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International audience; During ITER operation, it is expected that the large panel of plasma-wall interactions triggers the production of dust particles from the tungsten and beryllium first wall. These particles can be loaded with tritium (T) used as a fuel for the fusion reaction; T inventory is of prime importance for the safety assessment, particularly when considering dispersible matters that could be released in case of a Loss Of Vacuum Accident (LOVA),. The impact of accidental inhalation of such particles has therefore to be evaluated. Yet, particles properties in terms of tritium inventory and general behaviour are strongly dependent on their physical and chemical characteristics, and large uncertainties remain on those parameters; It is therefore important to obtain and characterize relevant W dust samples for toxicity studies before ITER operation starts. We produced model tungsten (W) Nano-Particles (NPs) by two different methods with characteristics closer to the plasma-wall interaction processes than grinding (usually used to produce commercial NPs): (i) magnetron plasma sputtering followed by gas condensation as well as (ii) laser ablation. The two types of tungsten NPs obtained exhibit very different properties investigated by a large characterization techniques panel; but both sets show similarities with samples collected in tokamak or observed in dusty plasmas setups, therefore could potentially be expected in ITER. Producing samples with strong differences is an asset to lead a first global study, highlighting which parameters are key, whether it affects the tritium inventory or the toxicity for lung cells during in vitro studies. In a second phase, it will help precise the impact of ITER particles when their definition will clarify. The aim of this paper is therefore to study and describe the characteristics of different types of W dusts, this knowledge being mandatory for the next steps of the project dealing with tritium inventory in the described W dusts and their suspension in various liquid media for cell exposure for toxicity studies.

International audience; The role grain boundaries play in the diffusion of hydrogen in polycrystalline alloys has long been debated. Some researchers have found that grain boundaries have an accelerating effect on the transport of hydrogen across a metal membrane, while others have stated this network of sites may slow the diffusion of hydrogen or have a mixed effect depending on grain size and orientation. Thermal desorption mass spectroscopy (TDS) was used to study the diffusion of deuterium, from 294 K to 550 K, in model single crystal and polycrystalline nickel base alloy, alloy 600, having a grain size of several tens of micrometers. Using a numerical routine, solving Fick's second law of diffusion, TDS spectra were fit or simulated. The derived diffusion constant parameters (D0 = (1.0 ± 0.5)·10−2 cm2 s−1 and ED = (45 ± 4) kJ mol−1) for the polycrystalline alloy adequately predict and simulate the deuterium desorption from the single crystal during TDS testing. Furthermore, in the temperature range and for the grain size studied no significant effect of grain boundaries on the diffusion of deuterium in alloy 600 was observed. Consequently, the measured diffusion parameters are representative of interstitial diffusion in the alloy.

International audience; In a context of nuclear fuel reprocessing, the free-of-fuel hulls and ends of cladding tubes are compacted. The possibility of hydrogen degasing or absorption from/into these tubes has been studied with and without gamma irradiation at 293 K by means of deuterium as isotopic tracer for hydrogen. Under irradiation, as without, the hydrides present in the Zircaloy-4 hulls seem stable. The oxide layer present at the surface of the hulls allows a slow diffusion of deuterium, and the irradiation appeared to have no specific effect on the diffusion process: in both cases, hydrogen diffusion coefficients of the order of 5·10−18 cm2 s−1 have been found. The subsurface activity of deuterium is increased by one order of magnitude at least under irradiation, probably due to an activation of the dissociation/absorption kinetic steps.

International audience; The stress corrosion cracking (SCC) of Ni-base alloys in high temperature water is an intricate phe-nomenon in which numerous metallurgical, mechanical and environmental variables play a role. The role of hydrogen in the SCC of Ni-base alloys exposed to high temperature water has been discussed in numerous studies. Among the H-alloy interactions leading to a loss of mechanical strength, an em-brittling role of hydrogen absorbed during primary water exposure has been suggested in different works. However, such effect would involve large values of the hydrogen activity at the crack tip. Such large values could only be provided by the cathodic reactions concomitant to the oxidation process.In this context, the present study aims at establishing the kinetics of H permeation through a Ni-base alloy membrane from the first hours of its exposure to simulated PWR primary medium in order to evaluate if the evolution of the H flux measured in these conditions is consistent with high transient hydrogen activities at the alloy/oxide interface. The permeation experiment was carried out in a recir-culation autoclave equipped with ion exchange resins. The H2 overpressure was monitored to ensure the desired dissolved hydrogen concentration at 325DC. On one side the specimen (permeation mem-brane) was exposed to the primary water, and the other side pumped under vacuum and connected to a mass spectrometer. The final oxide scale formed on the primary water side was TEM-characterized in order to determine the continuous protective oxide layer thickness and composition.The H permeation flux JH passing through the Alloy 690 membrane during its exposure to simulated PWR primary medium in isothermal conditions at 325 DC shows a decrease of tending towards quasi stationary regime. It is suggested that the H permeation kinetics are, at least partially, governed by a diffusion step through the oxide scale growing on the Alloy 690 membrane during its exposure to simulated primary medium. Permeation kinetic laws are proposed in this work, taking into account the transport across the oxide layer then transfer into the alloy. The proposed model allows for the study of the evolution of P(H2) at the oxide/alloy interface during the permeation test based on the experi-mental data. The results and kinetic modelling of H permeation showed for the first time that at the very beginning of oxidation, high H partial pressure could be reached at the oxide/alloy interface (15 bar), compatible with hydrogen involvement in the SCC mechanisms of Ni-base alloys at such temperatures. This cou-pling between modelling and experimental approaches seem to be a promising way to access to the evolution of H activity at the alloy surface during the oxide scale growth, therefore in further works to assess the local H activity at the SCC crack tip during its propagation.This study was performed with the financial support of Framatome and EDF.

