Time-resolved structural and chemical investigations of metal oxide - water systems under conditions of extreme temperature, pressure and radiation

现场x射线和拉曼光谱技术将用于在极端温度（300-700摄氏度）、压力和辐射条件下直接探测热液金刚石砧细胞中选定的金属氧化物-水系统的结构和组成。提出的实验将解决与超临界水冷堆腐蚀和腐蚀产物输送有关的三个重要问题。这些是：(1)氧化铬（III）在含过氧化氢的超临界水中的溶解度是多少？(2)金属氧化物纳米颗粒如何参与腐蚀产物的输送？(3)辐照对超临界水中过渡金属配合物的结构和稳定性有何影响？本研究将首次采用时间分辨、能量色散x射线吸收光谱（ED-XAS），以微秒分辨率监测同步加速器x射线诱导辐射溶解对超临界水中过渡金属离子局部结构和价态的影响。x射线吸收光谱还将用于研究超临界水中Cr和Fe纳米颗粒与过渡金属水离子的反应。同步加速器x射线荧光光谱（SXRF）将用于直接确定热液金刚石砧池中高温高压下流体的组成。预期的结果将大大提高我们对水性流体与候选材料的相互作用以及与GEN IV操作条件相关的水性流体中腐蚀产物的传输的理解。该研究还将为定量预测和控制水化学所需的数据库提供新的热化学数据，以最大限度地减少材料降解和高温下腐蚀产物的运输。

In situ x-ray and Raman spectroscopic techniques will be used to directly probe the structure and composition of selected metal oxide-water systems in hydrothermal diamond anvil cells at conditions of extreme temperature (300-700 degrees C), pressure, and radiation. The proposed experiments will address three important questions pertaining to corrosion and corrosion product transport in supercritical water cooled reactors. These are: (1) What is the solubility of chromium(III) oxide (eskolaite) in hydrogen peroxide-bearing supercritical water? (2) How might metal oxide nanoparticles participate in corrosion product transport? And, (3) What is the effect of irradiation on the structure and stability of aqueous transition metal complexes in supercritical water? Time-resolved, energy-dispersive x-ray absorption spectroscopy (ED-XAS) will be used in this study for the first time to monitor (with microsecond resolution) the effects of synchrotron x-ray induced radiolysis on the local structure and valence state of transition metal ions in supercritical water. X-ray absorption spectroscopy will also be used to investigate the reaction between Cr and Fe nanoparticles and transition metal aqua ions in supercritical water. Synchrotron x-ray fluorescence spectroscopy (SXRF) will be used to directly determine the composition of fluids at elevated temperatures and pressures in the hydrothermal diamond anvil cell. The anticipated results will significantly advance our understanding of the interaction of aqueous fluids with candidate materials and the transport of corrosion products in aqueous fluids at conditions relevant to GEN IV operating conditions. The research will also provide new thermochemical data for a database that is needed to quantitatively predict and control water chemistry in order to minimize material degradation and corrosion product transport at high temperatures.