• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1939-1950
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• 2019

The MELCOR code useful for a plant-specific hydrogen risk analysis has inevitable limitations in prediction of a turbulent flow of a hydrogen mixture. To investigate the accuracy of the hydrogen risk analysis by the MELCOR code, results for the turbulent gas behavior at pipe rupture accident were compared with CFX results which were verified by the American National Standard Institute (ANSI) model. The postulated accident scenario was selected to be surge line failure induced by station blackout of an Optimized Power Reactor 1000 MWe (OPR1000). When the surge line failure occurred, the flow out of the surgeline was strongly turbulent, from which the MELCOR code predicted that a substantial amount of hydrogen could be released. Nevertheless, the results indicated nonflammable mixtures owing to the high steam concentration released before the failure. On the other hand, the CFX code solving the three-dimensional fluid dynamics by incorporating the turbulence closure model predicted that the flammable area continuously existed at the jet interface even in the rising hydrogen mixtures. In conclusion, this study confirmed that the MELCOR code, which has limitations in turbulence analysis, could underestimate the existence of local combustible gas at pipe rupture accident. This clear comparison between two codes can contribute to establishing a guideline for computational hydrogen risk analysis.

• Journal of Bio-Environment Control
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• v.8 no.3
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• pp.192-201
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• 1999

This study was aimed to introduce the measurement of $CO_2$ concentration and leaf area index in the phytotron for predicting the effect of CO.E, light and leaf area index on the instantaneous photosynthetic rate of sweet pepper with the existing ASKAM model. Measurements were made in 2 semi-closed phytotron compartments in which three different $CO_2$ concentrations were applied at random. Plants were grown on containers with circulating nutrient solution at 21$^{\circ}C$ and 80-95% relative humidity. The model estimates crop net $CO_2$ uptake for short time intervals during the day based on short-term data of daily radiation, temperature and $CO_2$ concentration. During the photosynthesis measurements, $CO_2$ concentrations in both compartments and in the basement were measured every minute. This was also done for the flow of pure $CO_2$ into the compartment, global radiation, photosynthetic active radiation inside the compartment, temperature and relative humidity. Crop growth models summarize our knowledge on crop behavior and have as such a wide range of applications in analysis, crop management and thus as a farm management tool.

• Journal of Radiation Protection and Research
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• v.43 no.2
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• pp.39-49
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• 2018

Background: A model to assess the activity concentration of agricultural products and the public ingestion dose as result of a nuclear accident is necessarily required to manage the contaminated agricultural systems by the accident, or to estimate the effects of chronic exposure due to food ingestion at a Level 3 PSA. Materials and Methods: A dynamic compartment model, which is composed of three sub-modules, namely, an agricultural plant contamination assessment model, an animal product contamination assessment model, and an ingestion dose assessment model has been developed based on Korean farming characteristics such as the growth characteristics of rice and stockbreeding. Results and Discussion: The application study showed that the present model can predict well the characteristics of the activity concentration for agricultural products and ingestion dose depending on the deposition date. Conclusion: The present model is very useful to predict the radioactivity concentration of agricultural foodstuffs and public ingestion dose as consequence of a nuclear accident. Consequently, it is expected to be used effectively as a module for the ingestion dose calculation of the Korean agricultural contamination management system as well as the Level 3 PSA code, which is currently being developed.

• Journal of Environmental Science International
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• v.24 no.10
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• pp.1273-1283
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• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.450-461
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• 2006

