• 한국세라믹학회지
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• 제50권1호
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• pp.37-42
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• 2013

Tristructural-isotropic (TRISO)-coated particles were fabricated by a fluidized-bed chemical vapor deposition (FBCVD) method for use in a very high temperature gas-cooled reactor (VHTR). ZrC as a constituent layer of TRISO coating layers was deposited by a chloride process using $ZrCl_4$ and $CH_4$ source gases in a temperature range of $1400^{\circ}C$ and $1550^{\circ}C$. The change in the microstructure of ZrC depending on the deposition temperature and its effect on the hardness were evaluated. As the deposition temperature increased to $1500^{\circ}C$, the grain size of the ZrC increased and the hardness of the ZrC decreased according to the Hall-Petch relationship. However, at $1550^{\circ}C$, the ZrC layer was highly non-stoichiometric and carbon-rich and did not obey the Hall-Petch relationship in spite of the decrease of the grain size. A considerable amount of pyrolytic carbon at the grain boundaries of the ZrC as well as coarse granular pyrolytic carbon were locally distributed in the ZrC layer deposited at $1550^{\circ}C$. Therefore, the hardness decreased largely due to the formation of a large amount of pyrolytic carbon in the ZrC layer.

• 수산해양기술연구
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• 제27권1호
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• pp.64-68
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• 1991

In this paper, to percuss whether fish oil can substitute for marine fuel oil, the characteristics on the evaporation and ignition of 3 fish oils, Sardine oil, File fish oil and Alaska pollac oil, were investigated experimentally by suspending single fish oil droplel in hot atmosphere, and experiments on methanol and light oil were also carried out to compare the characteristics. The results abtained are summarized as follow; 1) Evaporation and ignition phenomena on the methanol and light oil by the present experimental method agreeded with the results of the earlier investigation. 2) The characteristic on evaporation and ignition of all 3 fish oils took the same pattern; in late stage of evaporation at atmospheric Temperature 55$0^{\circ}C$ droplet rapidly expanded and contracted, and then remained solid corbide, but in case of $650^{\circ}C$ rapidly expanded and ignitied, and then completly burned non-remained solid carbide. 3) As fish oil mixed with light oil (50% weight), in beginning stage of evaporation droplet depended on the characteristics of light oil, but in end stage depended on fish oil. 4) Ignition temperature of fish oil droplets was about 47$0^{\circ}C$, higher than about 25$0^{\circ}C$ of light oil, but atmospheric temperature to ignite droplet was about $650^{\circ}C$, lower than about 75$0^{\circ}C$ of light oil.

• 한국재료학회지
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• 제17권3호
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• pp.160-166
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• 2007

TRISO coatings on $ZrO_{2}$ surrogate kernels were conducted by a fluidized-bed chemical vapor deposition (FBCVD) method. Effects of the deposition temperature and the gas flow rate on the properties of SiC layer were investigated in the TRISO-coated particles. Deposition rate of the SiC layer decreased as the deposition temperature increased in the temperature range of $1460^{\circ}-1550^{\circ}C$. At the deposition temperature of $1550^{\circ}C$ the SiC layer contained an excess carbon, whereas the SiC layers had stoichiometric compositions at $1460^{\circ}C\;and\;1500^{\circ}C$. Hardness and elastic modulus measured by a nanoindentation method were the highest in the SiC layer deposited at $1500^{\circ}C$. The SiC layer deposited at the gas flow rate of 4000 sccm exhibited a high porosity and contained large pores more than $1{\mu}m$, being due to a violent spouting of particles. On the other hand, the SiC layer deposited at 2500 sccm revealed the lowest porosity.

• Journal of Radiation Protection and Research
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• 제22권2호
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• pp.77-83
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• 1997

사용 후 핵연료 수송용기 등에 사용되는 에폭시수지계 중성자 차폐재, KNS(Kaeri Neutron Shield)-101, KNS-102 및 KNS-103를 제조하였다. 기본물질은 에폭시수지이며, 첨가제로는 폴리프로필렌, 수산화알루미늄 및 탄화붕소이다. 이들 중성자 차폐재들은 유동성이 좋아 수송용기와 같은 복잡한 구조에 사용할 수 있다. 제조된 중성자 차폐재들을 가압경수로 사용 후 핵연료 28다발을 수송할 수 있는 수송용기에 적용하여 차폐능 평가를 수행하였다. 세가지 중성자 차폐재를 수송용기에 적용하여 ANISN 코드로 차폐능 평가를 수행한 결과 정상수송시 중성자 차폐재의 두께가 10 cm 이상 일때 수송용기 반경방향표면에서 최대 방사선량율은 $300{\mu}Sv/h$로 나타났으며, 수송용기 표면에서 100 cm 지점에서의 최대 방사선량율은 $97{\mu}Sv/h$로 나타났다. 이들은 모두 관련된 법규들에서 규정된 최대허용 방사선량율을 만족하는 것으로 나타났다.

