• 디지털콘텐츠학회 논문지
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• 제16권3호
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• pp.463-470
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• 2015

최근 개인선량계로 사용이 증가하고 있는 수동형 선량계인 OSLD와 능동형 선량계인 EPD의 상대 반응도(relative response), 측정 불확도(uncertainty of measurement)를 계산하여 방향의존성(angular dependence)을 비교, 분석하였다. OSLD는 수평, 수직방향의 $0^{\circ}{\sim}{\pm}90^{\circ}$ 범위에서 평균 상대 반응도는 0.97, 0.95의 작은 변화를 보였고 방향의존성에 대한 불확도는 0.65, 0.62로 전체 불확도에 미치는 영향은 미미한 것으로 판단되었다. EPD는 $0^{\circ}{\sim}{\pm}60^{\circ}$ 범위에서 수평, 수직방향 평균 상대 반응도는 0.94, 0.97로 확인되어 IEC 61526 규정을 만족하였다. 방향의존성에 대한 불확도는 수평, 수직방향에서 0.44, 0.40로 전체 불확도에 미치는 영향은 미미하였다. 그러나 수평방향에서 $+90^{\circ}$, $-90^{\circ}$ 방향의 상대 반응도는 0.60, 0.37이고 수직방향에서 $+90^{\circ}$ 방향의 반응도는 0.06으로 반응도의 큰 변화를 관찰할 수 있었다. OSLD의 방향 의존성은 $0^{\circ}{\sim}{\pm}90^{\circ}$ 범위까지 EPD에 비해 우수하였으며 EPD의 경우 구조적 특징으로 반응도가 급변하는 특정방향이 존재하였다. 따라서 수동형선량계와 보조선량계의 병행사용이 개인피폭선량측정의 정확도를 기할 수 있을 것으로 판단된다.

• 한국토양비료학회지
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• 제44권1호
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• pp.15-21
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• 2011

Transport of heavy metals such as Cd is affected by several rate-limiting processes including adsorption and desorption by exchange reactions in soils. In this study, column transport and batch kinetic experiments were performed to assess Cd mobility in a double-layered soil with a reclaimed saline and sodic soil (SSS) as top soil and macroporous granule (MPG) as a bottom layer. For individual soil layer having different physical and chemical properties, Cd was considered to be nonlinear reactivity with the soil matrix in layered soils. The dispersive equation for reactive solutes was solved with three types of boundary conditions for the interface between soil layers. The adsorption of Cd with respect to the saline-sodic sandy loam and the MPG indicated that the nature of the sites or the mechanisms involved in the sorption process of Cd was different and the amounts of Cd for both of samples increases with increasing amounts of equilibrium concentration whereas the amount of Cd adsorbed in saline-sodic sandy loam soil was higher than that in MPG. The results of breakthrough curve indicating relative Cd retardation accompanied by layer material and sequence during leaching showed that the number of pore volumes to reach the maximum relative concentration of 1 increased in the order of MPG, SSS, and double layer of SSS-MPG. Breakthrough curves (BTCs) from column experiments were well predicted with our double-layered model where independently derived solute physical and retention parameters were implemented.

• 대한화학회지
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• 제28권4호
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• pp.217-230
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• 1984

중앙 탄소 원자를 가진 계에서의 1,2-와 1,3-그리고 1,5-수소 시그마 결합 자리 옮김반응에 관하여 전이상태와 활성화 에너지 장벽을 결정하기 위하여 MINDO/3 방법을 이용하였다. 전이상태의 안정성을 설명하는 데에는 궤도의 대칭성 외에 입체효과와 방향성 그리고 궤도간의 상호작용 또한 기여됨을 알았다. 헤테로 원자를 가진 계의 경우, 고립 전자쌍의 궤도가 수소의 자리 옮김반응에 관여하므로 전이상태에서 요구되는 궤도의 비틀림을 줄이게 되며, 그에 따라 활성화 에너지 장벽이 낮게 나타났다. 더욱 정확한 ab initio 계산에 의하여 얻어진 결과와 비교했을 때, 본 연구에서의 MINDO/3방법으로 얻은 상대적인 에너지 장벽의 크기 순서는 일치하는 경향성을 보였다.

