PhD abstract

Isotopic analysis of actinides is necessary for fuel cycle management, non-proliferation treaty control or environmental monitoring. The accuracy of these analyses may be limited by the performance of the detector used but also by the uncertainties associated with the emission intensities available in the nuclear data tables. The disintegration of actinides is generally followed by intense X-ray and gamma photon emissions in the energy range below 100 keV. Their detection may be of particular interest for actinide analysis. However, conventional measurement techniques do not allow to properly separate the lines of the considered emissions. This thesis was devoted to the measurement of intensities using a cryogenic detector. The latter is based on a magnetic metallic calorimeter (MMC) that measures energy deposition as a temperature rise. The MMC, called SMX3, has four pixels and is specifically designed for high resolution X-ray and gamma spectrometry in the energy range below 100 keV to measure actinide emission intensities. In addition to the high resolution provided by SMX3 through its operating principle, this detector has a constant detection efficiency and almost equal to 100% over the energy range below 25 keV, where actinides' XL rays are emitted.The SMX3 yield curve was calibrated by a method that consists of a single standard source measurement of Am-241 combined with Monte Carlo simulations. The three actinides Pu-238, Pu-239, and Cm-244 were measured to provide absolute and relative intensities of Li-Yj emissions (with Y=L,M,N,O,P i=1,2,3 and j=1..7). Thanks to the very high energy resolution of the MMC, the individual XL lines of actinides can be separated. Satellite lines are also detected, their intensities relative to the diagram lines depend on the isotope according to the fundamental atomic parameters. The intensities of the individual XL lines could be determined for the first time, especially for the transitions L₁-L₃. In addition, the intensities of the XLi regions (i=1,2,3) were established. The intensities of the overall XL and XL groups are compared with the calculations and experimental data available in the literature.

Key words

metallic magnetic calorimeter, actinide, X and gamma rays spectroscopy

PhD thesis