We examined the effect of continuous radon inhalation on acute alcohol-induced oxidative damage of mouse liver and brain. Assay of antioxidative functions indicated that lipid peroxide levels in both the liver and brain of the alcohol-treated mice were significantly higher than those of the saline-treated mice. However, the lipid peroxide level in the liver, but not in the brain, of alcohol-treated mice was significantly decreased by radon inhalation whereas that in the brain of saline-treated mice, but not in the liver of saline-treated mice, was significantly increased by radon inhalation. These findings suggest that radon inhalation inhibits alcohol-induced oxidative damage of liver due to activation of antioxidative functions and that radon inhalation exert only a week effect on the brains in comparing with the livers. They further suggest that alcohol administration protects against oxidative damage of the brain that is induced by radon inhalation.

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  We isolated the luminous bacterium Vibrio phosphoreum H1 as a tool for education in radiation safety. It emits strong and steady luminescence. It is nonpathogenic, cannot be grown under normal low-salt conditions, and can be handled without any special equipment or reagents. We can cultivate it on a desk at room temperature, and can use a home-made broth containing a high salt concentration. Heat treatment at 37°C kills the bacterium, leading to its loss of luminescence. Although X-ray irradiation clearly kills it as the exposure dose increases, luminescence remains intact for some time, suggesting a delayed appearance of the biological effect of radiation exposure. We showed that the luminous bacterium Vibrio phosphoreum H1 can be used as a tool for teaching and learning about the effects of radiation. We proposed a practical plan that can be employed at high schools as well as universities.

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  Radiation sources were fabricated from potassium chloride chemicals that contained naturally occurring potassium-40 radioisotopes, and applied to training new workers in laboratory measurements in courses on protection against exposure to radiation at the National Institute for Fusion Science. The training involved four measurements of radiation, that to evaluate background radiation and three to assess the dependence on time, distance, and shielding effects. The counts of radiation emitted by the potassium chloride radiation sources were measured with a Geiger-Muller (GM) survey meter. Although data obtained in the training varied somewhat depending on the students, they could evaluate the level of natural radiation and understand the principles of protection against exposure to radiation. It was concluded that radiation sources fabricated from potassium chloride chemicals are convenient educational tools for illustrating naturally existing radiation and radioisotopes, and they enabled better comprehension of the principles of protection against exposure to radiation.

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  The ¹⁵²Eu/Eu ratios were measured at various surface positions of two granite samples (gravestones) in the vicinities of the hypocenter of the Hiroshima atomic bomb. The sample pieces were dissolved and the europium elements were chemically isolated. The radioisotopes of Actinium series in the rock samples were excluded from the europium samples. The measured ¹⁵²Eu/Eu ratio was not constant in each surface, and was low at the surface positions close to neighbor gravestone. The ¹⁵²Eu/Eu ratios were high at the positions that were largely open for the scattered neutrons from the soil ground. This suggests that the rock materials between sample and soil ground reduced thermal neutron fluence to the sample.

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  A homemade airflow pulse ionization chamber system was inexpensively made for the measurement of alpha-radioactivity in atmosphere. The signal electrode of the ionization chamber was divided into two for the reduction of common-mode noises, and pulse signals from each electrode were treated with electronic circuits based on a field programmable gate array (FPGA). Multichannel pulse-height analyzers, multichannel scalers and other related electronic modules were constructed for the analysis of alpha-radioactivity in the FPGA. The symmetrical structure of the electrodes of the ionization chamber was effective in the cancellation of common-mode noises induced by commercial electricity, mechanical vibration and others. An alpha-ray source (²⁴¹Am) was set inside the ionization chamber for the monitoring of air conditions. It was confirmed from an experiment with a mantle containing thorium ore that radon alpha-radioactivity in air could be well measured with this system.

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