Recent Japanese research activities on probabilistic fracture mechanics for pressure vessel and piping of nuclear power plant

This paper describes a review of recent Japanese activities on probabilistic fracture mechanics (PFM) analyses. Japan Atomic Energy Agency (JAEA: previously JAERI) had sponsored research committees on PFM organized by Japan Society of Mechanical Engineers (JSME) and Japan Welding Engineering Society (JWES) for more than a decade. This work still continues with the same members in JWES. The purpose of the continuous activity is to provide probabilistic approaches in several fields of integrity problems of nuclear power plant. This paper shows some of the newest results of the JWES research committee. First topic is evaluation of the new JSME code case with rules of Fitness-For-Service from the view of PFM, including reactor pressure vessel subject to pressurized thermal shock loading, piping with a crack of the allowable size and effect of sizing accuracy for piping integrity. The next one is development of new PFM techniques including reliability assessment of piping with domestic (Japanese) SCC data and maintenance optimization of LWRs based on risk and economic models. The last topic is the international round robin program just starting from 2008.     

Recycle for Sludge Scrap of Nd-Fe-B Sintered Magnet as Isotropic Bonded Magnet

The reduction diffusion method was performed for the sludge scrap of Nd-Fe-B sintered magnets with adding Ca metal to recover the oxidized Nd-Fe-B phase. After washing the resultant powders to remove Ca metal component, the powders obtained were recycled as an isotropic magnetic powder by the melt spinning method. The magnetic properties of powders as recycled were inferior, especially for the coercivity value, due to the deletion of rare earth metals during the washing process. The adjustment of metal composition, i.e., the addition of Nd metal, at the melt spinning process improved the magnetic properties to be Br=～0.75 T, Hcj=～0.93 mA·m-1, and(BH)max=～91 kJ·m-3. The magnetic properties of the bonded magnets prepared from the composition-adjusted powders were Br=～0.66 T, Hcj=～0.92 mA·m-1, and(BH)max=～70 kJ·m-3, which are approximately comparable to the commercially available MQPB boned one(Br=～0.73 T, Hcj=～0.79 mA·m-1, and(BH)max=～86 kJ·m-3).     

Protective Effects of Voluntary Exercise on Hepatic Fat Accumulation Induced by Dietary Restriction in Zucker Fatty Rats

Weight control based on dietary restriction (DR) alone can cause lipid metabolic failure and progression to fatty liver. This study aimed to investigate the effect of exercise on preventing DR-induced hepatic fat accumulation in Zucker fatty (ZF) rats by focusing on the relationship between adipose tissue lipolysis and hepatic fat uptake. Six-week-old male ZF rats were randomly assigned to obese, DR, or DR with exercise (DR + Ex) groups. The DR and DR + Ex groups were fed a restricted diet, with the latter also undergoing voluntary exercise. After 6 weeks, hepatic fat accumulation was observed in the DR group, whereas intrahepatic fat was markedly reduced in the DR + Ex group. Compared with the obese (Ob) group, the DR group exhibited 2.09-fold expression of hepatic fatty acid translocase (FAT)/CD36 proteins (p < 0.01) and 0.14-fold expression of hepatic fatty acid-binding protein (FABP)1 (p < 0.01). There were no significant differences between the DR + Ex group and the Ob group. FAT/CD36 and hepatic triglyceride (TG) expression levels were strongly positively correlated (r = 0.81, p < 0.001), whereas there was a strong negative correlation between FABP1 and hepatic TG expression levels (r = −0.65, p < 0.001). Our results suggest that hepatic fat accumulation induced by DR in ZF rats might be prevented through exercise-induced modifications in FAT/CD36 and FABP1 expression.     

Electronic state and magnetism of the rare-earth carbide GdCx (x 0.33)

The electronic state and the magnetism of GdC_x (x = 0.33) were investigated by the discrete variational (DV)-Xα calculation method together with those of Gd metal. Magnetic moments on the gadolinium atoms located at the center of the Gd₁₇ and Gd₄C₂ clusters extracted from Gd metal and Gd_tC were calculated to be 8.38 and 9.70 μ_B, in qualitative agreement with the experimental values (7.96 and 8.28 μ_B respectively). The exchange splitting of the Gd 4f band in Gd₃C was found to increase from that of Gd metal and accounts for the higher Curie temperature of GdC₁ compounds observed in experiments. The calculated results show that the carbon atoms are charge acceptors in these compounds. The higher Curie temperature values (T_c = 350 K) observed in the GdC_x (x 0.33) compounds compared with Gd metal (T_c = 293 K) are discussed on the basis of the spin-fluctuation theory.     

Competitive oxidation of formaldehyde and formate on amorphous copper-palladium-zirconium alloy electrodes in alkaline media

Raney-type Cu–Pd alloy electrodes were prepared from amorphous Cu–Pd–Zr ternary alloys by treatment with aq. HF, and competitive anodic oxidation reactions of HCHO and HCOO^– were studied on these electrodes in alkaline media. The initial HCHO oxidation product was HCOO^– even on Pd or Pd-rich alloy electrodes which should be more active to the HCOO^– oxidation than to HCHO. The product HCOO^– was oxidized only after a large decrease of the HCHO concentration in the electrolyte. The oxidation rate of HCOO^– was considerably lowered by the existence of even a small amount of HCHO, as well as by the introduction of CO. These results suggest that the HCHO electro-oxidation is accompanied by production of a surface contaminant such as adsorbed CO. The optimum nominal Pd atomic fraction in the Cu–Pd alloy electrodes suitable for the steady simultaneous oxidation of HCHO and HCOO^– in mixed solution was shown to be 0.25 and 0.4 in 1.0 M NaOH (M=moldm^–3) and 0.5 M K₂CO₃, respectively.     

