Summary Report on the Volatile Radionuclide and Immobilization Research for FY2011 at PNNL Prepared for U.S. Department of Energy Separations and Waste Forms Campaign D. M. Strachan, J. Chun, J. Matyàš, W.C. Lepry, B.J. Riley, J. V. Ryan, and P. K. Thallapally Pacific Northwest National Laboratory September 2011 FCRD-SWF-2011-000378 PNNL-20807 DISCLAIMER This information was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness, of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. References herein to any specific commercial product, process, or service by trade name, trade mark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof. Summary Report on Volatile Radionuclides Capture and Immobilization Research for FY11 at PNNL September 2011 iii SUMMARY Materials were developed and tested in support of the U.S. Department of Energy, Office of Nuclear Energy, Fuel Cycle Technology Separations and Waste Forms Campaign. Specifically, materials are being developed for the removal and immobilization of iodine and krypton from gaseous products of nuclear fuel reprocessing unit operations. During FY 2011, aerogel materials were investigated for removal and immobilization of 129I. Two aerogel formulations were investigated, one based on functionalized silica and the second on chalcogen- based glasses (i.e., chalcogels). A silica aerogel was tested at ORNL for total I2 sorption capacity. It was determined to have 48 mass% capacity while having little physisorbed I2 (I2 not chemically bound within the aerogel). Metal organic framework (MOF) structures were investigated for the removal and storage of Kr and a new MOF with about 8 mass% capacity for Xe and Kr was formulated and tested. The selectivity can be changed from Xe > Kr to Xe < Kr simply by changing the temperature. A patent disclosure has been filed. Lastly, silicon carbide (SiC) was loaded with Kr. The diffusion of Kr in SiC was found to be less than detectable values at temperatures as high as 500°C. Summary Report on Volatile Radionuclides Capture and Immobilization Research for FY11 at PNNL iv September 2011 Summary Report on Volatile Radionuclides Capture and Immobilization Research for FY11 at PNNL September 2011 v CONTENTS SUMMARY ................................................................................................................................................. iii ABBREVIATIONS ...................................................................................................................................... x 1. INTRODUCTION .............................................................................................................................. 1 2. Chalcogenide-based aerogel (chalcogel) work ................................................................................... 1 2.1 Progress on chalcogenide-based aerogels for the removal of I2 ............................................... 1 2.2 Literature studies ...................................................................................................................... 1 2.2.1 Candidate chalcogel materials and potential complimentary glass systems ............... 1 2.2.2 Search for alternative metals for improved iodine affinity ......................................... 3 2.2.3 Comparison of affinity for competing off-gas components ........................................ 4 2.3 Precursor synthesis ................................................................................................................... 5 2.3.1 K2MCl4 and KMCl3 precursors. .................................................................................. 5 2.3.2 Sn-S precursors. .......................................................................................................... 7 2.4 Chalcogel synthesis .................................................................................................................. 8 3. Metal Organic Framework (MOF) Materials ..................................................................................... 9 3.1 Experiment and apparatus ...................................................................................................... 11 3.1.1 Material synthesis ..................................................................................................... 11 3.1.2 Apparatus and procedure .......................................................................................... 11 3.2 Xe/Kr adsorption in MOFs .................................................................................................... 12 3.2.1 MOF Ni/DOBDC ...................................................................................................... 12 3.3 New MOFs ............................................................................................................................. 14 3.3.1 A new MOF .............................................................................................................. 14 3.3.2 MOF PNNL-5DB ...................................................................................................... 14 3.3.3 MOF PNNL-Mn ........................................................................................................ 15 3.4 Conclusions and Path Forward............................................................................................... 16 4. Silver-functionalized silica aerogels for capture and immobilization of gaseous radioiodine from reprocessing off-gas ................................................................................................................. 17 4.1 Summary ................................................................................................................................ 17 4.2 Iodine sorption performance .................................................................................................. 17 4.2.1 Breakthrough test at PNNL ....................................................................................... 17 4.2.2 Maximum sorption test at ORNL .............................................................................. 18 4.2.3 Densification behavior of silica aerogels .................................................................. 19 5. Immobilization of 85Kr in Silicon Carbide ....................................................................................... 23 5.1 Background ............................................................................................................................ 23 5.2 Experimental Procedure: ........................................................................................................ 24 5.2.1 Depositions ............................................................................................................... 24 5.2.2 Characterization ........................................................................................................ 26 5.3 Results .................................................................................................................................... 27 5.4 Conclusions ............................................................................................................................ 28 Summary Report on Volatile Radionuclides Capture and Immobilization Research for FY11 at PNNL vi September 2011 5.5 Future Work ........................................................................................................................... 29 29 6. References ........................................................................................................................................ 30 Summary Report on Volatile Radionuclides Capture and Immobilization Research for FY11 at PNNL September 2011 vii FIGURES Figure 1. The Tc and Tg of various Sn-Ge-S glasses (left) along with Tc – Tg plotted (right) to compare glass-formation ability. .................................................................................................. 2 Figure 2. Unit cells for the K2MCl4 (M = Co, Zn, and Mg) and KMCl3 (KNiCl3) structures. Structures were exported from Find-It® as .cif files and imported into Topas 4.2. The images above were exported as screen-shots out of the Topas structure viewer. The International Crystal Structure Database (ICSD) numbers for K2CoCl4, K2ZnCl4, K2MgCl4, and KNiCl3 are 661 (Vermin et al. 1976), 80860 (Kusz and Kucharczyk 1995), 4035 (Gibbons et al. 1975), and 10508 (Visser et al. 1980), respectively......................... 6 Figure 3. Solution-based approach to making K2CoCl4 (top) and KNiCl3 (bottom). ................................. 8 Figure 4. Picture of the Na4Sn2S6⋅14H2O precursor in a 20 mL scintillation vial. ...................................... 8 Figure 5. Chalcogel #14c [W-Co,Ni-S4] in a 20 mL scintillation vial. ....................................................... 8 Figure 6. Enhanced noble gas storage capacities for cylinders filled with MOF-5. ................................. 10 Figure 7. Quantachrome Autosorb IQ for static pure Xe and Kr adsorption measurement. ....................