Thermodynamic properties and equations of state for fast reactor safety analysis: Part II: Properties of fast reactor materials

In this paper, thermodynamic properties of reactor-core materials are newly evaluated for an analytic equation-of-state (EOS) model with flexible thermodynamic functions. This model has been developed for a multiphase, multicomponent fluid-dynamics code for fast reactor safety analysis. The most up-to-date and reliable sources for uranium dioxide, mixed-oxide fuel, stainless steel, and sodium available at present are first compiled, with particular emphasis on including new thermodynamic data of type 316 stainless steel. This compilation is used to develop the EOS data up to the critical point using basic thermodynamic relationships. The EOS model for use in the accident analysis code is then completed by determining all the EOS parameters in the thermodynamic functions. The thermodynamic consistency and accuracy of the evaluated EOS data are also discussed by comparison with the available sources. The thermodynamic properties of sodium vapor are successively reproduced using a van der Waals type equation extended to include the dimerization process of sodium vapor.     

Effects of pore diameter, bath surface pressure, and nozzle diameter on the bubble formation from a porous nozzle

The effects of the pore diameter, bath surface pressure, and nozzle diameter on the bubble formation from a porous bottom nozzle placed in a water bath and on the behavior of rising bubbles were investigated with still and high-speed video cameras and a two-needle electroresistivity probe. Three types of bubble dispersion patterns were observed with respect to gas flow rate, and they were named the low, medium, and high gas flow rate regimes. The transition boundaries between these gas flow rate regimes were expressed in terms of the superficial velocity at the nozzle exit, i.e., the volumetric gas flow rate per unit nozzle surface area. These transition boundaries were dependent on the pore diameter but hardly dependent on the bath surface pressure and the porous nozzle diameter. The characteristics of rising bubbles in each gas flow rate regime were investigated as functions of the three parameters.     

Prediction of survival of terminally ill cancer patients--a prospective study

Antibodies against oxidized low density lipoproteins (Ox-LDLs) have been proposed to be independent predictors of atherosclerosis development. The main aims of the current study were to (1) compare antibody titers to Ox-LDL in patients with heterozygous familial hypercholesterolemia (n=51) with those in matched controls (n=45) and (2) analyze whether the antibody titers were related to the extent of atherosclerosis, as assessed cross-sectionally and prospectively by ultrasonography in the 2 study groups. Antibody titers were determined with a solid-phase ELISA, and plates were coated with the antigens Ox-LDL or malondialdehyde-treated LDL (MDA-LDL) as well as with the postcoat only (5% dry milk powder). Antibody titers were expressed as absorbance [(value in patient serum minus that in postcoat) divided by (Internal Standard Serum minus postcoat)]. There were no significant differences in antibody titers against Ox-LDL or MDA-LDL between the group of patients with familial hypercholesterolemia and the controls. In cross-sectional comparisons, no significant associations were observed between the intima-media thickness of the carotid or femoral arteries and antibody titers against Ox-LDL or between plaque occurrence and these titers. Patients with a history of myocardial infarction had significantly lower IgM titers against Ox-LDL compared with patients without a history of myocardial infarction and with controls. In conclusion, mean values for antibody titers against Ox-LDL were not increased in the patient group compared with a healthy control group, and no positive, significant relationship was observed between antibody titers and the extent of atherosclerosis, as measured by ultrasound, in the carotid or femoral arteries. Taken together, these findings indicate that the relationship between the autoimmune response to Ox-LDL and the extent of atherosclerosis is more complex than previously anticipated.     

Serological survey of antibody to Neospora caninum in Japanese dogs

Prevalence of antibody to Neospora caninum (NC) in Japanese dogs were examined. The antibody was positive in 15 of 48 dogs (31.3%) reared in the dairy farms that had case of the abortions due to NC infection or had the cattle seropositive to NC, whereas the prevalence was 7.1% (14 of 198 dogs) among the dogs kept in urban areas. In one dog breeder, all 17 Shetland sheepdogs older than 7 months were seropositive, and one pup was diagnosed as neosporosis 2 months before the first serological examination. The antibody titers of the dogs kept at this breeder were almost unchanged for 1.5 years. Serological evidence of the dogs in the dairy farms and urban areas indicates the transmission of NC between dogs and cattle. Also serological results of the dogs in one breeder may suggest the potential horizontal transmission among dogs.     

In Situ Observation of Deformation in Semi-solid Fe-C Alloys at High Shear Rate

Synchrotron X-ray radiography at 125 frames per second was used to study deformation mechanisms in semi-solid Fe-C alloys at high solid fraction and shear strain rates of 10^?1/s. An image correlation approach was also used to quantify the shear strain fields and study shear-induced dilation and the origin of shear cracking. It was shown that, at high solid fraction (90 to 93 pct solid), rearrangement including rotation and translation of solid particles became restricted and shear strain localized into narrow liquid-filled channels/fissures. Shear cracking was shown to originate from inadequate liquid flow into the expanding spaces between solid particles caused by shear-induced dilation. At lower solid fraction (~85 pct solid), solid particles rearranged with a significantly higher component of rotation leading to more shear-induced dilation and a wider shear band.     