• 한국세라믹학회지
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• 제36권11호
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• pp.1261-1265
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• 1999

Effect of SiC particle size of the densification of Al2O3-SiC composite during pressureless sintering was investigated. Two types of SiC powders having average particle size of 0.15${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$ were used. Densification rate of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was slower than that of the specimen containg 3${\mu}{\textrm}{m}$ SiC particles. Although the relative density of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was below 90% of theoretical density after sintering at 155$0^{\circ}C$ the complete closure of open pores occurred. Therefore full densification could be obtained by subsequent HIP. On the other hand in the specimen containing 3${\mu}{\textrm}{m}$ SiC particles the complete closed pore was observed at 95% of theoretical density. Such a fast pore closure in the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles is likely to occur as a result of dense reaction layer formation on the specimen surface which is attributed to the high reactivity of small size particles with sintering atmosphere.

• 대한화학회지
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• 제19권4호
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• pp.218-224
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• 1975

바닥상태에 대한 자기무당착장 상호작용 에너지 이론을 2-치환-아크릴로니트릴과 시클로펜타디엔의 Diels-Alder 반응에 적용하여 반응성과 입체 선택성을 조사하였다. 출발점으로는 $\sigma$전자와 $\pi$전자를 다 고려하는 CNDO/2 MO가 사용되었다. 1차 상호작용 에너지 계산으로 정성적인 반응성이 얻어 졌으며 활성화 에너지 값은 실측치 범위의 것이 계산되었다. 2차 상호작용 에너지 계산으로 얻은 입체 선택성은 치환기에 대하여 모두 endo 선택성을 보여주었다. 비대칭 폐환의 원인을 반응원자의 원잣가 비활성 전자밀도로서 설명하였다.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.817-825
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• 2022

A recent benchmarking effort, under the auspices of the Organization for Economic Cooperation and Development (OECD) Nuclear Energy Agency (NEA), has been made to evaluate the current state of modeling and simulation tools available to model fluoride salt-cooled high temperature reactors (FHRs). The FHR benchmarking effort considered in this work consists of several cases evaluating the neutronic parameters of a 2D prismatic FHR fuel assembly model using the participants' choice of simulation tools. Benchmark participants blindly submitted results for comparison with overall good agreement, except for some which significantly differed on cases utilizing a molybdenum-bearing control rod. Participants utilizing more recently updated explicit isotopic cross sections had consistent results, whereas those using elemental molybdenum cross sections observed reactivity differences on the order of thousands of pcm relative to their peers. Through a series of supporting tests, the authors attribute the differences as being nuclear data driven from using older legacy elemental molybdenum cross sections. Quantitative analysis is conducted on the control rod to identify spectral, reaction rate, and cross section phenomena responsible for the observed differences. Results confirm the observed differences are attributable to the use of elemental cross sections which overestimate the reaction rates in strong resonance channels.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.359-374
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• 2024

A high-fidelity numerical analysis methodology was proposed for evaluating the fuel rod cladding integrity of a Prototype Gen IV Sodium Fast Reactor (PGSFR) during normal operation and Design basis events (DBEs). The MARS-LMR code, system transient safety analysis code, was applied to analyze the DBEs. The results of the MARS-LMR code were used as boundary condition for a 3D computational fluid dynamics (CFD) analysis. The peak temperatures considering HCFs satisfied the cladding temperature limit. The temperature and pressure distributions were calculated by ANSYS CFX code, and applied to structural analysis. Structural analysis was performed using ANSYS Mechanical code. The seismic reactivity insertion SSE accident among DBEs had the highest peak cladding temperature and the maximum stress, as the value of 87 MPa. The fuel cladding had over 40 % safety margin, and the strain was below the strain limit. Deformation behavior was elucidated for providing relative coordinate data on each active fuel rod center. Bending deformation resulted in a flower shape, and bowing bundle did not interact with the duct of fuel assemblies. Fuel rod maximum expansion was generated with highest stress. Therefore, it was concluded that the fuel rod cladding of the PGSFR has sufficient structural safety margin during DBEs.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4048-4056
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• 2023