Plasma-facing materials for next generation fusion devices, like ITER and DEMO, have to withstand intense fluxes of light elements (notably helium and hydrogen isotopes). For tungsten (W), helium (He) irradiation leads to major changes in the material morphology, rising concerns about properties such as material structure conservation and hydrogen (H) retention. The impact of preceeding He irradiation conditions (temperature, flux and fluence) on H trapping were investigated on a set of W samples exposed to the linear plasma device PSI-2. Positron annihilation spectroscopy (PAS) was carried out to probe the free volume of defects created by the He exposure in the W structure at the atomic scale. In parallel, tritium (T) inventory after exposure was evaluated through T gas loading and desorption at the Saclay Tritium Lab. First, we observed that the material preparation prior to He irradiation was crucial, with a major reduction of the T trapping when W was annealed at 1773 K for 2 h compared to the as-received material. PAS study confirms the presence of He in the bubbles created in the material surface layer, whose dimensions were previously characterized by transmission electron microscopy and grazing-incidence small-angle x-ray scattering, and demonstrates that even below the minimal energy for displacement of He in W, defects are created in almost all He irradiation conditions. The T loading study highlights that increasing the He fluence leads to higher T inventory. Also, for a given fluence, increasing the He flux reduces the T trapping. The very first steps of a parametric study were set to understand the mechanisms at stake in those observed material modifications, confirming the need to pursue the study with a more complete set of surface and irradiation conditions.

Corrosion tests, isotopic tracing and surface analyses were used to study the corrosion behavior and the related hydrogen absorption of a Fe–18Mn–0.6C alloy in aqueous solutions. The influence of alloying elements was investigated. Copper addition leads to the formation of an oxide layer enriched in metallic copper, which favors H recombination and decreases H absorption in the alloy. Aluminum addition decreases the average corrosion rate by the formation of an oxide layer enriched in aluminum, thus decreasing the hydrogen absorption during the corrosion process. In this Al-enriched alloy, the presence of phosphorus increases the corrosion kinetics and promotes hydrogen absorption.

Some illustrations of the use of deuterium or tritium for isotopic tracing of hydrogen absorption, transport and trapping in nuclear materials are presented. Isotopic tracing of hydrogen has been shown to be successful for the determination of the boundaries conditions for hydrogen desorption or absorption in a material exposed to a hydrogen source. Also, the unique capabilities of isotopic tracing and related techniques to characterize H interactions with point defects and dislocations acting as moving traps has been demonstrated. Such transport mechanisms are considered to play a major role in some stress corrosion cracking and hydrogen embrittlement mechanisms. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

This study aims at providing quantitative data concerning the oxygen and hydrogen diffusion through the oxide scale formed on alloy 600 in PWR primary medium conditions (325 °C) using 2 D and 18 O isotopes as markers. The diffusion coefficients were calculated according to a short-circuit diffusion of the tracers along the oxide grain boundaries (so-called “C-regime”). The values obtained are respectively D sc = 4.6 +/− 0.9 × 10 − 17 cm 2 /s for 18 O, and D sc = 5.2 +/− 1.2 × 10 − 17 cm 2 /s for 2 D. These experiments confirm that the transport mechanism of hydrogen through the oxide scale as hydroxide ions on the anionic sublattice is highly probable. The effect of hydrogen subsequent absorption by the alloy substrate, notably in stress corrosion cracking phenomenon is discussed.

International audience; During the corrosion in primary water of zirconium alloys, a fraction of hydrogen from the water diffuses through the oxide into the alloy. To better understand the hydriding process, isotopic tracers and SIMS experiments were performed on oxides grown on Zircaloy-4 alloy under simulated primary water conditions. Results showed the oxide film in pre-transition is divided into two sub-layers, an external one, highly permeable to hydrogen and an inner protective one. Thermal Desorption Spectroscopy analyses revealed two interaction sites of hydrogen, located in each oxide sublayer. Apparent diffusion coefficients of hydrogen in both oxide sublayers were estimated with different methods.

The electrochemical permeation technique was used to evaluate the effect of the microstructure on hydrogen diffusivity and hydrogen trapping at room temperature in martensitic steels. A detailed study of the electrochemical permeation technique was first performed in order to identify the boundary conditions of a permeation test in the selected experimental set-up. The validity of the apparent diffusion coefficient derived from this test is also discussed. A 34CrMo4 quenched steel has been selected and designed at three tempering temperatures (200°C, 540°C and 680°C) in order to obtain three different microstructures. According to permeation measurements, H diffusion strongly depends on the microstructure. The material tempered at 540°C exhibits the smallest diffusion coefficient and the largest fraction of reversible traps at room temperature.

Austenitic Fe-Mn-C steels are Ultra High Strength Steels which may be used for the production of deep drawn automotive parts containing extremely high residual stress and strain levels. In consequence, hydrogen absorption occurring during the corrosion process in aqueous environments may enhance the sensitivity of these steels to different kinds of hydrogen-induced damage, in particular Stress Corrosion Cracking (SCC). In order to predict and prevent SCC, it is important to study the behaviour of hydrogen in these austenitic steels exposed to aqueous environments and in particular the dependence on the alloy chemistry and microstructure. SIMS profiles of deuterium introduced by cathodic charging in selected specimens were used to characterize the diffusion of hydrogen in these steels. This allowed to be studied the role of chemical composition and microstructure on the kinetics of H absorption at room temperature. The competition between bulk matrix diffusion and short-circuit diffusion phenomena along grain boundaries was investigated. The results show a strong dependence of H diffusion and distribution on the alloy chemistry and grain size.

