Analysis of fuel rod behavior under normal operating conditions in Super Fast Reactor

A Super Fast Reactor is a pressure-vessel type, fast spectrum supercritical water-cooled reactor (SCWR) that is presently researched in a Japanese project. A preliminary core has been designed with 1.59E+06 W/m³ of power density [1]. In order to ensure the fuel rod integrity, the fuel rod behaviors under the normal operating conditions are analyzed using FEMAXI-6 code. Three types of the limiting fuel rods, with the maximum cladding surface temperature (MCST), maximum power peak (MPP) and maximum discharge burnup (MDB), are chosen to cover all the fuel rods in the core. The power histories of these fuel rods are taken from the neutronics calculation results in the core design. The available design range of the fuel rod design parameters, such as the initial gas plenum pressure, gas plenum length, grain size and pellet-cladding gap size, are found out in order to satisfy the following design criteria: (1) Maximum fuel centerline temperature should be less than 1900 °C. (2) Maximum cladding stress in circumstance direction should be less than 100 MPa. (3) Pressure difference on the cladding should be less than 1/3 of buckling collapse pressure. (4) Compressive stress to yield strength ratio should be less than 0.2. (5) Cumulative damage fraction (CDF) on the cladding should be less than 1.0. Finally the improved fuel rod design is proposed.     

Small-scale hydrogen liquefaction with a two-stage Gifford–McMahon cycle refrigerator

We manufactured a small-scale hydrogen liquefier with a two-stage 10 K Gifford–McMahon cycle (GM) refrigerator. It had a hydrogen tank with the volume of 30 L that was surrounded by a radiation shield. This liquefier continuously liquefied gaseous hydrogen with the volumetric flow rate of 12.1 NL/min. It corresponds to the liquefaction rate of 19.9 L/day for liquid hydrogen. We proposed a simple estimation method for the liquefaction rate and confirmed that the estimation method well explained the experimental result. To evaluate the estimation method, we applied the estimation method to other liquefiers. In case of a liquefier with the GM refrigerator, we confirmed the estimation method was available for predicting the liquefaction rate. However, in case of a liquefier with the pulse tube refrigerator, the results of the estimation indicated small values as compared with the experimental data. We discuss the details about the estimation method of the liquefaction rate for the small-scale liquefiers.     

PRECIPITATION BEHAVIOR IN A Cu—Sn—Ni—Zn—P LEAD FRAME MATERIAL

Transmission electron microscopy (TEM) observations were carried out for examining the precipitation behavior in a Cu-Sn-Ni-Zn-P lead frame material. TEM observations revealed that the precipitate is hexagonal Ni5P2 and the orientation relationship between the Cu matrix and Ni$Pi precipitate is (111)fcc//(0001)hcp, [101]fcc//[1120]hcp, where the suffix fcc denotes the Cu matrix and hep denotes the hexagonal Ni5P2 precipitate. The Ni5P2 precipitate is ovoidal in shape at the beginning of aging at lower temperature. By prolonging the aging time or increasing the aging temperature, Ni5P2 precipitate grows and shows a rod-like shape. The Ni added Cu based lead frame material has a comparative mechanical properties with that of TAMAC15 which has been developed and used in electrical industry.     

An index directly indicates land-based pollutant load contributions of domestic wastewater to the water pollution and its application

As indices directly indicate land-based pollutant load contributions to public water pollution, pollutant load per capita flowing into the water body (PLCwb) for the drainage areas of inner city rivers in Chiba City, Chiba Prefecture, Japan, was analyzed. It was reaffirmed that PLCwb was different by the drainage area. For example, the biochemical oxygen demand (BOD) load per capita flowing into the water body (PLCwb-BOD) was calculated as 0.83 g BOD person(-1) day(-1) for population served with wastewater treatment plant (WWTP). In regards to the three types of on-site domestic wastewater treatment methods in Japan: 0.4-2.1 g BOD person(-1) day(-1) for combined jokaso (CJ), 4.5-21 g BOD person(-1) day(-1) for simple jokaso (SJ) and 4.3-19 g BOD person(-1) day(-1) for night soil treatment (NST). In regards to nutrient parameters of the three on-site treatment methods, population weighted average of PLCwb were almost the same, however, relatively small PLCwb were observed for CJ and SJ through the analysis. Environmental accounting housekeeping (EAH) books for domestic wastewater were prepared based on the analysis results as the application of the indices. EAH books are effective tools for water pollution mitigation in public water bodies. The results of the preliminary correlation analysis of the indices showed that high-efficiency treatment methods including WWTP, agriculture village wastewater treatment facility (AVETF) and CJ are effective in reducing pollutant load flowing into the water body, and that PLCwb have second-order equation relationships with population density of the drainage area. Judging from these characteristics and the analytical results of this study, PLCwb may be useful as an index for demonstrating the benefit of wastewater treatment in reduction of water pollution in the water body.     

Porphyromonas gingivalis Components/Secretions Synergistically Enhance Pneumonia Caused by Streptococcus pneumoniae in Mice

Streptococcus pneumoniae is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of S. pneumoniae and Porphyromonas gingivalis, a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether P. gingivalis accelerates pneumococcal infections, we tested the effects of inoculating P. gingivalis culture supernatant (PgSup) into S. pneumoniae-infected mice. Mice were intratracheally injected with S. pneumoniae and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in S. pneumoniae-infected mice and S. pnemoniae and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of S. pneumoniae-infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with S. pneumoniae infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by S. pneumoniae, suggesting that virulence factors produced by P. gingivalis are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.     

A simple packet aggregation technique for fault detection

Packet monitoring has become a standard technique in network management and when applied to a large‐scale transit network yields a high volume of packets. To overcome this problem, we discuss the behavior of packets and present a symptom‐based packet aggregation technique which is useful for fault detection. Copyright © 2000 John Wiley & Sons, Ltd.     

Inducible expression system for the marine cyanobacterium Synechococcus sp. strain NKBG 15041c

Cyanobacteria have been recognized as promising host organisms to produce biofuel materials including hydrogen and hydrocarbons due to high biomass productivity and capability of transformation. Metabolic engineering has recently been employed for further enhancement of bioenergy production, while excess fuel materials could give rise to cytotoxicity. Therefore genetic tools are required in order to precisely control the gene expression involved in the fuel production metabolism. Thus far, inducible-expression systems in cyanobacteria have been established mainly in freshwater strains. However there are a few reports with regard to marine strains, which can use vast of ocean for cultivation. In this study, we established a tetracycline-inducible gene expression system in the marine cyanobacterium Synechococcus sp. strain NKBG 15041c. Since tetracycline-inducible system is a non-native regulation, it is expected for inherent metabolisms not to be disrupted. The de novo designed promoter including tetracycline operator elements was inactivated by the repressor protein, and inducer addition successfully initiated target protein expression. This is the first report to demonstrate tetracycline-induction system with strict on/off switching in marine cyanobacteria, and it should be useful for future bioenergy production.