안전조치 사찰을 위한 휴대형 HPGe 검출기 시제품 성능평가 실험

Kwak, Sung-Woo,Ahn, Gil Hoon,Park, Iljin,Ham, Young Soo,Dreyer, Jonathan 대한방사선방어학회 2014 방사선방어학회지 Vol.39 No.1

IAEA는 핵물질 계량 관리 검사를 위해 다양한 방사선 검출기를 사용하고 있다. 주로 HPGe, NaI(Tl), CZT 등이 사용되며, 정확한 측정이 요구되는 검사에는 고분해능 HPGe 검출기 활용도가 높다. HPGe 검출기는 추가적인 냉각장치로 인하여 부피가 크고 무거우며, 사용하기 전에 충분히 냉각시켜야 하기 때문에 측정의 준비 시간이 많이 걸린다는 단점이 있다. 이러한 문제점을 해결하기 위해 가볍고 짧은 사용 전 냉각이 요구되는 휴대형 HPGe가 개발되었다. 본 논문은 개발된 휴대형 HPGe 검출기 시제품을 실제 IAEA 사찰 현장에 적용하여 얻은 성능평가 결과를 기술한다. 휴대형 HPGe로 얻은 방사선 스펙트럼은 핵물질 종류와 농축도에 따라 다른 특징을 보였고, 또한 $^{235}U$과 $^{238}U$의 붕괴 계열에서 방출되는 감마선 및 우라늄의 특성 x-선 차이도 확인할 수 있었다. 그리고 휴대형 HPGe 검출기 시제품으로 측정한 농축도는 핵물질 종류에 따라 실제값과 9 ~ 27%의 상대적 오차를 보였다. 휴대형이라는 소형 검출기의 한계 때문에 일부 핵물질은 IAEA에서 요구하는 정확도를 만족시키지 못하는 경우도 있었지만 향후 추가적인 연구의 수행으로 이러한 문제점은 해결 가능할 것으로 판단된다. 본 논문은 새로운 휴대형 HPGe 검출기를 안전조치에 적용한 사례와 측정한 스펙트럼을 농축도 분석 코드로 분석한 결과를 다룬다. 따라서 국내 원자력시설의 우라늄 농축도 검증을 위한 IAEA 안전조치 사찰 결과를 분석한 논문이 별로 발표되지 않은 상황에서, 본 논문은 안전조치 검사 결과 분석에도 유익할 것으로 판단된다. 개발된 방사선 검출기의 개선 사항도 함께 논의하였으므로 향후 관련 분야 방사선 검출기 개발에도 기여할 것으로 예상된다. IAEA has employed various types of radiation detectors - HPGe, NaI, CZT - for accountancy of nuclear material. Among them, HPGe has been mainly used in verification activities required for high accuracy. Due to its essential cooling component(a liquid-nitrogen cooling or a mechanical cooling system), it is large and heavy and needs long cooling time before use. New hand-held portable HPGe has been developed to address such problems. This paper deals with results of performance evaluation test of the new hand-held portable HPGe prototype which was used during IAEA's inspection activities. Radioactive spectra obtained with the new portable HPGe showed different characteristics depending on types and enrichments of nuclear materials inspected. Also, Gamma-rays from daughter radioisotopes in the decay series of $^{235}U$ and $^{238}U$ and characteristic x-rays from uranium were able to be remarkably separated from other peaks in the spectra. A relative error of enrichment measured by the new portable HPGe was in the range of 9 to 27%. The enrichment measurement results didn't meet partially requirement of IAEA because of a small size of a radiation sensing material. This problem might be solved through a further study. This paper discusses how to determine enrichment of nuclear material as well as how to apply the new hand-held portable HPGe to safeguard inspection. There have been few papers to deal with IAEA inspection activity in Korea to verify accountancy of nuclear material in national nuclear facilities. This paper would contribute to analyzing results of safeguards inspection. Also, it is expected that things discussed about further improvement of a radiation detector would make contribution to development of a radiation detector in the related field.

