Effets d'irradiation et comportement des produits de fission dans la zircone et le spinelle

Commission d'examen : Président du Jury : Michel Genet (IPN Orsay)- Rapporteurs : Serge Bouffard (CIRIL Caen) et Léo Mazerolles (CECM Vitry) - Correspondant CEA : Michel Beauvy (DEN/DEC CEA Cadarache) - Correspondant EDF : Guy Chaigne (SEPTEN Villeurbanne) - Directeur de thèse : Lionel Thomé (CSNSM Orsay) - Commission d'examen : Président du Jury : Michel Genet (IPN Orsay)- Rapporteurs : Serge Bouffard (CIRIL Caen) et Léo Mazerolles (CECM Vitry) - Correspondant CEA : Michel Beauvy (DEN/DEC CEA Cadarache) - Correspondant EDF : Guy Chaigne (SEPTEN Villeurbanne) - Directeur de thèse : Lionel Thomé (CSNSM Orsay)Crystalline oxides, such as zirconia (ZrO2) and spinel (MgAl2O4), are promising inert matrices for the transmutation of plutonium and minor actinides. This work deals with the study of the physico-chemical properties of these matrices, more specifically their behaviour under irradiation and their capacity to retain fission products. Irradiations at low energy and incorporation of stable analogs of fission products (Cs, I, Xe) into yttria-stabilized zirconia and magnesium-aluminate spinel single crystals were performed by using the ion implanter IRMA (CSNSM-Orsay). Irradiations at high energy were made on several heavy ion accelerators (GANIL-Caen, ISL-Berlin, HIL-Varsovie). The damage induced by irradiation and the release of fission products were monitored by in situ Rutherford Backscattering Spectrometry experiments. Transmission electron microscopy was also used in order to determine the nature of the damage induced by irradiation. The results show that irradiation of ZrO2 and MgAl2O4 with heavy ions (~ hundred keV and ~ hundred MeV) induces a huge structural damage in crystalline matrices. Total disorder (amorphisation) is however never reached in zirconia, contrary to what is observed in the case of spinel. The results also emphasise the essential role played by the concentration of implanted species on their retention capacity. A dramatic release of fission products was observed when the concentration exceeds a threshold of a few atomic percent. Irradiation of implanted samples with medium-energy noble-gas ions leads to an enhancement of the fission product release. The exfoliation of spinel crystals implanted at high concentration of Cs ions is observed after a thermal treatment at high temperature.Certains oxydes sous forme cristalline, plus particulièrement la zircone (ZrO2) et le spinelle (MgAl2O4), sont des matrices potentielles pour la transmutation du plutonium et des actinides mineurs. Ce travail concerne l'étude des propriétés physico-chimiques de ces matrices, avec un accent particulier sur leur comportement vis-à-vis de l'irradiation et leur capacité à confiner les produits de fission. Les irradiations à basse énergie et l'incorporation d'analogues stables de produits de fission (Cs, I, Xe) dans des monocristaux de ZrO2 (phase cubique stabilisée avec Y2O3) et MgAl2O4 ont été réalisées avec l'implanteur d'ions du CSNSM-Orsay. Les irradiations à haute énergie ont été effectuées sur divers accélérateurs d'ions lourds (GANIL-Caen, ISL-Berlin, HIL-Varsovie). Les techniques de microanalyse nucléaire (RBS et canalisation) ont été mises en œuvre in situ sur l'accélérateur ARAMIS du CSNSM-Orsay pour caractériser le désordre créé par l'irradiation, et pour étudier le relâchement des produits de fission. Des expériences complémentaires de microscopie électronique à transmission ont été réalisées afin de déterminer la nature du désordre créé. Les résultats expérimentaux indiquent que l'irradiation de ZrO2 et MgAl2O4 avec des ions lourds de quelques centaines de keV ou de quelques centaines de MeV crée un désordre structural important dans les matrices cristallines. Le désordre total (amorphisation) n'est jamais atteint dans le cas de la zircone, contrairement au spinelle. Ces résultats montrent également l'influence déterminante de la concentration en produits de fission sur leur relâchement dans les deux matériaux étudiés, avec une forte augmentation du relâchement quand la concentration excède une valeur seuil, ou en présence de défauts produits par une irradiation avec des ions de gaz rares. Une exfoliation du spinelle implanté à forte concentration d'ions Cs est observée après traitement thermique à haute température

