The238U, 234U, 226Ra and228Ra 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 of238U and234U were 0.44 Bq/l and 0.91 Bq/l, respectively, while234U/238U showed the range of 1.50-2.37. The maximum levels of226Ra and228Ra were found to be 1.95 Bq/l and 0.76 Bq/l, respectively, while228Ra/226Ra mean value was 0.49. In the spring water at Misasa, the maximum levels of226Ra and228Ra were 0.60 Bq/l and 0.41 Bq/l, respectively, and228Ra/226Ra mean value was 0.55. From the above-mentioned result and the fact that228Ra is a decayed product of232Th, it is thought that the rocks of the Sanbe and Misasa districts contain much uranium and thorium.
The Ca/P atomic ratios of synthesized calcium-hydroxyapatite (Ca10 (PO4) 6 (OH) 2) were determined by neutron activation analysis. In order to obtain calibration curves, the standard samples, such as calcium monohydrogenphosphate, calcium dihydro-genphosphate, etc., were prepared. γ and β ray spectra, and β ray intensities of calcium-hydroxy-apatite and standard samples irradiated with reactor neutrons were measured by using a Ge (Li) detector, a low background β ray spectrometer and GM detector. Based on these results, deviation coefficient of the calibration curve, accuracy of the Ca/P atomic ratio, minimum determination limit, etc. were compared in detail. From the present analysis, the Ca/P atomic ratio of calcium-hydroxyapatite was able to obtain with the standard deviation of about 2% for 1 mg sample.