381 research outputs found

    Effect of ashing temperature on accurate determination of plutonium in soil samples

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    An acidic leaching method using HNO3 is widely employed to release the global fallout Pu from soil samples for further chemical separations in radioecology and toxicology studies, and in many applications using Pu as a useful tracer. In the method’s sample ash treatment step to decompose organic matter in soil, various ashing temperatures (400 – 900˚C) are used. However, the effect of ashing temperature on the accurate Pu analysis has not been well investigated. In this study, two standard reference soils (IAEA-soil-6 and IAEA-375) were used to determine the ashing temperature effect (from 375 to 600˚C) on HNO3 leaching method. The Pu analytical results of both standard reference materials showed that lower 239+240Pu activity was observed when the ashing temperature exceeded 450˚C, and the 239+240Pu activity continue to decrease as the ashing temperature was raised. Approximately 40% of the Pu content could not be leached out by concentrate HNO3 after ashing for 4 h at 600˚C. The Pu loss was attributed to the formation of refractory materials, which are insoluble in HNO3 solution. This hypothesis was confirmed by the XRD analysis of soil samples which revealed that plagioclase-like silicate materials were formed after high temperature ashing. To ensure the Pu release efficiency in HNO3 leaching, we recommend 450˚C as the ideal ashing temperature. This recommendation is also useful for analysis of other important artificial radionuclides (e.g. 137Cs, 90Sr, 241Am) for which an ashing process is needed to decompose the organic content in soil samples

    On the Examination of the Results from Quality Control and Field Measurements for Fujioka Dam

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    In the construction of recent high earth dams, sufficient field observations and maintenance after construction, as well as severe qality control during construction, are required in order to confirm high margin of safety of the embankment. In the present paper, field observation data for settlements, earth pressures, pore water pressures and discharge through the dam body and abutment foundations, which were obtained in an existing high earth dam, were examined and compared with quality control data during construction. Some remarks were then offered for the interpretation and the use of field data for improving the method of quality control

    Comparison of the simulated and LIDAR measured atmospheric density and temperature in transitional flow regime

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    The understanding of the atmosphere in the transitional flow regime is quite limited,due to the limited accuracy of measurement data.In the proposed paper,the atmospheric density and temperature at around 100 km altitude are analyzed,by using numerical simulation,empirical model,satellite data an..
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