• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(1)
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• pp.225-230
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• 1996

A three-dimensional reactor core simulation code, MASTER has been developed as a part of ADONIS which is the Korean core design package in KAERI. CASMO-3 is used as a precedent lattice code for two-group microscopic cross section and heterogeneous formfunctions. The pin power reconstruction capability of CASMO-3/MASTER was evaluated for a validation and verification Five B&W critical experiments were selected as benchmark problems. These problems included two experiments for CE-type and three for WH-type fuel assemblies. Two of them contained gadolinia rods as burnable absorber. Comparison of the calculated pin power distributions with the measured ones demonstrate that CASMO-3/MASTER can predict the pin power distribution as well as CASMO-3/SIMULATE-3.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(1)
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• pp.538-544
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• 1996

This paper presents the results of the core follow analysis for Yonggwang Unit 3 Cycle 1. The values of peaking factors (Fxy, Fq, Fr anf Fz) and core power distribution measured and processed by CECOR code［1］ are compared with those predicted by ROCS code［2］, The measured boron rundown is also compared with the predicted values. As results, the comparison of peaking factors, radial and axial power distributions and boron rundown between the measured and the predicted show good agreement throughout the cycle. Additionally, assembly burnup differences between CECOR and ROCS at EOC1 (13650 MWD/MTD are within 5% of core average burnup.

• 자원환경지질
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• 제29권3호
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• pp.235-246
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• 1996

베트남 홍케 광화대의 동도 및 호아하이 지역으로 부터 채취된 사금은 일반적으로 세립질로서, 동도 지역 사금은 호아하이 지역에 비하여 상대적으로 큰 입도와 낮은 분급도의 경향성을 보여준다. 이들 사금 입자의 산출형태는 장경과 단경의 비에 의하여 spherical, subprismoidal, prismoidal 및 irregular로 분류 할 수 있으며, spherical form이 ${\approx}75%$인 호아하이 지역에 비하여 동도 지역 사금 업자들의 형태는 다양하게 관찰된다. 이러한 산상에 의하면, 동도지역에 비하여 호아하이지역 사금의 이동거리 (또는 시간)가 걸었던 것으로 추정된다. 이들 사금은 그 화학조성에 의하여 electrum (type I, fineness=568~931), amalgam (type II, fineness=671~927), native gold (type III, fineness=923~999) 등으로 분류된다. Type I은 그 산출특정에 따라 상대적으로 낮은 함은량 (11~39 atomic % Ag)을 갖는 type IA와, 상대적으로 높은 함은량 (40~58 atomic % Ag)을 갖는 type IB로 세분되며, 이는 기원광상산 electrum의 화학조성을 보여주는 것으로 사료된다. Type II는 주로 호아하이지역에서 산출되며, 함수은량은 동도지역의 사금이 낮은 경향을 보여준다. Type III는 주로 type I 또는 type II 사금업자의 가장자리에 산출한다. 이들 type III의 gold-rich rim은 이동과 풍화과정중 산화환경에서 야기된 self-electrorefining과 silver의 preferential dissolution에 기인된 것으로 사료된다. 홍케지역 사금중 적어도 일부 높은 함수은량을 보이는 경우는 함금-은 천열수 광상과 유사한 환경에서 생성된 기원광상으로부터 유래되었을 것으로 추정된다.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.482-493
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• 2002

The MOX fuel for LWR is fabricated either by direct mechanical blending of UO$_2$ and PuO$_2$ or by two stage mixing. Hence Pu-rich particles, whose Pu concentrations are higher than pellet average one and whose size distribution depends on a specific fabrication method, are inevitably dispersed in MOX pellet. Due to the inhomogeneous microstructure of MOX fuel, the thermal conductivity of LWR MOX fuel scatters from 80 to 100 % of UO$_2$ fuel. This paper describes a mechanistic thermal conductivity model for MOX fuel by considering this inhomogeneous microstructure and presents an explanation for the wide scattering of measured MOX fuel＇s thermal conductivity. The developed model has been incorporated into a KAERI＇s fuel performance code, COSMOS, and then evaluated using the measured in-pile data for MOX fuel. The database used for verification consists of homogeneous MOX fuel at beginning-of-life and inhomogeneous MOX fuel at high turnup. The COSMOS code predicts the thermal behavior of MOX fuel well except for the irradiation test accompanying substantial fission gas release. The over-prediction with substantial fission gas release seems to suggest the need for the introduction of a recovery factor to a term that considers the burnup effect on thermal conductivity.

