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The objective of this paper is to give a short overview of how the bacteria, that may influence the corrosion behaviour of metals and alloys, are taken into account in the French concept of geological repository. It is important to underline that microbial induced corrosion is not a new corrosion phenomena but the presence of bacteria may modify (increase or decrease) anodic or cathodic corrosion reactions. In aerobic conditions, high corrosion rates may be obtained due to the bio-oxidation of pyrites. Under anaerobic conditions (longer period), bacteria may have negative (localised corrosion) or positive (consumption of hydrogen) effects. The mixed conditions (with and without oxygen) may be the most dangerous period for localised corrosion of metals and alloys due to the coupling and galvanic corrosion phenomena enhanced by aerobic and anaerobic bacteria. The first conclusions lead to consider that MIC is a ‘short term’ issue rather than a long term one.

In pressurised water reactors the cladding tubes in zircaloy-4 are oxidised up to several micrometres on the internal face by direct contact with the UO2 pellets. At the same time, fission products such as 129I are implanted by recoil. Until 1995, the cladding tube pieces called hulls were embedded in concrete. The concrete medium being very basic, this study simulates the corrosion of hulls in the perspective of a long-term disposal in these severe pH conditions. This paper is dedicated to the study of the partial dissolution of the oxide layer, which is the responsible mechanism for the activity release. In order to follow the solid–liquid interface, europium was implanted into the material surface as a marker. Next, the corrosion induced in autoclave at 300°C, 140 bars and in alkaline water was studied. The determination of europium profiles using Rutherford backscattering spectrometry analysis (RBS) allows to deduce the fraction of dissolved ZrO2. It was shown that this dissolution is not homogeneous in porous zirconia and gives rise to the formation of crevices. Using the nuclear microprobe of Pierre Sue laboratory, a more precise study of the specimen surface was performed.

Uranium metal and U-0.2wt.%V alloy are very sensitive to hydrogen contamination. Prevention of hydride formation, a basic problem, can be approached by modifying the surface characteristics. Implantations of oxygen, nitrogen, carbon and sulphur ions have been tested as a function of dose from 2 × 10 16 to 2 × 10 18 ions cm −2 . The main results are an increase in the induction time, which is multiplied by factors of 20–80 depending on the implanted species, and a change in the nucleation and growth mechanism from instantaneous nucleation (3 × 10 5 nuclei cm −2 , 125 °C, P H2 = 5 kPa) to a pitting attack (from 300 to less than 10 pits cm −2 ) according to the species. Characteristics of the implanted shells have been determined by secondary ion mass spectrometry and X-ray diffraction.

Publisher Summary The chapter offers the observation that carbon steels excavated from a battlefield of World War I exhibited two thick and heterogeneous corrosion layers, formed during the subsequent long period of burial in the soil. Considering that their further corrosion was limited by the properties of the internal layer, the modeling proposed in the chapter lets us draw two distinct conclusions: (1) The first series of experiments, carried out by electrochemical impedance spectroscopy, confirmed that the internal layer was porous, as was previously attested for the external one. The impedance diagrams showed that the corrosion was controlled by transport phenomena of the species through this porous internal layer. In Evian water, which has poor conductivity, it was necessary to consider simultaneously two processes: a diffusion process in the liquid medium filling the pores and a solid-phase transport process in the electrode material. (2) In the second series of experiments, chronoamperometry tests revealed that the internal corrosion layer was protective, in spite of its porosity. This layer plays a significant role in hindering the further evolution of corrosion, leading to a large fall in the corrosion rate.

ACE, NIMB; The aim of this paper is to study the effect of water radiolysis under 12 MeV proton irradiation on the corrosion behaviour of pure iron. Oxygen and hydrogen playing a crucial role during the corrosion process have been specifically investigated. Heavy desaerated water (enriched at 99.9% in D) was also used to determine the origin of hydrogen at the iron surface. Proton irradiations were performed at the CERI cyclotron in Orléans. Both sides of the Fe foil (respectively in contact with air and with water) were analysed with ion beam techniques: Alpha Rutherford Backscattering Spectrometry was used to profile oxygen, Elastic Recoil Detection analysis has allowed to profile hydrogen. The use of D$_2$O gives evidence that the hydrogen concentration present on the water face could originate from wet air. In addition, in case of the aerated deionised H$_2$O media, it is shown that the irradiation process induces a strong corrosion. Scanning electron microscopy experiments confirm the formation of oxide precipitates.

