マンガン化合物で被覆したアクリル繊維を利用する河川水中の228Ra/226Ra放射能比の測定

概要

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Radium isotopes (228Ra and 226Ra) in river-water samples from Japan having low concentrations were attempted to be collected by a Mn-impregnated acrylic fiber. The method was aimed at the in-situ collection of Ra isotopes in large amounts of river water by making effective use of the flow of the river to observe the 228Ra/226Ra activity ratio. Measurements of the 228Ra/226Ra activity ratios were made by non-destructive γ-ray spectrometry. Although the collection efficiency of Ra isotopes by Mn-impregnated acrylic fiber was observed to be dependent on the water pH and temperature, the Ra isotopes in river water in an effective range of pH and temperature could be successfully collected. The 228Ra/226Ra activity ratios observed in several rivers of Japan by the present method were in the range of 1.1∼2.9, which is slightly higher than those observed in rivers of the continental area.