The influence of the subsurface hydrogen activity on the hydrogen embrittlement (HE) susceptibility of a tempered 9%Cr–1%Mo ferritic-martensitic steel (T91) has been studied by constant extension rate tests (CERT) performed under cathodic charging during straining at 20 °C. Changes in the hydrogen activity on the surface were obtained by varying the cathodic current density imposed during a tensile test completed to fracture. The broken samples were observed by scanning electron microscopy (SEM). The results show a strong dependence of the extent of the brittle zone with the subsurface hydrogen activity. This effect could be attributed to an enhancement of the apparent diffusion coefficient of hydrogen when increasing H activity. Increasing H activity could enhance both the trapping rate on pre-existing and strain-induced traps and H dragging by moving traps such as dislocations.

The main purpose of this study is to investigate the mechanism responsible for the hydrogen absorption in alloy 600 exposed to pressurized water reactors primary water in order to evaluate the possible role of hydrogen in the stress corrosion cracking (SCC) of this alloy exposed to these environmental conditions. Alloy 600-like single-crystals were exposed to a simulated PWR medium where the hydrogen atoms of water or of the pressuring hydrogen gas were isotopically substituted with deuterium, used as a tracer. SIMS profiling of deuterium was used to characterize the deuterium absorption and localization in the passivated alloy. The results show that the hydrogen absorption during the exposure of the alloy to PWR primary water is associated with the water molecules dissociation during the built up of the passive film.

Les alliages de Zirconium sont couramment utilises comme materiaux de gainage dans les Reacteurs a Eau Pressurisee. Immerges dans le milieu primaire, alors que la face externe des crayons s'oxyde, une partie de l'hydrogene impliquee dans la reaction d'oxydation penetre dans le materiau et vient precipiter dans la matrice metallique sous la forme d'hydrures fragilisants, une fois la limite de solubilite de l'hydrogene atteinte a la temperature d'irradiation. Ce phenomene d'hydruration est l'un des facteurs limitant l'utilisation des alliages de type Zircaloy-4 (Zr-Fe-Cr-Sn-O). En tant que premiere barriere de confinement des produits de fission, l'integrite mecanique des crayons de combustible est essentielle, et la minimisation de la sensibilite de cet alliage a la prise d'hydrogene est requise. Cette demarche necessite notamment la comprehension des mecanismes regissant la prise d'hydrogene du materiau, ainsi que l'influence des hydrures sur son comportement en corrosion. Concernant l'etude des mecanismes de prise d'hydrogene, des echanges isotopiques en eau lourde primaire a 360°C ont ete entrepris et ont mene a l'identification, dans le film d'oxyde, a l'etape limitant la diffusion de l'espece hydrogenee. Afin d'y estimer le coefficient de diffusion apparent de l'hydrogene, nous nous sommes tout d'abord appuyes sur des profils SIMS de penetration du deuterium dans la partie dense du film d'oxyde. Dans un second temps, des estimations ERDA de la teneur en hydrogene presente dans l'oxyde associees a des dosages par fusion nous ont permis de determiner le flux d'hydrogene absorbe par l'alliage puis de deduire un coefficient de diffusion apparent a 360°C. Finalement, ces deux methodes convergent vers des valeurs analogues (entre 1.10 -14 cm 2 /s et 6.10 -14 cm 2 /s), en accord avec les donnees de la litterature. Concernant l'impact des hydrures sur la corrosion du Zircaloy-4, plusieurs echantillons pre-hydrures et vierges de reference ont ete oxydes simultanement en eau primaire a 360°C. La caracterisation des echantillons pre-hydrures a revele certaines differences notables avec les echantillons temoins, comme la presence du sous-oxyde Zr 3 O a l'interface metal/oxyde, une plus faible proportion de zircone quadratique dans l'oxyde, ainsi qu'une diffusion plus rapide de l'oxygene via les courts-circuits de la zircone (MET, μ-DRX, echanges isotopiques en 18 O). De plus, au cours de l'oxydation, l'hydrogene initialement present dans la phase hydruree reste dans la matrice metallique et conduit progressivement a la transformation allotropique δ-ZrH 1,66 → e-ZrH 2 .

The behavior of hydrogen and its isotopes in materials is a major concern in future nuclear systems both for the predictive analysis of the role of H, D, T in the environmental degradation of structural materials, for the confinement and inventory of tritium, and for the management of tritiated wastes. This study is focused on the characterization of the effect of the alloy microstructure, of desorption anneal and of oxide films on the tritium behavior (desorption kinetics, trapping, residual concentration) in various austenitic stainless steels. Different techniques (high temperature extraction of hydrogen, beta counting of tritium in massive samples) were used to study: the tritium absorption and desorption in several stainless steels, the role of the annealing conditions (temperature/time) on the tritium residual concentration and desorption flow, and the role of microstructural defects and of oxide films on the diffusion and trapping of tritium. (authors)

The stress corrosion cracking mechanism of Alloy 600 in pressurised water reactor (PWR) primary water has been investigated. U-bend specimens (extracted from tubular products) were tested in simulated PWR primary water containing H218O. After testing, crack tips was characterised by nanosecondary ion mass spectrometry (nanoSIMS) and unstressed areas were analysed by standard SIMS. The results allowed oxygen (16O, 18O) penetration into the material to be evaluated and the oxide present at crack tips to be characterised. Experimental data were compared with results obtained by calculations performed according to Fickian diffusion laws and Whipple Le Claire theory.

Advanced nano-secondary ion mass spectrometry analyses were used to investigate intergranular attack and improve the understanding of stress corrosion cracking in Alloy 600. Observations and analyses carried out on cross-sectioned samples without applied stress revealed penetrative intergranular attacks. Oxygen tracer evidence shows that oxide does not constitute a barrier against oxygen diffusion in oxide. This result allows us to investigate a new mechanistic model. Oxide growth seems to depend on oxygen diffusion in porous oxide associated with chromium diffusion in strained alloy to the grain boundary located beyond the crack tip. Strain should increase transport kinetics and promote oxide formation by increasing rates of defects such as dislocations.

