Tritium concentration of groundwater in the districts of Osaka, Japan

The tritium concentration of groundwater collected from deep wells in the southern cities of Osaka prefecture (Sakai and seven other cities) and those in the northern cities thereof (Takatsuki and five other cities) were measured. As a result, the groundwater veins of the southern cities can be classified into two groups, 1.5∼5 Bq/l and 0.1∼1 Bq/l. Those of the northern cities may also be classified in the 1.4∼2.6 Bq/l and 0.1∼0.8 Bq/l ranges. The tritium levels of these groundwater veins are considered to be nearly constant, except for their physical half life (12.4 years), since in these ten years the level of tritium precipitation is almost constant, with groundwater pumping being controlled by the Osaka prefecture authority. (author)