Nuclear Corrosion: Achievements and Challenges

International audienceCorrosion science faces new challenges in various nuclear environments. Three main areas may be identified where increases of knowledge and understanding have been done and are still needed to face the technical needs: (i) the extension of the service time of nuclear power plants from 40 years, as initially planned, to 60 years and probably more as expected now, (ii) the prediction of long term behaviour of metallic materials in nuclear waste disposal where the corrosion processes have to be predicted over large periods of time, some thousands years and more, (iii) the choice of materials for use at very high temperatures as expected in Generation IV power plants in environments like gas (helium), supercritical water, liquid metals or salts. Service time extension, deep geological waste repositories and high temperature reactors sustain researches and developments to model corrosion phenomena at various scales, from atoms to components

Radiolysis influence on water-saturated corrosion of carbon steels at 80°C

International audienceThe degradation of iron-based materials by atmospheric corrosion is a well-known issue that has to be taken into account, including for the disposal of high-level radioactive nuclear waste. In deep geological disposal conditions, the environment will be saturated with water either in an atmosphere with 100% humidity or with liquid water coming from the claystone host rock. During these periods, it is important to determine the corrosion damages and evaluate whether irradiation may influence these damages. In particular, the radiolysis of the water film in contact with air can lead to the formation of oxidizing species and to an increase in corrosion rates

Green Energies and Corrosion

International audienceAfter a short review based on the Intergovernmental Panel on Climate Changes (IPCC) of the United Nations (UN) regarding the low-carbon energies, corrosion issues related to these activities will be illustrated. One of the first issues will be to protect materials taking care of the environment. So, corrosion protection will need to follow the 12 principles of the green chemistry which will be recalled. Low carbon energies, like hydrolylic & wind powers, solar or geothermal energies, are often supposed to be "green" by essence and so free of industrial difficulties. In fact, these "green" facilities are also subject to corrosion issues. Not only examples are given of degradation of metallic materials used in these energies facilities, but it is even underlined that special attention has to be taken in some specific and particularly very corrosive environments like brine for geothermal energies or seawater for near and off shore wind mills or for hydro-turbines

The European Federation of Corrosion: from the past to the future

International audienceThe EFC is a federation of 38 organisations (Member Societies and Affiliate Members) with interests in corrosion based in 25 different countries within Europe and beyond. Taken together, its Member Societies represent the corrosion interests of more than 25,000 engineers and scientists. Founded in 1955, its aim is to advance the science of the corrosion and protection of materials by promoting cooperation in Europe and collaboration internationally. The EFC is registered in Belgium.The EFC Member Societies send delegates to a General Assembly which meets once a year to consider and approve policies.The administration of the Federation is in the hands of the Board of Administrators (BoA) and the scientific and technical affairs are the responsibility of the Science and Technology Advisory Committee (STAC) - members of both bodies being drawn from the EFC Member Societies.The day-to-day operation of the EFC is managed through the General Secretariat with offices in the UK, Germany and France and the Managing Officer.The EFC accomplishes its most important activities through twenty active working parties devoted to various aspects of corrosion and its prevention. The first working party, WP1 on Corrosion and Scale Inhibition was established in 1965 while the most recent, working party on Corrosion control in aerospace was formed in 2013. The working parties help to organise, singly or jointly with other working parties, strong technical sessions at EUROCORR. Other valuable activities include participation in collaborative research and testing programmes, the organisation of courses and workshops, and the preparation of reports, guidelines and proceedings for publication in the highly regarded EFC Series of 'green books' of which there are now over sixty The working parties are overseen by the Science and Technology Advisory Committee (STAC), to which all of the working party chairpersons and six other elected members belong. This is served by EFC's Scientific Secretary. Anyone with related interests is free to participate in working party meetings, which usually take place in conjunction with EUROCORR.EUROCORR, the EFC's annual conference is the flagship event of the European corrosion calendar. Attracting more than 1000 delegates, it is held in a different European country in September of each year. To date 38 of these conferences have been held and they have become noted for their high technical quality as well as the very enjoyable social programme.Important benefits available to EFC Member Societies include the opportunity to nominate candidates for the EFC Awards, which include the European Corrosion Medal, the Cavallaro Medal, and the Kurt Schwabe Prize. They can also appoint two voting members to each EFC Working Party and nominate candidates for election to the Board of Administrators, and the STAC. They can influence the direction taken by the EFC by voting at the annual EFC General Assembly. What is more, everyone who belongs to an EFC Member Society qualifies for reduced registration fees at EUROCORR and a discount on the prices of the EFC publications. European Member Societies can also submit bids to host EUROCORR conferencesThe EFC has recently expanded its horizons beyond the confines of Europe by admitting International Member Societies. Furthermore, companies and research organisations/ universities may join the Federation as Affiliate Members. The Federation has also become a founder member of the World Corrosion Organisation, a prime aim of which is to increase public and political awareness of corrosion and to advise governments, industries and communities about corrosion and its mitigation.The Young EFC is an initiative created in 2016 by the European Federation of Corrosion (EFC) who aims to support young researchers and engineers in the field of corrosion and protection of materials. Our vision has several cornerstones, namely: Building a bridge between young corrosion researchers and senior experts, Creating a network of young corrosionists, Organising and participating in conferences, workshops and other events, Promoting the interests of young researchers to the European Federation of Corrosion and the European Commission, Supporting the career at an early stag

