PURPOSE: An apparatus for injecting a core support tube in a nuclear reactor is provided to increase the amount of safety injection water by directly supplying the safety injection water between a core shroud and the core support tube. CONSTITUTION: Safety injection water is injected from the outside. A safety injection water pipe(30) injects the safety injection water between a core support tube(20) and a core shroud(40). A front pipe part(31) passes through a reactor container(10). A rear pipe part(32) passes through the core support tube.
