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Abstract  

Determination of Th and U in acidic hot spring and crater lake waters was investigated by neutron activation analysis (NAA). Before neutron irradiation, Th and U were preconcentrated and separated from interfering nuclides such as alkali metals and halogens by coprecipitation with aluminium. Irradiation was carried out in two ways, viz., irradiation with Cd foil wrapping (epithermal NAA) and irradiation without Cd foil wrapping (normal NAA). The final determined values of Th and U were at ppb levels. Higher reliability of the determined values was obtained for Th than for U. It was found that epithermal NAA was more effective for the determination of these two actinides than normal NAA and was more effective for the determination of U than that of Th.

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Abstract  

Contents of lanthanoids (Ln's) of rock salts have been measured by neutron activation analysis. Original salt samples were treated in advance of neutron irradiation so that Ln's were enriched and amounts of interfering nuclides were reduced. The contents of Ln's were at ppt-sub ppb levels and were comparable with or slightly lower than those of solar salts. The Ln abundance patterns of the salts were those with relative depletion in the heavy Ln's, thus having negative slopes. It was indicated that, when salt deposit was formed, Ln's were taken up by anhydrite more preferentially than by halite.

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Abstract  

Uranium and thorium contents of solar salts were measured by neutron activation analysis. In advance of neutron irradiation, U and Th were concentrated and separated from some interfering elements by neutralization in which they were precipitated with aluminium hydroxide from solutions obtained by dissolving the salts in water or dilute nitric acid solution. The uranium and thorium concentrations determined were from several hundred ppt to 10 ppb. It was strongly indicated that uranium tends to remain in the solution (brine from seawater) phase in the process of solar salt production while thorium tends to transfer to the solid (solar salt) phase.

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Abstract  

Determination of the lanthanoids, thorium and uranium in silicate rocks has been investigated by neutron activation analysis (NAA). Seven or eight lanthanoids and thorium and uranium were determined by non-destructive instrumental NAA. The numbers of the lanthanoids determined were increased and errors on the final values were reduced by pre-irradiation treatments, which included a coprecipitation process with aluminium as collector to remove the alkali metals and halogens and a solvent extraction process to eliminate iron. The necessity of scandium removal was indicated.

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Abstract  

Neutron activation analysis was successfully applied to the determination of Th and U at ppt levels in a neutral hot spring water. Blank test corrections were found to be essential to reach the final determined values. Normal NAA is a better method for the Th determination than epithermal NAA, while both NAAs are nearly equally effective for U determination.

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Abstract  

Determination of the lanthanoids in a neutral hot spring water has been studied by menas of neutron activation analysis. The aluminium coprecipitation process, which used aluminium as the collector of the lanthanoids, was incorporated in the preparation of a sample for irradiation. Nine lanthanoids, La, Ce, Nd, Sm, Eu, Tb, Tm, Yb and Lu, were determined at ppt levels with satisfactory precision, indicating the effectiveness of aluminium coprecipitation.

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Abstract  

Gases released during the conversion of NH4Zr2(PO4)3 to HZr2(PO4)3 were identified using an apparatus in which gases released from a sample placed in a thermogravimetric analyzer were directly introduced to a gas cell of an IR spectrometer. Such acidic gases as N2O and NO were detected besides the basic NH3 gas, and their formation mechanism was discussed.

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Abstract  

The contents of arsenic in soils collected in the Kusatsu hot spring area, Gunma, Japan, were determined by INAA, with the average content of 36 mg/kg, which was obviously higher than that reported for the Japanese crust. The remarkably high contents of arsenic, 170 and 130 mg/kg, were observed in the soils collected near the discharge point of the surplus hot spring water. The distribution of arsenic in the ground suggests that arsenic originated from hot springs has been diffusing into the ground accompanying the penetration of the hot spring water.

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Abstract  

A brine sample and two deposit samples of a salt lake in China were analyzed for their contents of lanthanoids (Ln's), thorium and uranium by neutron activation analysis. Five Ln's were determined at sub ppb levels. Th and U contents were at about the same levels as those of Ln's. The lanthanoid abundance patterns (Ln pattern) of the three samples are similar to each other, each having a negative slope in the light Ln region. There seems no substantial difference in distribution between the solution (brine) and solid (deposit) phases among Ln's.

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