Thyroid uptake of radioactive iodine incorporated into the body is inhibited by the administration of stable iodine tablets. In this paper, the thyroid retention functions in the case of the acute inhalation of 131I for Japanese were analyzed by using the biokinetic models of radioactive and stable iodine. The influence of the Wolff-Chaikoff effect that the composition of thyroid hormone is temporarily inhibited by the intake of superfluous stable iodine is newly taken into consideration in the analysis of stable iodine. By comparing the computed thyroid retention functions between with and without the administration of stable iodine tablets, the inhibitory effects of the 131I thyroid uptake are evaluated. As a result, the inhibitory effect reaches about 50% when administration was conducted 2days before 131I intake and it increases more than 80% in case of from 1day to just before the intake. On the other hand, the inhibitory effect falls rapidly when administration was conducted after the intake, resulting in 20% or less than 7% in case of 12hours or 1day after the intake.
Spatial distribution of radon concentration in spring water and its seasonal variation were investigated at Mt. Kirishima. Springs distributed at the elevation of 160 to 480m and 760 to 1063m have high radon concentration and those are mainly on the Middle to Late Pleistocene volcanic rocks. Seasonal variation of radon concentration was found on the 7 spring sites and examined. As a result, the condition of groundwater flow near the spring site would be affected to the seasonal variation of radon concentration without rainfall infiltration or volcanic gas.
This paper addresses the temporal variation of air dose rate and radioactive caesium activity at the lawn sites of baseball stadium located at the Chiba Prefectural Kashiwa-no-ha Park. Collected lawn samples were separated to vegetation part and soil part, and they were measured individually by gamma spectrometry using a germanium detector to determine the radioactive caesium activity. According to the results obtained, the thatch layer(surface layer of lawn with dense accumulation of death and living vegetation) showed higher activity of radioactive caesium compared to the soil lying underneath the thatch layer throughout the study period. We measured 70% of air dose reduction rate(the natural radiation derived from the ground was subtracted for calculation) at the height of 50cm above the ground when the lawn was uniformly mowed at the depth of 20mm, that is to say, removing the thatch layer is an effective decontamination method.
Neutron is very sensitive probe to observe hydrogen in materials, especially in metals. Since metal hydrides contain all kind of bonding(ionic, covalent and metallic bonding), they emerge a variety of properties and function. It is essential to observe the dynamics of hydrogen because of its wide spread wave functions and largely spaced vibrational energy levels. Neutron scattering technique is reviewed for the observation of hydrogen dynamics in metal hydride mainly consist of transition metals including lanthanoid element.