• 공업화학
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• 제7권3호
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• pp.597-604
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• 1996

사용후핵연료 수송용기 등에 사용되는 수지계 중성자 차폐재, KNS-115A, 115B 및 115C를 제조하였다. 기본물질은 에폭시수지이며, 첨가제로는 폴리프로필렌, 수산화알루미늄 및 탄화붕소이다. 이들 중성자 차폐재들은 유동성이 좋아 수송용기와 같은 복잡한 구조에 사용할 수 있다. 개발된 중성자 차폐재들의 차폐능, 연소특성, 난연성, 열적 및 역학적 성질 등을 평가하기 위해 여러 특성시험을 행하였다. 개발된 중성자 차폐재(수소원자 밀도, $6.1{\sim}6.2{\times}10^{22}atoms/cm^3$)들은 외국산 중성자 차폐재(NS-4-FR, $6.0{\times}10^{22}atoms/cm^3$)보다 수소원자 밀도가 높아 차폐능이 우수할 것으로 예측되며, 조사된 제반 특성들은 열분해온도; $267{\sim}270^{\circ}C$, 열전도도; $0.62{\sim}0.72W/m{\cdot}K$, 연소특성; $800^{\circ}C$ 이하, 평균연소시간; 5초 이하, 평균연소길이; 5mm 이하, 인장강도; $2.3{\sim}3.0kg/mm^2$, 압축강도; $5.3{\sim}13.3kg/mm^2$, 굴곡강도; $4.4{\sim}5.4kg/mm^2$ 등을 나타냈다.

• Composites Research
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• 제36권6호
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• pp.435-440
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• 2023

본 연구에서는 기존 사용후핵연료(Spent nuclear fuel) 운반/저장 용기에 사용되는 중성자 흡수용 B₄C/Al 복합소재의 열전도도를 개선하기 위해 탄화붕소(B₄C)와 입방정 질화붕소(cBN)를 동시에 강화재로 사용한 알루미늄(Al) 기지 복합소재를 제조하고 평가를 진행하였다. 이를 위해서 교반주조 공정을 통해 복합재 잉곳을 제조하고 이를 압연하여 중성자 흡수용 소재를 성공적으로 제조하였다. 제조된 소재의 평가를 위해 cBN 첨가에 따른 열전도도와 중성자 흡수능 변화를 관찰하였다. 열전도도 측정 결과, B₄C 단일 입자만을 사용한 복합소재 대비 B₄C, cBN을 함께 사용한 복합소재가 동일 체적률 조건 하에서 약 3%의 열전도도 증가가 발생하는 것을 확인하였으며 중성자 흡수 단면적 계산을 통해 중성자 흡수능이 무시할 수 있는 수준으로 저하가 발생하는 것을 확인하였다. 본 연구의 결과를 바탕으로, 중성자 흡수 소재의 새로운 설계 방안을 제시하고 고성능 운반/저장 용기의 개발에 기여할 수 있을 것으로 기대된다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.15-15
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• 2011

As you know, boron compounds, borax ($Na_2B_4O_5(OH)_4{\cdot}8H_2O$) etc. were known thousands of years ago. As for natural boron, it has two naturally occurring and stable isotopes, boron 11 ($^{11}B$) and boron 10 ($^{10}B$). The neutron absorption $^{10}B$ is included about 19~20% with 80~81% $^{11}B$. Boron is similar to carbon in its capability to form stable covalently bonded molecular networks. The mass difference results in a wide range of ${\beta}$ values between the $^{11}B$ and $^{10}B$. The $^{10}B$ isotope, stable with 5 neutrons is excellent at capturing thermal neutrons. For example, it is possible to decrease a thermal neutron required for the nuclear reaction of uranium 235 ($^{235}U$). If $^{10}B$ absorbs a neutron ($^1n$), it will change to $^7Li+^1{\alpha}$ (${\alpha}$ ray, like $^4He$) with prompt ${\gamma}$ ray from $^{11}B$ $^{11}B$ (equation 1). $$^{10}B+^1n\;{\rightarrow}\;^{11}B\;{\rightarrow}\; prompt \;{\gamma}\;ray (478 keV), \;^7Li+4{\alpha}\;(4He)\;\;\;\;{\cdots}\; (1)$$ If about 1% boron is added to stainless steel, it is known that a neutron shielding effect will be 3 times the boron free steel. Enriched boron or $^{10}B$ is used in both radiation shielding and in boron neutron capture therapy. Then, $^{10}B$ is used for reactivity control and in emergency shutdown systems in nuclear reactors. Furthermore, boron carbide, $B_4C$, is used as the charge of a nuclear fission reaction control rod material and neutron cover material for nuclear reactors. The $B_4C$ powder of natural B composition is used as a charge of a control material of a boiling water reactor (BWR) which occupies commercial power reactors in nuclear power generation. The $B_4C$ sintered body which adjusted $^{10}B$ concentration is used as a charge of a control material of the fast breeder reactor (FBR) currently developed aiming at establishment of a nuclear fuel cycle. In this study for new boron compound, silicon boride ceramics for capturing thermal neutrons, preparation and characterization of both silicon tetraboride ($SiB_4$) and silicon hexaboride ($SiB_6$) and ceramics produced by sintering were investigated in order to determine the suitability of this material for nuclear power generation. The relative density increased with increasing sintering temperature. With a sintering temperature of 1,923 K, a sintered body having a relative density of more than 99% was obtained. The Vickers hardness increased with increasing sintering temperature. The best result was a Vickers hardness of 28 GPa for the $SiB_6$ sintered at 1,923K for 1 h. The high temperature Vickers hardness of the $SiB_6$ sintered body changed from 28 to 12 GPa in the temperature range of room temperature to 1,273 K. The thermal conductivity of the SiB6 sintered body changed from 9.1 to 2.4 W/mK in the range of room temperature to 1,273 K.