Effets d'irradiation et comportement des produits de fission dans la zircone et le spinelle

Certains oxydes sous forme cristalline, plus particulièrement la zircone (ZrO2) et le spinelle (MgAl2O4), sont des matrices potentielles pour la transmutation du plutonium et des actinides mineurs. Ce travail concerne l'étude des propriétés physico-chimiques de ces matrices, avec un accent particulier sur leur comportement vis-à-vis de l'irradiation et leur capacité à confiner les produits de fission. Les irradiations à basse énergie et l'incorporation d'analogues stables de produits de fission (Cs, J, Xe) dans des monocristaux de ZrO2 (phase cubique stabilisée avec Y2O3) et MgAl2O4 ont été réalisées avec l'implanteur d'ions du CSNSM-Orsay. Les irradiations à haute énergie ont été effectuées sur divers accélérateurs d'ions lourds (GANIL-Caen, ISL-Berlin, HIL-Varsovie). Les techniques de microanalyse nucléaire (RBS et canalisation) ont été mises en œuvre in situ sur l'accélérateur ARAMIS du CSNSM-Orsay pour caractériser le désordre créé par l'irradiation, et pour étudier le relâchement des produits de fission. Des expériences complémentaires de microscopie électronique à transmission ont été réalisées afin de déterminer la nature du désordre créé. Les résultats expérimentaux indiquent que l'irradiation de ZrO2 et MgAl2O4 avec des ions lourds de quelques centaines de keV ou de quelques centaines de MeV crée un désordre structural important dans les matrices cristallines. Le désordre total (amorphisation) n'est jamais atteint dans le cas de la zircone, contrairement au spinelle. Ces résultats montrent également l'influence déterminante de la concentration en produits de fission sur leur relâchement dans les deux matériaux étudiés, avec une forte augmentation du relâchement quand la concentration excède une valeur seuil, ou en présence de défauts produits par une irradiation avec des ions de gaz rares. Une exfoliation du spinelle implanté à forte concentration d'ions Cs est observée après traitement thermique à haute température.Crystalline oxides, such as zirconia (ZrO2) and spinel (MgAl2O4), are promising inert matrices for the transmutation of plutonium and minor actinides. This work deals with the study of the physico-chemical properties of these matrices, more specifically their behaviour under irradiation and their capacity to retain fission products. Irradiations at low energy and incorporation of stable analogs of fission products (Cs, I, Xe) into yttria-stabilized zirconia and magnesium-aluminate spinel single crystals were performed by using the ion implanter IRMA (CSNSM-Orsay). Irradiations at high energy were made on several heavy ion accelerators (GANIL-Caen, ISL-Berlin, HIL-Varsovie). The damage induced by irradiation and the release of fission products were monitored by in situ Rutherford Backscattering Spectrometry experiments. Transmission electron microscopy was also used in order to determine the nature of the damage induced by irradiation. The results show that irradiation of ZrO2 and MgAl2O4 with heavy ions (~ hundred keV and ~ hundred MeV) induces a huge structural damage in crystalline matrices. Total disorder (amorphisation) is however never reached in zirconia, contrary to what is observed in the case of spinel. The results also emphasise the essential role played by the concentration of implanted species on their retention capacity. A dramatic release of fission products was observed when the concentration exceeds a threshold of a few atomic percent. Irradiation of implanted samples with medium-energy noble-gas ions leads to an enhancement of the fission product release. The exfoliation of spinel crystals implanted at high concentration of Cs ions is observed after a therminal treatment at high temperature.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

In situ characterization of irradiation-induced microstructural evolution in urania single crystals at 773 K

