Development of natural circulation analysis methods for a sodium cooled fast reactor

A natural circulation evaluation methodology has been developed to insure safety of a sodium cooled fast reactor (SFR) of 1500 MWe adopting a natural circulation decay heat removal system (NC-DHRS). The methodology consists of a one-dimensional safety analysis which can be applied to safety evaluation for SFR licensing taking into account the temperature flattening effect due to buoyancy force in the core, and a three-dimensional fluid flow analysis which can evaluate thermal-hydraulics for local convection and thermal stratification in the primary system and DHRSs. The one-dimensional safety analysis method and the three-dimensional fluid flow analysis method have been validated using the test results of a water test apparatus and a sodium test loop for some typical transient events selected from the design basis events of the SFR. Finally, it has been confirmed that a good agreement between the test results and analysis results has been obtained, and reliability of each method has been demonstrated.     

Purification and characterization of a novel alcohol oxidase from Paenibacillus sp. AIU 311

An oxidase catalyzing the conversion of glycolaldehyde to glyoxal was purified to the homogeneous state from Paenibacillus sp. AIU 311, and its properties were revealed. This enzyme was specific to glycolaldehyde and glyceraldehyde, and the reaction rates to other alcohols and aldehydes were less than 6% of that of glycolaldehyde. The Km values for glycolaldehyde and glyceraldehyde were estimated to be 13.2 and 7.5 mM, respectively. The glycolaldehyde oxidation was optimum at pH 6.5 and 50 degrees C. The molecular mass of this enzyme was 49 kDa, and it consisted of two identical subunits of 24 kDa. The NH2-terminal sequence was not homologous to those of alcohol oxidases. This is the first report of an oxidase exhibiting high specificity to a hydroxy group of aldehyde alcohols.     

Effects of particle size on flame spread over magnesium powder layer

The spreading of a flame over a layer of magnesium powder has been examined to clarify the mechanisms of flame spread over metal powder layers and to establish effective ways to extinguish metal fires. Four grades of magnesium powder were used, with average grain diameters of 60, 170, 360 and 500 μm. The flame spread rate for larger particle sizes (D>170 μm) increased slightly with increasing particle size. However, the flame spread rate for smaller particle sizes (D<63 μm) increased sharply. The detailed surface temperature history of the magnesium powder layer was measured using infrared thermography (IR). Based on the temperature distribution in the pre-heat zone, the characteristic length l, characteristic depth δ, and characteristic time τ were calculated. The characteristic scale ratio, L/δ, for the larger particle sizes (D>170 μm) is almost unity, which suggests that the dominant heat transfer mechanism is heat conduction through the magnesium powder layer (solid phase). However, the L/δ for the smaller particle sizes (D<63 μm) is about 2.7, suggesting that the dominant heat transfer mechanism is convection. The flame spread rate over the magnesium powder layer was calculated by the de Ris model, a one-dimensional flame spread model, and a surface flash model. For larger particle sizes (D>170 μm), there is good agreement between the experimental flame spread rate and the flame spread rate estimated by the one-dimensional model. However, the flame spread rate was underestimated by the de Ris model, apparently because the de Ris model only considers heat feedback from the gas phase. For small-particle sizes (D<63 μm), there is good agreement between the experimental flame spread rate and the flame spread rate estimated by the surface flash model. This suggests that the flame spread over a small-particle layer can be described by a mechanism rather similar to that of gas phase flame propagation.     

Reliability-based temporal and spatial maintenance strategy for integrity management of corroded underground pipelines

In this work, a novel stochastic model framework for predicting the external corrosion growth in buried pipeline structures has been developed, and a reliability-based temporal and spatial maintenance strategy is presented. The spatial correlation of soil properties is modelled via hidden Markov random field. The temporal correlation of the corrosion rate is characterised by the geometric Brownian bridge process. A Bayesian inferential framework is employed to estimate the model parameters of the corrosion growth model using in-line inspection data. The proposed corrosion growth model was validated with actual inspection data. In the reliability analysis, the impact of device detectability is considered and hence the estimated failure probability is more realistic. The proposed maintenance strategy is directly based on the time-specific and location-specific failure probability. The application of the proposed model and maintenance strategy is illustrated through a real-life pipeline system. The results indicate that the proposed maintenance strategy is an adaptive and dynamic scheme that is able to improve the efficiency of inspections.     

