Tensile tests and TEM investigations on LiSoR-2 to -4

Martensitic steel T91 will be used for the liquid lead bismuth eutectic (LBE) container of the MEGAPIE target. The irradiation assisted LBE corrosion and embrittlement effects on the behaviours of T91 steel have been studied by performing the LiSoR experiments, where T91 steel was irradiated with 72 MeV protons to doses up to 0.2 dpa at temperatures above 300 °C in flowing LBE with or without mechanical stress. Tensile tests on the T91 steel after irradiation demonstrated that the irradiation assisted LBE embrittlement was not evident at such a low irradiation dose. The irradiation produced small defect clusters and dislocation loops were observed in the inner tensile-stressed specimens (ITS-specimens) of LiSoR-3 and LiSoR-4. The main features of the dislocation structure in the ITS-specimen of LiSoR-2 and the test-section tubes (TS-tubes) were dislocation tangles and dislocation networks, and small defect clusters and dislocation loops were hardly observed due to the high irradiation temperatures. The TEM observations support the results of the tensile tests.