摘要：The natural radioactive nuclides in the spring water at Masutomi spa area were investigated in order to consider the safety for drinking. The samples of spring water were collected from 12 places of Masutomi spa area in 1963, and from 6 places in 1964 and 1965. The mean value of concentration of 226Ra was 21.7 pCi/liter and that of 222Rn was 1.3×10-2 μCi/liter at 6 sampling places where the water was used for drinking. The contents of natural U were very little generally and the maximum value of its concentration was 2.3 μg/liter among 2 times determination at 6 places. Comparing with 1/30 of the maximum permissible concentration in water for occupational people which was recommended by ICRP and NBS in the USA, the found values of concentration of 226Ra and 222Rn were much higher, while that of natural U was much lower. Considering the above mentioned results, it should be recommended that the mean daily intakes of spring water shall be less than 300 ml based on 226Ra content, whereas 150 ml on 222Rn content.
