par Meleshenkovskii, Iaroslav 
Président du jury De Lentdecker, Gilles
Promoteur Pauly, Nicolas
Co-Promoteur Labeau, Pierre-Etienne
Publication Non publié, 2019-08-27
Président du jury De Lentdecker, Gilles
Promoteur Pauly, Nicolas
Co-Promoteur Labeau, Pierre-Etienne
Publication Non publié, 2019-08-27
Thèse de doctorat
| Résumé : | In recent years, there has been a vast progress and development in the domain of room temperature medium resolution detector technologies for various fields of ionizing radiation detection and measurement. Indeed, introduction of the new generation of room temperature sensors based on compound semiconductors such as CdZnTe (CZT) and scintillation devices based on LaBr3(Ce) crystals have opened new possibilities for many practical applications which were previously limited to traditional detectors based on HPGe and NaI sensors. Room temperature medium resolution detectors represent a trade-off between their room temperature operation and significantly better spectroscopic performance compared to NaI detectors. Due to their attractive features and spectroscopic performance they become promising candidates for various fields of applied radiation detection and measurement. Among such fields are safeguards applications where room temperature operation and compact design coupled with attractive spectroscopic performance makes CZT and LaBr3(Ce) promising candidates for a wide range of tasks. Determination of uranium and plutonium isotopic composition is one of the tasks where room temperature medium resolution detectors are proposed as a feasible alternative to traditional HPGe and NaI detectors, allowing to address such disadvantages of the latter as the necessity of cooling, heavy, bulky instrumentation or poor energy resolution. To answer the question of room temperature medium resolution detectors feasibility for isotopic composition determination tasks in safeguards applications, adequate analysis tools used to derive the isotopic composition of uranium and plutonium materials measured with such a medium resolution quality are necessary. Among the most widely used in safeguards methods are passive X- and gamma-ray spectroscopy based methods used for non-destructive assay of uranium and plutonium materials. However, the traditional algorithms based on the formalism of such methods were optimized for high resolution HPGe detectors and require corresponding parameters and spectroscopic performance and thus cannot be used directly with medium resolution detectors, such as CZT and LaBr3(Ce). These algorithms require an adaptation of their underlying formalism and analysis routines to be suitable for the spectroscopic performance of room temperature medium resolution detectors. However, the traditional algorithms have conceptual limitations when applied to medium resolution spectra in terms of accuracy and uncertainty. To overcome the deficiencies of the latter, in this PhD project novel methodologies that are not constrained by the physics and statistical tools of the traditional algorithms are proposed and investigated. Such algorithms treat measured spectra using higher dimensionalities and can be fully disengaged from the interaction physics. The goals of this PhD project aim not only to investigate the performance of different passive non-destructive X- and gamma-ray based methods used with room temperature medium resolution detectors in application to uranium and plutonium tasks, but also to report on their limits and possibilities, corresponding accuracy and uncertainties, as well as to provide recommendations for isotopic composition determination tasks using such room temperature detectors in safeguards applications. |