This chapter synthesizes the possible role of hydrogen in stress corrosion cracking (SCC) of nickel-based alloys in a pressurized water reactor (PWR) environment. A literature review is first used to present the susceptibility of Ni-based alloys to hydrogen embrittlement (HE), as well as the main mechanisms and conditions required for HE to occur. Some recent results then are presented to discuss the validity of such conditions in a PWR environment. In spite of the need for further investigations, they suggest the possibility for both a direct and indirect role of hydrogen in SCC.

The cathodic discharge of hydrogen on the surface of massive specimens of NiZr intermetallic compound readily forms the trihydride NiZrH3 which exhibits the same crystallographic parameters as the trihydride obtained by gas phase charging. Moreover microstructural studies of the first stage of the hydriding process during cathodic charging of massive samples allow to follow the influence of the microstructure of NiZr on the germination of cracks and on the first stage of the decrepitation associated with H absorption. These results show that the NiZr microstructure could strongly affect both the hydriding kinetic, the hydride stability and further the amount of hydrogen stored in the intermetallic compound. The XPS analysis of the surface of NiZr after cathodic charging shows the coexistence of zirconium core levels characteristic of Zr–H and Zr–O bonds. The hydrogen absorption affects the electronic properties of Zr atoms in the intermetallic compound in a similar way of what is observed in pure Zr: an H-induced band is observed about 6 eV below the Fermi level together with a chemical shift of the Zr core levels characteristic of the hydride formation. The presence of oxygen on the surface decreases the intensity of the Ni2p core levels whereas the intensity drop of the satellite located at 5 eV (below Ni 2p) is associated with an H-induced filling of the 3d band of Ni atoms in NiZr. The cosegregation of oxygen and zirconium on the surface is clearly evidenced by XPS in the 20– 380 ∘ C temperature range. A preferential Zr enrichment of the surface is observed at higher temperature; the occupancy fraction of the surface sites by Zr atoms is as large as 98% at 600 ∘ C . This is presumably a consequence of both the oxygen dissolution in NiZr and a preferential segregation of Zr atoms on the surface.

International audience; This paper presents an extensive set of measurements from complementary surface analysis techniques performed for characterizing deuterium retention in carbon fiber composite Sepcarb®NB31 subsequently to a deuterium beam exposition: adsorption isotherm measurements and Hg porosimetry to characterize the porous network, coupled deuterium beam exposure and in situ µ-NRA analysis to follow the dynamics of the penetration of the retained deuterium in the material, TEM and Raman microscopy to investigate the change in the material structure induced by ion irradiation, and finally TPD to estimate the respective proportion of deuterium retained in the surface layer and in the bulk material. The parameters extracted from this set of characterizations are introduced in a 2D Monte Carlo model which couples the propagation of deuterium and eroded carbon atoms in a network of rectilinear pores and plasma–surface interaction parameters from the SRIM code. The simulations reproduce satisfactorily the main features of the measured deuterium concentration profile and behavior of the retained deuterium amount with incident fluence, validating the physical picture of deuterium retention in CFC as due to the simultaneous implantation of the incident ions in the few 10-nm-depth layer the closest to the surface and penetration of atoms deeper in the material (several tens of microns) through the pore network

International audience; Abstract Tritium adsorption and desorption from well characterized tungsten dust are presented. The dust used are of different types prepared by planetary milling and by aggregation technique in plasma. For the milled powder, the surface specific area (SSA) is 15.5 m2/g. The particles are poly-disperse with a maximum size of 200 nm for the milled powder and 100 nm for the aggregation one. Prior to tritiation the particles are carefully de-oxidized. Both samples are experiencing a high tritium inventory from 5 GBq/g to 35 GBq/g. From comparison with massive samples and considering that tritium inventory increases with SSA, it is shown that surface effects are predominant in the tritium trapping process. Extrapolation to the ITER environment is undertaken with the help of a Macroscopic Rate Equation model. It is shown that, during the life time of ITER, these particles can exceed rapidly 1 GBq/g. © 2014 Elsevier B.V.

In the framework of waste management strategy for future fusion reactor, it has been demonstrated that one of the major issue is to reduce the high level waste. The tritium activity strongly contributes to the waste classification. A better knowledge of the mechanisms involved in tritium trapping and desorption will allow to choose the most appropriate procedure to reduce the tritium constraint. This paper deals with the management of tritiated steels and the way to reduce tritium transfer. This experimental work concerns steel obtained by remelting under vacuum of tritiated austenitic stainless steel wastes. The goal of this study is to develop heat treatments in solid phase to lower the residual tritium concentration and its desorption kinetics at room temperature. The surface activity, the desorption of residual tritium at room temperature and the residual concentration have been measured for each condition (temperature, time, atmosphere, etc.). For reheating temperatures below 600 °C, the surface activity increases by one or two orders of magnitude; this is the consequence of the formation of a tritium rich oxide layer. After a 20 h annealing above 300 °C and removing of the tritium rich oxide layer, the surface activity is strongly reduced (80%) when compared with the value measured before annealing. For such annealing conditions, the amount of desorbed tritium is reduced by a factor 25 and the desorption kinetics yield a reduction factor of 40–50 after annealing at 400 °C for 20 h.

A Li–Na-containing borosilicate glass was submitted to aqueous corrosion in static mode in tritiated solutions of various pH at room temperature and 90 °C. Tritium counting, β-autoradiography, scanning electron microscopy (SEM) and ion beam analysis (IBA) techniques have been used to investigate the composition variations of the leached glass surfaces. In an acidic medium, the glass surface is covered by a thick hydrated silica layer; mobile elements like Li, Na and B and transition elements like Fe and Mo are strongly depleted. Near pH 7, relative enrichments of aluminium and iron are shown together with strong Li, Na and B depletions. In a basic medium, the glass surface exhibits iron and molybdenum enrichments whereas mobile elements seem to be kept at their nominal concentration level at the glass surface. The tritium activity and distribution on the leached glass surface is shown to depend strongly on the pH of the tritiated solutions. These observations are correlated with the observed changes of the surface morphology and chemistry characterized by IBA and SEM analysis. Elemental solubility versus pH of various chemical species have been calculated for comparison purpose with the experimental observations.

