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|All Authors / Contributors:||
Catherine Dodane; Eric Simoni; Université de Paris-Sud.
|Notes:||Thèse : 2002PA112013.|
|Description:||189 p. : ill. ; 30 cm.|
|Responsibility:||Catherine Dodane ; sous la dir. de Eric Simoni.|
The transmutation of minor actinides in-reactor is one solution currently being studied for the long time management of nuclear waste. In the heterogeneous concept the radionuclides are incorporating in an inert ceramic matrix. The support material must be insensitive to radiation damage. Fission product damage is the main radiation damage source during the transmutation process and therefore it is of the utmost importance to study their effects. We irradiated spinels MgA12O4 (matrix of reference) and ZnAl2O4 by fast ions (by example: (86)Kr of approximately 400MeV) simulating the fission products. Under these conditions, the damage is primarily due to the electronic energy losses (Se). One of the structural features of spinel AB2O4 is that the two cations (A(2+) and B(3+)) can exchange their site. This phenomenon is quantified by the inversion parameter. We highlight by XRD in grazing incidence that the structural changes observed in MgAl2O4 correspond to an order-disorder transition from the cation sub-networks and not to a phase shift as described in the literature. Using other techniques characterizing the space group (Raman spectroscopy) as well as the local order (NMR 27Al, spectroscopy of absorption X with the thresholds K of Al and Zn), we confirm this interpretation. Moreover, for a fluence of 101̂4 ions/cm2̂, the loss of the order at long distance is observed thus meaning a beginning of amorphization of material. The ZnA12O4 spinel presents the same behavior. For this last spinel, an evolution of the inversion parameter according to the stopping power to power 2 was highlighted after irradiation by ions (86)Kr from approximately 20MeV. We illustrate our study by the analysis of the results obtained in XRD of an irradiation out of composite fuel (MgAl2O4 + UO2) called THERMHET.