UO2 surface oxidation by mixtures of water vapor and hydrogen as a function of temperature

In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water vapor on the UO2 surface as a function of temperature. The experiments were performed in situ inside a high pressure chamber attached to the XPS instrument. UO2 samples were put in contact with either hydrogen or argon streams, saturated with water at room temperature, and the sample surface evolution was analyzed by XPS. In the case of the water vapor/argon experiments, one experiment at 350°C was performed and, in the case of the water vapor/hydrogen experiments, the temperatures used inside the reactor were 60, 120, 200 and 350°C. On one hand, in presence of argon, the results obtained showed that the water vapor in the argon stream oxidized 93% of the U(IV) in the sample surface. On the other hand, the degree of UO2 surface oxidation showed a different dependence on the temperature in the experiments performed in the presence of hydrogen: the maximum surface oxidation occurred at 120°C, where 65.4% of U(IV) in the sample surface was oxidized, while at higher temperatures, the surface oxidation decreased. This observation is attributed to the increase of hydrogen reducing effect when temperature increases which prevents part of the oxidation of the UO2 surface by the water vapor.Peer ReviewedPostprint (author's final draft

Radiation-induced preparation of antimony from solutions of antimony/III/ chloride in organic liquids

Electron irradiation induced separation of Sb from SbCl3 solutions in anhydrous alcohols, ethers, ketones, acids, ethers, and aromatic hydrocarbon

Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a $^{60}$Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO$_2$ was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments.Comment: 25 pages, 7 figure

Differences in fundamental reaction mechanisms between high and low-LET in recent advancements and applications of ionizing radiation

International audienceRecent applications of high-LET radiation include boron neutron capture therapy. UV treatment of electron-irradiated UHMWPE impedes degradation caused by allyl radicals. Radiation synthesis of PVP nanogels above 55 1C leads to intra-molecular crosslinking. PCBs in contaminated sediments can be dechlorinated by reactions with hydrated electrons. a b s t r a c t Differences among the mechanisms of energy deposition by high-linear energy transfer (LET) radiation, consisting of neutrons, protons, alpha particles, and heavy ions on one hand, and low-LET radiation, exemplified by electron beam and gamma radiation on the other, are utilized in the selection of types of radiation used for specific applications. Thus, high-LET radiation is used for modification of carbon nanotubes, ion track grafting, and the synthesis of membranes and nanowires, as well as for characterization of materials by means of neutron scattering. Recent applications of low-LET irradiation include minimization of radiolytic degradation upon sterilization of ultra-high molecular weight polyethylene (UHMWPE), radiolytic synthesis of nanogels for drug delivery systems, grafting of polymers in the synthesis of adsorbents for uranium from seawater, and reductive remediation of PCBs

Gamma Radiolytic Degradation of 4-Chlorophenol Determination of Degraded Products with HPLC and GC-MS

Contamination by chlorophenols of surface water and groundwater is an emerging issue in environmental science and engineering. After their usage as pesticide, herbicide and disinfectant, these organic compounds subsequently enter the aquatic environment through a number of routes. Some of the chlorophenols are slightly biodegradable, while others are more persistent and mobile in the aquatic environment especially chlorophenols. Gamma radiolytic degradation is one of advance oxidation process that has been thought to be one of the promising treatments to deal with this problem. This radiolytic study was carried out in methanolic 4-CP (4-chlorophenol) samples. Among several factors effecting radiolytic degradation of 4-CP, dose and concentration are important that were evaluated under atmospheric conditions. A degradation yield (G –value) for 4-CP of 0.38 and 1.35 was achieved in 20 and 100mg/dm3 solution. It was observed that degradation yield decreases with increasing 4-CP concentration. Gamma radiolysis produce free radicals in solvent which further react with 4-CP molecules to generate different products. The identification of degradation products was proposed using HPLC and GC-MS

Development of highly selective ligands for separations of actinides from lanthanides in the nuclear fuel cycle

This account summarizes recent work by us and others on the development of ligands for the separation of actinides from lanthanides contained in nuclear waste streams in the context of a future European strategy for nuclear waste management. The current status of actinide/lanthanide separations worldwide is briefly discussed, and the synthesis, development, and testing of different classes of heterocyclic soft N- and S-donor ligands in Europe over the last 20 years is presented. This work has led to the current benchmark ligand that displays many of the desirable qualities for industrial use. The improvement of radiolytic stability through ligand design is also discussed

Observation of dose-rate dependence in a Fricke dosimeter irradiated at low dose rates with monoenergetic X-rays

<p>Absolute measurements of the radiolytic yield of Fe3+ in a ferrous sulphate dosimeter formulation (6 mM Fe2+), with a 20 keV x-ray monoenergetic beam, are reported. Dose-rate suppression of the radiolytic yield was observed at dose rates lower than and different in nature to those previously reported with x-rays. We present evidence that this effect is most likely to be due to recombination of free radicals radiolytically produced from water. The method used to make these measurements is also new and it provides radiolytic yields which are directly traceable to the SI standards system. The data presented provides new and exacting tests of radiation chemistry codes.</p