Compositions and Microstructures of the Primary Ceramic Materials in the Paleolithic Age Through XRD, SEM, and TEM Analyses

The mineral compositions and microstructures of Paleolithic materials were first investigated by X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy in order to understand the primary ceramic material in human history. Shale and chalcedony artifacts excavated from upper Paleolithic sites were analyzed. As a result, from among various candidates with nonuniform mineral compositions, only limited materials containing polycrystals with approximately more than 95%α-quartz content were selected as tool materials. Moreover, every Paleolithic material invariably exhibited densely packed and homogeneous micrograins approximately 0.1–0.5 μm in size and an equigranular structure with few porosities at the grain boundaries.     

球形铁基金属玻璃单分散粒子的制备及评价

利用脉冲小孔法在He气氛下制备出了球形粒径可控的[(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄金属玻璃单分散微粒子, 这些粒子具有粒径均匀和圆球度高等优良特点. 通过XRD、DSC以及TEM对所获得的粒子进行了检测分析, 结果表明随着粒径尺寸的减小, 微粒子的微观结构从混合相逐渐向全金属玻璃相转变, 制备的粒子均为全玻璃相, 临界尺寸小于645 μm. 通过冷却速率的计算, 得到全玻璃相微粒子的临界冷却速率为800~1100 K/s, 该速度与环境气氛的改变无关, 并且该计算值低于同成分的大块金属玻璃合金TTT曲线的测量值.     

Effect of coprecipitation temperature on the properties and activity of fibroblast growth factor-2 apatite composite layer

Fibroblast growth factor-2 (FGF-2) apatite composite layers were formed on anodically oxidized titanium (Ti) rods at temperatures lower than the previously used 37 °C to reduce the risk of the inactivation of FGF-2 in calcium phosphate solution. A two-step procedure was used to coprecipitate FGF-2 apatite composite layers on Ti rods. Continuous and homogeneous carbonate-containing low-crystalline apatite layers incorporating FGF-2 were formed on the surface of the Ti. The amounts of apatite and FGF-2 coprecipitated on the Ti rod surface decreased with decreasing coprecipitation temperature. When the coprecipitation temperatures were 15 and 20 °C, the amounts of FGF-2 precipitated on the Ti rods were 0.19 ± 0.03 and 0.20 ± 0.03 μg/cm², respectively. A cell proliferation assay for evaluating the mitogenic activity of FGF-2 immobilized in the layer showed that when FGF-2 was coprecipitated at 15 and 20 °C, the number of NIH3T3 cells cultured with FGF-2 extract was significantly larger than that at 4, 10, 25 and 30 °C. To obtain the largest amount of active FGF-2 on a Ti surface, a temperature of 15 or 20 °C should be used for coprecipitating FGF-2.     

Effect of non-genetically modified (non-GM) soy varieties on the measured value of GM soy by a quantitative PCR method

It is very important to examine the effect of non-genetically modified (non-GM) soy varieties, which constitute the matrix of the testing sample used to quantify GM soy (RRS), on the measured value of RRS by quantitative PCR methods. Therefore, we quantified the amount of RRS in powder-mixed samples containing 1 or 5% RRS prepared by using 10 different varieties of non-GM soy as the matrix. The results revealed that the measured values were not in agreement with the powder-mixing levels and that the extent of the difference depended on the variety of non-GM soy used as the matrix. The yields of DNA extracted differed among the soy varieties. On the other hand, analysis of DNA-mixed samples, that were prepared with the DNAs extracted from RRS and non-GM soy varieties, showed that the measured values of RRS were in agreement with the DNA-mixing levels. These results strongly suggest that the proportions of DNA derived from RRS and non-GM soy were not consistent with the powder-mixing ratio in the case of some non-GM soy varieties used as a matrix, resulting in the discrepancy between the measured values and the powder-mixing levels.     

Oil Microsealing: A Robust Micro‐compartmentalization Method for On‐Chip Chemical and Biological Assays

A simple and robust method to compartmentalize aqueous solutions into an array of independent microchambers is presented. The array of microchambers fabricated in poly(dimethylsiloxane) are filled with the sample solution through a microfluidic channel and then sealed with oil to isolate the microchambers from each other. A water reservoir close to the microchambers allows the maintainance and incubation of sub‐nanoliter solutions (e.g., at 37 °C) within the chambers for hours without any problem of evaporation. Once assembled, the device is self‐sustainable and can be used for different application purposes. As a demonstration, the device configuration is shown to be suitable for spatiotemporal control of the inner solution conditions by light stimulation through a photomask. This method was applied for the generation of regular EmGFP (emerald green fluorescent protein) expression arrays, selective photobleaching, photopatterning of calcium concentration, and cell culture in independent microchambers.