Formation of studtite during the oxidative dissolution of UO2 by hydrogen peroxide:: A SFM study
Formation of studtite during the oxidative dissolution of UO2 by hydrogen peroxide:: A SFM study
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DOI：
10.1021/es0492891
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发表时间：
2004-12-15
影响因子：
11.4
通讯作者：
Rovira, M
中科院分区：
文献类型：
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作者：
Clarens, F;De Pablo, J;Rovira, M
了解乏核燃料表面蚀变相的形成，如在浸出实验中观察到的蚀变相，对于预测最终处置库近场放射性核素的浓度是必要的。过氧化氢已被确定为在乏核燃料存在下由水辐解形成的氧化剂之一;特别是由于α活性。这种物质在溶液中的存在有助于过氧化铀第二相的形成。在这项工作中，我们研究了合成的UO 2盘在两种不同浓度的过氧化氢溶液（5 × 10（-4）和5 × 10（-6）mol dm（-3））中的氧化溶解，两者都在pH 5.8 +/- 0.1。的磁盘的固体表面的演变已经通过非原位扫描力显微镜（SFM）测量，并已确定在溶液中的铀浓度由电感耦合等离子体质谱。在实验的第一阶段，SFM图像表明，只有二氧化铀发生溶解。142小时后，在5 × 10（-4）mol dm（-3）过氧化氢浓度下，在固体表面上观察到第二相。经X射线衍射鉴定，第二相为studtite（UO_4（.）4H（2）O）。根据对不同经过时间的SFM地形剖面的分析，已估计出该斜辉岩的沉淀速率在（8-32）x 10（-10）mol m（-2）s（-1）的范围内。
Understanding the formation of alteration phases on the surface of spent nuclear fuel, such as those observed during leaching experiments, is necessary in order to predict the concentration of radionuclides in the near-field of a final repository. Hydrogen peroxide has been identified as one of the oxidants formed by the radiolysis of water in the presence of spent nuclear fuel; especially due to alpha activity. The presence of this species in solution can contribute to the formation of uranium peroxide secondary phases. In this work, we have studied the oxidative dissolution of synthetic UO2 disks in hydrogen peroxide solutions of two different concentrations (5 x 10(-4) and 5 x 10(-6) mol dm(-3)), both at pH 5.8 +/- 0.1. The solid surface evolution of the disks has been followed by means of ex-situ scanning force microscope (SFM) measurements, and uranium concentration in solution has been determined by inductively coupled plasma mass spectrometry. During the first stage of the experiment, SFM images indicate that only UO2 dissolution is occurring. After 142 h, a secondary phase is observed on the surface of the solid at 5 x 10(-4) mol dm(-3) hydrogen peroxide concentration. This secondary phase has been identified by X-ray diffraction as studtite (UO4 (.) 4H(2)O). From the analysis of SFM topographic profiles at different elapsed times, a precipitation rate for the studtite has been estimated to be in the range of (8-32) x 10(-10) mol m(-2) s(-1).