Low-level determination of 129I in environmental samples by neutron activation

Low-level determination of 129I and 129I/127I ratio in environmental samples by neutron activation is described. The iodine was chemically separated from kombu (Laminaria japonica) samples by solvent extraction and subsequent reduction to an inorganic form prior to neutron irradiation, the activated 126I and 130I were measured by a germanium gamma-ray spectrometer after irradiation with a cooling time of 16 h. The lowest detection amount is estimated to be 10−3 Bq or a corresponding 129I/127I ratio of 10−11. The average 129I/127I ratio for kombu samples, collected from local markets, was found to be 10−10, lower than those of terrestrial samples reported elsewhere.