• Journal of Environmental Science International
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• v.29 no.11
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• pp.1089-1098
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• 2020

To assess the trophic function of an artificial macroalgal habitat, we compared the stable carbon and nitrogen isotope ratios of two amphipods (Caprella sp. and Ampithoe sp.) and their potential food sources in a transplanted macroalgal habitat (Grateloupia asiatica) with those in a natural habitat. There were no significant differences in the isotopic values of both consumers and their potential food sources between the transplanted and natural habitats. Such isotopic similarities between the two sites indicate a comparable resource consumer relationship. Additionally, our results showed similar isotopic niche areas and high dietary overlap (>65%) of the two amphipods between the transplanted and natural sites, suggesting that the transplanted habitat plays ecological roles similar to the natural habitat. Overall, isotopic assessment can provide information on the trophic function of diverse transplanted macroalgal habitats and improve post-monitoring efforts in the management of artificial ecosystems.

• The Korean Journal of Nuclear Medicine
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• v.19 no.2
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• pp.5-16
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• 1985

• Economic and Environmental Geology
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• v.28 no.3
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• pp.243-249
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• 1995

In order to investigate the origin of sulfate in rain waters and to evaluate the feasibility of using sulfur isotope method as a tracer of atmospheric pollutants, the sulfur isotopic ratio of sulfate in rain waters collected in Chonju city from October 1994 to March 1995 was monitored and was compared with those of possible sources proposed by previous works. The pH of rain waters shows an intermediate acidic range from 4.45 to 6.88 and their daily variation appears to be well correlated with to the amount of precipitation. The sulfur isotopic ratios of sulfate in rain waters show a highly restricted range from 0.0 to + 1.8‰. The ${\delta}^{34}S$ values are similar to those of soil and pine tree surrounding Chonju city, but largely deviate from those of China. D-parameter($d={\delta}D-8{\delta}^{18}O$) of rain waters varies from 9.4 to 28.8. The values indicate that the rain waters in Chonju city are originated from the rainy front of China continent. All data obtained from this study suggested that sulfate in the rain waters collected in Chonju city was mainly derived from the sulfur dioxide gas emitted by the petroleum combustion. Therefore, sulfur isotopic study for the precipitation provided an excellent tool for environmental assessment in this region and for tracing the source of atmospheric pollutants.

• Analytical Science and Technology
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• v.31 no.3
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• pp.134-142
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• 2018

The uranium isotopic ratio in environmental samples around nuclear facilities is important because it reveals information regarding illegal activities or anthropogenic pollution. Determination of uranium isotopes, however, is a challenging task requiring much labor and time because of the complex separation procedures and lengthy process. In this study, a rapid determination method for uranium isotopes in environmental samples was developed using. The sample was completely decomposed using the alkali fusion method. The separation procedure using extraction chromatography (UTEVA) was simplified in a single step without any further removal process for Si and major matrix elements. The established method can be completed within 3 h from sample dissolution to ICP-MS measurement. Most matrix elements and uranium isotopes in the soil samples were well separated and purified. Five types of were used to assess the method's accuracy and precision for a rapid uranium analysis method. The analytical accuracy for all CRM samples ranged from 95.1 % to 97.8 %, and the relative standard deviation was below 3.9 %. From the analytical results, one may draw conclusions that the evaluated method for uranium isotopes using alkali-fusion, the extraction chromatography process, and ICP-MS measurements is fast and fairly reliable owing to its recovering efficiencies. Thus, it is expected that the evaluated method can contribute to the improvement of environmental monitoring ability.

• Journal of Environmental Impact Assessment
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• v.27 no.6
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• pp.685-694
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• 2018

We measured ecological niche space (ENS) using carbon and nitrogen stable isotope ratios of benthic macroinvertebrates to estimate its applicability for large river assessment. In particular, we compared ENSs of selected macroinvertebrates between upper and lower area of Seungchon Weir in Yeongsan River to estimate the impact of weir on biological community. We also measured basic water quality and community indices including benthic macroinvertebrates index (BMI) to estimate their correlations with calculated ENS. ENS was calculated using the Bayesian Stable Isotope in R statistics (package "SIBER"). The results showed that seasonal variations in water quality and community indices were found, but there was no apparent tendency between upper and lower area of the Seungchon Weir in June (before rainy season) and August (after rainy season). However, ENS of benthic macroinvertebrates markedly decreased across the weir in both June and August regardless of changes in water quality. This means the physical change of the stream due to the weir cause decrease of ecological isotopic niche space of benthic macroinvertebrates regardless of water quality, suggesting physical modification by the weir can affect the interaction between habitat condition and macroinvertebrates. Therefore, the ecological isotopic niche space can be a useful supplementary indicator for the river ecosystem assessment.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.23-38
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• 1999

