Lower tie plate with stepped holes to control pressure drop and

Details Lower tie plate with stepped holes to control pressure drop and Lower tie plate with stepped holes to control pressure drop and

1989-03-13

1991-03-05

Walsh, Donald P.

Induced nuclear reactions: processes, systems, and elements

Fuel component structure

Plural fuel segments or elements

376443, 376445, G21C 332

Patent

active

049976214

ABSTRACT:
An improved lower tie plate having increased fluid flow resistance is disclosed for use in a boiling water nuclear reactor. The fuel bundle includes the lower tie plate, an upper tie plate, and a plurality of fuel rods supported therebetween in vertical upstanding relation, with the fuel rods surrounded by a square sectioned channel. In the preferred embodiment, some of the upper fuel rods are of partial length. The surrounding channel confines the fluid flow through the fuel bundles between the tie plates for the extraction of heat from the fuel rods undergoing a fission reaction. The lower tie plate includes a first group of apertures for the support of the fuel rods to selected positions in the 9x9 matrix; appropriate numbers of these apertures are threaded for tying the upper and lower tie plates together with tie rods. The matrix is interrupted at larger apertures for the support of moderator containing water rods. The tie plate also includes a second matrix of through holes acting as fluid energy dissipation orifices. These fluid energy dissipation orifices include a first small downwardly exposed fluid receiving aperture which discharges to a second and larger upwardly exposed flow area preferably formed in the shape of a concentric aperture. In the preferred embodiment the inlet to the first concentric and small downwardly exposed fluid receiving aperture is rounded for the intake of fluid with maximum flow predictability. The outlet from the first concentric and small downwardly exposed fluid receiving aperture is abrupt to produce maximum predictable energy dissipating turbulence in the upwardly exposed fluid discharge area. Passage of fluid through the energy dissipation apertures causes an increased pressure drop at the lower tie plate, for the suppression of thermal-hydraulic flow instabilities, and coupled thermal-hydraulic nuclear instabilities. A serendipitous effect is present in that the increased pressure drop causes uniform fluid flow in the interior of the fuel bundle immediate the lower tie plate.

REFERENCES:
patent: 4775510 (1988-10-01), Bryan
patent: 4828791 (1989-05-01), DeMario
patent: 4889684 (1989-12-01), Johansson

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