NATURAL-CIRCULATION BOILING WATER REACTOR AND CHIMNEY THEREFOR

The present invention provides a chimney for a natural-circulation boiling water reactor having structural soundness capable of standing a horizontal load generated by a flow-induced vibration, an earthquake and the like. The chimney for a natural-circulation boiling water reactor according to the present invention is characterized in that: the chimney is disposed in the inside of a reactor pressure vessel, and includes plural flow channels which guide a steam-water two-phase flow generated in a reactor core to the upper part of the reactor pressure vessel; each of the flow channels is formed partitioned by plural flow channel separation walls whose lower-most part is supported by a chimney lattice plate; and chimney spacers that support the horizontal load each other are arranged between the flow channel separation walls of the adjacent flow channels, and ring-like members that support the horizontal load are arranged at the outermost periphery of the plural flow channels that are supported by the chimney lattice plate.