Generation and Trapping of 2-Methyl-2-silanaphthalene

Kwak, Young-Woo,Lee, Jong-Bong,Lee, Kyung-Koo,Kim, Seong-Su,Boo, Bong Hyun 충남대학교 기초과학연구소 1994 연구논문집 Vol.14 No.-

There has been many reports of the generation and their reactions of silabenzene intermediate from the readily available allyl or chloro precursors. The intramolecular reacton of 1-methyl-2,3,4,5-tetraphenylsilacyclopentadienylmethlene to give silatoluene was reported by Anbo and Sekiguchi. West and coworkers reported the existence of the intermediacy of hexamethyl-1,4-disilabenzene. In 1978, Barton and Burns confirmed the first unambiguous generation and trapping of the silatoluene formed via a thermally induced retroene elimination of propene from the 1-allyl-1-methyl-1-silacy-clohexa-2,4-diene. There is precedent for the unsuccessful approach to produce 2-silanaphthalene intermediate from the thermolysis or photolysis of silyl diazo compound 1 in the presence of methanol.

Fe/N/S-doped mesoporous carbon nanostructures as electrocatalysts for oxygen reduction reaction in acid medium

Kwak, Da-Hee,Han, Sang-Beom,Lee, Young-Woo,Park, Hyun-Suk,Choi, In-Ae,Ma, Kyeng-Bae,Kim, Min-Cheol,Kim, Si-Jin,Kim, Do-Hyoung,Sohn, Jung-Inn,Park, Kyung-Won Elsevier 2017 Applied Catalysis B Vol.203 No.-

<P><B>Abstract</B></P> <P>Many alternatives to typical Pt-based catalysts have been developed to enhance oxygen reduction reaction (ORR) performance in acid medium due to their scarcity and high activation loss during the ORR. We synthesized mesoporous carbon nanostructures with multi-dopants such as iron, nitrogen, and sulfur as a cathode catalyst using the ordered silica templates and porphyrinic iron. The co-doped mesoporous carbon cathode catalysts exhibited a high ORR performance in an acid medium, <I>i.e.</I> complete ORR process and improved durability. The enhanced ORR properties of the catalysts might be ascribed to iron-containing catalytic active sites surrounded by nitrogen/sulfur species and a well-defined mesoporous carbon nanostructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Doped mesoporous carbon nanostructures were synthesized using a template method. </LI> <LI> The as-prepared samples exhibited a well-ordered mesoporous structure. </LI> <LI> The mesoporous carbon nanostructures contained multi-dopants such as Fe, N, and S. </LI> <LI> The doped carbon nanostructures showed highly improved ORR activity and stability. </LI> <LI> The improved properties were due to a well-doped mesoporous carbon nanostructure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Addition of α,α-Difluoroiodomethyl Ketones to Alkenes with a Copper Catalyst

Kwak, Kyung-Chell,Lee, Woo-Yiel,Zheshan, Quan,Lee, Young-Hang,Yun, Young-Gab,Kwak, Gyu-Beum,Chung, Hun-Taeg,Kwon, Tae-Oh,Chai, Kyu-Yun Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.1

The addition reactions of $\alpha$,$\alpha$-difluoroiodomethyl n-butyl ketone, α,α-difluoroiodomethyl cyclohexyl ketone, or $\alpha$,$\alpha$-difluoroiodomethyl phenyl ketone to alkenes were successfully accomplished in good yields in the presence of copper powder. The reaction was also applicable to alkenes containing a variety of functional groups such as ester, trimethylsilyl, or ether group. Acetonitrile was determined to be the best solvent in the present study and the reaction was performed at 55 ${^{\circ}C}$ for 15-22 h. This reaction provides a new, efficient and general method for the synthesis of $\alpha$,$\alpha$-difluoro functionalized ketones.

Ultrasmall PtSn alloy catalyst for ethanol electro-oxidation reaction

Kwak, Da-Hee,Lee, Young-Woo,Han, Sang-Beom,Hwang, Eui-Tak,Park, Han-Chul,Kim, Min-Cheol,Park, Kyung-Won Elsevier 2015 Journal of Power Sources Vol.275 No.-

