[Determination of 238U, 234U, 226Ra and 228Ra in spring waters of sanin district].

The 238U, 234U, 226Ra and 228Ra concentrations in the spring waters at the Sanbe and Misasa districts in Japan were investigated. In the spring water at Sanbe, high concentrations of the natural nuclides described above were found in which the maximum levels of 238U and 234U were 0.44 Bq/l and 0.91 Bq/l, respectively, while 234U/238U showed the range of 1.50 approximately 2.37. The maximum levels of 226Ra and 228Ra were found to be 1.95 Bq/l and 0.76 Bq/l, respectively, while 228Ra/226Ra mean value was 0.49. In the spring water at Misasa, the maximum levels of 226Ra and 228Ra were 0.60 Bq/l and 0.41 Bq/l, respectively, and 228Ra/226Ra mean value was 0.55. From the above-mentioned result and the fact that 228Ra is a decayed product of 232Th, it is thought that the rocks of the Sanbe and Misasa districts contain much uranium and thorium.