Hydrogen gas evolution induced by60Co gammaray irradiation of nnoparticles dispersed in water was investigated. Nanoparticles of TiO2and Al2O3, whose average sizes were within the range of 14-33 nm, were employed. Hydrogen-gas yield from a sample dispersion in a closed vial was measured by gas chromatography after the irradiation. The sample exhibited much larger hydrogen yields than that in the pure water radiolysis. The hydrogen yield increased with the absorbed dose and the amount of particles dispersed in water. These results support the fact that the reaction is activated by both the γ-ray irradiation and the dispersed particles. In conjunction with results of TEM observation, it was implied that these enhancement effects should depend on the size and/or shape of the particles rather than their chemical species. We calculated the G-values for the hydrogen-gas evolution. They will be useful for the discussion about the reaction.
Radiation hormesis was studied at an X-ray photography room. Seed of radish (Kaiwaredaikon) was irradiated by X-ray, from 10 to 3000mGy. Since the growth of plant was the highest around 500mGy, 100 seeds were irradiated at a dose of 500mGy. Fifty seeds were selected and the growth rate was measured after 1 and 2 weeks. After 2 weeks, the growth of the seeds irradiated (129±5mm) was found to be higher than those without irradiation (115±5mm) .