[en] A wirelike shape of Hf silicides, which is not observed in silicides directly grown on Si (0 0 1), has been obtained by oxide mediated epitaxy (OME). Hafnium deposition (∼0.4 and ∼0.2 ML) onto ultrathin (∼1 nm) SiO₂ and annealing at 900 deg. C resulted in the formation of self-assembled wirelike silicides via a silicate phase (Hf-O-Si bonding units) in the 600-800 deg. C temperature range. Silicide nanowires were found to be encapsulated in the bundle aggregates. The number density of OME-grown silicides apparently decreased as a form of nanowire bundles along with an increasing aspect ratio compared with the directly grown disilicides on Si (0 0 1). This finding has an implication for the use of an ultrathin SiO₂ layer in controlling the tradeoff between the number density and the aspect ratio of self-assembled silicides

[en] The thermal instability and silicidation behaviors of ultrathin HfO_x on Si(001) were studied by using scanning tunneling microscopy (STM) with in-situ X-ray photoelectron spectroscopy (XPS). A 1.5-nm-thick HfO_x layer was grown on Si(001) by using Hf deposition in an oxidizing ambient. In the low temperature (600 ∼ 800 .deg. C) region, hafnium oxide near the interface region easily reacted with the substrate silicon ions in order to form a silicate structure (Hf-O-Si bonding units). When the SiO evaporation proceeded in the high-temperature (≥ 900 .deg. C) region, silicon migration from the substrate became kinetically remarkable and transformed the Hf-O-Si units into Hf-Si bonds with some remnant Si-O bonds. In contrast with the multi-phase feature of crystalline HfSi₂ that has been reported to occur by annealing hafnium metal on ultrathin SiO₂, our STM study reveals the formation of 'irregularly shaped' silicides upon silicidation. These silicides contain some oxygen in the form of Si-O bonds, so they exhibit a slightly insulating behavior in the spectroscope mode of STM.

[en] Highlights: • Facile, scalable in-situ synthesis of lanthanide (La, Eu, Yb) doped graphene frameworks. • Efficient electrocatalytic performance towards HER and ORR. • Eu-Gr hybrid shows HER performance; onset & overpotential (81 & 160 mV), & Tafel slope (52 mV dec⁻¹). • Eu-Gr exhibits superior activity of ORR; onset potential (0.92 V), electron transfer number (4.03). • Excellent long-term stability in HER and ORR, comparable to those of commercial Pt/C catalysts. - Abstract: The design of efficient electrocatalysts for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) has received enormous consideration due to their effectiveness in modern renewable energy technologies such as fuel cells, electrolyzers, and metal–air batteries. Herein, we present a facile method to fabricate lanthanides (L = La, Eu, Yb)-doped graphene materials as catalyst for the HER and ORR that show desirable electrocatalytic activities as well as long-term stability. The Eu-graphene hybrid has showed unbeatable HER performance such as small values of onset potential (81 mV), overpotential (160 mV), and Tafel slope (52 mV dec⁻¹), along with a high exchange current density (7.55 × 10⁻⁶ A cm⁻²). The L-graphenes also exhibit superior electrocatalytic activity for ORR, including small Tafel slopes (96, 66, and 105 mV dec⁻¹ for La-Gr, Eu-Gr, and Yb-Gr, respectively), positive onset potential (∼0.83–0.92 V), high electron transfer numbers (∼3.84–4.03), and excellent enduring strength, analogous to those of viable Pt/C catalysts. The excellent electrocatalytic performance is attributed to the synergistic effect of abundant edges and doping sites, high electrical conductivity, large active surface areas and fast charge transfer; which renders lanthanide-based graphene hybrids as potentially great candidate for energy conversion systems.

[en] Environmental radiation monitoring was carried out with measurement of environmental radiation and environmental radioactivity analysis around KAERI nuclear facilities and Seoul Research Reactor are the follows: The average level of environmental radiation dose measured by NaI scintillation counter and accumulated radiation dose by TLD was almost same level compared with the past years. Gross α, β radioactivity in environmental samples showed a environmental level. γ-radionuclides in water samples were not detected. But only radionuclide K-40, which is natural radionuclide, was detected in the all samples and Cs-137 was detected in the surface soil and discharge sediment. The average level of environmental radiation dose around Seoul Research Reactor was almost same level compared with the past years, and Be-7 and Cs-137 were detected in some surface soil and discharge sediment by γ-spectrometry. (author). 37 refs., 67 tabs., 23 figs

