In situ HT-XRD study of the UO2_2-PuO2_2-Pu2_2O3_3 sub-system

International audienc

Reuse of medical face masks in domestic and community settings without sacrificing safety: Ecological and economical lessons from the Covid-19 pandemic

The need for personal protective equipment increased exponentially in response to the Covid-19 pandemic. To cope with the mask shortage during springtime 2020, a French consortium was created to find ways to reuse medical and respiratory masks in healthcare departments. The consortium addressed the complex context of the balance between cleaning medical masks in a way that maintains their safety and functionality for reuse, with the environmental advantage to manage medical disposable waste despite the current mask designation as single-use by the regulatory frameworks. We report a Workflow that provides a quantitative basis to determine the safety and efficacy of a medical mask that is decontaminated for reuse. The type IIR polypropylene medical masks can be washed up to 10 times, washed 5 times and autoclaved 5 times, or washed then sterilized with radiations or ethylene oxide, without any degradation of their filtration or breathability properties. There is loss of the antiprojection properties. The Workflow rendered the medical masks to comply to the AFNOR S76-001 standard as “type 1 non-sanitory usage masks”. This qualification gives a legal status to the Workflow-treated masks and allows recommendation for the reuse of washed medical masks by the general population, with the significant public health advantage of providing better protection than cloth-tissue masks. Additionally, such a legal status provides a basis to perform a clinical trial to test the masks in real conditions, with full compliance with EN 14683 norm, for collective reuse. The rational reuse of medical mask and their end-of-life management is critical, particularly in pandemic periods when decisive turns can be taken. The reuse of masks in the general population, in industries, or in hospitals (but not for surgery) has significant advantages for the management of waste without degrading the safety of individuals wearing reused masks

Cold atoms in space: community workshop summary and proposed road-map

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.publishedVersio

Cold atoms in space: community workshop summary and proposed road-map

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies

Cold atoms in space: community workshop summary and proposed road-map

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies

Influence of Phase Separation on the Oxidation of (U,Pu)O 2– x

International audienceThe oxidation of six (U1–y,Puy)O2–x powdered samples, with y = 14, 24, 35, 46, 54, and 62 mol %, was studied in situ by high-temperature XRD at different temperatures. The samples were first reduced at 1500 °C to an oxygen to metal ratio (O/M) lower than 2.00. Afterward, the temperature was rapidly decreased to a value between 200 and 800 °C, which was followed by a long isothermal plateau during which diffraction patterns were recorded continuously. We observed structural changes in the material as it oxidized, in some cases passing through a biphasic domain. We discuss the influence of phase separation on the formation of a passive layer and the kinetics of phase transformations. It was found that entering the biphasic fcc1 + fcc2 domain will inhibit the formation of a passive layer. We hypothesize that the reason behind this behavior is the dependence of oxygen diffusion on the concentration of oxygen defect

Biphasic MO 2+ x –M 3 O 8– z Domain of the U–Pu–O Phase Diagram

International audienceThe reduction of six mixed-oxide samples containing 14, 24, 35, 46, 54, and 62 mol % Pu was studied in situ by X-ray diffraction. The samples were first oxidized in air and subsequently reduced in a controlled atmosphere corresponding to a stoichiometric composition with an O/M = 2.00. After oxidation, we observed two structures, one cubic and one orthorhombic, MO2+x and M3O8–z. The two phases were subsequently reduced back to their stoichiometric O/M = 2.00 in a controlled atmosphere. The plutonium contents of the two resulting cubic structures differed from the initial one. We conclude that strong cation transport took place during oxidation, according to the shape of the tie lines in the biphasic MO2+x/M4O9–M3O8–z domain. The resulting overall O/M after oxidation was estimated. We propose the shape of the tie lines in the aforementioned biphasic domain and suggest a maximal plutonium solubility in the M3O8 structure at 8 ± 2 mol % (Pu/U + Pu) at 1573 K

In-Situ High Temperature XRD on U0.54Pu0.46O2-x A Study of the Miscibility Gap

International audienceIt has been shown in previous studies that a miscibility gap exists in the hypo-stoichiometric region UO2-PuO2-Pu2O3 with one phase poor in oxygen, and the other with an O/M (Oxygen to Metal ratio) close to 2.00. Data on the evolution of this region in temperature, especially in the vicinity of the oxygen content corresponding to the highest temperature at which the gap can be observed, is scarce. A high temperature X-ray diffractometer with a dedicated gas control setup was used to study the described region in-situ. We have observed reflections of the two cubic phases, with one increasing and the other decreasing in intensity during the thermal plateaus lasting up to 20 h. We compare the calculated lattice parameters with literature. We estimated the O/M evolution of our samples from a comparison of phase fractions values obtained by Rietveld refinement and calculations using the Calphad method

High Temperature X-ray Diffraction Study of the Oxidation Products and Kinetics of Uranium–Plutonium Mixed Oxides

International audienceThe oxidation products and kinetics of two sets of mixed uranium-plutonium dioxides containing 14%, 24%, 35%, 46%, 54%, and 62% plutonium treated in air were studied by means of in situ X-ray diffraction (XRD) from 300 to 1773 K every 100 K. The first set consisted of samples annealed 2 weeks before performing the experiments. The second one consisted of powdered samples that sustained self-irradiation damage. Results were compared with chosen literature data and kinetic models established for UO2. The obtained diffraction patterns were used to determine the temperature of the hexagonal M3O8 (M for metal) phase formation, which was found to increase with Pu content. The maximum observed amount of the hexagonal phase in wt % was found to decrease with Pu addition. We conclude that plutonium stabilizes the cubic phases during oxidation, but the hexagonal phase was observed even for the compositions with 62 mol % Pu. The results indicate that self-irradiation defects have a slight impact on the kinetics of oxidation and the lattice parameter even after the phase transformation. It was concluded that the lattice constant of the high oxygen phase was unaffected by the changes in the overall O/M when it was in equilibrium with small quantities of M3O8. We propose that the observed changes in the high oxygen cubic phase lattice parameter are a result of either cation migration or an increase in the miscibility of oxygen in this phase. The solubility of Pu in the hexagonal phase was estimated to be below 14 mol % even at elevated temperatures

New Insights into the Thermal Expansion of Neptunium Dioxide up to 2000K

AbstractWe report for the first time the thermal expansion of NpO2 up to 2000K and compare it to the one of UO2 and PuO2. Lattice parameters were measured as a function of temperature by in situ X-ray diffraction with neutral, reducing and oxidizing atmospheres. Data for NpO2 under neutral and reducing conditions perfectly superpose. Up to 1550K, thermal expansion varies linearly with increasing temperature. Above, thermal expansion presents a curvature towards higher lattice parameters. No bibliographic data were available for this temperature range for comparison. As for the thermal expansion of UO2, we propose this curvature is certainly inferred by the formation of lattice defects in the oxygen sub-lattice. Expression of thermal expansion and coefficients of thermal expansion at given temperatures for NpO2, are presented