Molecular Iodine Interactions with Fe, Ni, Cr, and Stainless Steel Alloys

Abstract

The adsorption behavior of molecular iodine is important for understanding the spread of radioiodine in a nuclear accident. Prior experiments indicate that, in addition to the interaction with Fe, molecular iodine [i.e., I 2(g) ] also interacts with the next most abundant components of austenitic stainless steel (i.e., Ni, and Cr) at room temperature. In this study, we investigate iodine adsorption on Fe, Ni, and Cr while focusing on understanding the variables affecting adsorption as well as the iodine compounds that are formed during adsorption. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize the surfaces of exposed metal particles and aid in the understanding of the morphology and chemistry of iodine interactions with the substrates. Inductively coupled plasma optical emission spectroscopy was used to detect low levels of metal iodides and X-ray photoelectron spectroscopy was used to confirm the formation of the metal iodides. The role of environmental factors (e.g., humidity and oxygen content) for iodine adsorption on metal substrates is addressed. The individual metals demonstrated formation of metal iodides for Fe and Ni particles from interaction with I 2(g) . The formation of metal iodides may indicate the affinity of iodine for the respective metal. In this study, the iodine affinities ranked Fe > Ni > Cr as determined by the quantity of chemisorbed iodine. This trend is also supported by the distributions and proportions of metals in the corrosion product of the stainless steels. The exposures without oxygen and humidity indicate the potential of a multistep iodine adsorption process where iodine first attacks the oxide layer and then chemisorbs to the exposed metal.

Corrosion of metal parts on satellites by iodine exposure in space

“…However, Nb, Al, Ti, and Fe similar to Cu [13,16] strongly react with iodine under these conditions. Our results confirm the findings of Beck et al [38] that the reactiveness towards iodine decreases from Fe via Ni to Cr. In case of Al and Ti treated by these conditions, the chemical reaction products even cause brittleness of the surface and deterioration of the structural integrity of the material in the vicinity of the surface.…”

Iodine Vapor Reactions with Pure Metal Wires at Temperatures of 100–139 °C in Air

“…It is also apparent from Figure 7b,c that the T m , so these types of parameters need to be considered. Regarding metal iodides, compounds like InI 3 are hygroscopic, where they can deliquesce in air and/or are highly water-soluble, 50,51 so they could have disadvantages regarding stability for long-term disposal in a repository. In a recent study, 52 it was shown that the relative humidity can also play a significant role in the reaction of metal substrates such as Ni 0 with I 2(g) , so this should also be considered for future sorbents.…”

Silver-Loaded Xerogel Nanostructures for Iodine Capture: A Comparison of Thiolated versus Unthiolated Sorbents

“…Several different types of radioiodine sorbents have been reported for capturing iodine as a gas in different forms [e.g., I 2(g) and CH 3 I (g) ] or as an ion from liquid effluents (e.g., I – and IO 3 – ). − The primary types of iodine capture systems include solid sorbents or liquid scrubber systems, often utilizing an aqueous hydroxide or molten hydroxide. ,, A wide range of solid sorbents have been reported that typically utilize active metal sites targeted to remove the iodine species from the environment through physisorption and/or chemisorption mechanisms. Some examples of solid sorbents include activated carbon; metal-exchanged zeolites like Ag-mordenite (Ag-MOR or AgZ), Ag-faujasite (Ag-FAU or AgX and AgY), and Ag-Linde type A (AgA); − metal–organic frameworks; , metal-loaded aerogels or xerogels; , metal-impregnated ceramics; and solid metal substrates. , The current work will focus primarily on chemisorption-based iodine capture.…”

“…Some examples of solid sorbents include activated carbon; 7 metal-exchanged zeolites like Ag-mordenite (Ag-MOR or AgZ), Ag-faujasite (Ag-FAU or AgX and AgY), and Ag-Linde type A (AgA); 8−14 metal−organic frameworks; 15,16 metalloaded aerogels or xerogels; 17,18 metal-impregnated ceramics; 19 and solid metal substrates. 20,21 The current work will focus primarily on chemisorption-based iodine capture.…”