Complete Iodine Loading of NO-Aged Ag⁰ -Functionalized Silica Aerogel (Milestone Report)

Technical Report · Fri May 29 04:00:00 EDT 2015

DOI:https://doi.org/10.2172/1210154· OSTI ID:1210154

Bruffey, Stephanie H. ^[1]; Patton, Kaara K. ^[1]; Jubin, Robert Thomas ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

In off-gas treatment systems within a nuclear fuel reprocessing plant, capture materials will be exposed to a gas stream for extended periods during their lifetime. This gas stream may be at elevated temperature and could contain water, NO_x gas, or a variety of other constituents. For this reason, it is important to understand the effects of long-term exposure, or aging, on proposed capture materials. One material under consideration for iodine sequestration is silver-functionalized silica aerogel (Ag⁰-aerogel). The aim of this study was to determine the effect of extended exposure at 150°C to an air stream containing NO on the iodine capture capacity of Ag⁰-aerogel. Ag⁰-aerogel was provided by the Pacific Northwest National Laboratory (PNNL), which manufactures the material at a lab scale. Prior to aging, the material has an iodine loading capacity of approximately 290 mg I/g Ag⁰-aerogel. Previous studies have aged the material in a dry air stream or in a moist air stream for up to 6 months. Both tests resulted in a 22% loss in iodine capacity. Aging the material in a static 2% NO₂ environment for up to 2 months results in a 15% loss of iodine capacity.3 In this study, exposure of Ag⁰-aerogel to 1% NO at 150°C for 2 months produced a loss of 43% in iodine loading capacity. This is largest loss observed for aerogel aging studies to date. The performance of Ag⁰-aerogel in this study was compared to the performance of reduced silver mordenite (Ag⁰Z) in similar studies. Ag⁰Z is a zeolite mineral considered to be the current standard technology for iodine removal from off-gas streams of a potential US used fuel processing plant. In an aging study exposing Ag⁰Z to 1% NO for 2 months, an iodine capacity loss of over 80% was observed. This corresponds to a silver utilization of 13.5% for 2 month NO-aged Ag⁰Z, compared to 57% silver utilization for 2 month NO-aged aerogel. While iodine loading capacity and silver utilization are critical parameters in evaluating these materials, other properties must also be considered when selecting the appropriate material (e.g., relative material densities and potential waste form production technology). The resistance of Ag⁰-aerogel to NO is promising, and investigations of this material for use in iodine capture should continue to be pursued.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1210154
• Report Number(s): ORNL/LTR--2015/258; AF5805010; NEAF327
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
aerogel
aging
iodine