Distributions and kinetics of inert radionuclides in environment

Recently there has been increased concern over the exposures not only in the nuclear energy field but in natural radiation environment. So this paper presents a study on distributions and kinetics of radioactive gases such as 41Ar and radon progeny in the Kyoto University Reactor, Research Institute (KUR-RI) and radon in the earth, which is one of the main radiation sources in out-door and has been continually generated. Amount of 41Ar released from the KUR has been decreased by about one-tenth within past seven years and further efforts have been focused on minimizing the released activity according to the concept of ALARA. The simultaneity of the diurnal variations in the radioactive dust observed in several buildings at the KUR-RI indicates that the concentration changes are not caused by the activities of man. Peak concentrations in vertical profile of radon are observed at ca 40 cm below ground surface and a rising of water table following precipitation causes a brust of radon concentration by upflow in ground. Exposure levels on workers and the public resulting from the KUR operation and natural radiation induced by radon progeny will be discussed at this meeting. (author)