環境試料中の^<127>I及び^<129>Iの中性子放射化分析法

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The analytical method of 127I and 129I in environmental samples has been studied and the background levels of these nuclides in soils, seaweeds and milk were measured.The analytical method consists of the combustion technique and neutron activation analysis (N. A. A.).The iodine was separated from samples by ignition at about 1, 000°C in a quartz combustion apparatus with an oxygen and a nitrogen stream, and was absorbed by small amounts of active charcoal. The iodine was then purified through the carbontetrachloride extraction method and the PdI2 decomposition method. Irradiation was conducted by JRR-4 (nth: 8×1013n/cm2·sec) for 40min. After irradiation, the iodine was purified by the solvent extraction method same as pre-irradiation extraction. Each activity of 126I and 130I, which was produced by 127I (n, 2n) 126I and 129I (n, γ) 130I reaction respectively, was measured by γ-spectrometry using a Ge-detector.The lower detection limits of 129I by this method were 4×10-7Bq/g for dry soil, 7×10-8Bq/g for fresh seaweeds and 7×10-6Bq/l for fresh milk, respectively. The relative standard deviation of 129I measurements in soil and milk were less than 10%.
日本保健物理学会の論文