• Nuclear Engineering and Technology
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• 제37권3호
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• pp.287-292
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• 2005

[ $\pi$ ]The effects of silica-based additives have been investigated to improve the creep property of a $UO_2$ pellet. The additive composition, $50wt\%SiO_2-47wt{\%}CaO-3wt\%Cr_2O_3$ (SCC), was selected according to the dihedral angle and the distribution of the second phase. It was observed that the creep rate of the $0.07 wt\%$ SCC-added $UO_2$ was slower than that of the pure $UO_2$. However, the creep rate of the $0.22 wt\%$ SCC-added $UO_2$ was about 3_48 times faster than that of the pure $UO_2$, depending on the applied stress in the lower stress range. In the case of the $0.35 wt\%$ SCC-added $UO_2$, the creep rate decreased in comparison with that of the $0.22 wt\%$ SCC-added $UO_2$. The observed enhancement in the creep rate might depend on a balance between the positive role of the viscous intergranular phase and the negative roles of the additives and the grain growth.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2299-2305
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• 2020

Zr alloy specimens were coated with Cr-Al alloy to enhance their resistance to oxidation. The coated samples were oxidized at 1200 ℃ in a steam environment for 300 s and showed extremely low oxidation when compared to uncoated Zr alloy specimens. The microstructure and elemental distribution of the oxides formed on the surface of Cr-Al alloys have been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A very thin protective layer of Cr₂O₃ formed on the outer surface of the Cr-Al alloy, and a thin Al₂O₃ layer was also observed in the Cr-Al alloy matrix, near the surface. Our results suggest that these two oxide layers near the surface confers excellent oxidation resistance to the Cr-Al alloy. Even after exposure to a high temperature of 1200 ℃, inter-diffusion between the Cr-Al alloy and the Zr alloy occurred in very few regions near the interface. Analysis of the inter-diffusion layer by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) measurement confirmed its identity as Cr₂Zr.

• Nuclear Engineering and Technology
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• 제35권4호
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• pp.299-308
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• 2003

Fabrication technique of $(Th,U)O_2$ pellets has been investigated. Powder mixtures of $ThO_2\;and\;UO_2$ were milled in two different ways-dry and wet milling. Milled powder was compacted and sintered to $(Th,U)O_2$ pellets. The wet-milled powder leads to a $(Th,U)O_2$ pellet having a high sintered density and uniform distribution of U and Th, compared to the dry-milled powder. The sintered density of a $(Th,U)O_2$ pellet tends to decrease by increasing the content of $ThO_2$. The thermal conductivity of $ThO_2\;and\;(Th,U)O_2$ pellets was measured by the laser flash method. The thermal conductivity of the $ThO_2$ pellet is higher than that of the $UO_2$ pellet, and the thermal conductivities of $(Th,U)O_2$ pellets containing $65wt\%\;and\;35wt\%\;ThO_2$ pellets are lower than that of the $UO_2$ pellet.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.376-385
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• 2016

A hexagonally arrayed 37-pin wire-wrapped rod bundle has been chosen to provide the experimental data of the pressure loss and flow rate in subchannels for validating subchannel analysis codes for the sodium-cooled fast reactor core thermal/hydraulic design. The iso-kinetic sampling method has been adopted to measure the flow rate at subchannels, and newly designed sampling probes which preserve the flow area of subchannels have been devised. Experimental tests have been performed at 20-115% of the nominal flow rate and $60^{\circ}C$ (equivalent to Re ~ 37,100) at the inlet of the test rig. The pressure loss data in three measured subchannels were almost identical regardless of the subchannel locations. The flow rate at each type of subchannel was identified and the flow split factors were evaluated from the measured data. The predicted correlations and the computational fluid dynamics results agreed reasonably with the experimental data.

• 방사성폐기물학회지
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• 제19권3호
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• pp.289-295
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• 2021

A laser scabbling experiment was performed using a high-power fiber laser to investigate the removal rate of the concrete block and the scabbled depth. Concrete specimens with a 28-day compressive strength of 30 MPa were used in this study. Initially, we conducted the scabbling experiment under a stationary laser beam condition to determine the optimum scan speed. The laser interaction time with the concrete surface varied between 3 s and 40 s. The degree of spalling and vitrification on the surface was primarily dependent on the laser interaction time and beam power. Furthermore, thermal images were captured to investigate the spatial and temporal distribution of temperature during the scabbling process. Based on the experimental results, the scan speed at which the optical head moved over the concrete was set to be 300 mm·min^-1 or 600 mm·min^-1 for the 4.8-kW or 6.8-kW laser beam, respectively. The spalling rates and average depth on the concrete blocks were measured to be 87 cm³·min^-1 or 227 cm³·min^-1 and 6.9 mm or 9.8 mm with the 4.8-kW or 6.8-kW laser beams, respectively.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.1988-1993
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• 2023

This experimental study investigated the effect of silica fume mixed in concrete blocks on laser-induced explosion behavior. We used a 5.3 kW fiber laser as a thermal source to induce explosive spalling on a concrete surface blended with and without silica fume. An analytical approach based on the difference in the removal rate and thermal behavior was used to determine the effect of silica fume on laser-induced explosive spalling. A scanner was employed to calculate the laser-scabbled volume of the concrete surface to derive the removal rate. The removal rate of the concrete mixed with silica fume was higher than that of without silica fume. Thermal images acquired during scabbling were used to qualitatively analyze the thermal response of laser-induced explosive spalling on the concrete surface. At the early stage of laser heating, an uneven spatial distribution of surface temperature appeared on the concrete blended with silica fume because of frequent explosive spalling within a small area. By contrast, the spalling frequency was relatively lower in laser-heated concrete without silica fume. Furthermore, we observed that a larger area was removed via a single explosive spalling event owing to its high porosity.