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

原位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顶压室中选定的金属氧化物-水系统的结构和组成。拟议的实验将解决与超临界水冷反应堆中的腐蚀和腐蚀产物传输有关的三个重要问题。它们是：(1)氧化铬(Ekolaite)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传输？以及，(3)在超临界水中，辐照对过渡金属络合物的结构和稳定性有什么影响？本研究首次使用时间分辨能量色散X射线吸收光谱(ED-XAS)来监测超临界水中同步辐射对过渡金属离子局域结构和价态的影响。X射线吸收光谱也将被用来研究超临界水中铬和铁纳米粒子与过渡金属水离子的反应。同步加速器X射线荧光光谱分析(SXRF)将被用来直接确定在高温和压力下热液金刚石顶压室中流体的组成。预期的结果将大大提高我们对水中流体与候选材料的相互作用以及在与第四代操作条件相关的条件下腐蚀产物在水中的传输的理解。这项研究还将为一个数据库提供新的热化学数据，该数据库需要定量预测和控制水化学，以便最大限度地减少高温下材料的降解和腐蚀产物的运输。

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.