Oxidation of a cold-worked 316L stainless steel in pressuriezd water reactor primary water environment

M. Maisonneuve (1) , C. Duhamel (2) , C. Guerre (1) , J. Crepin (2) , I. de Curieres (3) , L. Verchere (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 Mines Paris - PSL (École nationale supérieure des mines de Paris)
3 IRSN - Institut de Radioprotection et de Sûreté Nucléaire

Experience on Pressurized Water Reactors (PWR) shows cases of Stress Corrosion Cracking (SCC) affecting cold-worked stainless steel components (pressurizer heaters, thermocouple staples) in the primary circuit of those reactors. Many material, environment and mechanics-related parameters are known to have an influence on the oxidation and SCC susceptibility of stainless steels in this environment. Furthermore, oxygenated transients, i.e. reactor operating steps with oxygen injections in nominal primary water [5,6], may be a possible detrimental factor. Indeed, it was shown that the presence of oxygen changes the SCC cracks morphology from transgranular to intergranular and the surface oxidation film characteristics [8,9] (crystallographic structure of the external part, roughness of the internal part of the film). The global aim of this work is to study the influence of oxygenated transients on the SCC susceptibility in PWR primary water of a cold-worked 316L stainless steel, with a special attention paid to the coupling between strain localization and oxidation. For this purpose, slow strain rate tensile (SSRT) tests are performed on tensile pre-strained specimens. Several loading paths are applied, with pre-straining and SSRT testing directions identical or perpendicular to each other. The resulting cracking networks are correlated to the microstructural and local strain fields obtained by electron backscatter diffraction (EBSD) and digital image correlation (DIC), respectively. In parallel, the effect of oxygen on oxidation is studied on non-strained and cold-worked specimens. To this aim, the kinetics, structure and composition of the oxide films and oxide penetrations (grain boundaries, slip bands) are characterized by Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM).As a first step, the developed approach is applied to the oxidation and SCC behaviors of a 316L stainless steel in nominal primary water that will constitute our reference state. This presentation thus focuses on the first results obtained for these conditions.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

M. Maisonneuve, C. Duhamel, C. Guerre, J. Crepin, I. de Curieres, et al.. Oxidation of a cold-worked 316L stainless steel in pressuriezd water reactor primary water environment. EUROCORR 2017, Sep 2017, Prague, Czech Republic. ⟨cea-02434524⟩