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This work was devoted to understanding the effect of Si doping (1.27 wt%) on elastic-plastic fracture toughness (J IC) of T91 ferritic/martensitic (F/M) steel in liquid lead-bismuth eutectic (LBE, Pb 44.5 Bi 55.5 , wt%) under various parameters. The results showed that Si doping significantly promoted occurrence of liquid metal embrittlement (LME) and led to more severe degradation of fracture toughness at 350 °C, especially in oxygen-poor LBE. The LME susceptibility of T91-Si steel was found to be nearly independent on the loading speeds, while T91 F/M steel exhibited a stronger LME effect when the loading speed was decreased from 0.02 mm/min to 0.002 mm/min. Oxygen concentration had a mild effect. Detailed microstructural analyses showed that the fracture behavior of the T91-Si steel in LBE environment at 350 °C was analogous to cleavage fracture and the crack propagation was mainly transgranular. The crack wall was quite rough and locally faceted to low-index crystallographic planes of {110}. Numerous dislocations were also present in the vicinity of the crack tip. No solid evidence of diffusion of Pb and Bi into the steel bulk was discovered even at the atomic scale, which strongly suggests a crack tip surface adsorption-based LME mechanism. [ABSTRACT FROM AUTHOR]

The effect of temperature on the liquid metal embrittlement (LME) susceptibility of an Fe10Cr4Al ferritic alloy exposed to stagnant oxygen-depleted lead-bismuth eutectic (LBE) was investigated using slow strain rate tensile (SSRT) tests. The results show that the total elongation to rupture of the specimens tested in LBE decreases with increasing temperature from 150 to 350 °C, while an upward trend is observed in the temperature range of 350–500 °C. Such a strong temperature dependence is called a "ductility trough". This phenomenon is not observed in the specimens tested in Ar reference environment. Fractographic examinations reveal that LME occurs at 150 up to 450 °C and ductility fully recovers only at 500 °C. In addition, transgranular cleavage and intergranular cracking are the major fracture modes on the fracture surfaces affected by LME. • A "ductility trough" is found and the alloy is embrittled at 150–450 °C. • Ductility recovers only at 500 °C. • Cleavage and intergranular cracking are the major LME failure modes. [ABSTRACT FROM AUTHOR]

• MC3D used for HLM-water interaction studies for LFRs. • MC3D code comparison against SIMMER simulation results. • MC3D verification and validation against experimental data. Pool type Reactor Pressure Vessels (RPVs) containing steam generators with high secondary coolant pressure are adopted for a number of heavy liquid metal reactor conceptual designs. The primary side heavy liquid metal, e.g., liquid Lead-Bismuth Eutectic (LBE) with low pressure and secondary water with high pressure can come into contact in the event of Steam Generator Tube Rupture (SGTR) scenarios. Due to the pressure wave propagation and resultant sloshing of liquid LBE, the vigorous interaction between water and melt LBE can threaten the structural integrity of the reactor internals. Moreover, Reactor Pressure Vessel (RPV) pressurization, reactivity feedback as a result of steam entrance into the core as well as primary system pollution are also key concerns for SGTR accidents. The article aims to evaluate the capability of the MC3D code for LBE–water interaction in the event of SGTR scenarios. MC3D is a multidimensional numerical tool developed by IRSN for multi-phase flow studies and assessments in nuclear safety. Its field of application is mainly on Fuel-Coolant Interaction (FCI), especially the stages of premix and explosion in case of severe accidents. In order to evaluate the capability of MC3D for the Coolant-Coolant Interaction (CCI) of Liquid metal cooled Fast Reactors (LFRs), simulation of a small-scale experiment investigating water jet plunging into a pool of molten lead-bismuth alloy is carried out. Afterwards, experiments on LIFUS5/Mod2 facility at ENEA studying LBE-water interaction in the event of SGTR, for which a series of experiments have been conducted including the injection of sub-cooled water into LBE from the bottom of the test vessel, is simulated with MC3D as well. The simulation results for both facilities are then compared with those of the tests. The results predicted with MC3D for LIFUS5/Mod2 is also compared against the simulation results with SIMMER. The comparison implies that MC3D is generally capable for the phenomena of CCI in the event of SGTR for LFRs. Nevertheless, the potential employment of MC3D for intensive investigation of the LBE-water interaction will still need further experimental studies and improvement of physical models. [ABSTRACT FROM AUTHOR]

• The LME susceptibility of Fe10Cr4Al was tested in LBE at 350 °C. • This alloy is highly susceptible to LME. • Surface oxides can delay LME. • LME-induced fracture is dominated by cleavage and intergranular cracking. Liquid metal embrittlement (LME) of an Fe10Cr4Al (wt%) ferritic alloy was tested in lead-bismuth eutectic (LBE) at 350 °C using slow strain rate tensile tests. The results show that this alloy is highly susceptible to LME. The strong LME effect is manifested by a substantial reduction in ductility and completely cleaved fracture surfaces. Transgranular cleavage and intergranular cracking are the major fracture modes. The LME susceptibility is slightly weaker in oxygen-saturated LBE than oxygen-depleted LBE due to the presence of a double-layer scale consisting of magnetite and Al-rich spinel. The oxide scale is fragmented, indicative of a brittle nature. [ABSTRACT FROM AUTHOR]

Liquid metal embrittlement (LME) susceptibility of a high-entropy alloy (HEA) with a nominal composition of Fe 40 Mn 10 Ni 10 Co 20 Cr 20 (at.%) and a single face-centered cubic (fcc) structure was tested in oxygen-depleted lead-bismuth eutectic (LBE, Pb 44.5 Bi 55.5 , wt%) and argon (Ar) environments at 250 and 350 °C using slow strain rate tensile tests. A nominal strain rate of 5x10−5s−1 was employed for all tests. The results showed that LBE had no evident impact on the tensile mechanical properties including total elongation to rupture. Fractographic examinations revealed that the fracture surfaces were predominately dimpled, regardless of the environment and temperature tested. All the results indicate that this high-entropy alloy is not susceptible to LME under the experimental conditions tested in this study. However, severe dissolution corrosion with a corrosion depth of 50–100 μm occurred at the surface, although the specimens were pre-exposed to the oxygen-depleted LBE at 450 °C only for about 20h. This was due to the high contents of Ni and Mn, which are two elements having a high solubility in LBE at a high temperature. The dissolution corrosion and the subsequent tensile loading resulted in formation of numerous microcracks at the specimen surface, contrary to the cases tested in Ar. In this regard, the high-entropy alloy is poorly resistant to LBE dissolution corrosion at 450 °C. • Tensile behavior of a high-entropy alloy (HEA) was tested in LBE. • The HEA was not susceptible to LME under the testing conditions employed. • The HEA was poorly resistant to LBE dissolution corrosion. [ABSTRACT FROM AUTHOR]