Comportement électrochimique d'un acier inoxydable sous rayonnement et en milieu représentatif des réacteurs à eau pressurisée (REPs)

Cette thèse est dédiée à l'étude du comportement des aciers inoxydables sous irradiation exposés en condition primaire des réacteurs à eau pressurisée (REP). Le potentiel électrochimique de l'acier inoxydable austénitique 316L et les paramètres environnementaux comme la teneur en hydrogène, ont été mesurés de façon continue à haute température (HT) et haute pression (HT) grâce à un dispositif expérimental unique, la cellule HTHP. Deux sources d'irradiation ont été utilisées: les protons et les électrons. Le comportement électrochimique du 316L s'est avéré similaire dans les deux cas: (i) une augmentation du potentiel sous irradiation de l'ordre de la dizaine de millivolts ("réponse oxydative"); (ii) l'augmentation de la teneur en hydrogène diminue cette augmentation du potentiel sous irradiation; (iii) une synergie est observée entre le vieillissement à 300 C et la fluence qui conduit également à limiter la réponse oxydative sous irradiation. Les observations du film passif d'oxydes mettent en évidence la présence de nickel métallique dans l'ensemble des oxydes (interne et externe) en présence d'hydrogène, sans irradiation. Après les irradiations les plus fortes, des cavités (piqûres) sont observées en surface du 316L. Ces défauts sont attribués à l'effet de la radiolyse de l'eau et de l'irradiation de la couche passive. La radiolyse influence également l'évolution de la chimie du milieu primaire qui devient plus acide et plus oxydante. Il en résulte une augmentation du relâchement des cations métalliques et la présence d'hématite ( a-Fe2O3) sur le film d'oxyde externe de l'acier inoxydable lorsque les cavités (piqûres) sont formées.The dissertation focuses on the behaviour of stainless steel under irradiation and exposed to primary PWR conditions. The electrochemical potential of austenitic 316L stainless steel and the environmental parameters (hydrogen pressure, temperature, etc.,) have been measured continuously at high temperature (HT) and high pressure (HP) under irradiation, using a unique experimental HTHP working cell. Two sources of irradiation, proton and electron beams, have been employed in the study. A high similarity of electrochemical behaviour under both types of irradiations has been observed: (i) an oxidative potential response under irradiation (few tens of millivolts); (ii) an increase in the hydrogen pressure reduces the oxidative potential response; (iii) a synergetic effect of thermal ageing and fluence leading to a decrease of the oxidative response under irradiation. The observations of the oxide film showed that without irradiation, metallic nickel in the inner and outer oxide films has been observed under a high hydrogen pressure. Under irradiation, um scale cavities (pits) have been observed in the strongly electron irradiated oxide film formed on 316L stainless steel. These defects are induced by the effect of irradiation of the passive film and water radiolysis. It is also shown that water radiolysis influences the PWR water chemistry by making it become a stronger oxidant at the oxide/solution interface. As a result, the release of metallic cations is increased and a-Fe2O3 hematite has been observed on the irradiated outer oxide film where cavities were formed.PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

