BOILING WATER TYPE NUCLEAR REACTOR

PURPOSE:To accurately measure flow in a reactor core due to an internal pump by effectively utilizing a useless space in a nuclear reactor pressure vessel. CONSTITUTION:A pump shroud pipe 41 is standingly provided along the inner wall of a nuclear reactor pressure vessel 5 arranging a reactor core 1a therein, and an impeller 38 is arranged in the pump shroud pipe 41. The impeller 38 is fitted to the rotary shaft of an internal pump. A shroud deck opening part 41a communicated to the upper end of the pump shroud pipe 41 is provided on the shroud desk 54 of a shroud head 30a to cover the upper part of the reactor core 1a.