Abstract: The pressurized water reactor according an embodiment comprises: a cylindrical reactor pressure vessel (1) to which inlet nozzles are connected; fuel assemblies which are contained within the reactor pressure vessel (1); a cylindrical reactor core barrel (3) which surrounds the fuel assemblies and forms an annular downcomer (6) between the reactor core barrel (3) and the inner surface of the reactor pressure vessel (1); and radial supports. The radial supports are supports which are arranged below the downcomer (6) at intervals in the circumferential direction, each has vertical flow path formed therein, and position the reactor core barrel (3) and the reactor pressure vessel (1). The radial supports each has, for example, a flow path-equipped radial keys (21) and a key groove member (40).

Abstract: A pressurized water reactor comprises a reactor pressure vessel (11), a cylindrical core barrel (13), a core disposed in the core barrel (13), a lower core support plate (17), and a cylindrical porous plate (31). The core barrel (13) is provided in the reactor pressure vessel (11) and forms, with the inner side surface of the reactor pressure vessel (11), an annular downcomer (14) therebetween. The lower core support plate (17) is provided under the core so as to extend horizontally, and a large number of upward flow holes (80) are formed therein. The cylindrical porous plate (31) demarcates a lower plenum (16) and a bottom part of the downcomer (14), and a plurality of inward flow holes (83) that serve as flow paths from the bottom part of the downcomer (14) to the lower plenum (16) are formed therein. The inward flow holes (83) are inclined upward to the lower plenum (16) on the side on which the inward flow holes are open to the lower plenum (16).

Abstract: The pressurized water reactor according an embodiment comprises: a cylindrical reactor pressure vessel (1) to which inlet nozzles are connected; fuel assemblies which are contained within the reactor pressure vessel (1); a cylindrical reactor core barrel (3) which surrounds the fuel assemblies and forms an annular downcomer (6) between the reactor core barrel (3) and the inner surface of the reactor pressure vessel (1); and radial supports. The radial supports are supports which are arranged below the downcomer (6) at intervals in the circumferential direction, each has vertical flow path formed therein, and position the reactor core barrel (3) and the reactor pressure vessel (1). The radial supports each has, for example, a flow path-equipped radial keys (21) and a key groove member (40).

Abstract: A core inlet structure for coolant disposed in a reactor pressure vessel of a boiling water reactor includes a core support plate provided with a plurality of fuel support holes, a reinforcing beam supporting the core support plate, a plurality of control rod guide pipes standing perpendicularly and having upper end portions fitted to the fuel support holes, and a fuel support member inserted into upper end portions of the control rod guide pipes and supported by the core support plate so as to support lower end portions of fuel assemblies. An inlet orifice is formed to the fuel support member so as to adjust flow rate of a coolant flowing in the fuel assemblies, and a vortex control structure is provided for the inlet orifice or provided at a portion on a coolant upstream side of the inlet orifice.

Abstract: A steam isolation valve system for opening and closing a steam flow passage of a steam flow comprises a valve body, a valve disk accommodated in the valve body to be reciprocatingly movable for opening and closing the steam flow passage, and a drive mechanism for moving the valve disk along an axial direction of the valve body. The steam flow passage has a portion elliptical in section having a short axis in a direction of the reciprocating axis of the valve disk projected on a plane perpendicular to an axis of the steam flow passage. The steam flow passage has a throttling inlet passage which is deformed in shape from a circular tube portion having a diameter D on a steam upstream side to an elliptical tube portion having a long side diameter D and a short side diameter D cos.theta. (45.degree..ltoreq..theta..ltoreq.65.degree.

Abstract: A main steam isolation valve of a reactor power plant comprises a valve body provided with inlet and outlet portions through which a steam flows, a cylindrical valve disk accommodated in the valve body to be reciprocatingly movable therein along an inner peripheral surface of the valve body for opening and closing the steam flow inlet portion and a driving mechanism secured to the valve body and operatively connected to the valve disk for reciprocatingly moving the valve disk in the valve body. A coupling member is applied to an end opening of the valve body for holding the valve disk when the valve disk is shifted to a position fully opening the inlet portion. A tubular wall member is integrally formed with the valve body so as to surround the valve disk with a gap therebetween when the valve disk is fully opened. A guide rib is further disposed to the valve body for causing asymmetric steam flow in the inlet portion of the steam flow of the valve body.