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  • Author or Editor: T. Sasaki x
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Abstract  

Distribution coefficients /Kd/ of lanthanide elements on layered hydrous titanium dioxide, H2Ti4O9.nH2O /where n=1.2–1.3/, have been determined as a function of the pH of the aqueous phase. The plots of 1g Kd vs. pH gave straight lines with slopes equal to +3 except for the data for heavier lanthanides, suggesting ideal ion-exchange equilibria between tervalent cations in the aqueous phase and hydrogen ions in the hydrous oxide. Mutual separations of La–Cs and La–Ba have been achieved on a column of this material on the basis of large differences in affinities between the metal ion pairs.

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Abstract  

Copper phthalocyanine ( and forms) in neat solid or in dissolved state in conc. H2SO4 was neutron-irradiated, and retention values of64Cu and66Cu were estimated to study whether or not there is any isotope effect in retention between these two (n, )-produced radionuclides. The data show that there is an isotope effect expressed by the ratio of retention of66Cu to that of64Cu, ranged from 1.29±0.12 for form dissolved in conc. H2SO4 to 1.09±0.02 for form in neat solid irradiation. This result coincides with the tendency anticipated from the recoil energy spectra which were computed by a program using Monte-Carlo method.

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Abstract  

Recoiling behaviour of55Cr produced by54Cr/n, /55Cr reaction was studied by choosing solid Cr/acac/3 or its benzene solution as target material and by using rapid separation technique. The approximate retention value /R-value/ of55Cr, defined as the percentage of the activity retained in the benzene phase which was not extracted with an oxalic acid solution, was found to be higher than that of55Cr for practically all experimental runs tested /15 runs/. The ratio (55Cr/51Cr) was 1.115±0.027.

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Abstract  

A large reprocessing plant of spent nuclear fuel is now under construction in Rokkasho-village, Aomori Pref. Japan. We carried out the survey of tritium concentration in water vapor and precipitation on the top of Mt. Hakkoda, to grasp the behavior of tritium in the environment of Aomori Pref. The tritium concentration in water vapor and precipitation tended to increase from spring through summer. Deuterium concentration in water vapor is lower than precipitation and the effect of the isotope separation by evaporation was observed. The tritium concentration in water vapor, however, is a little bit higher than precipitation. The tritium concentration in water vapor showed the similar change on the top of Mt. Hakkoda and also the wide region covering Rokkasho-village from Aomori-City. Also, on the top of Mt. Hakkoda the correlation was observed between the tritium concentration in water vapor and ozone concentration.

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Abstract  

Separation method of a few ppb of uranium and thorium in tantalum metal by ion exchange for neutron activation analysis was established. After dissolving tantalum metal by hydrofluoric acid, uranium and thorium were separated from tantalum using cation exchange resin column in 0.5M hydrofluoric –0.65M boric acid media. Both of the yields for uranium and thorium during separation were above 95% and the remaining amount of tantalum be lowered below 400 ng.

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Understanding the relationship between the distribution of organisms and their environment is important for regional conservation planning. While most herpetofaunal community studies address environmental influence on species richness, few studies describe environmental influence on species composition at geographic scales. Field surveys of herpetofauna were conducted during 1994-2000 in Tochigi Prefecture, which covers ca. 6400 km_ of mainland Japan and includes a wide range of elevation, annual mean temperature, and human population densities. We evaluated whether (i) regional herpetofauna are distributed along a gradient of climate and elevation, as well as land cover and land use, and (ii) 'climate/elevation' and 'landcover' variables differ in their relative contribution. Ordination indicated a strong geographic gradient in species composition that was correlated with climate, elevation, land cover and land use. Reptiles were strongly influenced by land cover and land use (residential, agricultural, and forested area), while amphibians responded to all gradients (climate, elevation, and land cover and land use). All species with declining populations listed in the Prefectural Red Data Book were associated with mid-elevation regions, where anthropogenic modification is most intensive. All exotic species were strongly associated with anthropogenic gradients.

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Abstract  

The lowest retention values of51Cr hot atom in various forms of the -diketonetype complexes, Cr(bzac)3, Cr(dpm)3 and Cr(dbm)3, as well as Cr(acac)3 as a reference, were obtained in the experimental condition in which they are regarded as the primary retentions. From these retention values, the threshold energies for producing a hot atom, the appearance energies, were estimated using the calculated relationship between the primary retention and appearance energy, which was obtained by the recoil energy spectra computed by the method recently developed by us. The appearance energy increased steeply with increasing molecular weight of the complex. A theoretical interpretation for this result was attempted by setting a model in which a hot atom is produced in the center of the complex and receives the stopping action by the surrounding ligand molecule. The agreement between the observed and calculated values was good.

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Abstract  

Uranium concentration and the 234U/238U activity ratio have been measured for the Tatsunokuchi hot spring waters of Ishikawa Prefecture in Japan, collected periodically over a long period (1977-2000). The concentration of 238U varied drastically between 0.045 and 1.02 mBq/l (a factor of about 20), while the 234U concentration was almost unchanged, ranging from 2.30 to 3.07 mBq/l. Resultant 234U/238U activity ratios showed a wide range from 2.7 to 51. Equilibrium calculation by using the geochemical code showed that U for one end-member representing low uranium contents and very high 234U/238U ratios was expected to exist as UO2(CO3)2 2-. By using the U isotopic and 14C dating methods, the age of this water was roughly estimated to be in the range of 104-105 years.

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Abstract  

Environmental conditions were evaluated by element concentrations in hair of children living near the Aral Sea. Hair samples were provided by 63 children living near the Sea (K-district), and 143 children living about 600 km from the Sea (Z-district). PIXE was applied for the determination of elemental concentrations. The concentrations of Br, Na, Hg, and Ni were higher in K-district, and those of Al, Ca, Cr, P, S, and Si were higher in Z-district than in the other district, respectively. It is considered that these results reflect the environmental situation.

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Abstract  

The separation efficiency of hollow-filament polyimide membranes for 3H and 41Ar is preliminarily examined for a potential application to continuous gas monitoring systems for analysis of stack emission from accelerator facilities. The basic gas separation characteristics of the membranes are experimentally investigated, and a preliminary gas monitor design is proposed. The results indicate that the membranes are capable of selectively enriching hydrogen by more than 25 times, with negligible variation with respect to the species of isotope.

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