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 PdI
2 decomposition method. Irradiation was conducted by JRR-4 (
nth: 8×10
13n/cm
2·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%.
View full abstract