Reactor core for a boiling water nuclear reactor

A reactor core for a boiling water nuclear reactor with a plurality of vertical fuel assemblies (40), each fuel assembly containing

• a bottom-tie plate (11),
• a top-tie plate (12),
• a plurality of fuel rods (10) arranged between the bottom-tie plate and the top-tie plate,
• a vertical casing (6) surrounding the fuel rods,
• a number of spacers (13, 13a-f) for retaining the fuel rods in a spaced relationship,
• an inlet (3) for conducting water in through the bottom-tie plate through the space between the fuel rods and out through the top-tie plate,
• a hollow support member (7) of cruciform cross section forming
• a cruciform space (32), for conducting water in a vertical direction from below and upwards through the fuel assembly, and gaps (37a,37b) between the fuel assemblies, said gaps being traversed with water in a vertical direction from below and upwards through the core,
• wherein in some of the fuel assemblies outlet holes (43,41) are arranged in the casing (6) and in the support member (7) for release of water from the space between the fuel rods to the gaps between the fuel assemblies and to the cruciform space (32), and said outlet holes (43,41) are arranged at a level located above the centre of the active length of the fuel rods so that a greater flowrate in the space between the fuel rods in achieved below the level of the holes and a lower flowrate is achieved in the space between the fuel rods above the level of the holes.

A reactor core for a boiling water nuclear reactor with a plurality of vertical fuel assemblies (40), each fuel assembly containing

• a bottom-tie plate (11),
• a top-tie plate (12),
• a plurality of fuel rods (10) arranged between the bottom-tie plate and the top-tie plate,
• a vertical casing (6) surrounding the fuel rods,
• a number of spacers (13, 13a-f) for retaining the fuel rods in a spaced relationship,
• an inlet (3) for conducting water in through the bottom-tie plate through the space between the fuel rods and out through the top-tie plate,
• a hollow support member (7) of cruciform cross section forming
• a cruciform space (32), for conducting water in a vertical direction from below and upwards through the fuel assembly, and gaps (37a,37b) between the fuel assemblies, said gaps being traversed with water in a vertical direction from below and upwards through the core,
• wherein in some of the fuel assemblies outlet holes (41) are arranged in the hollow support member (7) for release of water from the space between the fuel rods to the cruciform space (32), and said outlet holes (41) are arranged at a level located above the centre of the active length of the fuel rods so that a greater flowrate in the space between the fuel rods is achieved below the level of the holes and a lower flowrate is achieved in the space between the final fuel rods above the level of the holes.

A reactor core for a boiling water nuclear reactor with a plurality of vertical fuel assemblies (44), each fuel assembly containing

• a bottom-tie plate (11),
• a top-tie plate (12),
• a plurality of fuel rods (10) arranged between the bottom-tie plate and the top-tie plate,
• a vertical casing (6) surrounding the fuel rods,
• a number of spacers (13, 13a-f) for retaining the fuel rods in a spaced relationship,
• an inlet (3) for conducting water in through the bottom-tie plate through the space between the fuel rods and out through the top-tie plate,
• a channel (45) arranged internally in the fuel assembly for conducting water in a vertical direction from below and upwards through the fuel assembly,
• a wall (46) surrounding the channel, and gaps (37a,37b) between the fuel assemblies, said gaps being traversed with water in a vertical direction from below and upwards through the core,
• wherein in some of the fuel assemblies outlet holes (43,47) are arranged in the casing (6) and in the wall (46) for release of water from the space between the fuel rods to the gaps between the fuel assemblies and to the channel, and said outlet holes (43,47) are arranged at a level located above the centre of the active length of the fuel rods so that a greater flowrate in the space between the fuel rods is achieved below the level of the holes and a lower flowrate is achieved in the space between the fuel rods above the level of the holes.