In this study, sorption kinetics of lead (Pb) and cadmium (Cd) onto coastal sediments were investigated at pH 5.5 using laboratory batch adsorbers. Four different models: one-site mass transfer model (OSMTM), pseudo-first-order kinetic model (PFOKM) ,pseudo-second-order kinetic model (PSOKM) and two compartment first-order kinetic model (TCFOKM) were used to analyze the sorption kinetics. As expected from the number of model parameters involved, the three-parameter TCFOKM was better than the two-parameter OSMTM, PFOKM and PSOKM in describing sorption kinetics of Pb and Cd onto sediments. Most sorption of Pb and Cd was rapidly completed within the first three hours, followed by slow sorption in the subsequent period of sorption. All models predicted that the sorbed amount at the apparent sorption ($q_{e,s}$) equilibria increased as the CEC and surface area of the sediments increased, regardless of initial spiking concentration ($C_0$) and heavy metal and the sediment type. The sorption rate constant ($k_s,\;hr^{-1}$) in OSMTM also increased as the CEC and BET surface area increased. The rate constant of pseudo-first-order sorption ($k_{p1,s},\;hr^{-1}$) in PFOKM were not correlated with sediment characteristics. The results of PSOKM analysis showed that the rate constant of pseudo-second-order sorption ($k_{p2,s},\;g\;mmol^{-1}\;hr^{-1}$) and the initial sorption rate ($v_{o,s},\;mg\;g^{-1}\;hr^{-1}$) were not correlated with sediment characteristics. The fast sorption fraction ($f_{1,s}$) in TCFOKM increased as CEC and BET surface increased regardless of initial aqueous phase concentrations. The sorption rate constant of fast fraction ($k_{1,s}=10^{0.1}-10^{1.0}\;hr^{-1}$) was much greater than that of slow sorption fraction ($k_{2,s}=10^{-2}-10^{-4}\;hr^{-1}$) respectively.

• Journal of Pharmaceutical Investigation
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• v.21 no.4
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• pp.247-251
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• 1991

Effects of aluminum magnesium hydroxide (A) and cimetidine (C) on the pharmacokinetics of minocycline (M) were investigated in female rats. Blood samples were collected at various time intervals until 36 hrs following oral dosing of drugs. Plasma minocycline concentrations were determined by HPLC. Control group (M), $T_1$ group (M+A), $T_2$ group (A+M after 2 hrs), $T_3$ group (M+A after 2 hrs), $T_4$ group (M+C) and $T_5$ group (C+M after 2 hrs) were divided to examine interaction of the drugs with minocycline. Plasma minocyline level-time curves were well described by two-compartment open model with first-order absorption in rats. Antacid treatment was associated with reduced of 71.0, 45.9, 35.7% in minocycline absorption rate $constant(K_{\alpha})$, maximum plasma $concentration(C_{max})$, and relative $bioavailability(F_{rel})$, respectively. Cimetidine treatment group exhibited no significant changes in plasma level-time curve when compared with control group and did not affect minocycline absorption as by any of these three parameters.

• YAKHAK HOEJI
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• v.39 no.6
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• pp.636-644
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• 1995

Comparison of bioavailabflity (BA) of three brands of ranitidine (RT) tablets has been studied m rats. The purpose of this study was to characterize the pharniacolunetics of RT tablets in the rat and to coinpare phannacolunetic parameters of three brands of RT tablets. In addition, it was investigated whether plasma RT concentrations m humans can be predicted from pharmacokinetic parameters obtained in rats. RT was administered intravenously in dose of RT.HCI 10mg/kg and orally in dose of RT.HCI 50mg/kg as solution or crushed sample of thablets. Plasma RT concentrations were determned by HPLC. Plasma RT concentrations as a function of time were fitted to two compartment model. Plasma RT concentrations declined with a terminal half life ($t_{{1}/2{\betha}}$) of 40.9 min. The plasma RT concentration-time curve showed two peak plasma concentrations following an oral administration of solution or crushed sample in rats like humans. No significant difference among pharmacokinetic parameters was observed except $T_{max2}$ (p<0.05). The BA for crushed sample A, B and C were found to be 54.6 40.7 and 40.0%, respectively. Equivalence of $C_{max1}$ and $T_{max2}$ were guaranteed in this study. However, it was concluded that three brands of RT tablets are bioequivalent, taking the following characteristics of RT into consideration;(1) rapid onset of the effect is not required, (2) $C_{max1}$ and $T_{max2}$ do not seem to influence the effectiveness of the drug during a long-term treatment by the usual administration of twice a day. Results from this study were combined with plarmacokinetic data for RT in dogs and humans to develop a basis for interspecies scale-up of the disposition characteristics of the drug. there were similarities in the general disposition of the drug. Allometric relationships were sought between pharmacokinetic parameters nd species body weight. Significant interspecies correlations were found for total body clearance($Cl_{t}$) and steady state volume of distribution ($Bd_{ss}$). Thus, plasma RT concentrations in humans can be predicted from pharmacokinetic parameters obtained in rats.

