The object of the researches on analyzing downward flow to groundwater using222Rn concentration in water as an indicator has been saturated flow. However, when groundwater table is low, downward flow from surface is unsaturated flow. In this paper, the authors represented the relationship between 222Rn concentration in soil water and degree of saturation, and measured the vertical distributions of222Rn concentrations in groundwater and222Rn concentration in water table in the fields. As the results, it was found that222Rn concentrations in the vicinity of groundwater table decreased by unsaturated downward flow. Moreover, from the variation of222Rn concentrations in groundwater table, it was possible to show the occurrence of the unsaturated downward flow by paddy fields irrigation, i.e., the downward flow of the soil water pushed out by irrigation water, the unsaturated percolation in the irrigation period, and the redistribution of the soil water after the release of ponding water. The degree of saturation in downward flow was calculated to be about 50% from222Rn concentrations in the irrigation period and in the non-irrigation period. It was deduced that the value was within reasonable range considering the difference of the hydraulic conductivities between of the upper layer and of the lower layer. These results proved that the relationship between222Rn concentrations in soil water and degree of saturation represented by the authors was reasonable and that the analytical method using222Rn concentrations in groundwater table as an indicator was useful to analyze the actual state of unsaturated downward flow.
Performance test of ion implantation system in tandetron MeV accelerator was investigated by measuring of dose and dose uniformity of implanted ion. The Au content of four samples which were cut from the alminum specimen were determined by a neutron activation analysis after implantation of 3.99 -5.1 MeV Au2+. The Au contents (DNAA) of samples were more than the Au doses (DICM) which were determined by current integration, because of charge changing of Au2+into lower. The dose uniformities were drifted, for reason of ion beam moving which occured in the Cs sputter ion source. From these finding, it was estimated that the doses increased 10% approximately and the dose uniformities had the error of 5% approximately as the ability of ion implantation system in tandetron MeV accelerator.
We developed a simple radiation protector that can be readily used in daily examination of nuclear medicine. This protector is an injector barrel shielded with lead. The leakage dose rate using this protector in examination with99mTc and201Tl as nuclides was 6-9%. This protector was not difficult to manipulate, and seemed to be practical for examination of nuclear medicine. In addition, use of a lead injector table reduced the exposure dose to lower body and the exposure dose at the time of bolus administration using a 3-way stop-cock.