Effects of oxidation on the deuterium permeation behavior of the SIMP steel

Reduced activation ferritic/martensitic (RAFM) steels are the primary candidate structure materials for the blanket in future fusion power plants. In the recent years, a novel 9-12 % Cr modified F/M steel named SIMP steel has been developed. The deuterium permeation behavior of the SIMP steel with and without oxide layer has been evaluated using a gas driven permeation (GDP) device. The permeability of original and oxidized SIMP steel has been derived and compared. In order to characterize the oxide layer, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) experiments have been carried out. GDP results show that the SIMP steel has similar deuterium permeability with the CLF-1 steel. The deuterium permeability of the oxidized SIMP steel is lower than that of the original SIMP steel. Heat treatment during the oxidization process has no influence on the deuterium permeability of the bare SIMP steel. The cross-section SEM pictures present that with the increase of the oxidation time, the thickness of the oxide layer is increased. The oxide layers are observed to be porous. The results of XRD and EDS show that the oxide layer mainly consists of chromium oxide and accumulation of chromium can be detected in the surface region. The formation of the chromium oxide in the surface of the SIMP steel could be the reason of the decrease of the deuterium permeability of the oxidized SIMP steel.