"Biocorrosion 2012" - From advanced technics towards scientific perspectives

Feron D, Neumann E. "Biocorrosion 2012" - From advanced technics towards scientific perspectives. Bioelectrochemistry. 2014;97: 1

Corrosion et altération des matériaux du nucléaire

International audienceLa maîtrise du phénomène de la corrosion est cruciale pour l'industrie nucléaire : il y va du rendement des installations, mais aussi de leur sûreté.Le nucléaire est confronté à la corrosion pour une grande variété de matériaux placés dans des environnements très divers. La corrosion métallique est, bien sûr, à l’œuvre dans le milieu chaud et aqueux des réacteurs à eau qui constituent l'essentiel du parc mondial. Les progrès réalisés dans la maîtrise de la corrosion des différents composants de ces réacteurs permettent de les faire fonctionner dans des conditions plus sûres. la corrosion est aussi présente dans les installations de l'aval du cycle électronucléaire (corrosion en milieu acide dans les usines de retraitement, corrosion des conteneurs de déchets en situation d'entreposage ou de stockage, etc.). Les systèmes nucléaires du futur élargiront encore la palette des matériaux à étudier et des situations dans lesquelles ils seront placés (corrosion par les métaux liquides ou les impuretés de l'hélium).La corrosion ressemble souvent dans sa description à un patchwork de cas particuliers. Les problèmes de corrosion rencontrés et leurs études sont présentés ici dans des chapitres relatifs aux grands secteurs du domaine nucléaire et y sont classés en fonction de leur phénoménologie. Cette monographie illustre les recherches en cours en présentant les résultats marquants obtenus récemment

Stress corrosion cracking of Ni-base alloys in pressurized water reactors: from the «Coriou effect» to the use of tracers

International audienceThis overview of stress corrosion cracking (SCC) of nickel base alloys in pressurized water reactors (PWRs) includes an historical perspective and assesses the latest developments on the investigations regarding the SCC mechanisms. The “Coriou effect” named the stress corrosion cracking of a nickel alloy (Alloy 600) in pure (or primary) water at high temperature. The SCC of Alloy 600 has been observed for the first time by Henry Coriou at the end the 1950s in pure water at 350°C. Even if these tests were more representative of water reactor conditions than those obtained in boiling magnesium chloride solutions where Alloy 600 is not susceptible to SCC, nevertheless, Alloy 600 has been used extensively in water reactors up to the 80s. Large researches and developments have been made and lead to the use of Alloy 800 or Alloy 690.In the second part of the presentation, updated knowledge of SCC in PWRs is summarized and focuses on the use of tracers to determine SCC mechanisms: (i) formation of oxide layers and intergranular oxidation are studied with the help of oxygen 18, (ii) using deuterated species (D2 versus D2O), the main hydrogen uptake by the alloy comes from the cathodic reaction on water molecules, (iii) in the oxide layer of Ni-base alloys, the transport of hydrogen and of oxygen is concomitant, as observed by comparing diffusion of D and 18O. These observations, together with some atomistic modelling, lead to a local intergranular approach where both oxidation and hydrogen may be involved in initiation and propagation of cracks in Ni-base alloys and under PWRs primary conditions (while impurities play a major role in secondary PWRs environments).In conclusion, the good behavior of Alloy 800 and of Alloy 690 is underlined and linked to the higher chromium content. The remaining question is to know if these alloys are SCC immune, or if it is only the initiation time which is longer, over decades in PWRs conditions

Radiolysis and corrosion of stainless steel in high temperature water environment

International audienceRadiolysis influences not only the electrochemical behaviour but also the oxide formation of stainless steel in high temperature water environments, like primary water of Pressurised Water Reactors (PWR). This paper focus on the corrosion behaviour of austenitic 316L stainless steel in PWR primary water under the influence of radiolysis, including experimental devices and main obtained results.After a short overview of the literature in the field, the approach is described with the use of a high energy proton beam to control the production of radiolytic species at the interface between stainless steel (316L type) and PWR water solution in a high temperature and high pressure electrochemical cell working up to 300°C and 100 bar. The corrosion potential of stainless steel was enhanced by the radiolysis causing by high energy proton beam. A high similarity of electrochemical behaviour was also observed under electron beam.The electrochemical oxidative response of the 316L/PWR solution interface under radiolysis is related to the surface characterization analysis (SEM, XPS, Raman spectroscopy, NRA…) on the oxide layers of 316L which are formed under or without irradiation. The radiolysis effect on the oxide film includes micron scale cavities which were observed in a highly irradiated oxide film. The observation of -Fe2O3 hematite on the outer oxide film where cavities were formed is in accordance with the electrochemical oxidative response

