• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2018년도 추계 학술논문 발표대회
• /
• pp.114-115
• /
• 2018

To develop an effective shielding material for spent fuel that emits fast neutrons is necessary. In this study, thermal neutron and fast neutron shielding performance of polyethylene coated boron carbide-incorporated cement paste was quantitatively analyzed by Monte Carlo N-Particle transport code (MCNP) simulations. As the results of the simulations, fast neutrons were effectively shielded through large quantity of hydrogen and boron elements in polyethylene and boron carbide.

• Journal of Electrochemical Science and Technology
• /
• 제6권1호
• /
• pp.16-25
• /
• 2015

Transition metal oxide nanocrystalline materials are playing major role in energy storage application in this scenario. Nickel oxide is one of the best antiferromagnetic materials which is used as electrodes in energy storage devices such as, fuel cells, batteries, electrochemical capacitors, etc. In this research work, nickel oxide nanoparticles were synthesized by combustion route in presence of organic fuels such as, glycine, glucose and and urea. The prepared nickel oxide nanoparticles were calcined at 600℃ for 3 h to get phase pure materials. The calcined nanoparticles were preliminarily characterized by XRD, particle size analysis, SEM and EDAX. To prepare nickel oxide electrode materials for application in supercapacitors, the calcined NiO nanoparticles were mixed with di-methyl-acetamide and few drops of nafion solution for 12 to 16 h. The above slurry was coated in the graphite sheet and dried at 50℃ for 2 to 4 h in a hot air oven to remove organic solvent. The dried sample was subjected to electrochemical studies, such as cyclic voltammetry, AC impedance analysis and chrono-coulometry studies in KOH electrolyte medium. From the above studies, it was found that nickel oxide nanoparticles prepared by combustion synthesis using glucose as a fuel exhibited resulted in low particle diameter (42.23 nm). All the nickel oxide electrodes have shown better good capacitance values suitable for electrochemical capacitor applications.

• Bulletin of the Korean Chemical Society
• /
• 제33권8호
• /
• pp.2539-2545
• /
• 2012

In the present study, we suggest a new way to reactivate performance of direct formic acid fuel cell (DFAFC) and explain its mechanism by employing electrochemical analyses like chronoamperometry (CA) and cyclic voltammogram (CV). For the evaluation of DFAFC performance, palladium (Pd) and platinum (Pt) are used as anode and cathode catalysts, respectively, and are applied to a Nafion membrane by catalyst-coated membrane spraying. After long DFAFC operation performed at 0.2 and 0.4 V and then CV test, DFAFC performance is better than its initial performance. It is attributed to dissolution of anode Pd into $Pd^{2+}$. By characterizations like TEM, Z-potential, CV and electrochemical impedance spectroscopy, it is evaluated that such dissolved $Pd^{2+}$ ions lead to (1) increase in the electrochemically active surface by reduction in Pd particle size and its improved redistribution and (2) increment in the total oxidation charge by fast reaction rate of the Pd dissolution reaction.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2012년도 춘계학술발표대회
• /
• pp.95.1-95.1
• /
• 2012

Very High Temperature gas cooler Reactor (VHTR) has been considered as one of the most promising nuclear reactor because of many advantages including high inherent safety to avoid environmental pollution, high thermal efficiency and the role of secondary energy source. The TRISO coated fuel particles used in VHTR are composed of 4 layers as OPyC, SiC, IPyC and buffer PyC. The significance of CVD-SiC coatings used in tri-isotropic(TRISO) nuclear coated fuel particles is to maintain the strength of the whole particle. Various methods have been proposed to evaluate the mechanical properties of CVD-SiC film at room temperature. However, few works have been attempted to characterize properties of CVD-SiC film at high temperature. In this study, micro tensile system was newly developed for mechanical characterization of SiC thin film at elevated temperature. Two kinds of CVD-SiC films were prepared for micro tensile test. SiC-A had [111]-preferred orientation, while SiC-B had [220]-preferred orientation. The free silicon was co-deposited in SiC-B coating layer. The fracture strength of two different CVD-SiC films was characterized up to $1000^{\circ}C$.The strength of SiC-B film decreased with temperature. This result can be explained by free silicon, observed in SiC-B along the columnar boundaries by TEM. The presence of free silicon causes strength degradation. Also, larger Weibull-modulus was measured. The new method can be used for thin film material at high temperature.

• Korean Chemical Engineering Research
• /
• 제53권1호
• /
• pp.6-10
• /
• 2015

효소 전극 anode와 PEMFC용 전극 cathode를 이용하여 효소연료전지를 구동하였다. 효소 anode는 그래파이트 분말과 효소로서 글루코스 산화제, 전자매개체로서 페로센을 혼합해 압축해서 만들고 Nafion 이오노머로 코팅하였다. anode 제조조건을 변화시키며 OCV를 측정해 효소 anode 제조 최적조건을 찾았다. 효소 anode 압축 시 최적 압력은 9.0 MPa였다. 효소 anode에서 그래파이트가 60%일 때 최고의 OCV를 나타냈다. anode 기질 용액의 최적 글루코스 농도는 1.7 mol/l이었으며, anode의 효소 활성은 7일 동안 안정적으로 유지되었다.

• Korean Chemical Engineering Research
• /
• 제54권2호
• /
• pp.171-174
• /
• 2016

효소 전극 cathode와 PEMFC용 전극 anode를 이용하여 효소연료전지를 구동하였다. 효소 cathode는 그래파이트 분말과 효소로서 Laccase, 산화환원 매개체로서 ABTS를 혼합해 압축해서 만들고 Nafion 이오노머로 코팅하였다. cathode 제조조건을 변화시키며 OCV를 측정해 효소 cathode 제조 최적조건을 찾았다. 효소 cathode 압축 시 최적 압력은 4.0 bar 였다. 효소 cathode에서 그래파이트가 95%일 때 최고의 OCV를 나타냈다. cathode기질 용액의 최적 글루코스 농도는 0.4 mol/l이었다.