• The Korean Journal of Nuclear Medicine
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• v.31 no.1
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• pp.73-82
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• 1997

Regional myocardial blood flow (rMBF) can be noninvasively quantified using N-13 ammonia and dynamic positron emission tomography (PET). The quantitative accuracy of the rMBF values, however, is affected by the distortion of myocardial PET images caused by finite PET image resolution and cardiac motion. Although different methods have been developed to correct the distortion typically classified as partial volume effect and spillover, the methods are too complex to employ in a routine clinical environment. We have developed a refined method incorporating a geometric model of the volume representation of a region-of-interest (ROI) into the two-compartment N-13 ammonia model. In the refined model, partial volume effect and spillover are conveniently corrected by an additional parameter in the mathematical model. To examine the accuracy of this approach, studies were performed in 9 coronary artery disease patients. Dynamic transaxial images (16 frames) were acquired with a GE $Advance^{TM}$ PET scanner simultaneous with intravenous injection of 20 mCi N-13 ammonia. rMBF was examined at rest and during pharmacologically (dipyridamole) induced coronary hyperemia. Three sectorial myocardium (septum, anterior wall and lateral wall) and blood pool time-activity curves were generated using dynamic images from manually drawn ROIs. The accuracy of rMBF values estimated by the refined method was examined by comparing to the values estimated using the conventional two-compartment model without partial volume effect correction rMBF values obtained by the refined method linearly correlated with rMBF values obtained by the conventional method (108 myocardial segments, correlation coefficient (r)=0.88). Additionally, underestimated rMBF values by the conventional method due to partial volume effect were corrected by theoretically predicted amount in the refined method (slope(m)=1.57). Spillover fraction estimated by the two methods agreed well (r=1.00, m=0.98). In conclusion, accurate rMBF values can be efficiently quantified by the refined method incorporating myocardium geometric information into the two-compartment model using N-13 ammonia and PET.

• Journal of Radiation Protection and Research
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• v.13 no.1
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• pp.8-20
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• 1988

The annual individual and collective doses to the thyroids of four age-dependent groups due to the in-take of I-131 released from the Younggwang nuclear power plant NU-1 & 2, Korea, are estimated using the model presented in ICRP 29. Sensitivity and robustness of the model are analyzed. In case of 0.12% fuel defect during normal operation, the collective dose is founded to be 3.05${\times}10^{-3}$man-thyroid-Sv, which is higher than the value calculated by the GASPAR code, 2.3${\times}10^{-3}$man-thyroid-Sv. The maximal individual annual doses resulting from an acute release are higher than those calculated under the assumption of continuous release by $1.4{\sim}1.7$ times. The most important pathway to the infant is milk and, in contrast, that to child, teen and adult is ingestion of crops. The model used is the calculation appears to be influenced by the variables such as roubstness-index. The weighted committed dose equivalent obtained by the ICRP 29 model is slightly higher than that calculated by the three-compartment model.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.575-578
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• 1997

Myocardial blood low (MBF) in human can be noninvasively quantified using dynamic N-13 ammonia PET and two-compartment tracer kinetic model. In this study, factor analysis was used to extract the "pure" blood-pool time-activity curves (TACs) and to generate actor images. ive human N-13 ammonia PET dynamic studies were obtained. Three actors and their corresponding actor images were extracted rom each study. The accuracy of MBF estimated by the actor analysis (FA/FA MBF) was examined by comparing to the values estimated using the conventional ROI method (ROI/ROI MBF). MBF obtained by the actor analysis linearly correlated with MBF obtained by the ROI method (slope=0.98, r=0.91). Input unctions obtained by the two methods agreed well. In conclusion, MBF can be measured accurately and noninvasively with dynamic N-13 ammonia PET imaging and actor analysis. This method is simple and acurate and can measure MBF without blood sampling, ROI drawing nor spillover correction.