Patent ID: 7860206

Claim:
A natural circulation boiling water reactor, comprising: a reactor pressure vessel having a core and a chimney provided above the core, the core and the chimney being disposed in the reactor pressure vessel; at least one movable control rod being arranged for movement with respect to the core; a feed water pipe connected to the reactor pressure vessel which supplies feed water to the reactor pressure vessel for natural circulation flow therethrough; a power control apparatus which outputs (a) a control rod operation signal until the rector power reaches a first set reactor power obtained by withdrawal of the at least one control rod from the core, and (b) a reactor water level set signal until the reactor power increases from the first set reactor power to a second set reactor power; a control rod driver which increases reactor power of the reactor by withdrawing the at least one control rod from the core until the reactor power reaches the first set reactor power, based on the control rod operation signal outputted from the power control apparatus; and a feed water controller which increases the reactor power of the reactor by increasing a feed water flow rate through the feed water pipe to the reactor pressure vessel based on the reactor water level set signal outputted from the power control apparatus.