Uranium distribution in the environment and its contribution to environmental radioactivity

Sato, Kazuhiko ; Ishibashi, Makoto*; Kawatsuma, Shinji

Clearance of materials and disposal of radioactive waste generated from uranium utilizing facilities which include uranium conversion and enrichment facilities, and fuel fabrication facility among the nuclear fuel cycle has been discussed in Japan. These materials are supposed to be contaminated with long-lived natural nuclide, i.e. uranium. Uranium is widely distributed among the environment, e.g. soil, rock, river-water, groundwater and so on. Furthermore, uranium is also contained in some building materials and consumer goods. Literature survey about distribution of uranium in the environment and measurement of uranium concentration in some materials were carried out. As a result, it is revealed that range of U-238 activities in soils in Japan is from 0.001 Bq/g to about 1 Bq/g. Addition to that, the range of building materials is overlapped by that of soils, while some consumer goods showed relatively high activities. Futermore, dose contribution of uranium series nuclides to the environmental radiation dose were discussed. It is suggested that, sum of environmental radiation dose in Japan is about 1.5 mSv/yr and dose contribution of uranium series nuclides is about 0.8 mSv/yr.