Micro-XAS studies with sorbed plutonium on tuff

Défis actuels et à venir en matière d'analyse de traces et d'ultra-traces

“…La spectroscopie d'absorption X permet également d'obtenir des informations très précieuses sur l'environnement chimique de composés adsorbés, et de décrire les liaisons ainsi que la géométrie implicant les espèces de surface. Les études concernant les actinides [39][40][41] et certains métaux homologues de produits de fission ou d'activation à vie longue [42] se multiplient.…”

Molecular environmental science : an assessment of research accomplishments, available synchrotron radiation facilities, and needs.

“…All of these general user facilities in the U.S. have become saturated as increasing numbers of users seek beam time. The most rapidly growing Micro-XRF Imaging Pu Lα α α α (from [5,6]) 8 synchrotron user communities over the past decade have been structural molecular biology (SMB) and molecular environmental science (MES). A typical growth plot for the MES area is shown in Figure 7.…”

“…MES research directly impacts the core missions of federal agencies through investigations related to (1) discovery of fundamental knowledge about environmental materials, and chemical interactions between these materials and environmental pollutants, microbial communities, and natural waters, (2) remediation of heavy metals contamination at U.S. sites, (3) quantification of radionuclide transport and risk assessment at highlevel waste disposal and radioisotope production sites, (4) science-based stockpile stewardship, (5) design of plant species to remediate contaminated soils, and (6) photooxidation of crude oils. For example, XAFS studies of core samples from beneath the Hanford Tank Farm are providing some of the first information about the chemical forms of chromium and uranium in the vadose zone beneath the Hanford High Level Waste Storage site.…”

“…19). The core sample (from the Topopah Spring Tuff site at Yucca Mountain) was exposed to an aqueous solution of 239 Pu 5+ for XRF and EXAFS studies [5,6]. Studies on the redox and speciation chemistry of Pu in synthetic and natural waters suggest Pu can be present in four oxidation states (III, IV, V, VI) simultaneously.…”

“…Bulk X-ray diffraction data on a piece of tuff from the same core sample showed the Mn-rich phase to be the highly disordered, high-surface area mineral rancieite. XANES and first shell EXAFS were measured on the highest concentration Pu spots (estimated to bẽ 2000 ppm in a 10 µm x 10 µm spot) at the Pu L 3 edge using a Si(Li) solid-state fluorescence detector [5,6].…”