New Approach to Join SiC for Accident-Tolerant Nuclear Fuel Cladding

Silicon carbide is used as a fuel cladding in nuclear power plants. A major outstanding problem is to join the end plug to the cladding tube in order to seal in the fuel pellets after loading them into the fuel rods. This has taken on added importance and urgency following the Fukushima Daiichi accident. None of the approaches developed for joining SiC in nuclear environments survived irradiation and flowing water tests mimicking in-service reactor conditions. EWI has developed a novel brazing approach that could meet these requirements. Unlike other processes, it does not require extensive heating times or high pressures. The joining interlayer is a two-phase mixture of Si and Al and some alloying elements. The joined microstructure provides crack arresting paths, imparting high toughness to the joined assembly. Test results (three-point bending; thermal cycling; irradiation) and SEM-EDS analyses of alpha-hexoloy SiC block joints are given.