• 한국결정성장학회지
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• 제26권5호
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• pp.188-192
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• 2016

본 연구에서는, 실리카 분말과 왕겨의 혼합체로부터 탄화된 물질로부터, 탄화규소 (SiC) 분말이 합성되었다. 탄화왕겨와 실리카의 열탄화환원 반응을 통해 얻어진, SiC 시료는 XRD 회절 패턴, FE-SEM 및 FE-TEM을 통해 분석되었다. 시료들은 XRD 패턴에서, $35^{\circ}$ 부근의 (111) peak는 매우 높은 intensity를 나타내었고, $60^{\circ}$, $72^{\circ}$ 부근의 (220), (311) peak 등 탄화규소 결정상에 대한 peak pattern이 명확하게 관찰되었다. Ar 분위기에서 탄화왕겨와 실리카의 혼합비율이 6 : 4인 혼합물로부터 합성된 시료는 XRD 패턴에서 잔류카본이 검출되지 않았으며, hexagonal 결정상의 비율이 비교적 낮고, cubic SiC 결정상이 주도적으로 나타내었다. 탄화왕겨와 실리카의 혼합비율이 6 : 4인 경우에 합성된 시료는 $5{\mu}m$ 이하의 미세한 입자들이 관찰되었으며, TEM 분석결과에서, SiC 결정질상의 (110) 회절패턴 형태를 나타내었다.

• 방사성폐기물학회지
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• 제16권2호
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• pp.233-242
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• 2018

본 연구에서는 탄소강 심부시추공 처분용기가 가지는 고온에서의 물성 저하와 내부식성 문제 등을 해결하기 위하여, 열전도도가 우수한 SiC를 이용한 심부시추공 처분용기의 제작 가능성을 살펴보았다. 먼저 사용후핵연료 집합체 1다발을 수용할 수있는 심부시추공 처분용기를 설계하였으며, 설계된 처분용기는 내부 SiC 기밀용기와 취급 편의와 심부정치를 위한 외부 스테인리스 용기로 구성하였다. 그리고 SiC 세라믹 용기의 제작 가능성을 확인하기 위해, 1/3 규모의 소형 SiC 용기를 실제 제작하였다. 제작된 SiC 용기에서 시편을 추출하여 열전도도를 측정하였으며, KURT 지하 $70^{\circ}C$ 고온조건에서 3년간 내구성 시험도 실시하였다. 그 결과 SiC는 $100^{\circ}C$에서도 $70W{\cdot}m^{-1}{\cdot}K^{-1}$ 이상의 열전도도를 보였으며, 내구성 시험 후에도 변화가 전혀 보이지 않았다. 따라서 SiC는 높은 열전도도와 우수한 내부식성을 갖고 있어, 심부시추공 처분용기 재료로 적합하다고 보았다.

• 대한금속재료학회지
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• 제46권6호
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• pp.351-356
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• 2008

Thermally sprayed tungsten carbide-based powder coatings are being widely used for a variety of wear resistance applications. The coating deposited by high velocity processes such as high velocity oxy-fuel (HVOF) thermal spraying is known to provide improved wear resistant property. In this study, optimal coating process (OCP) is obtained by the study of coating properties such as surface hardness, porosity, surface roughness and microstructure of 9 coatings prepared by Taguchi program for 3 levels of four spray parameters. The Friction and wear behaviors of HVOF WC-CoCr coating prepared by OCP, electrolytic hard chrome (EHC) plating and Inconel718 (In718) are investigated by reciprocating sliding wear test at $25^{\circ}C$, $450^{\circ}C$. Friction coefficients (FC) of all of the 3 samples are decreased as increasing sliding surface temperature from $25^{\circ}C$ to $450^{\circ}C$. FC of WC-CoCr decreases as increasing the surface temperature from $0.33{\pm}0.02$ at $25^{\circ}C$ to $0.26{\pm}0.02$ at $450^{\circ}C$, showing the lowest FC among the 3 samples. Wear trace (WT) and wear depth (WD) of WC-CoCr are smaller than those of EHC and In718 both at $25^{\circ}C$ and $450^{\circ}C$. These show that WC-CoCr is highly recommendable for protective coating on In718 and other metal components.