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This work addresses the effect of deformation twinning on the dissolution corrosion behaviour of 316 L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE). For this purpose, plastically deformed 316 L steel specimens with distinctly different deformation twin densities were simultaneously exposed to oxygen-poor (

Heavy liquid metals such as lead bismuth eutectic (LBE) are chosen as the coolant to innovative Generation IV (Gen IV) reactors where ferritic/martensitic T91 steel is a candidate material for high temperature applications. It is known that LBE has a degrading effect on the mechanical properties of this steel. This degrading effect, which is known as liquid metal embrittlement (LME), has been screened by several tests such as tensile and small punch tests, and was most severe in the temperature range from 300 °C to 425 °C. To meet the design needs, mechanical properties such as fracture toughness should be addressed by corresponding tests. For this reason liquid-metal embrittlement of T91 steel was investigated by fracture toughness tests at 350 °C. Tests were conducted in Ar-5%H 2 and LBE under the same experimental conditions Tests in Ar-5%H 2 were used as reference. The basic procedure in the ASTM E 1820 standard was followed to perform tests and the normalization data reduction (NDR) method was used for the analysis. Comparison of the tests demonstrated that the elastic–plastic fracture toughness (J 1C ) of the material was reduced by a factor in LBE and the fracture mode changed from ductile to quasi-cleavage. It was also shown that the pre-cracking environment played an important role in observing LME of the material since it impacts the contact conditions between LBE and steel at the crack tip. It was demonstrated that when specimens were pre-cracked in air and tested in LBE, wetting of the crack surface by LBE could not be achieved. When specimens were pre-cracked in LBE though, they showed a significant reduction in fracture toughness.

The chemical and electrochemical conditions within a crevice of Type 316 stainless steel in boric acid–lithium hydroxide solutions under PWR-relevant conditions were modelled with a computational electrochemistry code. The influence of various variables: dissolved hydrogen, boric acid, lithium hydroxide concentration, crevice length, and radiation dose rate was studied. It was found with the model that 25 ccH 2 /kg (STP) was sufficient to remain below an electrode potential of -230 mV she , commonly accepted sufficient to prevent stress corrosion cracking under BWR conditions. In a PWR plant various operational B–Li cycles are possible but it was found that the choice of the cycle did not significantly influence the model results. It was also found that a hydrogen level of 50 ccH 2 /kg (STP) would be needed to avoid substantial lowering of the pH inside a crevice.

The local environment in an occluded region of a pressurized water reactor (PWR) depends on its geometry, its access to the bulk and the nature of the electrode kinetics at the metal surfaces. In PWR-relevant, oxygen-free, boric acid–lithium hydroxide solutions the dominant anodic and cathodic electrode reactions are found to be hydrogen oxidation and water reduction, respectively. The hydrogen oxidation reaction kinetics have been quantified using potentiostatic measurements – at 300 °C, under various dissolved hydrogen concentrations, for 1000 ppmB and 2 ppmLi. The reaction kinetics have been verified by modelling of a crevice experiment performed in an autoclave at 300 °C for 1000 ppmB, 2 ppmLi and 25 STP ccH 2 /kg.