Re-evaluation of Radiation-Energy Transfer to an Extraction Solvent in a Minor-Actinide-Separation Process Based on Consideration of Radiation Permeability

ABSTRACT

Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process.     

Contribution of metal vapor mass at periphery part of pulsed arc to electromagnetic force in weld pool

The arc welding has been used in various welding methods because it is inexpensive and high in strength after welding. However, it is a problem that accidents such as collapse of the bridge occur because of the welding defects. The welding of low cost and high productivity is required without the welding defects. The pulsed TIG welding is inexpensive and capable of high‐quality welding. The electromagnetic force contributing to penetration changes because the transient response of arc temperature and iron vapor generated from anode occurs. However, the analysis of pulsed TIG welding with metal vapor has been elucidated only metal vapor concentration near anode with transient phenomenon and heat flux. Thus, the theoretical elucidation of penetration depth with control factor has not been researched. In this paper, the contribution of metal vapor mass at the periphery part of pulsed arc to the electromagnetic force in the weld pool is elucidated. As a result, the iron vapor mass at periphery part decreased with increasing the frequency. The iron vapor was stagnated at axial center within one cycle. The electromagnetic force to the penetration depth direction in weld pool increased at axial center. Therefore, the metal vapor mass at periphery part plays an important role for the electromagnetic force increment at axial center.     

Functional activation of cerebral blood flow abolished by scopolamine is reversed by cognitive enhancers associated with cholinesterase inhibition: a positron emission tomography study in unanesthetized monkeys

The effects of somatosensory stimulation on the regional cerebral blood flow (rCBF) response were studied in unanesthetized monkeys before and after treatment with scopolamine and three cognitive enhancers (physostigmine, E2020 and tacrine) that inhibit cholinesterase, using 15O-labeled water and high-resolution positron emission tomography. Under control conditions, somatosensory stimulation induced a significant increase in the rCBF response in the contralateral somatosensory cortex of monkey brain. Intravenous administration of scopolamine (50 microg/kg) resulted in abolishment of the rCBF response to stimulation. The rCBF response abolished by pretreatment with scopolamine was recovered by administration of physostigmine (1 or 10 microg/kg), E2020 (10 or 100 microg/kg) or tacrine (100 or 1000 microg/kg), in a dose-dependent manner. The effect of E2020 (100 microg/kg) on the rCBF response lasted for >4 hr, whereas the effects of physostigmine and tacrine were of shorter duration. These findings suggest that these compounds reversed the scopolamine-abolished rCBF response to somatosensory stimulation via enhancement of cholinergic neurotransmission, which was mainly induced by cholinesterase inhibition.     

Facile optical resolution of amino acid esters via hydrolysis by an industrial enzyme in organic solvents

Racemic amino acid esters were optically resolved via hydrolysis in organic solvents by the catalysis of an industrial alkaline protease, “Alcalase”. The products which were composed mainly of L-amino acids were insoluble and easily separated by filtration. The activity of the enzyme and enantiomeric excess of the products were significantly dependent on the nature of solvent and the water content in the reaction media. Generally, high values of enantiomeric excess were obtained at low water contents. Many natural and unnatural amino acids were resolved by this method.     

Water structure and improved mechanical properties of phospholipid polymer hydrogel with phosphorylcholine centered intermolecular cross-linker

We investigated the water structure and the mechanical properties of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer hydrogels cross-linked with a novel hydrophilic 2-(methacryloyloxy)ethyl-[N-(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC) for soft contact lenses (SCL) applications and commercial methacrylic cross-linkers were in addition used for comparison with MMPC. Water structure in hydrogels, which influences the protein adsorption by dehydration was determined by differential scanning calorimetry. MMPC increased the freezing water content of the MPC polymer hydrogel compared with hydrophilic N,N′-methylenebisacrylamide (BIS) at the same water content. MMPC also improved fracture strength of the MPC polymer hydrogel to 120 kPa in tensile, which was considerably higher than that hydrogel cross-linked with BIS. It is suggested that MMPC shows higher cross-linking reactivity with MPC than BIS. We concluded that the MMPC increase both the free water content and the tensile properties. The MPC polymer hydrogel cross-linked with MMPC can be a useful SCL biomaterial.     