[en] Water spray cooling has been widely used in a variety of industrial applications. The present study concentrated on quantitative measurements of the heat flux and heat transfer coefficient by water spray as it impinges on the rough surface of a hot steel plate at 900 .deg. C. A novel experimental technique was developed for a high temperature heat flux gauge with a test block, cartridge heaters, and thermocouples that was used to measure the surface heat flux information on the hot steel plate for local heat flux measurements. The roles of the surface roughness on heat transfer are presented in this paper for well-characterized four rough surfaces with average rms roughness heights of 40-80 μm. The results show that the local heat transfer for rough surfaces is higher than that for a smooth surface. Heat transfer can be significantly increased by the presence of surface roughness elements, which can disrupt the thin thermal boundary layer. In addition, the heat transfer enhancement mechanism on a rough surface can be investigated by a different boiling regime

[en] Performance test facility for RCP (reactor coolant pump) is essential to verify the performance and reliability of RCP before installation in the nuclear power plant. The development of RCP for new-type reactor and the performance verification of hydraulic revolving body also needs the RCP test facility. The design concept of test loop and the technology of flow rate measurement are investigated in this research

[en] This paper aims at studying on the fracture behavior due to crack propagation at compact tension specimen composed of inhomogeneous metal materials with holes near main crack. In this study, the experiments were performed for compact tension specimens produced by the mutual bonding metals of stainless steel and brass, and the simulation analyses to verify these experiments were conducted. When the preceding study results are confirmed, the design of structures with no holes near a crack becomes more durable on the strength aspect than the design of structures with holes existing near the crack. The design for highest strength is possible if no holes are pierced in inhomogeneous metal materials bonded with adhesives. On the other hand, in case the holes due to additional bolt and rivet fastening must be pierced, the most similar tendency to that of materials without holes is exhibited when the hole center is placed by about 20 mm from the crack tip. A great difference in strength occurs according to the hole position near the main crack at inhomogeneous metal materials bonded with adhesives. So, the design considering this aspect is deemed important. The data for different positions where the crack propagations occur can be confirmed at analysis and experimental results. Therefore, the changes inside the material that are actually difficult to confirm due to the crack growth characteristics at inhomogeneous materials can be expected through an analysis. The fracture behavior of inhomogeneous metal materials bonded by adhesives was investigated through the experiment and analysis. The basic data through this study could be secured at contributing to the developed design of light-weight composite materials as well as bonding the technology for mutually different materials.

[en] The analysis of the uncertainties in experimental measurements and results is a powerful tool, particularly when it is used in the planning and design of experiments. The uncertainty analysis, when used in the initial planning phase of an experiment, can identify such situations and save the experimentalist much time, money and embarrassment. The current study focuses on making detailed determination and estimation of the convective heat transfer coefficient as it is frequently encountered in the field of thermal engineering applications. The quantitative uncertainty analysis was carried out based on the ANSI/ASME PTC 19.1-2005 standard. The actual application of the uncertainty analysis is provided by the detailed example which is performed at the submerged impinging jet heat transfer case. The results show that the convective heat transfer coefficient can be determined by its individual contributors of measurands.

[en] This paper focuses on the current status of measures used to prevent, detect and respond to potential insiders at nuclear facilities in the Republic of KOREA. Measures against insiders are then analyzed based on IAEA guidelines. Insiders are able to take advantage of their access rights and knowledge of a facility to bypass dedicated security measures. They can also threaten cyber security, safety measures, and material control and accountancy (MC and A). Insiders are likely to have the time to plan their actions. In addition, they may work with an external adversary who shares their objectives. An insider threat is a great risk to a security system because of the access, authority, and special knowledge that someone within a facility possesses. Therefore, it is imperative that effective measures be taken to prevent insider incidents. A combination of preventive and protective measures offers the best solution to mitigating rogue elements within a facility

[en] Paris Agreement on Climate Change(2015) requires to reduce the greenhouse gas emission. One of the responses to the requirement is to change the proportion of power generation, which is summarized to the decrease in thermal power and the increase in new and renewable power. This article conducts a comparative analysis on the economic effects between thermal- and new and renewable- power generations, using the Input-Output Table from The Bank of Korea. The results of this analysis show that the new and renewable power generation has got the larger effects in production-inducing, value-added-inducing, employment-inducing, and supply-shortage scopes, while the smaller effect in price-pervasive scope than the thermal power generation. According to these results, the complex consideration should be taken into when the changes in power generation mix are tried. Especially, the political efforts to reduce the supply-shortage effect of new and renewable power and the price-pervasive effect of thermal power will be important.