<P><B>Abstract</B></P> <P>To improve the electrocatalytic properties for an ethanol electro-oxidation reaction, modifications of Pt nanocrystallites have been used by alloying with other elements such as Ru, Sn, and Au. Here we demonstrate carbon supported Pt<SUB>3</SUB>Sn alloy electrocatalyst (Pt<SUB>3</SUB>Sn/C) synthesized using a thermal-decomposition method. The PtSn/C prepared by the present synthetic process shows a homogeneous distribution of ultrasmall alloy nanoparticles (∼2.5 nm) in the presence of Pt and Sn metallic states. At 0.45 V, the Pt<SUB>3</SUB>Sn/C (0.35 mA cm<SUP>−2</SUP>) exhibits much higher current density as compared with Pt/C (0.13 mA cm<SUP>−2</SUP>). In an electrochemical stability test, the Pt<SUB>3</SUB>Sn/C supported quite high current density and thus showed 3% current reduction after the stability test.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pt<SUB>3</SUB>Sn nanoparticles with an ultrasmall size of 2.5 nm were synthesized. </LI> <LI> Pt<SUB>3</SUB>Sn nanoparticles showed improved electrocatalytic activity and stability. </LI> <LI> The improved activity may be attributed to a well-defined alloy formation. </LI> </UL> </P>

Preclinical pharmacokinetic characterization of 2-(4-(4-(5-(2-phenyl-5-(trifluoromethyl)oxazole-4-carboxamido)-1H-benzo[d]imidazol-2-yl)phenyl)cyclohexyl) acetic acid, a novel DGAT-1 inhibitor

Kwak, Eun-Young,Im, So Hee,Seo, Hyewon,Cho, Woon-Ki,Lee, Ye-Lim,Woo, Jaechun,Ahn, Sunjoo,Ahn, Sung-Hoon,Kwak, Hyun Jung,Ahn, Jin Hee,Bae, Myung Ae,Song, Jin Sook Informa UK Ltd. 2014 Xenobiotica Vol.44 No.5

<P>1. <?ri?>A novel diacylglyceride acyltransferase-1 (DGAT-1) inhibitor, 2-(4-(4-(5-(2-phenyl-5-(trifluoromethyl) oxazole-4-carboxamido)-1H-benzo[d]imidazol-2-yl)phenyl)cyclohexyl) acetic acid (KR-69232), was synthesized for a potential therapeutic use against several metabolic disorders, such as obesity, insulin resistance, and type II diabetes, characterized by excessive triglycerides (TGs) in the blood.</P><P>2. <?ri?>The half-lives against phase I metabolism were measured as 75.3 ± 20.9 min and over 120 min in rat and human liver microsomes, respectively. In Caco-2 cell monolayers, extremely low permeability (<0.13 × 10<SUP>−6 </SUP>cm/s) was seen in the absorptive direction, predicting limited intestinal absorption of KR-69232. This compound was highly bound to rat and human plasma proteins (>99.8%).</P><P>3. <?ri?>With the intravenous administration of KR-69232 in rats (1, 2, and 5 mg/kg), non-linear kinetics were observed at the highest dose, with significantly higher systemic clearance, higher volume of distribution, and lower dose-normalized AUC. Following oral administration, it exhibited low bioavailability (<10%) and was absorbed slowly (<I>T</I><SUB>max</SUB>, 3.8-5.2 h) over the dose range. We also confirmed that considerable KR-69232 remained in the intestine at <I>T</I><SUB>max</SUB>, demonstrating its limited absorption into the systemic circulation.</P>

Synthesis and Characterization of Oligomers Composed of Alternating 2,5-Bis(ethynylenedimethylsilylene)thienylene and Arylene Units

Kwak, Young-Woo,Lee, Kyung-Koo,Cha, Seung-Hun,Lee, Sang-Koo,Lee, In-Sook,Park, Yong-Tae,Lee, Jae-Keun,Yoh, Soo-Dong,Kim, Woo-Sik Korean Chemical Society 2003 Bulletin of the Korean Chemical Society Vol.24 No.4

The reactions of 2,5-bis(ethynyldimethylsilyl)thiophene (1) with aromatic dihalides(1,4-dibromobenzene, 4,4'- dibromobiphenyl, 9,10-dibromoanthracene, 2,5-dibromopyridine, 2,5-dibromothiophene, and 2,6-diiodo-4- nitroaniline) were carried out in the presence of a $[(PPh_3)_2PdCl_2]$-CuI catalyst in refluxing triethylamine to give poly{[2,5-bis(ethynylenedimethylsilylene)thienylene](arylene)} (2-7) with molecular weights of 2200-7400. The oligomers reveal characteristic absorption in the UV/visible region. The thermal behavior of 2-7 was examined by thermogravimetric analysis in an argon atmosphere.