International audienceImplantations with low-energy ions (Xe, La) on UO2 single crystals at 773 K were performed to investigate the role played by both the radiation damage and the incorporation of foreign elements on the matrix destabilisation. The radiation damage was monitored by both in situ RBS-C and in situ TEM during ion irradiation experiments performed at 773 K. RBS-C data shows a similar regular increase of the radiation-induced disorder in crystals for both Xe and La ions followed by a saturation plateau at about 3–4 dpa. An unexpected difference of the value of the saturation plateaus is observed, with a higher value recorded for Xe-irradiated crystals. In situ TEM images show the apparition and evolution of several defects as a function of the ion dose up to 40 dpa, irrespective of the nature of the bombarding ion: ‘black dots’ defects, dislocation loops and lines, and finally a dislocation network at high dpa. Nanometre-sized gas bubbles were observed at 773 K for the Xe-implanted crystal for doses larger than 3 dpa. Neither precipitate nor cavity were observed on La-implanted crystals. The difference in the saturation plateau as seen by RBS-C can be ascribed to the formation of the Xe aggregates that lead to an increase of the dechannelling yield

Channeling Study of the Damage Induced in Ion-Irradiated Ceramic Oxides

International audienceThe evaluation of the damage generated in crystalline ceramic oxides placed in a radiative environment is a major challenge in many technological domains. The use of the channeling technique is particularly well adapted to measure the depth distribution of the irradiation-induced disorder and to monitor the damage build-up. This paper describes the methodology used for the study of radiation damage with the channeling technique, presents a new method of analysis of channeling data based on Monte-Carlo simulations and provides recent results concerning the damage induced in ion-bombarded ceramic oxide single crystals in both nuclear (low-energy ion irradiation) and electronic (high-energy ion irradiation) slowing-down regimes

Helium bubble nucleation and growth in alloy HT9 through the use of in situ TEM: Sequential He-implantation and heavy-ion irradiation versus dual-beam irradiation

International audienceThe formation of He bubbles in Ferritic/Martensitic steel HT9 is investigated through the use of in situ Transmission Electron Microscopy coupled with He implantation and heavy ion irradiation. Of particular interest is the effect of increasing He appm/dpa ratio on the formation and growth of the bubbles, as well as the effect of the sequential order of ion irradiation i.e. Hepre-implantation followed by heavy-ion irradiation versus true dual-beam irradiation. The role of He is discussed

Formation of crystallographically oriented metastable Mg1.8_{1.8}Si in Mg ion-implanted Si

International audienceMetastable hexagonal Mg–Si was synthesized by implanting Mg ion into Si. Single-crystalline Si(111) was irradiated with Mg ions at elevated temperature followed by thermal annealing under vacuum. Microstructural analysis with transmission electron microscopy revealed the formation of precipitates with sizes of several 10 nm in the damaged crystalline Si matrix. Using electron diffraction, the precipitates were identified as Mg1.8Si, and the crystallographic orientation relationship between Mg1.8Si precipitates and Si was determined. The phase stability of Mg1.8Si in the Si matrix is discussed in terms of the internal stress generated during the precipitation process

Nature of Defects Induced by Au Implantation in Hexagonal Silicon Carbide Single Crystals

International audienc

In situ TEM observations of ion irradiation damage in boron carbide

International audienceThis paper presents an in situ Transmission Electron Microscopy (TEM) study of the damage formation process in ion-irradiated boron carbide used as neutron absorber for fast nuclear reactors. We focused our experiment on the damage induced by 1 MeV gold ions irradiation performed on the JANNuS-Orsay in situ dual ion beam TEM facility. The effects of the crystallographic orientation and the temperature (RT, 500 °C and 800 °C) on the ion-irradiated boron carbide structure were studied. The different steps of damage formation leading to amorphization are described. At RT, material amorphization is observed at a damage dose threshold around 7.5 displacements per atom (dpa). It is also shown that no amorphization occurred when irradiation is performed at 500 °C or 800 °C up to the highest fluence studied (3 × 1015 ions cm−2, i.e. 7.6 dpa)

in-situ TEM observations of irradiation damage in boron carbide

International audience→ Lamella preparation using the Focused Ion Beam (FIB) technique → Observe the formation of ballistic damage induced by heavy ions (Au +) irradiation → Observe the crystallographic orientation effects on the damage formation → Identify the amorphisation threshold (comparison with recent results of D