FUNCTIONALIZED SILICA AEROGELS: ADVANCED MATERIALS TO CAPTURE AND IMMOBILIZE RADIOACTIVE IODINE

摘要

To support the future expansion of nuclear energy, an effective method is needed to capture and safely store radiological iodine-129 released during reprocessing of spent nuclear fuel. Various materials have been investigated to capture and immobilize iodine. In most cases, however, the materials that are effective for capturing iodine cannot subsequently be sintered/densified to create a stable composite that could be a viable waste form. We have developed chemically modified, highly porous, silica aerogels that show sorption capacities greater than 440 mg of I_2 per gram at 150 °C. An iodine uptake test in dry air with a concentration of iodine 44 mg/m~3 demonstrated no breakthrough after 3.5 h and indicated a decontamination factor in excess of 310. Preliminary densification tests showed that the I_2-loaded aerogels retained more than 92 mass% of I_2 after thermal sintering with pressure assistance at 1200 °C for 30 min. These high capture and retention efficiencies for I_2 can be further improved by optimizing the functionalization process and the chemistry as well as the sintering conditions.