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Orléans, France

De Bilbao E.,Prisme Institute | Blond E.,Prisme Institute | Michel C.,Albi-Carmaux School of Engineering | Cutard T.,Albi-Carmaux School of Engineering | And 2 more authors.
InterCeram: International Ceramic Review | Year: 2010

This paper proposes a new method to determine the Young's modulus by means of high temperature bending test. Considering that the global behaviour of the experimental device and the sample is purely elastic during the unload phase and by exploiting that the effects of the indentation under the contact are lower at the beginning of the unloading, it is proposed to deduce the Young's modulus from the slope of the unloading curve. It can be shown that the Young's modulus for different silicon carbide (SiC) based refractory materials obtained by using this method is in good agreement with results of others tests such as tensile test or ultrasonic measurement.

Plevacova K.,CEA Cadarache Center | Journeau C.,CEA Cadarache Center | Piluso P.,CEA Cadarache Center | Poirier J.,Cemhti
Ceramics International | Year: 2014

In the frame of the Generation IV Sodium Fast Reactor (SFR) safety studies, a core catcher with a sacrificial material could be placed at the bottom of the nuclear reactor. Its role is to dilute the (U, Pu)O2 molten fuel in case of a hypothetical core meltdown accident. A Al2O 3-HfO2 ceramic is a candidate for the sacrificial material. To understand how the molten fuel would mix with this sacrificial material, the UO2-Al2O3-HfO2 system was investigated at CEA Cadarache PLINIUS corium platform. The eutectic position of the UO2-Al2O3-HfO2 was determined: the eutectic temperature is 1728±22 C (2001±22 K) and the eutectic composition is 30 wt% UO2-35 wt% Al2O 3-35 wt% HfO2. Then, the pseudo-binary UO2-(50 wt% Al2O3-50 wt% HfO2) phase diagram has been proposed. © 2013 Elsevier Ltd and Techna Group S.r.l.

Plevacova K.,CEA Cadarache Center | Journeau C.,CEA Cadarache Center | Piluso P.,CEA Cadarache Center | Zhdanov V.,National Nuclear Center | And 2 more authors.
Journal of Nuclear Materials | Year: 2011

Since the TMI and Chernobyl accidents the risk of nuclear severe accident is intensively studied for existing and future reactors. In case of a core melt-down accident in a nuclear reactor, a complex melt, called corium, forms. To be able to perform experiments with prototypic corium materials at high temperature, a coating which resists to different corium melts related to Generation I and II Water Reactors and Generation IV sodium fast reactor was researched in our experimental platforms both in IAE NNC in Kazakhstan and in CEA in France. Zirconium carbide was selected as protective coating for graphite crucibles used in our induction furnaces: VCG-135 and VITI. The method of coating application, called reactive wetting, was developed. Zirconium carbide revealed to resist well to the (U x, Zr y)O 2-z water reactor corium. It has also the advantage not to bring new elements to this chemical system. The coating was then tested with sodium fast reactor corium melts containing steel or absorbers. Undesirable interactions were observed between the coating and these materials, leading to the carburization of the corium ingots. Concerning the resistance of the coating to oxide melts without ZrO 2, the zirconium carbide coating keeps its role of protective barrier with UO 2-Al 2O 3 below 2000 °C but does not resist to a UO 2-Eu 2O 3 mixture. © 2011 Elsevier B.V. All rights reserved.

Valensi F.,University of Orleans | Pellerin N.,Cemhti | Pellerin N.,University of Orleans | Pellerin S.,University of Orleans | And 2 more authors.
High Temperature Material Processes | Year: 2010

The shielding gas used in the welding process has a strong influence on the metal transfer characteristics. When the gas is chemically active the physicochemical properties of the electrodes can be strongly altered which can increase or decrease arc stability. In order to get a better control over the process it is essential to understand how the electrodes are affected. As the electrode extremities are molten they can easily adsorb gases from the shielding gas, which can affect their microstructure. CO2 is one of the most commonly used active shielding gases. It is then interesting to know if the liquid metal at the extremity of the electrode can adsorbed the carbon it supplies, as it has strong influence on steel mechanical properties. Besides, various phases can form during metal cooling, depending on its concentration. It is then possible to get information on the carbon content by studying the ratio between phases. In order to show a possible enrichment, only the relative spatial evolution can be studied and no accurate phase identification is needed. Cross sections of the samples have been studied, using mainly optic microscopy. The two main phase ratio have been calculated after processing the obtained images. The results show a higher ratio of the phase associated to the highest carbon content close to the sample periphery, which support the hypothesis of carbon adsorption by the molten metal.

Bazin D.,University Paris - Sud | Andre G.,French Atomic Energy Commission | Weil R.,University Paris - Sud | Matzen G.,Cemhti | And 4 more authors.
Urology | Year: 2012

Objective: Bacterial imprints are always observed on highly carbonated apatite kidney stones but not struvite kidney stones. Struvite and carbonated apatite stones with a high CO 3 2/PO 4 3 rate are believed to develop from infections, but their structural differences at the mesoscopic scale lack explanation. Methods: We investigated 17 urinary calculi composed mainly of struvite or carbonated apatite by Fourier transform infrared, scanning electron microscopy, and powder neutron diffraction techniques. Results: Carbonated apatite but not struvite stones showed bacterial imprints. If the same stone contained both carbonated apatite and struvite components, bacterial imprints were observed on the carbonated apatite but not the struvite part. Moreover, neutron powder diffraction experiments revealed the crystal size of struvite stones were larger than that of carbonated apatite stones (250 ± 50 vs 50 nm). Conclusion: Bacterial imprints may appear more easily on kidney stones with small nanocrystals, such as carbonated apatite than with large nanocrystals, such as struvite. This approach may help identify bacteria contributing to stone formation, perhaps with negative results of urine culture. © 2012 Elsevier Inc. All Rights Reserved.

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