High-Temperature Corrosion Behaviors of Structural Materials for Lead-Alloy-Cooled Fast Reactor Application

Abstract

The corrosion of nuclear-grade steels in lead–bismuth eutectic (LBE) complicates the realization of high coolant temperatures. Corrosion tests of T91, HT9, and SS316L were performed in static cells at 600 °C for 2000 h at an oxygen level of 10−6 wt.%. The obtained corrosion surfaces of post-processed samples were characterized by several microscopy methods. Up to 1000 h, all the alloys exhibited an evolution of duplex oxide layers, which were spalled until 2000 h due to their increased thickness and decreased integrity. Following the spallation, a thin internal Cr-rich oxide layer was formed above the Cr-depleted zone for T91 and HT9. SS316L was penetrated by LBE down to 300 μm in severe cases. A comparison on the corrosion depths of the materials with regard to the parabolic oxidation law with abundant literature data suggests that it may lose its validity once the duplex layer is destroyed as it allows LBE to penetrate the metal substrate.

Environmental degradation of structural materials in liquid lead- and lead-bismuth eutectic-cooled reactors

“…Similar effects are expected in steels containing Si and/or Al, as regions depleted in corrosion-resistant elements are invariably observed next to the inner oxide scale layers [113]. In T91 and HT-9 F/M steels exposed to static liquid LBE (C O ≈ 10 − 6 wt%) at 600 • C for 2000 h, a thin Cr-rich oxide was observed to re-form above the Cr-depleted steel region [114].…”

Electrochemical Sensors for Controlling Oxygen Content and Corrosion Processes in Lead-Bismuth Eutectic Coolant—State of the Art

“…As not all oxygen is bound in this reaction, the remaining molecules migrate through the oxide layer and react with both iron and chromium under the film, increasing the thickness of the ferro-chromium spinel layer. As a result, a two-layer oxide film is formed on the surface of the structural material, in which only the inner layer has protective functions [ 12 , 13 ].…”

“…The areas of lead oxides and protective films formation depending on the temperature and oxygen concentration in the LBE [ 13 , 17 , 18 ] are shown in Figure 1 .…”

“… Conditions of lead oxide and protective films formation according to Martynov [ 17 ] and Müller [ 18 ]. The red line indicates the maximum core temperature for currently designed reactors with LBE [ 13 ]. …”

Analysis of fuel performance under normal operation conditions of MicroURANUS: Micro long-life lead-bismuth-cooled fast reactor

“…In general, austenitic steels in leadbismuth eutectic systems between 450 and 500 °C oxidize with the formation of dual-layer porous magnetite (Fe 3 O 4 )/compact inner spinel layer for short-term operation (Müller, Schumacher and Zimmermann, 2000). However, it was verified that a uniform and protective Fe-Cr spinel single layer is formed in austenitic steel SS316L and 15-15Ti during long-term operation at a temperature below 450 °C (Tsisar et al, 2016;Lee et al, 2021) Therefore, the single layer oxidation parabolic law of 15-15Ti was applied, and the parabolic rate constant and activation energy were calculated by fitting the literature data on long-term oxidation at 400 °C, 450 °C, and 550 °C in flowing LBE (2 m/s) with 10 -7 mass% of dissolved oxygen. (Tsisar et al, 2016).…”