Shojiro Kimura

Oxidized tritium around a research reactor site

The concentration and distribution of tritium in environmental samples obtained from sites near the Kyoto University Research Reactor were studied. About 5 GBq of tritium is discharged yearly from the KURR stack. The concentrations of tritium in the exhaust air, atmospheric moisture and precipitates were monitored to estimate not only any effects of tritium sources on the concentrations in the nearby environment but also the dilution factor of pollutants at the site boundary. The concentrations of tritium in surface water at the site were also monitored to identify the possibility of pollution in the water system. In both cases, there was slight contamination in samples near the site. The increased annual dose to an adult from tritium discharged in the atmosphere was estimated to be about five orders of magnitude lower than that from natural background radiation.

Electron spin resonance spectral analysis of irradiated royal jelly.

The analysis of unpaired electron components in royal jelly was carried out using electron spin resonance (ESR) with the aim to develop a detection method for irradiated royal jelly. The ESR spectrum of royal jelly had natural signals derived from transition metals, including Fe(3+) and Cu(2+), and a signal line near g=2.00. After irradiation, a new splitting asymmetric spectrum with overall spectrum width ca. 10mT at g=2.004 was observed. The intensities of the signals at g=2.004 increased in proportion to the absorbed dose in samples under different storage conditions: fresh frozen royal jelly and dried royal jelly powder at room temperature. The signal intensity of the fresh frozen sample was stable after irradiation. One year after 10kGy irradiation of dried powder, the signal intensity was sevenfold greater than before irradiation, although the intensity continued to steadily decrease with time. This stable radiation-induced radical component was derived from the poorly soluble constituent of royal jelly.

Volume Reduction of Municipal Solid Wastes Contaminated with Radioactive Cesium by Ferrocyanide Coprecipitation Technique

Municipal solid wastes (MSW) with elevated concentrations of radioactive cesium (rad-Cs hereafter) have been generated in some areas of Japan in the aftermath of the Fukushima Daiichi Nuclear Power Plant (F1 hereafter) accident. Both recycling and final disposal of the contaminated MSW have become a difficult problem in the affected areas, resulting in accumulation of treated residues in the treatment facilities.

Effect of spring water on the radon concentration in the air at Masutomi spa in Yamanashi Prefecture, Japan

The concentrations of 222Rn existing in air have been studied by using a convenient and highly sensitive Pico-rad detector system at Masutomi spa in Yamanashi Prefecture, Japan. The measurements in air were carried out indoors and outdoors during the winter of 2000 and the summers of 1999 and 2005. The concentrations of 222Rn in spring water in this region were measured by the liquid scintillation method. The concentrations of natural radionuclides contained in soils surrounding spa areas were also examined by means of the γ-ray energy spectrometry technique using a Ge diode detector to investigate the correlation between the radionuclides contents and 222Rn concentrations in air at each point of interest. The atmospheric 222Rn concentrations in these areas were high, ranging from 5 Bq/m3 to 2676 Bq/m3. The radon concentration at each hotel was high in the order of the bath room, the dressing room, the lobby, and the outdoor area near the hotel, with averages and standard deviations of the concentration of 441 ± 79 Bq/m3, 351 ± 283 Bq/m3, 121 ± 5 Bq/m3, and 23 ± 1 Bq/m3, respectively. The source of 222Rn in the air in the bath room is more likely to be the spring water than the soil. The spring water plays carries the radon to the atmosphere. Our measurements indicated that the 222Rn concentration in the air was affected by the 222Rn concentration in spring water rather than that in soil.