Studies were carried out to investigate iodine contents in human milk with relation to dietary algae consumption by nursing women and to estimate stable iodine intake by breast-fed babies. The iodine contents in human milk collected from the Tokai-mura area showed a fairly wide variation ranging from 80 to 7, 000μg/l, though the highest frequency was around 150μg/l. It was observed that high contents were closely related to the intake of tangle (Konbu), Laminariaceae, specifically tangle stock and/or tangle shavings (Tororokonbu) as soup. The temporal increase was followed by the rapid decrease when the mothers stopped taking the tangle stock and/or tangle shavings soup. It was observed that water-extractability of iodine from tangle was much higher than that from the other algae, and the water-extractable iodine was absorbable to the human body.
A sampling system for atmospheric tritium in the form of water vapor, hydrogen and hydrocarbons was designed and built. The air was passed first through molecular sieve which adsorbed water vapor, then over palladium catalyst which oxidized hydrogen and adsorbed resulting water in situ, and finally over hot Hopcalite catalyst, which oxidized hydrocarbons and the resulting water was adsorbed on a following molecular sieve column. Three water samples were extracted from adsorbers and their tritium contents were measured by liquid scintillation counting. Performances of this sampler were examined for retrieval of tritiated water from molecular sieve, oxidation of hydrogen on palladium catalyst and oxidation of methane on Hopcalite. The portable sampler was applied to analyze tritium in a duct air of a heavy water moderated research reactor. More than 99% of total tritium was in vapor form. Trace amounts of tritiated hydrogen and hydrocarbon were also detected. This tritium sampler is applicable to detect all of atmospheric tritium as high as ten times of ambient levels.
Thermoluminescent dosimeter-CaSO4/Teflon discs were prepared by the authors. Series of experiments were applied to investigate the photon energy dependence of these TLD discs. The results showed that the energy dependence of TLD discs is almost the same as that of TLD powder. The decrease of the proportion of TL phosphor embedded in teflon does reduce the sensitivity but not affect the energy dependence of TLD discs unless the grain size of TL phosphor is smaller than several microns. A personnel beta-gamma dosimeter in connection with proper filters was designed. The photon energy dependence can be corrected and the effects of beta and gamma can be distinguished in this dosimeter.
In the reactor room of the Kyoto University Research Reactor Institute, the measurements of radon (Rn) and its short-lived decay products (Rn-Dts) were carried out under ventilated and non-ventilated conditions. The indoor activities were equal to outdoor ones under ventilated condition and those activities increased till about 10 times of outdoors under non-ventilated condition. We attempted to explain these results on a basis of a simple model. The calculations were performed taking into account: (1) supply of Rn and Rn-Dts from outdoor, (2) the emanation rate of Rn from the wall materials of building, (3) the removal rate of Rn-Dts by ventilation and wall deposition, and (4) the attachment rate of unattached atom to aerosols. In addition, natural ventilation were considered during periods without artificial ventilation.
A particle size analyzer with multiple size channels has a finite window width in each channel. It is possible that the error in the subsequent data analysis results from the finite window width, even if the particle size analyzer measures the size distribution with sufficient accuracy. In order to estimate the error, a numerical experiment was made as an example on the measurement of particle penetration through the air filter. The error was found to be negligible only around two positions of the most penetrating particle size through the filter and the count median diameter of test particles. As the particle size in question separated from these positions, a difference between the theoretical penetration and the experimental increased. The difference also increased in proportion to the window width. In the multistage filtration system, it was found that the filter performance was underestimated, as the particle penetration through each filter increased at each successive filter.