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[en] A method for the determination of radium in environmental water by means of a liquid scintillation counting technique has been developed. The radium was collected on cation exchange resin with 100% recovery by the batch method. The other radionuclides except uncomplexed elements such as cesium can be removed by washing the resin with 0.01 M EDTA solution at pH 8. The counting sample was prepared by immersing the resin into emulsion liquid scintillator in a Teflon vial. The chemical procedure took about 2 h and the detection limit was 0.03 pCl of 226Ra/L
[en] Excitation functions for the proton induced reactions on 151Eu and 153Eu have been measured by activation method up to Esub(p) = 52 MeV. The measurements are carried out on reactions to the residual nuclei- sup(146,147,148,149,151,153)Gd and sup(146,147,148,149) Eu. The measured excitation functions are discussed with the theory based on the statistical model of the compound nucleus. (author)
[en] Although radon loss should be taken into account when determining the amount of radon in a water sample, only a few papers have exclusively investigated the factors connected to radon loss. To clarify radon loss behavior, this study examines the temporal changes in depth profiles using a large volume of natural water in a simple system where the effects of external factors (pressure, stirring, air convection, etc.) are suppressed. Analyzing the results using a box model indicates that at low temperature, the depth profile of the residual radon at the surface remarkably decreases, but at high temperature the depth profile is uniform. The exponential decrease of the total residual radon in water depends on the elapsed time and temperature. In addition, the box model analysis provides the activation energies of transfer from water to air and in water. The water depth profiles are formed by the supply balance of radon from deep water to the surface and the discharge of radon from the surface to the air. (author)
[en] Time-resolved absorption imaging using synchrotron radiation X-rays allows us to observe solidification of metallic alloys of interest. This paper presents peritectic solidification in Sn-Cd alloy and Fe-C alloys. In unidirectional solidification of Sn-Cd alloy, the formation of a banded structure, in which two phases were alternatively piled up in the growth direction, was clearly observed. Sequence of nucleation or fluctuation of triple junction (primary phase / secondary phase / liquid) resulted in the banded structure. Ease of nucleation for both phases contributed to the banded structure formation. In carbon steel (Fe-0.45mass%C), the transformation from δ phase to γ phase was observed. At lower cooling rates, γ phase was produced in semisolid state of δ phase and liquid, indicating the peritectic reaction occurred during solidification. In contrast, δ phase transformed into γ phase when solidification nearly completed at temperatures 100K below the liquidus temperature. Namely, the transformation seemed to be massive. The observation showed that two different transformation modes operated in Fe-C alloy.
[en] Massive radionuclides were released into the environment due to the Fukushima Daiichi nuclear power plant (FDNPP) accident in March 2011. The concentrations of Pu and 110mAg in a soil sample that was collected in Futaba-machi located at 4 km north-west of FDNPP were measured by α-spectrometry and γ-spectrometry, respectively. The analytical result suggests that Pu isotopes are deposited in the soil as particles with high radioactivity (hot particles), although the 110mAg isotope is deposited uniformly like as Cs isotopes in a soil sample. (author)
[en] Due to Fukushima Daiichi nuclear power plants accident, a large amount of radionuclides were released into environment. The radioactivities of "1"3"4Cs, "1"3"7Cs, "1"1"0"mAg, "2"3"8Pu, and "2"3"9"+"2"4"0Pu in a soil sample collected in Futaba, Fukushima were determined by α spectrometry or γ spectrometry. We searched for the dispersion of these radioactivities in a soil sample, which suggests the existence of hot particles for Pu contamination. (author)
[en] Time-resolved in situ observations using synchrotron radiation X-rays showed that γ nucleation difficulties resulted in a massive transformation from the δ phase to the γ phase. The massive transformation occurred even in high-carbon steel (0.45 mass% C) at a cooling rate of 0.33 K/s or more. A crystallographic relationship in which the close-packed (111) plane of the γ phase tended to coincide with the close-packed (110) plane of the δ phase suggested that the γ phase nucleated in a favorable plane in the δ phase. Observations of the sequence in the initial stage of solidification showed that the induced strain and strain rate in the massive transformation were larger than those expected in peritectic solidification. These observations will help us to understand deformation of solidifying shells and to build a physical model.
[en] Indoor Rn (222Rn) concentrations in Japan were measured to estimate the effective dose to the general public due to Rn and its progeny. Twenty houses were selected in each prefecture throughout Japan. As a total, 940 houses were subjected to the measurement using passive Rn monitors. The Rn monitor was installed in a bedroom or a living room in each house for four successive three-month periods. The annual mean indoor Rn concentration was estimated from the four measurements in each house. The mean, median and geometric means of indoor Rn concentration in Japan were obtained to be 15.5, 11.7 and 12.7 Bq m-3, respectively. The Rn concentration shows approximately a log-normal distribution. Seasonal and structural dependence of Rn concentration was observed. The effective dose to the general public due to Rn and its progeny was estimated to be 0.45 mSv y-1 in Japan. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)