Molecular Environmental Science Using Synchrotron Radiation: Chemistry and Physics of Waste Form Materials

[摘要] Production of defense-related nuclear materials has generated large volumes of complex chemical wastes containing a mixture of radionuclides. The disposition of these wastes requires conversion of the liquid and solid-phase components into durable, solid forms suitable for long-term immobilization. Specially formulated glass compositions and ceramics such as pyrochlores and apatites are the main candidates for these wastes. An important consideration linked to the durability of waste-form materials is the local structure around the waste components. Equally important is the local structure of constituents of the glass and ceramic host matrix. Knowledge of the structure in the waste-form host matrices is essential, prior to and subsequent to waste incorporation, to evaluate and develop improved waste-form compositions based on scientific considerations. This project used the soft-x-ray synchrotron-radiation-based technique of near-edge x-ray-absorption fine structure (NEXAFS) as a unique method for investigating oxidation states and structures of low-Z elemental constituents forming the backbones of glass and ceramic host matrices for waste-form materials. In addition, light metal ions in ceramic hosts, such as titanium, are also ideal for investigation by NEXAFS in the soft-x-ray region. Thus, one of the main objectives was to understand outstanding issues in waste-form science via NEXAFS investigations and to translate this understanding into better waste-form materials, followed by eventual capability to investigate ???real??? waste-form materials by the same methodology. We conducted several detailed structural investigations of both pyrochlore ceramic and borosilicate-glass materials during the project and developed improved capabilities at Beamline 6.3.1 of the Advanced Light Source (ALS) to perform the studies.

[发布日期] 2011-04-21

[学科分类] 材料科学（综合）

[关键词] ADVANCED LIGHT SOURCE;APATITES;BOROSILICATE GLASS;CERAMICS;CHEMICAL WASTES;CHEMISTRY;FINE STRUCTURE;GLASS;MATRICES;MIXTURES;PHYSICS;PRODUCTION;PYROCHLORE;RADIOISOTOPES;SYNCHROTRON RADIATION;TITANIUM;VALENCE;WASTE FORMS;WASTES Molecular Environmental Science;Waste-Form Materials;Borosilicate Glasses;Pyrochlores