• Korean Chemical Engineering Research
• /
• 제49권6호
• /
• pp.710-714
• /
• 2011

본 연구에서는 열 플라스마 용사 코팅 법을 사용하여 고체산화물 연료전지에서 사용되는 $La_{0.8}Ca_{0.2}CrO_{3}$(LCC), $La_{0.8}Sr_{0.2}CrO_{3}$(LSC), $La_{0.8}Ca_{0.2}CrO_{0.9}Co_{0.1}O_{3}$(LCCC) 세라믹 연결재를 코팅하여 코팅 층의 특성평가를 수행하였다. 열 플라즈마 코팅에 앞서 각 세라믹 연결재 입자의 특성평가를 위해 X선 회절, 미세 구조, 입자 측정 및 비표면적 분석을 수행하였다. 세라믹 연결재 입자의 특성평가 후, 열 플라스마 용사 코팅 법을 사용하여 연료극 지지체 위에 코팅하였으며, 코팅 층의 특성을 평가하기 위해 코팅 층의 표면, 파단면 분석, 가스 누출 속도 및 전기 전도도 측정을 수행하였다. 이러한 특성 평가 결과를 바탕으로 열 플라스마 용사 코팅 법을 통해 코팅된 LCCC 코팅 층이 고체산화물 연료전지의 세라믹 연결재로서 적합함을 확인하였다.

• 대한금속재료학회지
• /
• 제50권9호
• /
• pp.685-690
• /
• 2012

Decalcomania is a new method for SOFCs (solid oxide fuel cells) unit cell fabrication. A tight and dense $5{\mu}m$ Yttria-stabilized zirconia (8YSZ) electrolyte layer on anode substrate was fabricated by the decalcomania method. After 8YSZ as the electrolyte starting material was calcined at $1200^{\circ}C$, the particle size was controlled by the attrition mill. The median particle size (D50) of each 8YSZ was $39.6{\mu}m$, $9.30{\mu}m$, $6.35{\mu}m$, and $3.16{\mu}m$, respectively. The anode substrate was coated with decalcomania papers which were made by using 8YSZ with different median particle sizes. In order to investigate the effect of median particle sizes and sintering conditions on the electrolyte density, each sample was sintered for 2, 5 and 10 h, respectively. 8YSZ with a median particle size of $3.16{\mu}m$ which was sintered at $1400^{\circ}C$ for 10 had the highest density. With this 8YSZ, a SOFCs unit cell was manufactured with a $5{\mu}m$ layer by the decalcomania method. Then the unit cell was run at $800^{\circ}C$. The Open Circuit Voltage (OCV) and Maximum power density (MPD) was 1.12 V and $650mW/cm^2$, respectively.

• Nuclear Engineering and Technology
• /
• 제39권2호
• /
• pp.111-122
• /
• 2007

The current energy supply system is burdened by environmental and supply problems. The concept of a hydrogen economy has been actively discussed worldwide. KAERI has set up a plan to demonstrate massive production of hydrogen using a VHTR by the early 2020s. The technological gap to meet this goal was identified during the past few years. The hydrogen production process, a process heat exchanger, the efficiency of an I/S thermochemical cycle, the manufacturing of components, the analysis tools of VHTR, and a coated particle fuel are key areas that require urgent development. Candidate NHDD plant designs based on a 200 MWth VHTR core and I/S thermochemical process have been studied and some of analysis results are presented in this paper.

• Nuclear Engineering and Technology
• /
• 제47권5호
• /
• pp.608-616
• /
• 2015

The migration of silver (Ag) in silicon carbide (SiC) and $^{110m}Ag$ through SiC of irradiated tristructural isotropic (TRISO) fuel has been studied for the past three to four decades. However, there is no satisfactory explanation for the transport mechanism of Ag in SiC. In this work, the diffusion coefficients of Ag measured and/or estimated in previous studies were reviewed, and then pre-exponential factors and activation energies from the previous experiments were evaluated using Arrhenius equation. The activation energy is $247.4kJ{\cdot}mol^{-1}$ from Ag paste experiments between two SiC layers produced using fluidized-bed chemical vapor deposition (FBCVD), $125.3kJ{\cdot}mol^{-1}$ from integral release experiments (annealing of irradiated TRISO fuel), $121.8kJ{\cdot}mol^{-1}$ from fractional Ag release during irradiation of TRISO fuel in high flux reactor (HFR), and $274.8kJ{\cdot}mol^{-1}$ from Ag ion implantation experiments, respectively. The activation energy from ion implantation experiments is greater than that from Ag paste, fractional release and integral release, and the activation energy from Ag paste experiments is approximately two times greater than that from integral release experiments and fractional Ag release during the irradiation of TRISO fuel in HFR. The pre-exponential factors are also very different depending on the experimental methods and estimation. From a comparison of the pre-exponential factors and activation energies, it can be analogized that the diffusion mechanism of Ag using ion implantation experiment is different from other experiments, such as a Ag paste experiment, integral release experiments, and heating experiments after irradiating TRISO fuel in HFR. However, the results of this work do not support the long held assumption that Ag release from FBCVD-SiC, used for the coating layer in TRISO fuel, is dominated by grain boundary diffusion. In order to understand in detail the transport mechanism of Ag through the coating layer, FBCVD-SiC in TRISO fuel, a microstructural change caused by neutron irradiation during operation has to be fully considered.