CORROSION BEHAVIOUR OF PHYSICAL VAPOUR DEPOSITED COATINGS ON NUCLEAR COMPONENTS AND Fe-Cr-Al ALLOY UNDER NORMAL OPERATION AND ACCIDENT SCENARIOS

摘要

As a result of a loss of coolant accident,temperatures within the fuel cladding can reach in excessof 1000 °C, resulting in thermal energy release andhydrogen generation. To combat this, candidate accidenttolerant fuel cladding (ATFC) materials and coatings arebeing investigated. Physical vapour deposited (PVD) CrNand TiAlN coatings have shown promising results to actas protective barriers for zirconium alloys. Fe-Cr-Alalloys are also considered as potential ATFC candidatematerials due to the formation of alumina at hightemperatures, which acts as a protective oxide and hasslow growth kinetics. PVD CrN and TiAlN coatings on aZircaloy-2 substrate were exposed to reactor primarysideconditions (300°C and pH25°C 10.2) for up to180 days to assess their corrosion resistance undernormal operating conditions. To evaluate the oxidationresistance of these coatings and a Fe-Cr-Al alloy underaccident conditions, samples were exposed to hightemperature steam (1000 °C) for up to 24 hours. Basedupon the current results, it was found that CrN coatingsacted as a barrier to corrosion under normal operatingconditions and a temporary barrier under accidentscenarios due to the formation of a Cr-rich oxide. The Fe-Cr-Al alloy was found to have decreased corrosion ratesin comparison with stainless steels and zirconium alloyswhen exposed to accident scenarios due to the protectivenature of the formed Al_2O_3 layer.