Synchrotron Radiation High Energy Resolution X-ray Absorption And Emission Spectroscopies And Their Application On The Research Of Actinide Materials

Synchrotron radiation X-ray absorption spectrum(XAS)and X-ray emission spectrum(XES)are important spectroscopy techniques based on the synchrotron radiation light source to research the material structure information,which could be used to acquire the valence state and electronic state of the goal atom,the species,numbers of the atoms around the selected atoms and the information about the local structure.The broadening of XAS and XES are decided by the lifetime of the core hole.The shorter lifetime of the core hole results in the increased broadening of the XAS and XES.Because of the short lifetime of the inner core hole,the conventional XAS and XES have large broadening which results in some information will be covered.Based on the conventional XAS and XES,the high energy resolution XAS and XES have the high energy resolution,which are the advanced spectroscopy techniques.The main research works of this thesis have supplied a technology of high energy resolution XAS and XES for BL14W1 beamline of Shanghai Synchrotron Radiation Facility(SSRF).This technology has been applied on the studies of actinide elements.The accomplished works include:1.The one crystal spectrometer has been updated at BL14W1 of SSRF and the performance parameters of energy resolution and signal-to-noise have been enhanced to the international level of the similar equipment;2.The design,construction and debugging of a three crystals spectrometer has been accomplished successfully,which provides the multi-crystal spectrometer with the more excellent performance parameters for the BL14W1 beamline.The performance of the three crystal spectrometer up to the international level of the similar equipment;3.The research of the high energy resolution XAS and XES of actinide elements has been realized in domestic.The combination of the one crystal spectrometer and the in-situ cell has supported the study of the oxidation process of UO2 under the variation temperatures.The acquisition of high energy resolution XAS under different temperatures provides the information of the valence state of UO2 in the oxidation process.The research of the Th O2 doped UO2 has been accomplished,which provides the information of the outer energy levels of Th in ThO2.A one crystal spectrometer and a three crystal spectrometer have been provided in this thesis,which is the equipment foundation for the development of the technology of the high energy resolution X ray XAS and XES.The information of valence state of U,which is acquired in the study of the oxidation process of UO2 under different temperatures,has supported the research of nuclear fuel cycle and the disposal of nuclear waste in theory.The information of the energy levels of Th in the mixed oxides,which is acquired in the study of UO2 doped ThO2,is helpful to understand the physical and chemical properties of the reaction products from the Th based reactor.