Stability of zinc stearate under alpha irradiation in the manufacturing process of SFR nuclear fuels

The manufacture of new fuels for sodium-cooled fast reactors (SFRs) will involve powders derived from recycling existing fuels in order to keep on producing electricity while saving natural resources and reducing the amount of waste produced by spent MOX fuels. Using recycled plutonium in this way will significantly increase the amount of 238Pu, a high energy alpha emitter, in the powders. The process of shaping powders by pressing requires the use of a solid lubricant, zinc stearate, to produce pellets with no defects compliant with the standards. The purpose of this study is to determine the impact of alpha radiolysis on this additive and its lubrication properties. Experiments were conducted on samples in contact with PuO2, as well as under external helium ion beam irradiation, in order to define the kinetics of radiolytic gas generation. The yield results relating to the formation of these gases (G0) show that the alpha radiation of plutonium can be simulated using external helium ion beam irradiation. The isotopic composition of plutonium has little impact on the yield. However, an increased yield was globally observed with increasing the mean linear energy transfer (LET). A radiolytic degradation process is proposed

The camera of the fifth H.E.S.S. telescope. Part I: System description

In July 2012, as the four ground-based gamma-ray telescopes of the H.E.S.S. (High Energy Stereoscopic System) array reached their tenth year of operation in Khomas Highlands, Namibia, a fifth telescope took its first data as part of the system. This new Cherenkov detector, comprising a 614.5 m^2 reflector with a highly pixelized camera in its focal plane, improves the sensitivity of the current array by a factor two and extends its energy domain down to a few tens of GeV. The present part I of the paper gives a detailed description of the fifth H.E.S.S. telescope's camera, presenting the details of both the hardware and the software, emphasizing the main improvements as compared to previous H.E.S.S. camera technology.Comment: 16 pages, 13 figures, accepted for publication in NIM

Surfactant controlled zwitterionic cellulose nanofibril dispersions

Zwitterionic cellulose nanofibrils (ZCNF) with isoelectric point of 3.4 were obtained by grafting glycidyltrimethylammonium chloride onto TEMPO/NaBr/NaOCl-oxidised cellulose nanofibrils. ZCNF aqueous dispersions were characterized via transmission electron microscopy, rheology and small angle neutron scattering, revealing a fibril-bundle structure with pronounced aggregation at pH 7. Surfactants were successfully employed to tune the stability of the ZCNF dispersions. Upon addition of the anionic surfactant, sodium dodecyl sulfate, the ZCNF dispersion shows individualized fibrils due to electrostatic stabilization. On the contrary, upon addition of the cationic species dodecyltrimethylammonium bromide, the dispersion undergoes charge neutralization, leading to more pronounced flocculation

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Radiolyse alpha du ligand DOTA en solution aqueuse

International audienc

Comportement sous rayonnement alpha de la butyraldoxime, un substituant potentiel à l'hydrazine dans le procédé PUREX

National audienceCette étude concerne le comportement sous rayonnement alpha de la butyraldoxime, un substituant potentiel au nitrate d'hydrazinium lors du retraitement du combustible nucléaire irradié, et plus précisément lors de la phase de séparation uranium-plutonium. La méthode expérimentale employée pour étudier la radiolyse de ce composé est dans un premier temps détaillée autour d'un exemple, la production de peroxyde d'hydrogène. Puis, quelques résultats concernant la stabilité de la molécule et la formation de produits gazeux et de produits en phase liquide sont présentés

Kinetics of nitrous acid formation in a two-phase tri-n-butylphosphatediluent/aqueous nitric acid extraction system under the effect of power ultrasound

International audienc