L’anemie est un syndrome frequemment rencontre en pratique quotidienne chez le chien dont le diagnostic etiologique permet l’initiation d’un traitement approprie. Une etude retrospective rapporte que 151/456 (33 %) cas d’anemie accompagnaient une neoplasie, 130 (28 %) une condition inflammatoire et 35 (7,7 %) une « infection » au sens large [1] . Alors que l’importance des hemopathogenes vectorises (HV) est grandissante en Europe, le caractere retrospectif de l’etude n’a pas permis d’identifier leur frequence. Une seule serie chez des chiens anemies rapporte une frequence des HV de 287/2037 (14,1 %) [2] , qui a probablement ete mesestimee, en l’absence de recherche par PCR. A ce jour, aucune etude n’a evalue l’implication des HV lors d’anemie chez le chien en France, par recherche PCR exhaustive systematique. Notre etude prospective rapporte la frequence, l’impact clinique et hematologique des HV chez des chiens anemies, admis dans un centre hospitalier veterinaire universitaire sur une periode de 1 an (mai 2014–mai 2015) via a une recherche systematique PCR et serologique. Les chiens anemies sont inclus avec un hematocrite (Ht) = 37 % et une hemoglobine (Hb) = 12 g/dL et exclus lors d’administration prealable de doxycycline ou d’imidocarbe le mois precedent l’admission. La recherche et l’identification des HV sont basees sur des methodes directes (microscopie optique et PCR detectant Babesia sp., Ehrlichia canis, Anaplasma platys/phagocytophilum, des rickettsies du groupe des fievres boutonneuses, Mycoplasma haemocanis (MH) – Candidatus M. haematoparvum et Hepatozoon spp). Des recherches indirectes sont realisees en complement (SNAP® 4Dx, SNAP® Leish). Un cas d’anemie accompagne d’un HV (AHV) est defini par un resultat PCR positif valide par sequencage. Par ailleurs, l’etiologie de l’anemie est etablie pour chaque cas par un resident de medecine interne (MI) encadre par une equipe de specialistes. L’analyse statistique decrit la frequence des AHV dans la population globale, l’epidemiologie, la frequences des anomalies cliniques et paracliniques globales (test binomial avec intervalle de confiance a 95 % [IC95 %]) et compare ces parametres entre les cas d’AHV et les non-cas d’AHV (analyse univariee test de Fisher : p = 0,05, autorisant une regression logistique multivariee : ACM avec evaluation des risques relatifs : RR). Sur la periode d’etude, 155/7038 chiens anemies sont repertories (2,20 %, IC95 %, 1,87–2,57) dont 21 exclus, car traites avec de la doxycycline ou imidocarbe. Les 134 cas inclus regroupent 62 femelles, 72 males, âges de 6 a 204 mois, dont 56, 41 et 37 hospitalises en cancerologie, MI et soins intensifs. Les Bouviers bernois sont surrepresentes par rapport a la population repertoriee la meme annee (p = 0,01). Les symptomes frequents sont : abattement (56 %, 47,1–64,5), hyperthermie (44,0 %, 35,5–52,9) et pâleur (35,8 %, 27,7–44,6). On compte 25/134 cas d’AHV (18,7 %, 12,5–26,3). Ils incluent 11 positifs pour MH (44,0 %), 9 piroplasmoses (36,0 %), 2 piroplasmoses positives pour MH (8,00 %), 2 anaplasmoses plaquettaires (8,00 %) et une ehrlichiose monocytaire (4,00 %). Onze autres chiens ont un test serologique positif (10 SNAP 4Dx® et 1 SNAP Leish®). La frequence des cas positifs pour MH est significativement plus importante parmi les chiens suivis en cancerologie (10/56, 17,9 % contre 3/78, 3,85 %, RR : 2,69, IC95 %, 1,00–7,32, p = 0,01). Les HV sont la premiere cause d’hyper-hemolyse (14/44, 31,8 %, 18,6–47,6). A l’analyse multivariee, les indices epidemio-cliniques ne different pas entre les cas et les non-cas d’AHV. Par contre, les cas d’AHV presentent une anemie significativement moins severe, plus regenerative et une numeration blanche significativement plus importante que les non-cas d’AHV (p = 0,005). La frequence des AHV (18,7 %) est plus elevee que celle rapportee precedemment [1] , [2] . D’autre part, les cas d’AHV semblent moins severes que les non-cas d’AHV (anemies moderee, regeneration plus forte), sans cause evidente. Les HV peuvent declencher une anemie par de multiples mecanismes. Ils peuvent perturber l’hematopoiese par suppression cytokinique (inflammatoire), anomalie de maturation des precurseurs erythroides (myelodysplasie transitoire secondaire), phenomenes hemorragiques (thrombopenie ou vascularite) ou, dans le cas le plus frequent ici, une hemolyse (mecanique directe, par augmentation de la fragilite osmotique des hematies, stress oxydatif, lyse immunologique ou combinaison de ces mecanismes) [3] . MH est l’HV majoritaire (13/25), surtout chez des chiens sous chimiotherapie : sa frequence globale (13/134, 9,7 %) est neanmoins proche de celle rapportee en France chez des chiens sains (15,4 %) [4] . Son impact clinique et son role dans la genese de l’anemie restent donc peu evidents ici. L’absence de suivi, ne permet pas comparer le pronostic entre les sous-groupes. En conclusion, ces donnees propres a notre institution, confirment l’importance des HV que le clinicien doit considerer dans son diagnostic differentiel face a une anemie chez le chien.

