Burn-up characteristics of ADS system utilizing the fuel composition from MOX PWRs spent fuel

Burn-up characteristics of accelerator-driven system, ADS has been evaluated utilizing the fuel composition from MOX PWRs spent fuel. The system consists of a high intensity proton beam accelerator, spallation target, and sub-critical reactor core. The liquid lead–bismuth, Pb–Bi, as spallation target, was put in the center of the core region. The general approach was conducted throughout the nitride fuel that allows the utilities to choose the strategy for destroying or minimizing the most dangerous high level wastes in a fast neutron spectrum. The fuel introduced surrounding the target region was the same with the composition of MOX from 33 GWd/t PWRs spent-fuel with 5 year cooling and has been compared with the fuel composition from 45 and 60 GWd/t PWRs spent-fuel with the same cooling time. The basic characteristics of the system such as burn-up reactivity swing, power density, neutron fluxes distribution, and nuclides densities were obtained from the results of the neutronics and burn-up analyses using ATRAS computer code of the Japan Atomic Energy research Institute, JAERI.     

Prenatal Exposure to Polycyclic Aromatic Hydrocarbons and Birth Outcomes

The effect of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) at the environmental level on birth size was examined. The concentration of 1-hydroxypyrene (1-OHP) in spot urine samples collected from 50 pregnant women in Tokyo was measured and was related to birth weight, length, and head circumference of the newborns the subjects delivered. Analysis of inter- and intra-individual variation in 1-OHP concentration in spot urine samples from non-smoking subjects revealed that single spot urine can represent the subject's exposure to PAHs over several weeks and utility of spot urine for assessing PAHs exposure level of non-smokers was indicated. Geometric mean urinary concentration of 1-OHP of the subjects was 0.056 μmol/mol creatinine, and smoking mothers (n = 7) excreted more 1-OHP (0.200 μmol/mol-cre) than non-smoking mothers (0.046 μmol/mol-cre). Multiple regression analysis using birth outcomes as the dependent variable and urinary 1-OHP and other covariates as independent variables revealed that urinary 1-OHP was not a significant variable to explain birth outcomes among non-smoking mothers.     

Friction and wear of carbon steel near T1-transition under dry sliding

The wear phenomenon of metals under dry sliding is, generally, divided into two modes of severe and mild wear. A discontinuous transition between the wear modes often takes place in a certain load range. The T₁-transition is usually observed at lower levels of load or sliding velocity. There is a great difference in wear rate between severe and mild wear. This indicates that the occurrence of severe wear should be avoided, especially in the field of machine design to prevent energy loss, occurrence of noise and vibration, and life reduction of machines and their components. Therefore, it is important for machine designers to know the relationship between friction and wear and the difference in properties of the wear surfaces in the two wear modes. In this study, wear tests of 0.35% C steel in contact with itself under constant load were conducted in moist air at various contact loads under dry sliding. The friction and wear were measured continuously throughout each test. After the tests, the relationship between friction and wear and the difference in properties of the wear surfaces were investigated in each wear mode. From the results, the upper and lower critical loads (P_acr and P_Acr) appeared between severe and mild wear. The phenomenon of zero wear has been newly found in the early period at very low loads. The zero wear continued for a long sliding distance and then changes to mild wear. The critical load between zero wear and mild wear is defined as P_zerowear. The load was changed once in a step-wise manner from low to high levels in process of test. Since the rubbing history under mild wear condition at the low load in the first stage affected the properties of wear surface, the wear mode at the high load in the second stage changed from ‘mild wear’ to ‘quasi-mild wear’ having a low rate. From the relationship between sliding distance necessary for the appearance of quasi-mild wear and contact load in the first stage, the boundary curve between severe wear and quasi-mild wear in the second stage is hyperbolic. This curve gradually approaches P_zerowear with decreasing contact load. Thus, P_zerowear is one of the important critical loads for elucidating the test results under varying load.     

Comparative analysis of the determinants of fees charged by fee-based homes for the elderly in urban and suburban areas

This study contributes to establishing the payment function of fee-based homes for the elderly. Disclosure statements from such homes for the elderly in selected urban and suburban cities in Fukuoka Prefecture, Japan—considered a typical prefecture with adjoining urban and suburban areas—were examined. The study compared the determinants of the amounts charged by the homes based on the distinct geographic features of urban and suburban areas. The hedonic price model was combined with a two-stage least squares regression to determine the determinants of lump-sum and monthly payments. We found that the factors that influence monthly payments in urban areas include distance to a park, distance to the coast, meals offered, number of care staff, and initial lump-sum payment. In contrast, factors such as room size, distance to a bus stop, distance to a park, and the number of night staff influence monthly payments in suburban areas. We conclude that the surrounding landscape has a greater influence on monthly payments in urban areas than in suburban areas. Moreover, in suburban areas, the number of night staff has a substantial impact on monthly payments. The results can help provide investment suggestions in certain cases depending on the amount of investment capital.

     

Effect of BaF2 powder addition on the synthesis of YAG phosphor by mechanical method

Here, we report on the effect of BaF₂ powder addition on the mechanical synthesis of Ce³⁺-doped Y₃Al₅O₁₂ (Y_2.97Al₅O₁₂:Ce_0.03³⁺, YAG:Ce³⁺) phosphors for white light emitting diodes. The YAG phosphors were synthesized by the mechanical method using an attrition-type mill. When BaF₂ was added at 6 wt% to the raw powder materials and milled, the synthesis of YAG:Ce³⁺ was favorably achieved at the vessel temperature of 255 °C, which was about 1200 °C lower than the YAG phosphor synthesis temperature by solid-state reaction. The synthesized YAG:Ce³⁺ phosphor revealed the maximum internal quantum yield of 57%.     

Boiling heat transfer from a horizontal flat plate in a pool of liquid hydrogen

Heat transfer from a flat plate facing upward immersed in a liquid hydrogen pool was measured for the pressures from atmospheric to 1.1 MPa. The flat plate heater used was 10 mm in width, 100 mm in length and 0.1 mm in thickness. Critical heat fluxes (CHFs) in saturated boiling increased with the increase in pressure up to around 0.3 MPa and then decreased with further pressure increase. The CHFs under subcooled condition at each pressure increased with the increase in sub-cooling. Discussions were made on the experimental results by comparing with those of the other cryogenic liquids and also the Kutateladze’s equations under saturated and subcooled conditions. The experimental CHFs were much smaller than the Kutateladze’s equation for higher pressure up to critical. The heater surface temperature was found to reach the critical temperature before the occurrence of hydrodynamic instability and jump to the film boiling regime at the lower heat flux in the higher pressure range. It was suggested that the CHFs are determined not by the heat flux but by the temperature in the higher pressure range.