The feasibility of using the Monte Carlo code MCS to generate multigroup cross sections for nodal diffusion simulations RAST-F of liquid metal fast reactors is investigated in this paper. The performance of the MCS/RAST-F code system is assessed using steady-state simulations of the ANTS-100e core. The results show good agreement between MCS/RAST-F and MCS reference solutions, with a keff difference of less than 77 pcm and root-mean-square differences in radial and axial power of less than 0.5% and 0.25%, respectively. Furthermore, the MCS/RAST-F reactivity feedback coefficients are within three standard deviations of the MCS coefficients. To validate the internal thermal-hydraulic (TH) feedback capability in RAST-F code, the coupled neutronic/TH1D simulation of ANTS-100e is performed using the case matrix obtained from MCS branch calculations. The results are compared to those obtained using the MARS-LBE system code and show good agreement with relative temperature differences in fuel and coolant of less than 0.8%. This study demonstrates that the MCS/RAST-F code system can produce accurate results for core steady-state neutronic calculations and for coupled neutronic/TH simulations.

• 한국광물학회지
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• 제18권2호
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• pp.127-134
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• 2005

금속제련공학 및 환경과학 분야에 있어서 물질전체를 구성하고 있는 화학적 조성이 중요한 요소이나, 입자 표면의 화학조성과 미분화된 입자들의 표면 반응성을 제어함과 동시에, 입자 계면에서 일어나는 중금속과 유기물질등의 반응은 제련공정과 환경오염에 중요한 역할을 한다. 그러므로, 수용액상에 존재하는 여러 종류의 화학 물질과 광물입자 표면 사이에서 일어나는 계면반응 과정의 이해는 상당히 중요한 것이다. 일반적으로 입자 표면 분석에는 ex-situ 법을 사용하는 X-ray photo-electron spectroscopy (XPS) 분석 방법이 많이 적용되고 있으나, 이는 분석대상시료의 크기가 보통 100 마이크론에서 1 cm 정도의 범위 안에 혼재-혼합되어있는 고체 입자들을 분석하기 때문에 채취 분석된 X-ray의 원래 발산한 입자표면을 분석할 수는 없다. 그래서 본 연구에서는 Time-of-Flight Secondary-Ion Mass Spectroscopy (TOF-SIMS)를 응용하여 황화광물의 부유선광 공정 중 생성된 미세한 유화광물입자$(30\~75\;microns)$ 표면에 형성된 무기, 유기물의 반응 관찰을 통해 이들의 정성분석 및 상대적 정량분석법을 연구하고자 하였다.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1349-1354
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• 2010

The geometries and isomerization of the alkylidene silylenoid $H_2C$ = SiLiF as well as its insertion reactions with R-H (R = F, OH, $NH_2$) have been systematically investigated at the B3LYP/6-311+$G^*$ level of theory. The potential barriers of the three insertion reactions are 97.5, 103.3, and 126.1 kJ/mol, respectively. Here, all the mechanisms of the three reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted silylene ($H_2C$ = SiHR) and LiF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the three reactions are -36.4, -24.3, and 3.7 kJ/mol, respectively. Compared with the insertion reaction of $H_2C$ = Si: and R-H (R = F, OH and $NH_2$), the introduction of LiF makes the insertion reaction occur more easily. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the three insertion reactions should be as follows: H-F > H-OH > H-$NH_2$.