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Communication Dans Un Congrès Année : 2015

Joint dissolution and oxidation behaviour of 316LN steel at 550°C in liquid sodium containing low concentration of oxygen

Résumé

– The sodium cooled fast reactor is selected in France as the 4th generation of nuclear power plant. 4th generation's reactor vessel, primary loop structures and heat exchangers will be made of austenitic stainless steels (316LN). To assess reactor service life time, corrosion of austenitic stainless steel by liquid sodium is studied in normal operating conditions as well as in transient conditions either expected or not. Oxygen, one of the main impurities, but present in trace amounts (1 to 10 µg/g or ppm weight), plays a major role on corrosion phenomena of the steel, although not totally understood yet. Literature reports an increased dissolution rate of steel or even of pure iron with increasing oxygen content although no thermodynamically stable iron oxide exists at low oxygen content. Oxygen is only known to form sodium chromite scale (NaCrO 2), those behaviour is, however, little documented. Based on corrosion tests performed in the static sodium test device (" CorroNa ") at 550°C for an oxygen content initially of about 1 ppm in weight or lower, and about 5-10 ppm after 4600h of test, either a really small dissolution rate or small sodium chromite scale formation (NaCrO 2) are observed. Dissolution and carburation are observed for specimen immersed since the beginning of the test, while oxidation is the main feature observed for the specimen immersed during the last periods of the test. Some aspects of the morphologies of this oxide scale obtained by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) as well as by Glow Discharge Optical Emission Spectroscopy (GD-OES) are presented. Discussions and explanations of these apparently opposing results are given based on thermodynamic analysis, as well as their possible consequences for reactor operation.
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Dates et versions

hal-01810165 , version 1 (07-06-2018)

Identifiants

  • HAL Id : hal-01810165 , version 1

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J. L. Courouau, Matthieu Rivollier, V. Lorentz, Michel Tabarant. Joint dissolution and oxidation behaviour of 316LN steel at 550°C in liquid sodium containing low concentration of oxygen. ICAPP, May 2015, Nice, France. ⟨hal-01810165⟩
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