Chemical state mapping of simulant Chernobyl lava-like fuel containing material using micro-focused synchrotron X-ray spectroscopy.
Chemical state mapping of simulant Chernobyl lava-like fuel containing material using micro-focused synchrotron X-ray spectroscopy.
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DOI：
10.1107/s1600577521007748
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发表时间：
2021-11-01
影响因子：
2.5
通讯作者：
Hyatt NC
中科院分区：
文献类型：
--
作者：
Ding H;Dixon Wilkins MC;Mottram LM;Blackburn LR;Grolimund D;Tappero R;Nicholas SL;Sun S;Corkhill CL;Hyatt NC
这项工作阐述和评估的方法来建设的2D形态图，在努力最大限度地提高灵敏度的U氧化态在U L 3-边缘，适用于一套合成切尔诺贝利熔岩标本。铀的形态和氧化还原行为在核燃料循环中至关重要。X射线吸收近边光谱（XANES）通常用于探测核材料中铀和其他元素在宏观和微观尺度上的氧化态和形态。二维（2D）形态图，来自微焦点X射线荧光和XANES数据，提供了重要的信息的氧化还原活性元素，如铀的氧化态的空间变化和梯度。在目前的工作中，我们阐述和评估的方法来建设的二维形态图，在努力最大限度地提高灵敏度的U氧化态在U L 3-边缘，适用于一套合成切尔诺贝利熔岩标本。我们的分析表明，校准的形态分布图可以提高通过确定的归一化的X射线吸收的激发能量选择，以最大限度地提高氧化态的对比度。将图校准到相关参比化合物的UL 3 XANES光谱的归一化吸收，使用反正切和伪Voigt函数的组合建模（以表示光电吸收和多重散射贡献）。我们验证了这种方法，通过微焦点X射线衍射和XANES分析的兴趣点，这提供了平均U氧化态与化学状态图估计的非常一致。这种简单易行的方法具有普遍性和可移植性，将有助于今后分析真实的熔岩状含燃料材料，以了解其环境退化情况，这是切尔诺贝利掩蔽所内放射性粉尘产生的一个来源。
This work elaborates and evaluates approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L 3-edge, applied to a suite of synthetic Chernobyl lava specimens. Uranium speciation and redox behaviour is of critical importance in the nuclear fuel cycle. X-ray absorption near-edge spectroscopy (XANES) is commonly used to probe the oxidation state and speciation of uranium, and other elements, at the macroscopic and microscopic scale, within nuclear materials. Two-dimensional (2D) speciation maps, derived from microfocus X-ray fluorescence and XANES data, provide essential information on the spatial variation and gradients of the oxidation state of redox active elements such as uranium. In the present work, we elaborate and evaluate approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L 3-edge, applied to a suite of synthetic Chernobyl lava specimens. Our analysis shows that calibration of speciation maps can be improved by determination of the normalized X-ray absorption at excitation energies selected to maximize oxidation state contrast. The maps are calibrated to the normalized absorption of U L 3 XANES spectra of relevant reference compounds, modelled using a combination of arctangent and pseudo-Voigt functions (to represent the photoelectric absorption and multiple-scattering contributions). We validate this approach by microfocus X-ray diffraction and XANES analysis of points of interest, which afford average U oxidation states in excellent agreement with those estimated from the chemical state maps. This simple and easy-to-implement approach is general and transferrable, and will assist in the future analysis of real lava-like fuel-containing materials to understand their environmental degradation, which is a source of radioactive dust production within the Chernobyl shelter.