Synergistic effect of multiple stress conditions for improving microalgal lipid production

Kwak, Ho Seok,Kim, Jaoon Young Hwan,Woo, Han Min,Jin, EonSeon,Min, Byoung Koun,Sim, Sang Jun Elsevier 2016 Algal research Vol.19 No.-

<P><B>Abstract</B></P> <P>This increasing consumption of fossil fuels and emission of greenhouse gases causes climate change. Thus, the development of alternative energy sources such as biofuel is necessary. Microalgae have been spotlighted as renewable energy resources because the potential for producing biofuels from CO<SUB>2</SUB>. However, the unit cost for the production of algae-based biofuel must be reduced for commercialization compared to the petroleum. The optimization of culture conditions of microalgal strains is crucial to increase lipid production for economically viable biofuels. We rapidly analyzed the combined effect of various stress conditions (nitrogen starvation, temperature, pH, and salt concentration) on the lipid production in various strains using a multiplex microfluidic system, enabling multiple operations from cell culture to lipid extraction of different strains. We found the lipid productivity was enhanced by 25 to 54% under combinations of two stress condition compared to the single stress condition. However, the combination of more than three stress conditions reduced the lipid productivities of all microalgal strains because of more stressful environment to the cells compared to the combinations of two stress conditions. We further validated the synergistic effect of combined stress conditions in flask culture with the increases in lipid productivities by up to 106% compared to the single stress condition. We also observed that fatty acids composition, which influences the quality of algal biofuels, was changed according to the combination of stress conditions. In particular, <I>C. protothecoides</I> can be good candidate for production of high quality of biodiesel, because it has high CN, IV and low CFPP which is suitable for high quality of biodiesel. These results indicate that combination of multiple stress conditions can be efficient strategy for the optimization of microalgal cultivation to produce algal biofuels with high quality and economic feasibility.</P>

Preparation Method of Co₃O₄ Nanoparticles Using Ordered Mesoporous Carbons as a Template and Their Application for Fischer–Tropsch Synthesis

Kwak, Geunjae,Hwang, Jongkook,Cheon, Joo-Young,Woo, Min Hee,Jun, Ki-Won,Lee, Jinwoo,Ha, Kyoung-Su American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.4

<P>Co<SUB>3</SUB>O<SUB>4</SUB> nanoparticles (NPs) with a narrow particle size distribution were fabricated via a facile and novel method using mesoporous carbon materials (CMK-3, MSU-F-C) as sacrificial templates. The particle size distribution of the Co<SUB>3</SUB>O<SUB>4</SUB> NPs varied depending on the pore size of the templates. Synthesis of the NPs with concurrent complete removal of the templates was achieved at 593 K, which is lower than the temperatures utilized in previous reports. It was verified that the carbon template was decomposed by catalytic oxidation with cobalt and NO<SUB><I>x</I></SUB> species generated by thermal decomposition of the cobalt nitrate precursor in air. The prepared NPs, and particularly the Co<SUB>3</SUB>O<SUB>4</SUB> NPs synthesized from CMK-3, acted as excellent catalysts for the Fischer–Tropsch synthesis (FTS). The high catalytic performance was associated with the optimum particle size (6–10 nm) of the nanoparticles for FTS and enhanced reducibility.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-4/jp3106698/production/images/medium/jp-2012-106698_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp3106698'>ACS Electronic Supporting Info</A></P>

Customized microfluidic reactor based on droplet formation for the synthesis of monodispersed silver nanoparticles

Kwak, Cheol Hwan,Kang, Sung-Min,Jung, Euiyoung,Haldorai, Yuvaraj,Han, Young-Kyu,Kim, Woo-Sik,Yu, Taekyung,Huh, Yun Suk THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.63 No.-

<P><B>Abstract</B></P> <P>A customized droplet-based microfluidic reactor was fabricated for the synthesis of silver nanoparticles (Ag NPs) using silver nitrate (AgNO<SUB>3</SUB>) and branched polyethyleneimine (BPEI) as a precursor and a reducing agent, respectively. The effects of static mixing, temperature, and the volumetric flow rates of AgNO<SUB>3</SUB> and BPEI on the particle size were investigated. The use of a static mixer and the optimization of the reaction temperature enhanced the monodispersity of the Ag NPs. In addition, the size of the Ag NPs was manipulated by changing the flow rate ratio of AgNO<SUB>3</SUB> to BPEI at 60°C for 60min.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>