An original approach for Raman spectroscopy analysis of radioactive materials and its application to americium‐containing samples

Abstract

An approach for Raman measurements of highly radioactive samples is presented here. The innovative part of this approach lies in the fact that no single part of the Raman equipment is in direct contact with the radioactive sample, as the sample is sealed in an alphatight capsule. Raman analysis is effectively performed through the optical-grade quartz window closing the capsule. This allows performing micro-Raman measurements on radioactive samples with no limitations on the laser source wavelength, polarisation mode, spectrometer mode and microscope mode (provided the focal length of the microscope objective is greater than the thickness of the quartz window and with sub mg samples). Some example results are shown and discussed. In particular, some spectral features of americium-containing oxide nuclear fuel specimens are presented. Raman spectra clearly reveal in these specimens the presence of abundant oxygen defects induced in the fcc fluorite lattice by trivalent americium. In order to complete the analysis the Raman spectrum of pure americium dioxide was also measured with a lower energy excitation source compared with previous research. The current results seem to be consistent with the possible occurrence of a photolysis process induced by the Raman laser, resulting in the formation of hyperstoichiometric americium sesquioxide Am 2 O 3 + z . Such a photolytic process is deemed to be unavoidable when visible lasers are used as excitation sources for the Raman analysis of americium dioxide.

Chemically stabilized δ-Bi2O3 phase: Raman scattering and X-ray diffraction studies

“…We suggest that this mode at 719 cm -1 is related to oxygen defects in the structure. Similar behavior has been observed in fluorite structure having punctual defects [29][30][31] , i.e. interstitial oxygens as in case of UO 2+x 31 or oxygen vacancies as in UO 2 doped trivalent metals 29,30 .…”

Recent advances in linear and non‐linear Raman spectroscopy. Part X

“…Naji and co‐workers reported an original approach for Raman spectroscopy analysis of radioactive materials and its application to americium‐containing samples. The innovative part of this approach lies in the fact that no single part of the Raman equipment is in direct contact with the radioactive sample, as the sample is sealed in an alpha‐tight capsule . Okajima et al .…”

“…The innovative part of this approach lies in the fact that no single part of the Raman equipment is in direct contact with the radioactive sample, as the sample is sealed in an alpha-tight capsule. [166] Okajima et al report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N 2 .…”

Raman spectrum of plutonium dioxide: Vibrational and crystal field modes

“…The whole procedure has been described in details elsewhere. 17 The Raman microscope was equipped for the present measurements with a long working distance (10.6 mm) objective which offers a 0.5 numerical aperture with x50 magnification. The Raman spectrometer employed in this research is a Jobin-Yvon T 64000 equipped with a 1800 grooves per mm grating, a low noise liquid nitrogen cooled symphony CCD detector, a subtractive pre-monochromator (in triple mode) which allows access to anti-Stokes spectrum lines while blocking the elastic Rayleigh line.…”

“…The experimental part of this study was carried out with the help of an original encapsulation technique, described in a very recent publication. 17 Among other things, this technique permits, for the investigation of such highly radioactive materials, the use of different excitation laser sources, and the employment of the triple subtractive spectrometer configuration. The first feature is important for the analysis of resonant and energy dispersive modes and for the detection of fluorescence features in the Raman spectra; the second is necessary for the study of low-energy Raman lines and anti-Stokes peaks.…”