Evaluation of phosphate thermodynamic properties for spent electrolyte recycle

Adaptation of the phosphate conversion technique was undertaken and evaluated for application to the recycle process of the spent electrolyte generated from metal electrorefining process. In order to confirm the conversion behaviors of fission product (FP) chlorides to the phosphates, conversion experiments were carried out for some alkali metal, alkaline earth metals and rare-earth elements and their results were compared with that of thermodynamic calculations of previous study [I. Amamoto, H. Kofuji, M. Myochin et al., in: Proceedings of Global 2007, Boisi, Idaho, USA, 2007]. Among these elements, rare-earth chlorides were converted into phosphates and Cs was not, according to the prediction by the calculation. As for alkaline earth metals, their equilibrium constants were nearly 1 based on the results of the calculations, the conversion reactions were difficult to occur. In addition, it was clarified that phosphates were thermally unstable, easily to decompose at higher temperature, through the measurements of their heat flow and vapor pressure.     

Phosphates behaviours in conversion of FP chlorides

The spent electrolyte of the pyroprocessing by metal electrorefining method should be considered for recycling after removal of fission products (FP) such as, alkali metals (AL), alkaline earth metals (ALE), and/or rare earth elements (REE), to reduce the volume of high-level radioactive waste. Among the various methods suggested for this purpose is precipitation by converting FP from chlorides to phosphates. Authors have been carrying out the theoretical analysis and experiment showing the behaviours of phosphate precipitates so as to estimate the feasibility of this method. From acquired results, it was found that AL except lithium and ALE are unlikely to form phosphate precipitates. However their conversion behaviours including REE were compatible with the theoretical analysis; in the case of LaPO₄ as one of the REE precipitates, submicron-size particles could be observed while that of Li₃PO₄ was larger; the precipitates were apt to grow larger at higher temperature; etc.     

A novel prototype of auxiliary edge resonant bridge leg link snubber‐assisted soft‐switching sine‐wave PWM inverter

This paper proposes a new circuit topology of the three‐phase soft‐switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg‐commutation‐link soft‐switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three‐phase soft‐switching PWM double converter is more suitable and acceptable for a large‐capacity uninterruptible power supply, PFC converter, utility‐interactive bidirectional converter, and so forth. In this paper, the soft‐switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high‐power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three‐phase inverter switching. This three‐phase soft‐switching commutation scheme can effectively minimize the switching surge‐related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three‐phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have a trade‐off relation in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three‐phase soft‐switching PWM double converter can improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor device which is much improved regarding low saturation voltage. The effectiveness of this is verified from a practical point of view. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 64–76, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20207     

Long-range transport of fluoride in East Asia monitored at Noto Peninsula, Japan

Airborne particulate matter was collected at Wajima, the Noto Peninsula, Ishikawa, Japan by a high-volume air sampler with a quartz fiber filter every week from September 17, 2004 to September 16, 2005. The filter was newly changed every week. There are no major emission sources of atmospheric pollutants near the sampling site. Water-soluble fluoride anion extracted from the filters was analyzed by ion chromatography. The concentration of non-sea-salt fluoride was higher during the heating period of China (from October 15, 2004 to April 15, 2005), significantly higher during the period of Asian Dust (from the mid of April to the beginning of May in 2005), than that in the other seasons. This result suggests that the main contributor of fluoride in the period of Asian Dust was high-fluoride-concentrated soil from the arid area of China. A noticeable positive correlation (r = 0.54, n = 28, p < 0.01) between the level of non-sea-salt fluoride and PAHs was observed, when only the data obtained during the period of Asian Dust was excluded. In view of the fact that PAHs emitted from Northeast China were long-range transported to Japan during the heating period of China, fluoride emitted from coal combustion long-range transported from the Asian continent to Japan during the same period appears to be another main source of fluoride.     

