CRC technology of nozzle. Water level instrumentation nozzle

Inconel 182 is used for welding joint material between Reactor Pressure Vessel (RPV) nozzle and nozzle safe-end in nuclear power plants (Nozzle indicates an only water level instrumentation nozzle in this paper). Corrosion Resistant Cladding (CRC) is the method which is welded a Stress Corrosion Cracking (SCC) resistant material cladding to the welding joint portion. Still more CRC technology is applied to the internal surface of nozzle made of Inconel 600 which is known to have SCC sensitivity. This technology prevents from the SCC initiation of material. In actual work after cutting nozzle safe-end, small-sized welding machine is put into the nozzle whose inside diameter is about 50 mm. These nozzles are installed at the three different levels of RPV. In case of the lowest nozzle, which placed near the core, it is necessary to build the shielding blocks outside RPV, and keep the reactor water in the vessel to protect workers' radiation exposure. Therefore a water-proof working box is installed around nozzle area inside RPV to perform CRC in dry environment. This technology had been applied to a couple of operating plants. (author)