Increased vascular endothelial growth factor production in the lungs of rats with hypoxia-induced pulmonary hypertension

Vascular endothelial growth factor (VEGF) is a potent mitogenic and permeability factor targeting predominantly endothelial cells. At least two tyrosine kinase receptors, Flk-1 and Flt-1, mediate its action and are mostly expressed by endothelial cells. VEGF and VEGF receptor expression are upregulated by hypoxia in vivo and the role of VEGF in hypoxia-induced angiogenesis has been extensively studied in a variety of disease entities. Although VEGF and its receptors are abundantly expressed in the lung, their role in hypoxic pulmonary hypertension and the accompanying vascular remodeling are incompletely understood. We report in this in vivo study that hypoxia increases mRNA levels for both VEGF and Flk-1 in the rat lung. The kinetics of the hypoxic response differ between receptor and ligand: Flk-1 mRNA showed a biphasic response to hypoxia with a significant, but transient, rise in mRNA levels observed after 9-15 h of hypoxic exposure and the highest levels noted after 3 wk. In contrast, VEGF mRNA levels did not show a significant increase with acute hypoxia, but increased progressively after 1-3 wk of hypoxia. By in situ hybridization, VEGF mRNA was localized predominantly in alveolar epithelial cells with increased signal in the lungs of hypoxic animals compared with controls. Immunohistochemical staining with anti-VEGF antibodies localized VEGF peptide throughout the lung parenchyma and was increased in hypoxic compared with normoxic animals. Furthermore, hypoxic animals had significantly higher circulating VEGF concentrations compared with normoxic controls. Lung vascular permeability as measured by extravasation of Evans Blue dye was not significantly different between normoxic and hypoxic animals, although a tendency for increased permeability was seen in the hypoxic animals. These findings suggest a possible role for VEGF in the pulmonary response to hypoxia.     

Inter-subassembly heat transfer of sodium cooled fast reactors: Validation of the NETFLOW code

This paper describes the prediction of temperature at the exit of subassemblies of a sodium cooled fast reactor using the NETFLOW code. Until present time, this plant dynamics calculation code is expected as a tool of nuclear education, and has been validated using data obtained at facilities or reactors cooled with water or sodium. A natural circulation test was conducted in the experimental fast reactor ‘Joyo’ with a 100 MW irradiation core. Also a turbine trip test was conducted in the prototype fast breeder reactor ‘Monju’. These tests were chosen to validate a model to calculate inter-subassembly heat transfer consisting of heat conduction and heat transfer by inter-wrapper flow. Based on the calculation for the natural circulation test in primary and secondary loops of ‘Joyo’, the model to calculate the heat transfer in radial direction of the inter-subassemblies simulated reasonable sodium temperature behaviors at the exit of subassemblies. Good agreement was also obtained in prediction of temperatures at the exit of the ‘Monju’ subassemblies. Through these validations, it was shown that the one-dimensional plant dynamics code NETFLOW could trace temperatures at the exit of the subassemblies of fast reactors with the inter-subassembly heat transfer model.     

Using selective precipitant for uranyl ions — Fundamental studies for evaluating the precipitant performance

We have developed a simple reprocessing process for spent FBR fuels using N-cyclohexyl-2-pyrrolidone (NCP) which has selective precipitation ability for UO₂²⁺ ions. It was confirmed that NCP has sufficient precipitation ability for UO₂²⁺ ions, decontamination capability (separation of UO₂²⁺ from simulated fission products), and resistance to γ-ray radiation in nitric acid solutions. These findings indicate that NCP is applicable to our reprocessing process. We have also evaluated performances of other precipitants such as N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), and N-n-butyl-2-pyridone (NBPyr). It was found that higher decontamination factors (DFs) are obtained by using NProP and NBP. This can be interpreted that the hydrophobicity of NProP and NBP is lower than that of NCP. Furthermore, we have obtained an experimental result that the resistance of NBPyr to γ-ray radiation is superior to that of NCP.     

Permeation measurements for investigating atomic hydrogen flux and wall pumping/fuelling dynamics in QUEST

In order to investigate the overall atomic hydrogen background and the dynamic characteristics of wall pumping/fuelling phenomenon, a permeation probe system has been developed and applied in the spherical tokamak QUEST. Reliability of measurements, within ±3% accuracy and a positive correlation with the hydrogen line emission over three orders of magnitude have been demonstrated for more than 3000 various plasma discharges. By comparison of the experimental permeation (flux) curves with the numerically simulated curves, the net incident atomic hydrogen flux is evaluated in the range of 1 × 10¹⁹ H m^?2 s^?1 to 4 × 10²⁰ H m^?2 s^?1. The atomic flux has been investigated as a function of various plasma operation parameters like RF power, gas pressure and magnetic configuration. Using the static particle balance and permeation measurements, the progress in wall conditioning has been investigated. An inverse correlation between the atomic hydrogen flux and improvement in wall pumping has been observed over the two campaigns.