Abstract
The environmental performance of structural materials (e.g., corrosion and environmental assisted cracking) is one of the critical issues being addressed in the development of Generation IV fast reactors. This work aims to support the study of the performance of the ferritic-martensitic steel T91 in liquid lead, under close to operation conditions, in order to assess its suitability for an application in lead fast reactors. T91 steel was tested in air and liquid lead at 400 °C using static and slow loading regimes. Applied stresses were chosen to be slightly above the yield strength in order to evaluate the threshold stress and strain for crack initiation. Three-point bending static exposure and constant extension tests of tapered specimens were performed. Post-test surfaces and cross sections of specimens were observed using scanning electron microscopy techniques in order to detect cracks and to analyze oxide layers. The effect of strain rate of the oxide layer cracking was observed. In conclusion, T91 was not susceptible to liquid metal embrittlement, a special case of environmentally assisted cracking under the testing conditions. The cracking conditions are discussed based on previous experience.
Highlights
The choice of structural materials based on their compatibility with the coolant is one of the most critical issues in the development of lead-cooled generation IV fast reactors (LFRs)
An optimal oxygen concentration to grow stable and protective oxide scales in liquid LBE and Pb was calculated to about one range, this being around 10−7 wt. % at 400 ◦ C and 10−6 wt. % at 500 ◦ C [15]
According to the described data, it can be concluded that liquid metal embrittlement (LME) might occur in the T91 steel/liquid lead system under above
Summary
The choice of structural materials based on their compatibility with the coolant is one of the most critical issues in the development of lead-cooled generation IV fast reactors (LFRs). The compatibility of materials under LFR operational conditions needs to be investigated by means of corrosion-mechanical testing under selected conditions. These conditions should include a liquid lead environment, with specific oxygen content at temperatures ranging from 380 to 550 ◦ C and application of stress up to the level allowed in operational design [1]. One of the HLM coolant operation strategies is to maintain a specific oxygen content in liquid metals to build protective oxides on the steel, these media (Pb and LBE) do not have the same effect on materials. An optimal oxygen concentration to grow stable and protective oxide scales in liquid LBE and Pb was calculated to about one range, this being around 10−7 wt. Corrosion testing of T91 steel in Materials 2018, 11, 2512; doi:10.3390/ma11122512 www.mdpi.com/journal/materials
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