Search Results
You are looking at 1 - 10 of 13 items for
- Author or Editor: H. Ishikawa x
- Refine by Access: All Content x
Abstract
The application of stable isotope analysis using neutron-induced prompt 
-ray analysis (PGA) with cold/thermal neutron beams for the tracer study of geological materials are discussed. Silicon has three natural isotopes differing in abundance:28Si (92.23%),29Si (4.67%) and30Si (3.10%). For the purpose of the assessment of Si migration in engineered barrier material, enriched30Si can be used as a tracer due to its nuclear and chemical properties. Isotope analysis of30Si was performed by PGA during the tracer study. Neutron intensity at the sample position was 1.4·108 n¢cm–2·s–1, 2.4·107 n·cm–2·s–1 for cold and themal neutron guided beams of JRR-3M, respectively. Calibration curves and analytical sensitivity of30Si were determined based on measurement of standard samples. BG and detection limits for30Si analysis were also measured in Japanese bentonite (Kunigel V1 and Kunipia F) and their pore water. Fiffteen elements were determined simultaneously using PGA.
Abstract
Water originated from groundwater systems can have relatively high concentration of radon. In many situations, radon is released from the water and mixes with the indoor air. In the present study, laboratory experiments were conducted to characterize the airborne radon released by showering and the use of a washing machine. The followings were discussed: (1) a comparison between the loss of waterborne radon and the increase of airborne radon, (2) time-related changes in airborne radon after the water use, (3) changes in the equilibrium factor, and (4) the relationship between radon concentration and the distance from the source of radon release.
Abstract
The resolution of a 33±3 
m microprobe focussed with quadrupole doublet installed at the 3 MV Van de Graaff of the National Institute of Radiological Sciences was used for this analysis. Brown algae, Hijiki,Hizikia fusiforme was the sample target bombarded with a 2 MeV proton beam collimated mechanically into a rectangular image of 100 m × 700 m. Scanning across the sample target prepared into a longitudinal section from the caulis of the algae provided the following observations. More than 12 elements such as Al, Si, P, Cl, Ca, Mn, Fe, Cu, Zn, As, Br and Sr were determined simultaneously, together with their distributional information across the diameter. In the medullary layer, Mn and Zn were specific in their accumulation, while the deposition of Fe, Cu, As and Br were observed to be high in the epithelial layer, especially Fe and Cu which were found on the surface, where they contact ambient sea water, but no significant change in pattern was indicated for such elements as Al, P and Cl. The PIXE microprobe analysis was, therefore, effective in its detectability for elements below a few ppm level, resultantly provides further possibilities for collecting information from bio-medical and environmental samples on trace characterization of elements.
Abstract
A convenient non-destructive method for the determination of low level210Pb and226Ra with an ordinary high-purity Ge-detector is presented. The ordinary Ge-detectors used in this work were available to measure 46.5 keV 
-rays of210Pb. These detectors were also useful for the non-destructive analysis of low-level226Ra in lime-stone and calcium chemicals when a stream of nitrogen gas was maintained around the detectors. By this method, measurements could be carried out not only for210Pb and226Ra but also for other -emitting radionuclides simultaneously, using the same detector. The detection limits of about 1 Bq per sample for210Pb and about 0.05 Bq per sample for226Ra, respectively, were estimated, when the samples were counted for 1–2 days.
Abstract
The balance of essential elements in organisms can be changed by environmental stresses. A small fresh water fish, the medaka, was irradiated with X-rays (total dose: 17 Gy, which is not a lethal dose for this fish). Essential elements in the liver, gall bladder, kidney, spleen, heart and brain of the fish were measured by the particle induced X-ray emission (PIXE) method and compared with those of a control fish. Various changes in the elemental balance shift were observed. The PIXE method can analyze many elements in a small sample simultaneously, and so the changes in elemental content induced by irradiation were readily determined.
Abstract
Microbeam analysis is used in biomedical and environmental sciences to determine the presence and concentration of trace elements. However, quantitative analyses of biological samples are challenging because the chemical and physical compositions of existing standards differ from those typically encountered in biological samples. We developed a thin standard using polyvinyl alcohol and assessed its quality by microbeam scanning particle induced X-ray emission (micro-PIXE) analysis. The relationship between metal concentration and X-ray intensity was linear for certain standards up to 500 μg·g−1. Using this new thin standard, micro-PIXE analysis of Zn content in samples of human hair agreed well with analysis performed by inductively-coupled plasma mass spectrometry, validating the use of these new thin standards for quantitative mapping with microbeam analysis.
Abstract
The cesium isotope 135Cs has an extremely long half-life (τ1/2 = 2.3 · 106 y) and its high water solubility leads to the anxiety of exudation to ground water during geological disposal. Such a LLFP 135Cs would be converted into 136Cs (Its half-life is 13.16 d and it becomes stable 136Ba) by neutron capture reaction. However intermingling 133Cs of which the natural abundance is 100% disturbs this nuclear converting reaction because 133Cs also absorbs neutrons and produces 135Cs again. For separating 135Cs from other cesium isotopes, laser-chemical isotope separation (LCIS) is believed to be suitable mainly due to the light absorption and emission stability. Isotope separation of alkali metal 85Rb/87Rb was successfully achieved, showed 23.9 of head separation factor by LCIS. The measured isotope shift of Cs D2 line is within the reach of available semiconductor lasers having emission line width of less than 1 MHz, which shows that the selective excitation of 135Cs may turn to be possible. It is known that cesium excited to the 62P3/2 state may forms cesium hydride while ground-state cesium does not. Therefore if the lifetime of 62P3/2 state is sufficiently longer than the inverse rate of the chemical reaction, 135Cs can be extracted as cesium hydride. Applicability of the Doppler-free two-photon absorption method for selective excitation and further evaluation on Rydberg states and ionization should be investigated.
Abstract
Positron annihilation lifetime measurement and Fourier transform infrared spectrometry were applied to the study of temperature dependencies of free volume parameters and hydrogen bonds in segmented polyurethane, specially fabricated as a shape memory polymer. The variation of free volumes in amorphous region were correlated to that of hydrogen bonding and the shape memory mechanism of polyurethane is elucidated from a microscopic point of view. The relationship between free volume contents and the formation of hydrogen bonds significantly suggests that the shape memory occurs due to the configurational recovery of the microscopic regulation around urethane bundles of hard segment and consequent restoration of soft-segment in polyurethane.
Abstract
Indoor airborne radon concentration released from water was estimated over several months based on experimental measurements. When heated water including radon was used, the radon level became high in the entire house. Filling the bathtub with hot water had a strong effect on the indoor radon level. In winter, the indoor radon concentration was high due to windows being closed. The radon transfer coefficient was estimated 2.5·10−4 in this test house. This is 2.5 times higher than the average radon transfer efficiency estimated by UNSCEAR.
Abstract
Eleven elements in hepatocyte of mice fed with zinc deficient diet and those fed with control diet were determined by INAA. Zinc concentration, especially, in cytosolic fraction of zinc deficient mice was lower than that of control ones. On the other hand, cobalt concentrations in all fractions of zinc deficient mice were higher than those of control ones. However, when SDS-PAGE was performed for cytosolic fraction of hepatic cells, the positions and the number of the protein bands on gel developed for zinc deficient mice were not different from those for control ones.
