SUPERFACT: A Model Fuel for Studying the Evolution of the Microstructure of Spent Nuclear Fuel during Storage/Disposal

The transmutation of minor actinides (in particular, Np and Am), which are among the main contributors to spent fuel α-radiotoxicity, was studied in the SUPERFACT irradiation. Several types of transmutation UO$_{2}$-based fuels were produced, differing by their minor actinide content ($^{241}$Am, $^{237}$Np, Pu), and irradiated in the Phénix fast reactor. Due to the high content in rather short-lived alpha-decaying actinides, both the archive, but also the irradiated fuels, cumulated an alpha dose during a laboratory time scale, which is comparable to that of standard LWR fuels during centuries/millenaries of storage. Transmission Electron Microscopy was performed to assess the evolution of the microstructure of the SUPERFACT archive and irradiated fuel. This was compared to conventional irradiated spent fuel (i.e., after years of storage) and to other $^{238}$Pu-doped UO$_{2}$ for which the equivalent storage time would span over centuries. It could be shown that the microstructure of these fluorites does not degrade significantly from low to very high alpha-damage doses, and that helium bubbles precipitate

Role of self-irradiation defects on the ageing of 239PuCoGa5

6 pages, 18 referencesInternational audienceLow-temperature accumulation and annealing experiments, in conjunction with electrical resistivity and critical current density measurements, were used to study the ageing of the actinide superconductor PuCoGa5. These measurements reveal that 2-nm sized non-superconducting point-like regions are the main damage formed during room temperature ageing; smaller point-like defect were irrelevant to transport properties. Defect sizes and densities deduced from experiment agree with Transmission Electron Micoscopy observations

Evidence of SARS-CoV-2 bacteriophage potential in human gut microbiota

Background: In previous studies we have shown that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replicates in vitro in bacterial growth medium, that the viral replication follows bacterial growth, and it is influenced by the administration of specific antibiotics. These observations are compatible with a 'bacteriophage-like' behaviour of SARS-CoV-2. Methods: We have further elaborated on these unusual findings and here we present the results of three different supplementary experiments: (1) an electron-microscope analysis of samples of bacteria obtained from a faecal sample of a subject positive to SARS-CoV-2; (2) mass spectrometric analysis of these cultures to assess the eventual de novo synthesis of SARS-CoV-2 spike protein; (3) sequencing of SARS-CoV-2 collected from plaques obtained from two different gut microbial bacteria inoculated with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Results: Immuno-labelling with Anti-SARS-CoV-2 nucleocapsid protein antibody confirmed presence of SARS-CoV-2 both outside and inside bacteria. De novo synthesis of SARS-CoV-2 spike protein was observed, as evidence that SARS-CoV-2 RNA is translated in the bacterial cultures. In addition, phage-like plaques were spotted on faecal bacteria cultures after inoculation with supernatant from faecal microbiota of an individual positive to SARS-CoV-2. Bioinformatic analyses on the reads obtained by sequencing RNA extracted from the plaques revealed nucleic acid polymorphisms, suggesting different replication environment in the two bacterial cultures. Conclusions: Based on these results we conclude that, in addition to its well-documented interactions with eukaryotic cells, SARS-CoV-2 may act as a bacteriophage when interacting with at least two bacterial species known to be present in the human microbiota. If the hypothesis proposed, i.e., that under certain conditions SARS-CoV-2 may multiply at the expense of human gut bacteria, is further substantiated, it would drastically change the model of acting and infecting of SARS-CoV-2, and most likely that of other human pathogenic viruses

Comparative study of fission product release of homogeneous and heterogeneous high-burn up MOX fuel by Knudsen Effusion Mass Spectrometry supported by EPMA, SEM/TEM and thermal diffusivity investigations

publishedVersio

From Fission towards Fusion

see attachmentJRC.E.3-Materials researc

Studies on the Mechanism of Damage Creation and Track Formation in UO2 Induced by Swift Heavy Ions

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Simulation of Fission Damage in UO2 and Study of the Behaviour of Xe in UO2

In order to better understand the mechanisms of damage creation in nuclear fuels, 3mm diam. UO2 disks were implanted with 173 MeV Xe ions with fluences varying between 7.10x10 and 6.10x14 ions.cm-2. Come of these disks were analysed by TEM and SEM. Cross-sectional SEM of a UO2 sample implanted at the highest fluence revealed the Xe-rich zone to be located at a depth of 9.5 +-0.56 um. This is in good agreement with the calculated Xe-distribution profile and the displacement distribution produced by the Xe ions in UO2 and is, at the same time, a confirmation of the TRIM code at these high energies.JRC.E-Institute for Transuranium Elements (Karlsruhe

Heavy Ion Induced Damage in MgAl2O4, an Inert Matrix Candidate for the Transmutation on Minor Actinides.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

Fission-Fragment Spikes in Uranium Dioxide.

Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe

The high burnup structure in nuclear fuel

During its operating life in the core of a nuclear reactor, nuclear fuel is subjected to significant restructuring processes determined by neutron irradiation directly through nuclear reactions and indirectly through the thermo-mechanical conditions established as a consequence of such reactions. In today's light water reactors, starting after ~4 years of operation the cylindrical UO2 fuel pellet undergoes a transformation affecting its outermost radial region. The discovery of a newly forming structure required answering important questions concerning the safety of extended fuel operation, and still today poses a fascinating scientific challenge to fully understand the microstructural mechanisms responsible for its formation.JRC.DG.E.2-Hot cell