Ethanol production from raw starch by a recombinant yeast having saccharification and fermentation activities

In order to develop a method for converting raw starch into ethanol efficiently, direct fermentation of ozonized raw starch using a recombinant yeast was investigated. Ozonolysis was carried out as a pretreatment to convert raw starch into ethanol rapidly and efficiently, and then the effect of the ozone degradation conditions on the degree of polymerization and the amount of amylose in a raw starch was determined. Since the degree of polymerization was low and the amount of amylose was high, raw starch treated with an ozone concentration of 40 gm^?3 and an ozonation time of 30 min was the material chosen for alcohol fermentation. Though the recombinant yeast could not convert the untreated raw starch, it converted the soluble starch and the ozonized raw starch at a comparatively high yield into ethanol. About 56% of the ozonized raw starch decomposed, and the ethanol concentration obtained from the ozonized raw starch was markedly greater than that obtained from untreated raw starch. The dynamic behavior of cell growth, substrate degradation, and ethanol production was examined in a continuous culture under various dilution rates, and the optimal dilution rate, ie 0.15 h^?1, was determined for maximizing the ethanol productivity (amount of ethanol produced per unit time). © 2002 Society of Chemical Industry     

Coal liquefaction by in-situ hydrogen generation.: 2. Zinc-water model compound reactions

Model compound studies were carried out to elucidate the reaction mechanisms taking place during the liquefaction of coal with the hydrogen produced from the reaction of zinc and water. In compounds of the type Ph-(CH₂)_n-Ph the splitting of the aliphatic bridge was easier with higher n values. Ether type compounds such as diphenylether were unreactive although the C-O bond in dibenzylether was easily cleaved. Condensed ring aromatic compounds gave low conversion with hydrogenation being facilitated by an increase in ring number. Phenolic compounds such as phenol did not react well, but the reactivity increased with increase in aromatic ring size. The cleavage of the aliphatic bridge was accelerated by the OH group, for example, in the case of 4-hydroxydiphenylmethane bond scission was about 15 times higher than that of diphenylmethane. Heterocyclic compounds were unreactive.     

Anodic polarization of aluminium in organic electrolytes

The polarization characteristics of aluminium anodes have been studied in various organic electrolytes containing aluminium chloride. The small amount of oxide present on the metal was dissolved by an anodic pre-treatment. The charge transfer number of the overall reaction was three. The current density supported by the electrolytes decreased in the order nitromethane>acetonitrile >propylene carbonate, formamide>tetrahydrofuran. The rest potential increased in the order formamide     

Thermodynamic Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylammonium Propionate

The phase equilibrium temperature and dissociation heat of tetrabutylammonium propionate (TBAPr) hydrate are reported. TBAPr hydrate is a type of ionic semiclathrate hydrates and also could potentially be used as thermal energy storage material. The temperature‐composition phase diagram of the TBAPr hydrate was determined in a defined range of mass fractions. Considering the dissociation heat of differential scanning calorimetry (DSC) measurements, multiple peaks of heat flow were observed in the TBAPr‐water system at the TBAPr mass fraction lower than 0.35, and there was a single peak at the mass fraction higher than 0.37.     

Optimal Digital Controller Design for a Servo Motor Taking Account of Intersample Behavior

A continuous‐time plant with a discretized continuous‐time controller does not yield stability if the sampling rate is lower than some certain level. Thus far, high‐performance electronic control has made use of expensive hardware needed to implement discretized continuous‐time controllers; low‐cost hardware generally does not have a sufficiently high sampling rate. This technical note presents results comparing performance indexes with and without intersample behavior, and provides some answers to the question of how a low‐specification device can control a plant effectively. We consider a machine simulating wafer handling robots, which is an electromechanical system driven by a direct drive motor, at a semiconductor factory. We illustrate the controller design for the robot with and without intersample behavior, and present simulations and experimental results using these controllers. Taking intersample behavior into account proves to be effective in improving control performance and makes it possible to choose a relatively long sampling period. Controller design in terms of the performance index with intersample behavior makes it possible to deal with situations in which a sufficiently short sampling period may not be employed, and freedom of controller design may be widened, especially regarding the choice of the sampling period.