Wavelength demultiplexer using GaInAs-InP MQW-based variable refractive-index arrayed waveguides fabricated by selective MOVPE

A GaInAs-InP multiple quantum well (MQW)-based wavelength demultiplexer composed of an arrayed waveguide in which the refractive index varies across the array was fabricated. Since optical path length differences between waveguides in the array are achieved through refractive-index differences that are controlled by SiO/sub 2/ mask design in selective metal-organic vapor phase epitaxy (MOVPE), straight waveguide gratings having reduced optical propagation losses can be achieved. Furthermore, by employing MQW waveguides, variations in the refractive index may be induced through an applied electric field, allowing the device to manipulate wavelengths dynamically. A straight arrayed waveguide device having a 1.4% difference in refractive index was fabricated using an asymmetric side mask via a single selective MOVPE growth. The achievement of a diffraction angle difference of 4.40/spl deg/ between wavelengths of 1520 and 1580 nm was confirmed experimentally. In addition, a preliminary wavelength demultiplexer with a wavelength separation of approximately 25 nm and a free spectral range (FSR) of approximately 100 nm was also fabricated.     

Application of eddy current inversion technique to the sizing of defects in Inconel welds with rough surfaces

This paper evaluates the applicability of eddy current inversion techniques to the sizing of defects in Inconel welds with rough surfaces. For this purpose, a plate Inconel weld specimen, which models the welding of a stub tube in a boiling water nuclear reactor is fabricated, and artificial notches machined into the specimen. Eddy current inspections using six different eddy current probes are conducted and efficiencies were evaluated for the six probes for weld inspection. It is revealed that if suitable probes are applied, an Inconel weld does not cause large noise levels during eddy current inspections even though the surface of the weld is rough. Finally, reconstruction of the notches is performed using eddy current signals measured using the uniform eddy current probe that showed the best results among the six probes in this study. A simplified configuration is proposed in order to consider the complicated configuration of the welded specimen in numerical simulations. While reconstructed profiles of the notches are slightly larger than the true profiles, quite good agreements are obtained in spite of the simple approximation of the configuration, which reveals that eddy current testing would be an efficient non-destructive testing method for the sizing of defects in Inconel welds.     

Metabolism of 5'-ether prodrugs of 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil in rats

1-beta-D-Arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU) is a selective antiherpesviral agent that has been shown to be metabolically stable in mice. However, E-5-(2-bromovinyl)uracil (BVU) is the major metabolite found after oral dosing in animals other than mice. When BV-araU was given orally to germ-free rats, only small amounts of BVU were found in the plasma, suggesting an important role of enterobacteria in the formation of BVU. Then, the metabolism of BV-araU prodrugs was studied in specific-pathogen free rats to select oral prodrugs of BV-araU with enhanced metabolic stability. 5'-O-Ethyl BV-araU (Et-BV-araU) gave about a 2-fold higher BV-araU blood concentration 3 and 6 hr after administration than after oral dosing of BV-araU, while the level of BVU was lower. Other aliphatic alkyl prodrugs also gave a lower level of BVU, but did not give the same elevation in blood concentration of BV-araU as did Et-BV-araU. Dosing of 5'-O-acetyl BV-araU resulted in blood concentrations of BV-araU and BVU similar to those after oral administration of BV-araU. 5'-O-Aromatic alkyl prodrugs showed poor bioavailability. A nearly 2-fold higher urinary recovery rate was seen for Et-BV-araU than for BV-araU or 5'-O-acetyl BV-araU. The conversion of Et-BV-araU to BV-araU was demonstrated in vitro using rat liver extract in the presence of co-factors, although the reaction was slow. The 5'-O-aliphatic alkyl prodrugs were completely resistant to degradation by enterobacteria, whereas the esters were partially degraded to BVU. Et-BV-araU may be a useful oral prodrug of BV-araU due to its increased metabolic stability and bioavailability.     

Enhanced hot-carrier degradation due to water-related components inTEOS/O3 oxide and water blocking with ECR-SiO2film

The authors point out that a TEOS/O₃-oxide layer used as an interlevel dielectric enhances hot-carrier degradation of MOSFETs due to the water-related components (water and/or silanols) contained in the layer. This results mainly from enhanced hot-electron trapping in the gate oxide and also from interface-trap generation. By applying an ECR-SiO₂ layer under the TEOS/O₃-oxide layer, tolerance against hot-carrier damage is improved to the level of MOSFETs without the TEOS/O₃ oxide. From ESR measurement results, it is found that the spin density of the ECR-SiO₂ film under the TEOS/O₃ oxide is two orders lower than that of the ECR-SiO ₂ film only. It is suggested that the dangling bonds in the ECR-SiO₂ film effectively trap water diffusing from the water-containing overlayer