Iodine immobilization form

Nakazawa, T., Kato, H., Okada, K., Ueta, S. Mihara, M. 2001. Iodine immobilization by Sodalite waste form. Materials Research Society Symposium Proceedings, 663, 51-58. 

If the waste is isolated in a geologic repository, the iodine form should be stable to at least 100°C and possibly at 250°C depending on the repository site. If the waste form satisfies the thermal stability requirement, the most likely release mechanism then becomes leaching in the event that groundwater contacts the immobilization form. Allard et al. (11) report log Kd values for silicate minerals ranging from -0.5 to -3.5. Fried et al. (12) found little retention of iodine (as iodide or iodate) by Los Alamos Tuff. Thus, once the Iodine has been removed by leaching, it will potentially move at the same velocity as the groundwater. 

Iodine Immobilization Three different waste forms were proposed for 1-129 in the 1980s (Trevorrow et al., 1983). Two of these utilized zeolites for capture. Two of the final waste forms incorporated cement into the system for immobilization and the third consisted of pellets. As Trevorrow et al. (1983) stated in their report "The very small release limit for 1-129 specified by 40 CFR 190 (Table 14.10) makes extreme demands on technologies of collection and retention for this nuclide. Furthermore, the assessment of whether the technologies will comply with this limit is affected by uncertainties such as the distribution of iodine in the plant or the efficiency of the technology for collecting 1-129 from gas streams" (Me Kay, 1980). 

Figure 12.6 The immobilized glucose oxidase/lactoperoxidase system radioiodinates proteins through the intermediate formation of hydrogen peroxide from the oxidation of glucose. H2O2 then reacts with iodide anions to form reactive iodine (I2). This efficiently drives the formation of the highly reactive H2OI+ species that is capable of iodinating tyrosine or histidine residues (see Figure 12.2).

Figure 265 IODO-BEADS contains immobilized Chloramine-T functional groups that can react with radioactive iodide in aqueous solution to form a highly reactive intermediate. The active species may be an iodosulfonamide derivative, which then can iodinate tyrosine or histidine residues in proteins.

CDs can form inclusion complexes with iodine, which makes them candidates for iodine-sorption from nuclear waste gases. In model experiments, it was shown that the aqueous solutions containing CDs and crosslinked CD polymers were selective and effective iodine absorbers [86]. Especially the cr-CD derivatives (methylated and crosslinked) have high sorption capacity. On the basis of the results, the binding of elemental and organic iodine emitted into the air by chemical and nuclear power plants can be made effectively by immobilizing iodine vapor in aqueous CD solutions or in CD polymer gel beds. Such new sorbents can be employed in the air filtration systems (Table 8.4). 

Instead of a dormant species, a conventional radical initiator can be immobilized on the surface to conduct reverse LRP. Reverse iodine transfer polymerization (RITP) has been established in solution by Lacroix-Desmazes and colleagues [42-44] and Tatemoto and Nakagawa [38]. A conventional radical initiator such an azo compound (R-N=N-R) and molecular iodine (I2) are used as starting compounds then, the alkyl iodide (R-1) formed in situ is used for the polymerization. Wang... 

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