BWR type reactor

In the BWR type reactor of the present invention, a water stream from an internal pump is rectified to decrease the stress in the joined portion between a control rod housing and a stab tube. That is, a rectification plate is disposed along the bottom plate of a reactor pressure vessel. The circumferential edge of the rectification plate is aligned with the upper edge of a reactor water flowing port in the lower portion of the shroud, and the radius of curvature of the plate is made substantially identical with that of the bottom plate of the reactor pressure vessel and the stab tubes are passed through and secured to the plate. Further, openings are distributed between the portions of the plate where stab tubes are passed through. With such a constitution, the reactor water discharged from the internal pump flows into the shroud passing through the openings of the rectification plate. Accordingly, the stream of the reactor waster is made substantially parallel with the control rod housing and the stab tubes. Accordingly the amount of the force of the fluid applied to them by the discharged reactor water is extremely reduced and the stress caused by the force of the fluid is also minimized. (I.S.)