class D with velocity of 5m/s was applied to calculate dispersion of hazard material. Also, 8-point method was employed to the effects of accidents for wind distribution. Furthermore, historical record, FTA(Fault Tree Analysis) and ETA(Event Tree Analysis) were used to estimate the probability or frequency of accidents. Eventually, the individual risk shows isorisk contour and the societal risk shows F-N curve around hazard facility, especially in chemical plants. Caulculated results, which both individual and societal risk, by using IAEA manual show simillar results to those of calculation by numerical method of CPQRA.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.891-896
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• 2009

The puff models have been developed to simulate the advection-diffusion processes of dredging suspended solids, either alone or in combination with Eulerian models. Computational efficiency and accuracy are of prime importance in designing these hybrid approaches to simulate a pollutant discharge, and we characterize two relatively simple Lagrangian techniques in this regard: forward Gaussian puff tracking (FGPT), and backward Gaussian puff tracking (BGPT). FGPT and BGPT offer dramatic savings in computational expense, but their applicability is limited by accuracy concerns in the presence of spatially variable flow or diffusivity fields or complex no-flux or open boundary conditions. For long simulations, particle and/or puff methods can transition to an Eulerian model if appropriate, since the relative computational expense of Lagrangian methods increases with time for continuous sources. Although we focus on simple Lagrangian models that are not suitable to all environmental applications, many of the implementation and computational efficiency concerns outlined herein would also be relevant to using higher order particle and puff methods to extend the near field.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.393-396
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• 2002

Submerged gas-injected system can be applied to various industrial field such as metallurgical and chemical processes, So this study aims at presenting the relevant relationship between gas phase and liquid phase in a gas-injected bath. In a cylinderical bath, local gas volume fraction and bubble frequency were measured by electroconductivity probe and oscilloscope. The temperature of each phase was measured using thermocouple and data acquisition system. In vertical gas injection system, gas-liquid two phase plume was formed, being symmetry to the axial direction of injection nozzle and in a shape of con. Lacal gas-liquid flow becomes irregular around the injection nozzle due to kinetic energy of gas and the flow variables show radical change at the vicinity of gas(air) injection nozzle As most of the kinetic energy of gas was transferred to liquid in this region, liquid started to circulate. In this reason, this region was defined as 'developing flow region' The Bubble was taking a form of churn flow at the vicinity of nozzle. Sometimes smaller bubbles formed by the collapse of bubbles were observed. The gas injected into liquid bath lost its kinetic energy and then was governed by the effect of buoyancy. In this region the bubbles which lost their kinetic energy move upward with relatively uniform velocity and separate. Near the gas nozzle, gas concentration was the highest. But it started to decrease as the axial distance increased, showing a Gaussian distribution.