Effect of non-equilibrium fission gas and fuel creep on swelling and release in irradiated carbide fuels

The code UCSWELL was developed to simulate fission gas behavior in carbide fuels. In the present work, one of the limiting assumptions in UCSWELL - that matrix gas bubbles are in equilibrium with gas atom concentration - is removed and non-equilibrium matrix fission gas bubbles are allowed, but with relaxation to equilibrium by means of vacancy diffusion and thermal and radiation-induced creep of the fuel. For a given grain size, the difference in swelling between equilibrium and non-equilibrium with relaxation bubble fission gas treatment increases with decreasing irradiation temperature. At a given temperature, the non-equilibrium effect is more pronounced for larger grain fuel. This is to be expected because the creep rate (and hence the rate at which bubbles grow to an equilibrium size) decreases as temperature decreases and/or as grain size increases. At temperatures, where the creep rate is grain size insensitive, grain size remains important to the equilibrium process in so far as the grain boundary is a source of vacancies to the non-equilibrium bubbles. While the difference in these quantities is at the most on the order of 20% for the steady operating conditions considered, it is anticipated that the non-equilibrium effects become more pronounced during reactor overpower and undercooling transients.     

Oxidation properties of Zr-Nb alloys at 500-600 °C under low oxygen potentials

Zr-Nb alloys with 1-10 wt.% Nb content were oxidized at 500-600 °C in the CO-CO₂ gas mixtures. The oxidation weight gain increased with Nb content and the kinetics except for Zr-1Nb alloy changed from cubic rate to linear one at 600 °C for a long period of time, 7 d. The cubic rate constant was almost insensitive to oxygen potential of oxidizing atmosphere. As the oxidation resistance deteriorated, the volume ratio of tetragonal to monoclinic zirconia phase and the relevant compressive stress in oxide film decreased with increase of Nb content. Before and after oxidation, Nb re-distribution could not be observed under the present experimental condition.     

Development of a contact-type probe for measurements of ultra-fine-pitch gears and application to pseudo roughness evaluation

Gears used in actuators for robot articulations are showing a trend toward having smaller modules. Thus, profile measurements of small module gears are strongly desired. Our aim was to develop a probe artifact that enables ultra-fine-pitch cylindrical gears to be measured, by minimizing the size of the probe head. The configurations of the contact-type probe and holder were designed under consideration of interference with an adjacent tooth during profile measurements of an objective tooth. After manufacturing the artifact, a 0.1-module spur gear was measured as a trial, and reasonable results were obtained. In addition, a calibration plate for roughness was measured using the developed probe artifact. The evaluated roughness showed a strong correlation with the “true roughness”. Therefore, the developed probe can be expected to enable “pseudo” roughness to be evaluated.     

Evaluation of thermal properties of UO2 and PuO2 by equilibrium molecular dynamics simulations from 300 to 2000 K

The thermal properties of UO₂ and PuO₂ have been investigated by the equilibrium molecular dynamics (EMD) simulations between 300 and 2000 K using the Born–Mayer–Huggins interatomic potential with the partially ionic model (PIM). The thermal expansion behaviors of UO₂ and PuO₂ are well reproduced by assuming that the effective ion valence is 67.5% for PIM. The constant-pressure heat capacities deduced only by the present EMD simulation are a little smaller than experimental data. This result explains that the electronic contribution, Schottky or small polaron contribution, is not small for the heat capacity of the actinide oxide including 5f-electrons. The thermal conductivity estimated by the Green–Kubo formula under the NVE ensemble is comparable with experimental data at temperatures greater than 500 K.     

Mechanical Stability of Mesoporous Materials, MCM-48 and MCM-41

The structural collapse of mesoporous molecular sieves, MCM-48 and MCM-41 materials by mechanical compression was found to occur mechanochemically through hydrolysis of Si–O–Si bonds. Their ordered structures were retained by compressing the well-dried samples under dry N2. Trimethylsilylation of mesoporous materials proved effective in eliminating their instability to compression through enhancing hydrophobicity.     

