Transformations biochimiques et structurales de la protéine de transfert de lipides de l'orge (LTP1) au cours des procédés de maltage et de brassage (conséquence sur les propriétés moussantes de la bière)

BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Experimental approach to study the alteration of MOX MIMAS fuels in an underwater storage situation

International audienceAfter irradiation in a nuclear reactor, the irradiated Mimas MOX (Mixed Oxyde) fuel assemblies are stored in a pool before reprocessing or geological disposal. This long-term storage requires considering an incidental scenario corresponding to the presence of a through defect in the zircaloy cladding, responsible for a containment breach and potential degradation of the defective rod.This defect leads to the direct interaction between the spent fuel and the pool water. The pool water is pure aerated water that can contain boric acid at a concentration of 2g/L used as neutron absorber with a pH ranging from 4 to 6.5. It is also submitted to an intense gamma radiation field (around 1 k Gray/h) due to the presence of many fuel assemblies. The temperature of the pool ranges from 40 to 80°C because of the residual power released by the radioactive decay of the fuel assemblies.These conditions are favorable to the oxidizing dissolution of the fuel under alpha and beta gamma radiolysis of water which produces hydrogen peroxide H2O2, the main oxidizing species. This alteration can lead to the release of radionuclides in solution as well as to the formation of (U,Pu)O2+x oxidized layers and to the precipitation of secondary phases such as studtite or schoepite. These phases having a density lower than that of the fuel can induce a worsening of the defect and thus impact the mechanical strength of the rods. It is therefore important to study these degradation mechanisms with the aim of recovering the rods after several years and decades of storage. In order to assess this problem, an experimental approach coupling the study of simulating materials and highly radioactive materials is developed. It aims to describe the alteration mechanisms of fuels in contact with water as well as the reaction kinetics of dissolution/precipitation. This approach consists in implementing leaching experiments on materials ranging from model compounds (U, Th)O2, to MOX Mimas fuel (U, Pu)O2 irradiated or not in reactor. The model materials are developed at the ICSM by using thorium as a redox free plutonium surrogate. Thorium has the advantage of being easily manipulated but also of having a stable +IV valence, moreover like PuO2, ThO2 crystallizes in a fluorite structure Fm-3m. Homogeneous materials (U,Th)O2 are synthesized by hydroxide route in a first step. They are used as a precursor for the synthesis of materials with a heterogeneous microstructure produced by powder mixing in order to mimic the heterogeneous character of the MOX Mimas. Moreover, after irradiation in a reactor, the chemical composition of MOX is modified by the production of fission products that are classified into four families ((I) volatile fission products, (II) metallic precipitates, (III) oxide precipitates and (IV) FPs in solid solution in the fuel [3]. Two types of FPs are also simulated in the (U,Th)O2 model materials by addition of lanthanides (category IV) and platinum group metal elements (category (II)) during the synthesis of [4].Leaching experiments for these model or plutonium-containing materials are performed using two approaches:-Under dynamic conditions at the ICSM on (U,Th)O2 simulant/surrogate materials. These multiparametric experiments allow to study the effect of fuel heterogeneity and chemistry as well as water chemistry (boric acid, [H2O2], pH) on the oxidative dissolution of the fuel.-Under static conditions in a shielded cell in the Atalante facility at Marcoule on highly radioactive materials. The gamma dose rate within an assembly will be reproduced experimentally using a 60Co source given the small amount of fuel involved for the leaching experiment.These alteration experiments will be monitored over time by analyzing the solutions chemically and radiometrically and using surface characterization tools, the main one being Raman spectroscopy. This technique allows monitoring the evolution of many key parameters such as the chemical composition of the solid/solution interface, uranium oxidation state and the nature of the precipitated phases. It is also an isotopically sensitive technique for studying oxidation processes at the atomic scale [5, 6]. All this work will improve our understanding of the mechanisms of fuel oxidation and secondary phase precipitation in order to develop mechanistic model coupling chemistry to transport of chemical species in a defective rod. It will also contribute to the analysis of data acquired on defective rods extracted from storage pools

Protein Analysis of Surface Active Macromolecular Fractions Isolated From Various Champagne Wines

International audienc

The mechanisms of alteration of a homogeneous U0.73Pu0.27O2 MOx fuel under alpha radiolysis of water

International audienc

Alteration of a Mimas MOX fuel subjected to water radiolysis: surface characterization by optical/SEM image analysis and Raman spectroscopy.

International audienc

Raman and PAS Characterization of Electron Irradiated UO2 to Determine U Displacement Threshold

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Raman and PAS Characterization of Electron Irradiated UO2 to Determine U Displacement Threshold

International audienc

NKp30 isoforms and NKp30 ligands are predictive biomarkers of response to imatinib mesylate in metastatic GIST patients

Despite effective targeted therapy acting on KIT and PDGFRA tyrosine kinases, gastrointestinal stromal tumors (GIST) escape treatment by acquiring mutations conveying resistance to imatinib mesylate (IM). Following the identification of NKp30-based immunosurveillance of GIST and the off-target effects of IM on NK cell functions, we investigated the predictive value of NKp30 isoforms and NKp30 soluble ligands in blood for the clinical response to IM. The relative expression and the proportions of NKp30 isoforms markedly impacted both event-free and overall survival, in two independent cohorts of metastatic GIST. Phenotypes based on disbalanced NKp30B/NKp30C ratio (Delta BClow) and low expression levels of NKp30A were identified in one third of patients with dismal prognosis across molecular subtypes. This Delta BClow blood phenotype was associated with a pro-inflammatory and immunosuppressive tumor microenvironment. In addition, detectable levels of the NKp30 ligand sB7-H6 predicted a worse prognosis in metastatic GIST. Soluble BAG6, an alternate ligand for NKp30 was associated with low NKp30 transcription and had additional predictive value in GIST patients with high NKp30 expression. Such GIST microenvironments could be rescued by therapy based on rIFN-alpha and anti-TRAIL mAb which reinstated innate immunity