This study is related to the nuclear waste management and to the long-term behaviour of radionuclides in deep storage. The aim of this paper is to study the corrosion of zirconium in deep storage. In order to simulate the inner side of zircaloy cladding tubes, the zirconium samples were oxidised in air at 500°C during 3 h. Two hundred keV-implanted europium ions were used as marker to follow the evolution of the ZrO2–liquid interface. In a first step, air annealings were performed in the temperature range 850–950°C. Diffusion profiles were measured using 3 MeV alpha-particles Rutherford backscattering spectrometry (RBS) at each step of annealing. By extrapolation it is shown that at 300°C the europium diffusion in ZrO2 is negligible. In a second step, the specimens were exposed to a basic solution (pH 13.5) at 300°C in autoclave under a 107 Pa pressure. By means of RBS, it was possible to deduce the fraction of dissolved ZrO2. It was shown that this dissolution is inhomogeneous. These results are confirmed by scanning electron microscopy (SEM).

During the reactor processing, fission products among which iodine are implanted by recoil inside the zircalloy cladding tube: most of them being distributed in the first 2 μm. At the same time oxidation of the cladding tube occurs, hence in the waste storage phase zirconia will act as a migration barrier. In order to determine diffusion data, stable and radioactive iodine atoms were introduce in zirconium oxidized samples by mean of ion implantation. Iodine thermal-release was measured either by Rutherford Backscattering Spectroscopy or γ spectroscopy. Two depths range were studied, the subsurface (

The large uranium fission cross section leading to iodine and the behaviour of this element in the cladding tube during energy production and afterwards during waste storage is a crucial problem, especially for 129I which is a very long half-life isotope (T = 1.59 × 107yr). Since a combined external and internal oxidation of the zircaloy cladding tube occurs during the reactor processing, iodine diffusion parameters in zirconia are needed. In order to obtain these data, stable iodine atoms were first introduced by ion implantation into zirconia with an energy of 200 keV and a dose equal to 8 × 1015at cm−2. Diffusion profiles were measured using 3 MeV alpha-particle Rutherford Backscattering Spectrometry at each step of the annealing procedure between 700°C and 900°C. In such experiments a reduced iodine concentration was observed, which correlated to a diffusion-like process. Similar analysis has been performed using radioactive 131I implanted at a very low dose of 109 at cm−2. In this case the iodine release is deduced from gamma-ray spectroscopy measurements. The results are discussed in this paper.

Ion implantation and ion mixing are applied to improve the corrosion behavior of two uranium alloys: UV0.2 and UTi0.75, in three specific media: hydrogen, humid air and salt fog. This experiments shows particularly that high dose nitrogen implantation might be effective for both corrosive environment, hydrogen and humid air. Ion mixing of aluminum coatings on UTi0.75 alloy induces microcracks in these films and reduce their protective characters in salt fog medium.

This paper presents a state-of-the-art analysis of the expected degradation processes of a variety of candidate container materials for the disposal of high-level waste and/or spent nuclear fuel. The work, focusing on the most recent developments, has been performed under the auspices of the Implementing Geological Disposal Technology Platform in the context of an international conference hosted by the Nuclear Waste Management Organisation of Canada (NWMO). The scope of the analysis includes the expected corrosion and environmentally assisted cracking behaviour of copper, carbon steel and titanium in contact with relevant buffer materials (e.g. bentonite, cement) and in conditions expected in an underground disposal facility (long-term anoxic conditions). Considerations relative to the expected evolution of the environmental conditions (especially in the period following backfilling) are also presented. Beyond summarising the current state of knowledge, areas in which opportunities for international collaboration may be present are also highlighted. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.

This paper presents a state-of-the-art analysis of the expected degradation processes of a variety of candidate container materials for the disposal of high-level waste and/or spent nuclear fuel. The work, focusing on the most recent developments, has been performed under the auspices of the Implementing Geological Disposal Technology Platform in the context of an international conference hosted by the Nuclear Waste Management Organisation of Canada (NWMO). The scope of the analysis includes the expected corrosion and environmentally assisted cracking behaviour of copper, carbon steel and titanium in contact with relevant buffer materials (e.g. bentonite, cement) and in conditions expected in an underground disposal facility (long-term anoxic conditions). Considerations relative to the expected evolution of the environmental conditions (especially in the period following backfilling) are also presented. Beyond summarising the current state of knowledge, areas in which opportunities for international collaboration may be present are also highlighted. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.