Investigation on extraction methods of environmental iodine

In analysis of environmental iodine, samples containing low I-129 and low iodine amount are subject to contamination from reagents and apparatus. We measured the isotopic ratio of I-129/I-127 in brine that was collected at Mobara in Chiba prefecture and was characterized as having a high iodine concentration and a low isotopic ratio. The results, however, showed high isotopic ratios. We suspected that the contamination was caused by using halogen containing reagents because the samples treated with Cl-form anion exchange resin in iodine extraction process were strongly contaminated. In this study, we have conducted halogen-free extraction processes such as ion exchange and solvent extraction whose recovery has been investigated with gamma spectrometry of I-126 produced through photonuclear reaction with the KURRI LINAC. The total iodine recovery through ion exchange with NO3-form anion exchange resin and solvent extraction with dodecane was more than 80%. To investigate contamination from laboratory environment, we have compared AgI samples prepared at KURRI and at another laboratory apart from KURRI. (author)