The purpose of this study is to investigate the role of temperature and hydrogen charging conditions on hydrogen and oxygen dissolution and segregation on the surface of zirconium. X-Ray photoelectron spectroscopy was used to follow the changes as a function of temperature in the electronic properties of the surface before and after in situ or ex situ exposure to hydrogen. In situ annealing of Zr samples favors the oxygen decontamination of the surface and increases its reactivity with H. In situ (gas) or ex situ (cathodic) exposure of Zr to hydrogen at 20 °C promotes the nucleation of a Zr hydride on the surface which decomposes with increasing the temperature up to 600 °C. A segregation of oxygen on the surface is also associated with the local hydrogen enrichment.

International audience; Deriving the kinetic reaction constants associated with hydrogen diffusion and trapping in metals from thermal desorption mass spectroscopy (TDS) spectra proves to be complicated and the existing analysis methods are subject to debate. This article will provide a brief background of several commonly employed analysis techniques and discuss the necessity of a more complex and rigorous analysis method for the determination of the kinetic constants associated with hydrogen trapping interactions. Furthermore, a numerical simulation method will be proposed using the McNabb & Foster equations to fit experimental TDS spectra in order to derive both diffusion and trapping/detrapping parameters, including the respective pre-exponential constants and activation energies associated with these interactions in metals.

International audience; This study aims at characterizing the interactions of hydrogen with point defects and their clusters in nickel-based superalloys. For this, nickel ion implantation was used to create defects in the sub-surface of alloy 690 coupons. The interaction of hydrogen with these defects was studied thanks to SIMS depth profile analysis performed after deuterium cathodic charging, and different annealing treatment. In parallel, TEM observations were carried out in order to qualify and quantify the defects responsible for the trapping, and to observe their evolution in the presence of hydrogen. All the results exhibit a strong interaction of hydrogen with implantation-defects, up to high temperatures (325 °C). Also, hydrogen is shown to assist defects reorganisation, in a way similar to the effect of temperature. The effect of hydrogen on the alloy atoms as explored by SIMS, combined with the TEM investigation of defects evolution in the presence of hydrogen, allows to suggest that the main mechanism for hydrogen-assisted motion of defects is by lowering the lattice friction, thus decreasing the activation volume for the unfaulting or motion of point defect clusters, up to dislocation loops.

International audience; Tritium retention in plasma facing materials such as tungsten is a major concern for future fusion reactors. During ITER operating mode, the reactor could generate tritiated tungsten dust-like particles which need to be characterized in terms of amount of trapped tritium, tritium source and radiotoxicity. This study is focused on the preparation and characterization of tungsten particles and on a comparative analysis of tritium absorption/ desorption kinetics in these particles and in massive samples. An original gas phase thermal charging procedure was used successfully for tritium incorporation in tungsten powders and massive samples. Much larger tritium amounts are incorporated in W particles than in massive samples indicating important surface effects on tritium absorption, desorption and trapping in W. Tritium desorption from particles occurred at different temperatures related with different interactions on the particles surface and in the bulk; the tritium behavior in massive samples was also shown to depend on the metal microstructure. According to these experimental results tritium absorption/desorption in W particles may have important implications on tritium management in ITER reactor.

In the framework of waste management for the ITER reactor, steel detritiation is an important challenge since nuclear waste storage already assigns and plans limited tritium contents. A study has been initiated to determine a detritiation process drawing on a melting process currently used on a semi-industrial scale at the CEA/DAM (Commissariat a l'Energie Atomique/Direction des Applications Militaires). The first part of the project consists in characterizing these ingots. The measurements performed at the CNRS ORSAY (Centre National de Recherche Scientifique), permit to assess, by autoradiography, tritium distribution in two directions (longitudinal and transverse) and to measure tritium desorption using an original β counting device. The second part of the project should allow us to assess the possibility of improving the process in terms of detritiation rates using bubbling argon and hydrogen during melting to improve mixing, and thus facilitate the removal of tritium.

Il est maintenant bien etabli que les proprietes mecaniques des alliages a base de titane et notamment des aluminiures de titane soumis a differents types de sollicitation (traction uniaxiale, fatigue, fatigue-corrosion,…) sont sensibles a la presence d'humidite dans l'atmosphere dans laquelle est effectue l'essai. Cependant les mecanismes responsables de cette perte des proprietes mecaniques restent mal connus. Des profils de diffusion du deuterium ont ete mesures par analyse ionique (SIMS) dans des aluminiures de titane presentant differentes microstructures (α 2 , γ, ou α 2 +γ) et exposes a la temperature ambiante a des environnements deuteres (air humide ou solutions aqueuses). Les resultats mettent en evidence,un mecanisme de dissociation de l'eau a la surface des aluminiures de titane exposes a ces environnements. Ce mecanisme conduit a une absorption d'hydrogene dans les alliages dont l'amplitude depend du pH de la solution aqueuse, de la microstructure de l'alliage et de sa deformation plastique en presence de l'environnement. Le film d'oxyde naturel forme a l'air a la surface du materiau limite a la fois la dissociation de l'eau et la diffusion de l'hydrogene dans l'alliage. Les proprietes mecaniques d'un alliage α 2 +γ brut de coulee sollicite en traction uniaxiale dependent a la fois de l'orientation des lamelles α 2 et γ par rapport a l'axe de traction et de la nature de l'environnement au contact de l'eprouvette au cours de l'essai. Une perte de ductilite est observee lors de sollicitations en presence de solutions aqueuses. L'effet predominant de l'environnement semble etre de favoriser l'amorcage de fissures a la surface du materiau en relation avec l'absorption d'hydrogene.