Crack initiation strength of an interface between a submicron-thick film and a substrate

The focus of this study was to evaluate the fracture initiation criteria of the interface between a thin film and a substrate by Bogy’s, Kitamura’s and Griffth’s methods. The critical stress intensity parameter K_ijC in Bogy’s method and the concentrated stress parameter σ_ijC in Kitamura’s method were calculated based on the singular stress field near the interface edge. The work of separation per unit area Γ_ο in Griffth’s method was calculated based on the work of fracture process. The results obtained show that in comparison among interface strengths, the fracture toughness K_θθC and the concentrated stress parameter σ_θθC were respectively applied to material combinations with specific edge geometry and with weak stress singularity, while the work of separation per unit area Γ_ο was applied in all cases.     

Important roles of Fischer–Tropsch synfuels in the global energy future

This paper examines the potential roles of Fischer–Tropsch (FT) synfuels in the 21st century with a global energy model treating the entire fuel supply chain in detail. The major conclusions are the following. First, FT synfuels become a major alternative fuel regardless of CO₂ policy due to their low transportation costs and compatibility with existing petroleum infrastructure and vehicles. Secondly, the FT process brings stranded gas to world markets until around 2050. In a 550 ppm CO₂ stabilization case thereafter, producing FT synfuels from biomass, whose competitiveness is robust against its capital costs, and their interregional trade enable a worldwide diffusion of carbon-neutral fuels. This provides a significant source of income for developing regions, such as Latin America and Sub-Saharan Africa. Thirdly, FT synfuels play a crucial role in meeting the growing transportation energy demand and assuring diversified supplies of transportation fuels. Increasing portions of FT liquids are refined to FT-kerosene to be provided for the rapidly growing aviation sector in the second half of the century. Furthermore, upgrading FT-naphtha into FT-gasoline proves to be critically important. FT synfuels’ participation could help the development in Africa through technological contributions of the South African leading companies in the world synfuel industry.     

Measurement of cold neutron-beam focusing effect of a permanent sextupole magnet

The magnetic focus effect of cold neutron beam was measured using a permanent sextupole magnet and a gain of more than 35 was observed. The result was analyzed with a numerical simulation.     

Thermal stability of dye-sensitized solar cells with current collecting grid

Several endurance tests were carried out to investigate thermal stability of a dye-sensitized solar cell (DSC). In the case of applying an ionic liquid-based electrolyte, no obvious leakage of electrolyte components such as iodine was detected on keeping the cell at 85 °C. In addition, double-sealing package was applied to the cell by way of separate cell components from outer moisture. Based on the result, large-sized DSCs with current collecting Ag grid were fabricated, and over 1000 h stability of the cell was accomplished under the heat and humidity environment (85 °C, 85% RH). It was also showed almost no degradation of the performance under the heat and cool cycle stress (?40 and 90 °C) for more than 200 cycles.     

Thermal model of human body fitted with individual characteristics of body temperature regulation

To develop a thermal model that can predict the thermal responses of the human body under given environmental conditions, it is necessary for the model to be fitted with the individual characteristics of human body temperature regulation. As the basis for this, in this paper, it is shown that the coefficients that represent the thermoregulatory responses in the two-node model (thermal model of human body) can be identified for individuals. Six coefficients related to the regulation of sweating and skin blood flow in the two-node model are tuned for the individuals involved in the experiments—the core and skin temperatures calculated by the model are fitted with the measured results for the entire thermal transient processes, including exposures to heat and cold.     

Magnetic image detection of the stainless-steel welding part inside a multi-layered tube structure

The stainless-steel welding part inside a multi-layered tube was successfully detected using low-frequency magnetic imaging. The magnetic images were obtained by the developed measurement system, consisting of an exposure coil, magnetoresistive (MR) sensor, lock-in amplifier, x–y stage, revolving stage with a horizontal level stage and personal computer. To expose the magnetic field to a wide area of the stainless-steel sample, the radius of the exposure coil was made comparable to the sample size. The MR sensor measured the vector components of the magnetic field generated from the sample within the range of low frequencies between 50 Hz and 1 kHz. A cylindrical stainless-steel sample was fabricated as a tube by rolling a stainless-steel sheet and welding each edge using arc welding with argon as shielding gas. The normal components (B_z) and tangential components (B_x and B_y) to the sample surface were measured by scanning the MR sensor on the sample surface and the magnetic characteristics of each of the component images were documented. As a result, the difference in permeability between the weld area and the base material was successfully visualized as magnetic images.