This study addresses the reference spent fuel and its characteristics for developing a geological repository concept. As a disposal capacity of the reference repository system to be developed, spent fuel inventories were projected based on the basis of the Nuclear Energy Plan of the Long-term National Power Program. The reference spent fuel encompassing a variability in characteristics of all existing and future spent fuels of interest was defined. Key parameters in the reference fuel screening processes were the nuclear and mechanical design parameters and the burnup histories for existing spent fuels as of 1996 and for future spent fuels with the more extended burnup the initial enrichment and its expected turnup. The selected reference fuel was characterized in terms of initial enrichment, bumup, dimension, gross weight and age. Also the isotopic composition and the radiological properties are quantitatively identified. This information provided in this study could be used as input for repository system development and performance assessment and applied in fuel material balance evaluation for the various types of back-end fuel cycle studies.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2415-2421
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• 2020

The axial heterogeneous void distribution in a fuel channel is a relevant and important issue during nuclear reactor analysis for LWR, especially for boiling water channel-type reactors. Variation of the coolant density in fuel channel has an effect on the neutron spectrum that will in turn have an impact on the values of absolute reactivity, the void reactivity coefficient, and the fuel isotopic compositions during irradiation. This effect is referring to as the history effect in light water reactor calculations. As the void reactivity effect is positive in RBMK type reactors, the underestimation of water density heterogeneity in 3D reactor core numerical calculations could cause an uncertainty during assessment of safe operation of nuclear reactor. Thus, this issue is analysed with different cross-section libraries which were generated with WIMS8 code at different reference water densities. The libraries were applied in single fuel model of the nodal code of QUABOX-CUBBOX/HYCA. The thermohydraulic part of HYCA allowed to simulate axial water distribution along fuel assembly model and to estimate water density history effect for RBMK type fuel.

• Analytical Science and Technology
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• v.22 no.6
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• pp.449-457
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• 2009

Total PCBs (62 congeners) has been determined in the retailed foods by the isotopic dilution method and the exposure assessment has been performed. Put into a food sample $^{13}C$-labeled standard for recovery was added and then it was extracted, cleaned-up by multi-layer column chromatography and then analyzed by HRGC/MS. The average levels (ng/g) detected was 0.1 for rice, 1.8~3.4 for meats, 0.3~3.7 for milk and dairy products, 10.0 for egg and 0.8~34.4 for fishes. Distribution of total PCBs was in order of fishes (94.4%) > meats (2.3%) > eggs (1.7%) > milk and dairy products (1.3%) > rice (0.3%). The estimated daily intake(EDI) was 14 ng/kg bw/day. It was concluded that there was no health risk at all.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.06a
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• pp.73-73
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• 2009

There are many factors to evaluate nuclear fuel cycle such as safety, public acceptance, economics, etc.. Transparency, proliferation, environment issues, public acceptance and safety are essential to expansion of nuclear industry and proliferation resistance is one of key constraints in the deployment of advanced nuclear energy systems. Proliferation resistance is being considered as one of the most important factors in assessing advanced and innovative nuclear systems. IAEA defmes proliferation resistance as characteristics of nuclear energy system that impedes the diversion or undeclared production of nuclear material [1]. Barriers to proliferation is consist of intrinsic and extrinsic barriers(institutional measures). Intrinsic barriers are characterized in material barriers and technical barriers in general. Material barriers is intrinsic, or inherent, qualities of materials that reduce the inherent desirability or attractiveness of the material as an explosive. Isotopic, chemical, radiological, mass and bulk, detectability barriers are considered as material barriers attributes [2]. Proliferation resistance is examined for several nuclear fuel cycles based on previous study which is focused on the intrinsic barriers [3-4]. Pyroprocessing and DUPIC are considered as reprocessing technologies in Korea and the PWR direct disposal is considered. Comparative assessments of the proliferation attributes and merits of different fuel cycle systems will be performed and the optimal back-end fuel cycle and strategy will be proposed.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2830-2838
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• 2021

This work deals with the assessment of the burnup capabilities of the Serpent Monte Carlo code to predict spent nuclear fuel (SNF) isotopic concentrations for low-enriched uranium (LEU) fuel at different burnup levels up to 47 MWd/kgU. The irradiation of six UO₂ experimental samples in three different VVER-1000 reactor units has been simulated and the predicted concentrations of actinides up to ²⁴⁴Cm have been compared with the corresponding measured values. The results show a global good agreement between calculated and experimental concentrations, in several cases within the margins of the nuclear data uncertainties and in a few cases even within the reported experimental uncertainties. The differences in the performances of the JEFF3.1.1, ENDF/B-VII.1 and ENDF/B-VIII.0 nuclear data libraries (NDLs) have also been assessed and the use of the newly released ENDF/B-VIII.0 library has shown an increased accuracy in the prediction of the C/E's for some of the actinides considered, particularly for the plutonium isotopes. This work represents a step forward towards the validation of advanced simulation tools against post irradiation experimental data and the obtained results provide an evidence of the capabilities of the Serpent Monte-Carlo code with the associated modern NDLs to accurately compute SNF nuclide inventory concentrations for VVER-1000 type reactors.