• Nuclear Engineering and Technology
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• 제36권5호
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• pp.388-402
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• 2004

A phenomena identification and ranking table(PIRT) was developed for a main steam line break (MSLB) event for the Advanced Power Reactor-1400 (APR-1400). The selectee event was a double-ended steam line break at full power, with the reactor coolant pump running. The developmental panel selected the fuel performance as the primary safety criterion during the ranking process. The plant design data, the results of the APR-1400 safety analysis, and the results of an additional best-estimate analysis by the MARS computer code were used in the development of the PIRT. The period of the transient was composed of three phases: pre-trip, rapid cool-down, and safety injection. Based on the relative importance to the primary evaluation criterion, the ranking of each system, component, and phenomenon/process was performed for each time phase. Finally, the knowledge-level for each important process for certain components was ranked in terms of existing knowledge. The PIRT can be used as a guide for planning cost-effective experimental programs and for code development efforts, especially for the quantification of those processes and/or phenomena that are highly important, but not well understood.

• 한국표면공학회지
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• 제55권5호
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• pp.247-260
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• 2022

Since the first report on ferroelectricity in Si-doped hafnia (HfO2), this emerging ferroelectrics have been considered promising for the next-generation semiconductor devices with their characteristic nonvolatile data storage. The robust ferroelectricity in the sub-10-nm thickness regime has been proven by numerous research groups. However, extending their scalability below the 5 nm thickness with low temperature processes compatible with the back-end-of-line technology. In this review, therefore, the current status, technical issues, and their potential solutions of atomic layer deposition (ALD) of HfO₂-based ferroelectrics are comprehensively reviewed. Several technical issues in the physical scaling of the ferroelectric thin films and potential solutions including advanced ALD techniques including discrete feeding ALD, atomic layer etching, and area selective ALD are introduced.

• Journal of Applied Biological Chemistry
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• 제51권1호
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• pp.28-35
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• 2008

The physico-chemical properties of kapok fibers were altered via the combination processes of chlorite-periodate oxidation, in order to assess their efficacy as a heavy metal adsorbent. The chemically-oxidized kapok fibers were found to harbor a certain amount of polysaccharides, together with lowered lignin content. This alteration in lignin characteristics was clearly confirmed via FTIR and NBO yield. Moreover, chemically oxidized kapok fibers retained their hollow tube shape, although some changes were noted. The chemically oxidized kapok fibers evidenced elevated ability to adsorb heavy metal ions with the best fit for the Langmuir adsorption isotherm model. Three cycles of adsorption-desorption were conducted with in-between regeneration steps. Our experimental results indicated that chemically oxidized kapok fibers possessed excellent adsorption characteristics, and the modified kapok fibers could be completely regenerated with almost equimolar diluted sodium hydroxide. Pb, Cu, Cd and Zn ions evidenced adsorption rates of 93.55%, 91.83%, 89.75%, and 92.85% on the chemically oxidized kapok fibers. The regeneration efficiency showed 73.58% of Pb, 71.55% of Cu, 66.87% of Cd, and 75.00% of Zn for 3rd cycle with 0.0125N NaOH.

• Nuclear Engineering and Technology
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• 제40권7호
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• pp.593-606
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• 2008

In this study, data on radionuclide migration and retardation processes in the engineered and natural barriers of High-Level Radioactive Waste (HLW) repository have been reviewed and compiled for use in the performance assessment of a HLW disposal system in Korea. The status of the database on radionuclide migration and retardation that is being developed in Korea is investigated and summarized in this study. The solubilities of major actinides such as D, Th, Am, Np, and Pu both in Korean bentonite porewater and in deep Korean groundwater are calculated by using the geochemical code PHREEQC (Ver. 2.0) based on the KAERI-TDB(Korea Atomic Energy Research Institute-Thermochemical Database), which is under development. Databases for the diffusion coefficients ($D^b_e$ values) and distribution coefficients ($K^b_d$ values) of some radionuclides in the compacted Korean Ca-bentonite are developed based upon domestic experimental results. Databases for the rock matrix diffusion coefficients ($D^r_e$ values) and distribution coefficients ($K^r_d$ values) of some radionuclides for Korean granite rock and deep groundwater are also developed based upon domestic experimental results. Finally, data related to colloids such as the characteristics of natural groundwater colloids and the pseudo-colloid formation constants ($K_{pc}$ values) are provided for the consideration of colloid effects in the performance assessment.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1297-1303
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• 2021

Most thickness measurement techniques using X-ray radiation are unsuitable in field processes involving fast-moving organic films. Herein, we propose a Compton scattering X-ray radiation method, which probes the light elements in organic materials, and a new simple, non-destructive, and non-contact calibration-free real-time film thickness measurement technique by setting up a bench-top X-ray thickness measurement system simulating a field process dealing with thin flexible organic films. The use of X-ray fluorescence and Compton scattering X-ray radiation reflectance signals from films in close contact with a roller produced accurate thickness measurements. In a high-thickness range, the contribution of X-ray fluorescence is negligible, whereas that of Compton scattering is negligible in a low-thickness range. X-ray fluorescence and Compton scattering show good correlations with the organic film thickness (R² = 0.997 and 0.999 for X-ray fluorescence and Compton scattering, respectively, in the thickness range 0-0.5 mm). Although the sensitivity of X-ray fluorescence is approximately 4.6 times higher than that of Compton scattering, Compton scattering signals are useful for thick films (e.g., thicker than ca. 1-5 mm under our present experiment conditions). Thus, successful calibration-free thickness monitoring is possible for fast-moving films, as demonstrated in our experiments.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.254-254
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• 2016

