Iodine: Radionuclides

Abstract

This article provides a review of iodine with regard to the basic chemistry, occurrence, speciation, separation, analysis, fate, and transport. Biogeochemical cycling of iodine in the environment is complex because iodine occurs in multiple oxidation states (ranging from −1 to +7), and inorganic and organic species may be hydrophilic, atmophilic, and biophilic. Organically bound iodine can be a significant fraction of total iodine in the atmosphere, biosphere, hydrosphere, and lithosphere. Nuclear‐fuel reprocessing facilities constitute the major source (>90%) of 129 I released to the environment. It has been recognized that 129 I is a very important dose contributor in risk assessment because of its tendency to concentrate in the human thyroid gland, long half‐life, and presumably high mobility. Speciation, input concentration, and residence time effects will influence the biogeochemical cycling of anthropogenic 129 I deposited on surface soils.

Electrochemical behavior of iodide ions in molten fluoride salts

“…The 129 I is the isotope with the longer period (t1/2= 1.57 . 10 7 years), but other isotopes with a shorter time of live are also produced, as 131 I (t1/2= 8.02 days), 133 I (t1/2= 20.8 hours), 135 I (t1/2= 6.57 hours), 132 I (t1/2= 2.30 hours) and 134 I (t1/2= 52.5 minutes) [1]. The isotopes 129 I and 127 I (stable isotopes) represent 87 % of the total iodine.…”

“…The methodology developed for the removal of iodine was based in HF sparging. The next equilibrium described the chemical reaction in the fluoride melt: HF (g) + I -⇋ F -+ HI (g) (1) Another procedure developed by ORNL for the extraction of radionuclides from the fuel consisted in the fluorination. The fluorine production is realized by electrolysis of 2HF-KF molten salt at 368 K. The fluorine gas might to oxide all the elements dissolved in the molten salt until their maximum oxidation state stable in the salt.…”