Secondary ion mass spectroscopy (SIMS) analysis of deuterium profiles was performed in different α 2 , γ or (α 2 +γ) Ti–Al alloy specimens exposed at room temperature to deuterated aqueous solutions or humidified air. The results support a mechanism of water dissociation on the surface of titanium aluminides leading to the absorption of hydrogen in the alloys. The deuterium penetration depth strongly depends on the pH of the aqueous solution, on the microstructure and on the deformation of the alloy in the considered environments. The natural surface oxide layer is shown to impede the water dissociation and to act as a barrier to hydrogen diffusion in the alloys. This phenomenon strongly depends on the microstructure of the (α 2 +γ) industrial alloys as evidenced by comparing the behavior of α 2 and γ single phase alloys in the same environments. The tensile properties of an as cast (α 2 +γ) alloy depends both on the orientation of the α 2 and γ lamellae with respect to the tensile axis and on the nature of the environment. Straining in aqueous solutions at room temperature induces a ductility loss of the alloy and promotes crack initiation on the surface.

Les phenomenes de fragilisation par l'hydrogene et de corrosion sous contrainte des materiaux metalliques mettent en jeu differents mecanismes, selon le materiau considere et les sollicitations auxquelles il est soumis, Les parametres vitesse de diffusion de l'hydrogene et piegeage, qui gouvernent les quantites d'hydrogene en mouvement ainsi que la concentration locale peuvant conduire a une perte des proprietes mecaniques, sont fortement dependants de la microstructure du materiau. Dans les metaux purs comme dans les materiaux industriels a microstructure complexe les interfaces comme les joints de grains ainsi que les dislocations jouent un role particulierement important, en constituant des sites privilegies pour l'aceumulation de l'hydrogene ou au contraire en facilitant son transport L'objectif de cet article est d'illustrer les differents roles joues par les interfaces sur la mobilite et le piegeage de l'hydrogene dans des materiaux de structure cristallographique et de microstructure variees.

Hydrogen transport by dislocations is one of the mechanisms reported in the literature to be responsible for the hydrogen embrittlement (H.E.) of some metals even if it needs to be associated with one or several cracking mechanisms. This study brings new evidence of dislocation sweeping of hydrogen and some arguments in favor of its contribution to the H.E. mechanism of Alloy 600 (Ni–Cr–Fe). A study of tritium desorption assisted by the plastic deformation has been conducted by coupling a β counting technique and a tensile test. The experimental results obtained with Alloy 600 strongly support the mechanism of hydrogen transport by dislocations. The H.E. characteristics of Alloy 600 have been measured on smooth tensile specimens in relationship with the microstructure and the testing conditions. The influence of different parameters including the prestrain level, the strain rate and the temperature supports the role of hydrogen transport in the embrittlement process and the existence of local hydrogen enrichment associated with dislocations pile-ups.

Hydrogen deformation interactions have been shown to strongly control the mechanisms of hydrogen embrittlement (H.E.) and stress corrosion cracking (SCC) of numerous metals and alloys. Among the different reported interactions an accelerated transport of hydrogen by mobile dislocations was first suggested by Bastien and Azou. This paper reports the first results of an experimental work aimed at the quantitative characterization of the hydrogen transport by mobile dislocations in a nickel base alloy. The procedure was chosen with the goal of correlating the tritium desorption from a tritiated sample undergoing a tensile straining, with the stress/strain curve.

Several studies have shown the high sensitivity of titanium aluminides to environmental effects with a detrimental role of water vapor. Water is considered to dissociate on bare metallic surfaces resulting from the rupture of the surface oxide, leading to hydrogen diffusion in the bulk and the subsequent embrittlement of the material. However very limited direct experimental evidence of the phenomenon of water dissociation and of hydrogen entry remain unclear whereas controversial results have been reported on the hydrogen embrittling effect in these alloys. The use of deuterium or tritium as tracers can help to characterize water dissociation and H entry in materials exposed to aqueous solution or moist atmospheres. The study of deuterium profiles as a function of various parameters such as the nature and pH of the environment, the temperature, the applied stress and strain,... is currently performed by Secondary Ion Mass Spectrometry (SIMS) analysis. The first results showed that a precise measurement of the deuterium penetration in the alloy exposed to a deuterated medium requires preliminary investigations on the influence of the surface preparation on the hydrogen and deuterium profiles before exposure to the environment. In this study a special attention has been paid to the effect ofmore » the oxide layer on hydrogen absorption during mechanical grinding under water.« less

International audience; Understanding the dynamic of in-depth migration and retention of hydrogen in Carbon Fiber Composites (CFCs) used as plasma facing material has for long time been complicated by the lack on in situ analyzing tools. A dedicated experimental setup coupling an ECR ion source to the Saclay nuclear microprobe was developed to expose CFC samples to deuterium implantation at 200–300eV and fluences from 1022 to 1024D/m2, and then to perform in situ μNRA analysis for 3D deuterium profiles. Once the technique proven as non perturbative, we observed that while we have a homogeneous, fluence-independent deuterium concentration at the surface, the in-bulk deuterium is concentrated in the porosities and increases with the incident fluence, up to very large depth (500μm). For the first time, it was evidenced that these two distinct mechanisms are simultaneous to the implantation. D profiles evolve very little with in-vacuum storage time.

Quelques applications recentes de l'analyse ionique du deuterium et de l'autoradiographie du tritium a des mesures quantitatives de concentration en hydrogene illustrent la diffusion et le piegeage de l'hydrogene en relation avec la microstructure des superalliages a base de nickel monocristallins, l'enrichissement en hydrogene en tete de fissure dans un acier type 4120 soumis a des conditions de corrosion sous contrainte et la distribution du tritium dans des toles d'aciers inoxydables austenitiques avant et apres soudage.