Automated bone marrow analysis using the CD4000 automated haematology analyser

At present, bone marrow analysis is performed microscopically, but is time consuming and labour intensive. No automated methods have been successfully applied to classification of bone marrows cells because automated blood cell analysers have been incapable of identifying erythroblasts. The present study was designed to evaluate automated analysis of bone marrow aspirates with the CELL-DYN 4000 (CD4000) haematology analyser, which enables automated determination of erythroblast counts in both the normal mode (haemolytic time; 11.5s) and the resistant RBC mode (34.0s). The percentages of subpopulations including lymphocytes, neutrophils and erythroblasts were obtained with the CD4000, and as a reference, differential counts by microscopic observation of May-Grünwald-Giesa-stained films of bone marrow aspirates were performed (n=98). Significant correlations (P < 0.01) between the results obtained with the two methods were observed for total nucleated cell count and lymphocytes, neutrophils, erythroblasts and myeloid/erythroid (M/E) ratio. However, there were biases in the average percentages of erythroblasts, lymphocytes and M/E ratio obtained using the normal mode with the CD4000 toward values lower than those obtained with the microscopic method. Using the RBC resistant mode with the CD4000, the average percentages of erythroblasts, lymphocytes and M/E ratio approximated those obtained with the microscopic method. In conclusion, the CD4000 in resistant RBC mode is more useful for analysis of bone marrow aspirates than is the normal mode, because the former better approximates the M/E ratio than the latter.     

Propane gas leak detection by infrared absorption using carbon infrared emitter and infrared camera

The present study investigated the ability of a system using a carbon infrared emitter (CIE) and an infrared (IR) camera to detect a combustible gas, propane. The CIE transmitted infrared at wavelengths ranging from 1 to 5 μm, and the infrared absorption band of propane gas (3.37 μm) was obtained using a bandpass filter to remove other infrared wavelengths. The intensity of infrared radiation passing through the propane gas decreased as a result of infrared absorption. A clear, real-time image of the gas leak was also obtained using this system. Furthermore, a hazard evaluation of the leakage propane gas was made from a correlation between infrared intensity and the concentration–pathlength product.     

Synthesis of a potent wide-spectrum serotonin-, norepinephrine-, dopamine-reuptake inhibitor (SNDRI) and a species-selective dopamine-reuptake inhibitor based on the gamma-amino alcohol functional group

Mortality data for B6CF1 mice exposed to 60Co gamma rays for the duration of life were used to make quantitative predictions of age-specific mortality observed in comparably exposed beagles. Simple Kaplan-Meier survival curves for the beagles and their 95% confidence intervals were computed for each dose-rate group observed. A dose-response equation was estimated from the mortality data for mice using a proportional hazard model. The dose-response model for mice was then used to generate predicted survivorship curves at dose rates that would recreate the dose burdens observed in the beagle at comparable points within the life span of the two organisms. When these predicted survivorship curves were scaled to adjust for species differences in the life span of control animals, the predictions for the mouse fell within the confidence intervals observed for the beagle. The successful interspecies extrapolation of age-specific mortality risks for species as different as the mouse and dog enhances both the value of studies involving laboratory animals and the potential relevance of the animal studies to the prediction of health effects in humans.     

Noninvasive pump flow estimation of a centrifugal blood pump

A flow rate estimating method was investigated for a centrifugal blood pump developed in our institute. The estimated flow rate was determined by the power consumption, the rotating speed of the motor, and the hematocrit value. The power consumption and the rotating speed of the motor were measured with a wattmeter. The examinations were performed in a closed mock loop filled with goat blood with hematocrit values of 21.5%, 28%, 34%, and 42%. Measured values of blood viscosity were 2.47, 3.09, 3.71, and 5.07 mPa.s at a share rate of 37.5/s, respectively. A linear correlation between the power consumption and the pump flow rate was observed in all hematocrit values. But variations in hematocrit caused a difference in the flow rate up to 1.1 L/min at the same power consumption and rotating speed. Effects of blood viscosity on the flow estimation were corrected by the hematocrit value. The value of the coefficient of determination, R2, between the estimated flow rate and the measured flow rate was 0.988. These results may indicate that the flow estimating method calculated by the power consumption of the motor, the rotating speed, and the hematocrit value is useful in the clinical situation.