Determination of technetium-99 from the aspect of environmental radioactivity

A radioanalytical procedure has been developed for the determination of99Tc in environmental samples. The procedure consists of precipitation, solvent extraction, ion exchange, electrodeposition and radiation measurement. Rhenium was used as a non-isotopic carrier of99Tc. On the basis of 3σ counting error, the detection limits were 4.9·10−5 Bq/l, 7.4·10−3 Bq/kg wet and 7.4·10−2 Bq/kg dry for water, biota and soil samples, respectively. Sea water, seaweeds (brown algae) and soils were collected to evaluate the present levels of99Tc in Japan. The level of99Tc in sea water was ca. 1·10−4 Bq/l around Japan. Among the seaweeds (brown algae), Ishige okamurai showed the highest concentration of 5.8·10−2 Bq/kg wet tissue and the highest concentration factor of 583. The level of99Tc in the organic rich surface soil was ca. 1 Bq/kg dry soil in Fukuoka.