Core structure for nuclear power plants

Purpose: To prevent excess deformation due to earthquakes in fuel assemblies. Constitution: In a bwr type reactor having fuel assemblies incorporated in the shroud within a pressure vessel, a plurality of buffle plates are provided to a generally annular-shaped gap formed between the shroud and the fuel assemblies for preventing reactor core water from rotating upon its flowing. The buffle plates can prevent the reactor core water from rotation also against the earthquake vibrations to thereby improve the damping effect for the reactor core water and reduce the effect of vibration on the fuel assemblies. (Ikeda, J.)