Stable isotopes used in the definition of corrosion mechanisms

International audienceThe ability of secondary-ion mass spectrometry (SIMS) to separate isotopes and to analyze thin layers by sputtering provides unique tools for studying corrosion mechanisms. The methodology with oxygen 18 has been tested with success at the beginning of the 70s for the oxidation of tantalum (Ta) by water in two steps: first oxidation by H216O and subsequent one by H218O [1]. Nevertheless, very few corrosion studies have taken the advantage of isotope substitution for the investigation of corrosion mechanisms. The objective of the paper is to show that the use of stable isotopes has been a major step in the understanding and the modeling of several corrosion phenomena. The first illustrations will be linked to the localization of the anodic and cathodic reactions on archeological analogues. Then the use of isotopic tracers will be shown in more complex environments.In liquid lead-bismuth, sequential experiments with dissolved 18O and 16O have been performed to determine the mechanisms of growth of the duplex structure oxide layer: It was found that the magnetite layer grows at the Pb–Bi/oxide interface whereas the Fe–Cr spinel layer grows at the metal/oxide interface. The modeling of the growth mechanisms of the duplex layer lead to the evaluation of corrosion damages, in accordance with available data. It should be underlined that the same type of growth of duplex layer has been observed in supercritical water with the subsequent used of H216O followed by an exposure to H218O.Stress corrosion cracking of Alloy 600 in water at 300-350°C has been investigated with Alloy 600 (nickel base alloy with 15% Cr and more than 72% Ni) samples exposed to heavy water with dissolved hydrogen (D2O / H2, diss) or to natural water with dissolved deuterium (H2O / D2, diss). SIMS analysis of D (2H) and 16O were done to determine the deuterium concentration profiles together with the oxide film thickness on the alloy surface. Almost no deuterium is observed for samples exposed in the H2O/D2 environment and only in the oxide layer, whereas the intensity of the deuterium profile is much larger in D2O/H2 with deuterium observed not only in the oxide layer but also in the alloy. Clearly, the main source of hydrogen is the cathodic reaction (water dissociation). Two mechanisms may be proposed for modelling the hydrogen transport associated with the oxide growth during alloy passivation: (i) diffusion of hydrogen as an interstitial proton through the oxide lattice, or (ii) diffusion as a hydroxide ion towards the oxide in the anionic sub-lattice. The latter hypothesis implies the oxygen and hydrogen diffusivities through the oxide layer to be the same. To check which hypothesis is correct, Alloy 600 specimens have been exposed in PWR primary conditions using 2H and 18O as markers. The values obtained for diffusion coefficient of 2H and 18O are very close (around 5 10-17 cm2/s) which supports the idea of a hydrogen transport mechanism through the oxide layer as hydroxide ions. The strong correlation between hydrogen absorption and oxidation occurs not only for the formation of the oxide layer on the surface of the alloy, but also during intergranular oxidation of grain boundaries. The question here is to assess whether the oxide grown at the grain boundaries in the case of intergranular corrosion would act as a barrier to hydrogen arrival to the oxide/crack tip or not. After a primary oxidation in nominal primary water followed by a short period under the same conditions but with D and 18O isotopes, deuterium and oxygen 18 are found at the tip of the intergranular oxidation, even for short exposure times. The results lead to the conclusion that oxygen and hydrogen transport in the oxidized grain boundary are not the rate-controlling step for SCC initiation in PWR nominal conditions. To check if chromium diffusion is the limiting step, diffusion experiments with 54Cr in Ni-Cr alloys have been performed.The conclusive remarks will include some recommendations and some interests for the use of radioactive tracers to determine corrosion kinetics