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Ab Asea-atom

Bertil Scholin

Olov Nylund

Mahdi Majed

Patricia Quaglia

Pierre Lorek

A reactor core for a boiling water nuclear reactor comprises a plurality of vertical fuel assemblies (40a, 42, 44), each one containing a plurality of fuel rods (10), which are arranged between a bottom-tie plate (11) and a top-tie plate (12) in a surrounding vertical casing (6) and which extend through a number of spacers (13, 13a-f) which are arranged in spaced relationship in the vertical direction and which together with the bottom-tie plate and the top-tie plate retain the fuel rods in spaced relationship in the lateral direction. Each fuel assembly is designed with an inlet (3) for water for conducting water in through the bottom-tie plate, through the space between the fuel rods in the vertical casing, and out through the top-tie plate. Some of the fuel assemblies, at a level located above the center of the active length of the fuel rods and below at least two of the uppermost spacers (13a, 13b), are provided with outlet holes (41, 43, 44) for release of water from the space between the fuel rods to vertically directed spaces (32, 37a, 37b), arranged outside the fuel assembly and traversed by water, or to a vertically directed channel (45), arranged internally in the fuel assembly and traversed by water.

Reactor core for a boiling water nuclear reactor

A fuel assembly for a boiling water nuclear reactor contains a plurality of vertical fuel rods, which are arranged between a bottom-tie plate and a top-tie plate (12) in a surrounding vertical casing part. The fuel rods extend through a number of spacers which are arranged in a spaced relationship in the vertical direction and which together with the bottom-tie plate and the top-tie plate retain the fuel rods in a spaced relationship in the lateral direction. The fuel assembly is designed for conducting water in through the bottom-tie plate, through the space between the fuel rods in the vertical casing part, and out through the top-tie plate. To counteract unfavourable temperatures caused by dryout, each fuel rod, in at least a majority of the fuel rods, is adapted to give off a considerably lower power in those parts of the fuel rod which are located immediately below the spacers in at least the uppermost one-third of the active length of the fuel rod than in the remaining parts of the active length of the fuel rod.

Fuel assembly for a boiling water nuclear reactor

A method and a device for controlling the coolant flow to the fuel rods (1) in the fuel assembly of a pressurized-water reactor, fuel assembly including an elongated bundle of control rod guide tubes and fuel rods (1) which is arranged between a top nozzle and a bottom nozzle. The bundle is retained by spacers (2) supported by the control rod guide tubes and the top and bottom nozzles are provided with a plurality of openings for the coolant flow. According to the invention, the coolant flow along the fuel rods (1) of a fuel assembly which is under low load is reduced by the insertion of special, or the activation of existing, throttle or guide members (10,11,12,13,16) on the spacers (2) or on the fuel rods (1) between the spacers (2) such that the coolant flow is diverted to one or more adjacent fuel assemblies.

Method and a device for control of the coolant flow in the fuel assembly

A fuel assembly for a boiling water reactor is provided with at least one vertical channel for a by-pass flow through the fuel assembly. The channel is supplied with water through a vertical supply tube surrounded by the base of the assembly, the supply tube being arranged with its lower end in the vicinity of the lower end of the base.

Fuel assembly with a water flow separated from the fuel rodsr

A fuel assembly for a boiling water reactor is provided with at least one vertical water channel (4, 5) for a by-pass flow through the fuel assembly. At its lower end the channel is connected to a radial tube (10) which opens out at the outer side surface of the fuel assembly. Below the radial tube, the wall of the assembly base (2) is provided with a through-hole (12).

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Vaster.ang.s, Sweden

Bertil Scholin