Tin dioxide (SnO2) thin film is one of the most important n-type semiconducting materials having a high transparency and chemical stability. Due to their favorable properties, it has been widely used as a base materials in the transparent conducting substrates, gas sensors, and other various electronic applications. Up to now, SnO2 thin film has been extensively studied by a various deposition techniques such as RF magnetron sputtering, sol-gel process, a solution process, pulsed laser deposition (PLD), chemical vapor deposition (CVD), and atomic layer deposition (ALD) [1-6]. Among them, ALD or plasma-enhanced ALD (PEALD) has recently been focused in diverse applications due to its inherent capability for nanotechnologies. SnO2 thin films can be prepared by ALD or PEALD using halide precursors or using various metal-organic (MO) precursors. In the literature, there are many reports on the ALD and PEALD processes for depositing SnO2 thin films using MO precursors [7-8]. However, only ALD-SnO2 processes has been reported for halide precursors and PEALD-SnO2 process has not been reported yet. Herein, therefore, we report the first PEALD process of SnO2 thin films using SnCl4 and oxygen plasma. In this work, the growth kinetics of PEALD-SnO2 as well as their physical and chemical properties were systemically investigated. Moreover, some promising applications of this process will be shown at the end of presentation.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 추계 학술대회 논문집
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• pp.134-142
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• 2005

지하매질에서 핵종이동현상을 가시적으로 관찰할 수 있는 실험실규모 실험장치를 개발하여 이동실험을 수행하였다. 이 실험장치는 $50{\times}50cm$ 규모 화강암과 아크릴상층부로 구성되어있다. 실험에는 삼중수소, 음이온, 수착성양이온 뿐만 아니라 이동경로를 관찰할 수 있는 유기염료도 포함하였다. 시간에 따른 물질이동양태를 사진을 찍어 컴퓨터에 저장하였다. 또. 이동과정을 모사하고 단위공정별로 분석해 볼 수 잇는 이동모델도 개발하였다. 컴퓨터모사를 통해 균열내 흐름장에서 압력과 유속분포를 계산하고, 균열내 이동양태와 유출곡선을 계산해 실험결과와 비교 평가하였다.

• 한국세라믹학회지
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• 제42권3호
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• pp.188-192
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• 2005

무기 고분자인 polycarbosilane(PCS)으로부터 탄화규소 (SiC) 세라믹스로의 전환을 열산화에 의한 불융화 처리를 한 후 열분해 하는 공정과 불응화 처리를 하지 않고 열분해 하는 두 공정으로 각각 행하고, 수율 및 산소 함량을 비교하였다. 또한 두 공정으로 얻어진 SiC 세라믹스의 고온 안정성 평가를 위해 진공분위기의 고온에서 열처리 하여 무게 감량을 비교하였다. 열산화에 의한 불융화 처리를 한 후 열분해 하여 얻어진 SiC 세라믹스의 수율이 불융화 처리를 하지 않고 열분해 하여 얻어진 SiC세라믹스의 수율보다 높게 나타났으나, 이를 고온의 진공분위기에서 열처리 하였을 때는 열산화에 의해 불융화 처리를 한 공정으로부터 얻어진 SiC 세라믹스의 무게 감량이 크게 나타났다.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.613-623
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• 2016

Molybdenum-99 ($^{99}Mo$) is the most important isotope because its daughter isotope, technetium-99m ($^{99m}Tc$), has been the most widely used medical radioisotope for more than 50 years, accounting for > 80% of total nuclear diagnostics worldwide. In this review, radiochemical routes for the production of $^{99}Mo$, and the aspects for selecting a suitable process strategy are discussed from the historical viewpoint of $^{99}Mo$ technology developments. Most of the industrial-scale $^{99}Mo$ processes have been based on the fission of $^{235}U$. Recently, important issues have been raised for the conversion of fission $^{99}Mo$ targets from highly enriched uranium to low enriched uranium (LEU). The development of new LEU targets with higher density was requested to compensate for the loss of $^{99}Mo$ yield, caused by a significant reduction of $^{235}U$ enrichment, from the conversion. As the dramatic increment of intermediate level liquid waste is also expected from the conversion, an effective strategy to reduce the waste generation from the fission $^{99}Mo$ production is required. The mitigation of radioxenon emission from medical radioisotope production facilities is discussed in relation with the monitoring of nuclear explosions and comprehensive nuclear test ban. Lastly, the $^{99}Mo$ production process paired with the Korea Atomic Energy Research Institute's own LEU target is proposed as one of the most suitable processes for the LEU target.

• 한국표면공학회지
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• 제57권3호
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• pp.208-213
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• 2024

With the development of industry, miniaturization and densification of semiconductor components are rapidly progressing. Particularly, as demand surges across various sectors, efficiency in productivity has emerged as a crucial issue in semiconductor component manufacturing. Maximizing semiconductor productivity requires real-time monitoring of semiconductor processes and continuous reflection of the results to stabilize processes. However, various unexpected variables and errors in judgment that occur during the process can cause significant losses in semiconductor productivity. Therefore, while the development of a reliable manufacturing system is important, the importance of developing sensor technology that can complement this and accurately monitor the process is also growing. In this study, conducted a basic research on the concept of diagnostic sensors for thickness based on the physical changes of thin films due to etching. It observed changes in resistance corresponding to variations in thin film thickness as etching processes progressed, and conducted research on the correlation between these physical changes and thickness variations. Furthermore, to assess the reliability of thin film thickness measurement sensors, it conducted multiple measurements and comparative analyses of physical changes in thin films according to various thicknesses.