International audience; The trapping of hydrogen by VC precipitates and structural defects in high strength Fe-Mn-C steel was studied by small angle neutron scattering. No interaction between H and V in solid solution has been detected but a significant interaction between H and structural defects introduced by plastic deformation has been measured. This last effect was reversible upon outgassing of the H. Moreover a significant interaction between H and VC precipitates has been measured; 5 ppm wt. of H could be trapped in the precipitates. This is consistent with the homogeneous trapping of H within the precipitates rather than at the precipitate/matrix interface. (C) 2011 Elsevier B.V. All rights reserved.

Tritium autoradiography was used to study the tritium distribution in laser and arc (TIG) weldments performed on tritiated AISI 316 samples. Quantitative values of the local tritium concentration were obtained from the microdensitometric analysis of the autoradiographs. This procedure was used to map the tritium concentration in the samples before and after laser and TIG treatments. The effect of the detritiation conditions and of welding on the tritium distribution in the material is extensively characterized. The results illustrate the interest of the technique for predicting a possible embrittlement of the material associated with a local enhancement of the tritium concentration and the presence of helium 3 generated by tritium decay.

The electronic properties and the microstructure associated with room temperature (RT) cathodic charging of Ce, Ni, and CeNi 2 massive specimens have been investigated by XPS analysis and microscopic observations. The use of a cooling stage allows us to study the hydride formed by cathodic charging on the nickel surface and to evidence by XPS the hydrogen induced filling of the 3d band in nickel. A thin hydride layer (CeH 2.53 ) is readily formed at RT on Ce. In spite of a hydrogen induced lowering of the valence band intensity, conduction states at E F are present in this hydride. The XPS spectra of the Ce 3d and 4d core levels also demonstrate the existence of a hybridization effect of the 4f electrons with those of the conduction band which raises the intensity of the f 0 and f 2 satellites. Needle-shaped hydride precipitates are observed at the very beginning stage of the cathodic charging of CeNi 2 ; they are readily replaced by an amorphous CeNi 2 H 4 hydride. The hydrogenated surface exhibits a metal-hydrogen band at 6 eV below E F ; the presence of hydrogen also increases the relative intensity of the f 0 and f 2 satellites in the 3d and 4d core levels.

International audience; Alloy 600, a nickel base alloy containing 15 % chromium, is used in primary circuit of Pressurized Water Reactor (PWR). This alloy is well known to be susceptible to Stress Corrosion Cracking (SCC) in PWR primary water. Despite the fact that many laboratory studies have been performed and that many models are proposed in the literature, the mechanisms involved are still not well known. In the proposed model, the transport of species (oxygen, hydrogen and chromium) is considered as playing a key role. Therefore, experiments and calculations are performed in order to study the transport of chromium, hydrogen and oxygen in Alloy 600 and in model alloys. The results lead to the conclusion that the transport of oxygen and hydrogen cannot be considered as the rate-controlling steps. The dissymmetric aspect of the crack tip and of the chromium depletion ahead of the crack lead to the conclusion that chromium diffusion could play a significant role in the mechanism.

Shot-peening surface treatments were performed on a low-carbon steel and a 304 stainless steel. The influence of residual stresses on hydrogen permeation and distribution was investigated. The results were correlated with the tensile properties measured in air after cathodic charging and in a NACE medium under slow load-rate straining. The role of shotpeening on the hydrogen embrittlement of the low-carbon steel is strongly dependent on the severity of the hydrogen environment and testing conditions. The detrimental effect of shotpeening on the hydrogen embrittlement of the stainless steel is related to phase transformations induced by cold work.

Publisher Summary The strain-assisted transport and redistribution of tritium in tritiated tensile specimens are investigated by β counting at room temperature in order to characterize the interactions of hydrogen with moving dislocations in Ni-based alloys. A predictive analysis of the existence of these interactions as a function of the most pertinent parameters such as temperature, hydrogen activity, strain level, and strain rate is performed and compared with the results of experiments designed to characterize the mechanism of hydrogen-induced intergranular fracture. Tensile tests conducted on hydrogen precharged tensile specimens of alloy 600 at various temperatures and strain rates shows that hydrogen-induced intergranular cracking requires hydrogen segregation to grain boundaries during plastic deformation. These experimental data are used to identify a temperature/strain rate domain at which hydrogen-induced intergranular rupture of alloy 600 is observed. Its concordance with the domain of hydrogen transport by dislocations provides support for a major influence of a mechanism of hydrogen-accelerated transport and supersaturation in the vicinity of grain boundaries. This influence is apparent in the intergranular rupture observed in the 180–500 K temperature range.

Mesure du changement de l'activite du tritium en fonction du temps lors de l'electrolyse de LiOD avec une electrode de palladium. Mesure de la quantite de tritium introduite dans l'electrode de palladium pendant l'electrolyse. Mesures comparatives realisees dans les conditions similaires dans l'hydroxyde de lithium deuterie et non deuterie

International audience; The liquid scintillation counting of solid samples (LSC-SS technique) was successfully used to study the role of microstructure and heat treatments on the behavior of residual tritium in several austenitic stainless steels (as-cast remelted tritiated waste, 316LN and 321 steels). The role of desorption annealing in the 100-600 degrees C range on the residual amount of tritium in tritiated waste was investigated. The residual tritium concentration computed from surface activity measurements is in good agreement with experimental values measured by liquid scintillation counting after full dissolution of the samples. The kinetics of tritium desorption recorded with the LSGSS technique shows a significant desorption of residual tritium at room temperature, a strong barrier effect of thermal oxide films on the tritium desorption and a dependance of the tritium release on the steels microstructure. Annealing in the 300-600 degrees C range allows to desorb a large fraction of the residual tritium. However a significant trapping of tritium is evidenced. The influence of trapping phenomena oil the concentration of residual tritium and on its dependance with the annealing temperature was investigated with different recrystallized and sensitized micro structures. Trapping is evidenced mainly below 150 degrees C and concerns a small fraction of the total amount of tritium introduced in austenitic steels. It presumably occurs preferentially on precipitates such as Ti(CN) or on intermetallic phases.