科研之友
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摘要
A reliable method to probe and characterise the oxidation of actinide oxides by means of Raman spectroscopy is introduced. The present so-called Raman laser heating method enables studying the behaviour of various compounds at high temperatures and under a given atmosphere with the unique alteration of a small amount of sample, which is certainly advantageous in terms of safety when handling hazardous or radioactive materials. The approach is based on a dual use of the laser beam, which is at the same time employed as excitation source for the Raman analysis and as heating source, by exploiting the possibility to vary the beam power density reaching the sample surface. A high laser power density can lead to a significant increase of the analyte surface temperature by up to several hundred of degrees. A sufficiently low power density allows us to subsequently acquire the corresponding Raman spectrum at the same point without distorting the measurement. In this work, UO2 powder has been subjected to Raman laser heating in air as a proof of this method's applicability, attaining a sequential acquisition of the characteristic Raman spectra of the different oxides involved in the oxidation from UO2 to U3O8. The temperature at which such sequence of phase transformations started to occur was estimated to be around (560 +/- 40)K. The temperature at the sample surface was estimated from the Stokes/anti-Stokes intensities ratio, using a similar set-up to that used in the Raman laser heating experiments. These results are particularly appealing in remote analyses, like those required in the study of nuclear fuel and nuclear waste.
- 出版日期2018-5
