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Technical preparations for atmospheric radioactivity monitoring

Miyamoto Y., Oda T., Adachi T., Noguchi H., Nishimura H., Usuda S.

Nukleonika

2001

Vol. 46, nr 4

123-126

To evaluate the suitability of a location for a radionuclide monitoring station of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) at Takasaki, Japan, the assessment was done in terms of the concentration of natural background radioactive nuclides in airborne dust and soil samples. The samples were taken four times at the proposed site and several points around the site, then their radioactivities were measured by gamma-ray spectrometry. For the airborne dust samples, only natural background radionuclides: 212Pb, 7Be and 214Pb were detected. The radioactivity concentrations of these radionuclides varied in four sampling periods but were almost the same as the previous measurements. For the soil samples, the concentration of an anthropogenic radionuclide, 137Cs, fluctuated among the different sampling points and periods, but the concentration of 40K was constant. These concentrations were 2 to 3 times lower than those of the soil taken at JAERI Tokai. Based on these results, the proposed site was evaluated and has been accepted by the CTBT Organization as a CTBT radionuclide monitoring station.

In situ obsevations of solid-solid reaction : decomposition of barium titanyl oxylate and formation of barium titanate

Isshiki T., Nishio K., Shiojiri M., Noguchi H., Deguchi Y., Yamamoto H.

Electron Technology

1998

Vol. 31, No. 2

202-207

The thermal decomposition of BaTiO(C₂O₄)₂ 4H₂O and formation of BaTiO₃ were investigated by thermogravimetric analysis (TGA), differential thermal analysis combined with mass-spectroscopy (DTA-MS), high-temperature X-ray diffraction (XRD), and in situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TGA and DTA-MS showed that the dehydration occurred in a temperature range of 25 ÷ 240°C, followed by the decomposition of BaTiO(C₂O₄)₂ 4H₂O to BaCO₃, TiO₂, CO and CO₂ in a range of 240 ÷ 470°C. A porous structure showing the escape of CO and CO₂ gases was observed in an SEM image of a specimen at 400°C. Only diffuse peaks appeared in XRD charts in 200 ÷ 500°C, indicating that the BaCO₃ and TiO₂ are amorphous and/or micro-crystalline. XRD also disclosed that hexagonal BaTiO3 crystallites were formed by the solid-state reaction of the BaCO₃ and TiO₂ in range of 500 ÷ 650°C and then transformed to cubic crystals above 650°C. The direct formation of cubic BaTiO₃ crystals also occurred as a retareded reaction of the BaCO₃ and TiO₂ above 730°C.