Interaction of radioactive iodine gaseous species with nuclear-grade activated carbons
✍ Scribed by Victor R. Deitz
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 851 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0008-6223
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✦ Synopsis
Carbons from different sources and impregnations were systematically exposed to unfiltered outdoor air and all degraded with respect to radioactive methyl iodide trapping efficiency. The same carbons, exposed to air flows of known contaminant species and concentrations under controlled laboratory conditions, behaved similarly. Local meteorological conditions of high humidity combined with atmospheric pollutants in the test vicinity contributed jointly to the degradation. When service activated carbons were exposed to radiation levels of lo'-lo9 rads, the iodine isotope exchange capacity was regenerated. The efficiency for iodine isotope exchange was vastly improved, but the removal of methyl iodide-127 was only slightly improved or not at all. It was possible to regenerate the iodine isotopeexchange efficiency by reaction with airborne chemical reducing agents such as hydrazine with little or no improvement in methyl iodine-127 retention. The removal of radioactive iodine by impregnated activated carbons depends on three distinguishable reactions: (1) adsorption on the carbon networks of the activated carbons, (2) iodine isotope exchange with impregnated iodine-127 and (3) chemical combination with impregnated tertiary amines when present. After the carbon is placed in service, the three mechanisms of iodine removal are degraded by the contaminants of the air at different rates; the adsorption process degrades faster than the other two.