Patent Number: 048896845
Section: claims

1. In a fuel bundle for confining fuel rods for the generation of steam in a steam water mixture passing interior of the fuel bundle and wherein said fuel bundle includes; a lower tie-plate for supporting said fuel rods and permitting flow from the lower exterior portion of said fuel bundle into the interior portion of said fuel bundle; a plurality of fuel rods, said fuel rods supported on said lower tie-plate extending upwardly to and towards the upper portion of said fuel bundle for the generation of steam in a passing steam and water mixture interior of said fuel bundle;  an upper tie-plate for maintaining said fuel rods in side-by-side relation and permitting a threaded connection between a plurality of said fuel rods with said threaded connection being at said upper and lower tie-plate, said upper tie-plate permitting escape of a steam water mixture from the top of said fuel bundle;  a fuel bundle channel extending from a position surrounding said upper tie-plate to a position surrounding said lower tie-plate, the improvement to said lower tie-plate comprising;  a labyrinth seal configured in said lower tie-plate, said labyrinth seal configured in the interstitial volume between the upper portion of said lower tie-plate adjacent the interior of said channel and said channel at the point of overlap to said lower tie-plate for providing rapid pressure decline, whereby the lower portion of said channel is not loaded by pressure and reinforces the overlying stressed portion of said channel.  a plurality of fuel rods supported on said lower tie-plate and extending upwardly in side-by-side relation;  an upper tie-plate for maintaining said fuel rods in side-by-side relation and permitting threaded connection between a plurality of said fuel rods and said upper and lower tie-plates, and for permitting the escape of a steam water mixture from the top of said fuel bundle;  a fuel bundle channel extending from a position surrounding said upper tie-plate to the position surrounding said lower tie-plate for confining steam and water flow between said tie-plates around said fuel bundles, the improvement to said lower tie-plate at the channel comprising:  a flow aperture followed by a diffuser; said flow aperture being disposed towards the top of said lower tie-plate and said diffuser being disposed away from said aperture to and towards the core bypass region at the lower portion of said tie-plate to produce a pressure decline;  whereby the pressure at said aperture and diffuser is below the pressure of said core bypass region whereby the lower portion of said channel reinforces the upper pressure loaded portion of said channel against channel deflection.  a lower tie-plate for supporting said fuel rods and permitting flow from the lower exterior portion of said fuel bundle into the interior portion of said fuel bundle;  a plurality of side-by-side fuel rods supported on said lower tie-plate and extending upwardly of said fuel bundle;  an upper tie-plate for maintaining said fuel rods in side-by-side relation and permitting threaded connection through said rods between a plurality of fuel rods to join said upper and lower tie-plate, said upper tie-plate forming an aperture for permitting the escape of steam and water mixture from the top of said fuel bundle;  a fuel bundle channel extending from a position surrounding said upper tie-plate to a position surrounding said lower tie-plate, the improvement at said lower tie-plate comprising in combination a flow aperture and diffuser configured at a corner section of said fuel bundle between said core bypass region and the interior of said fuel bundle; said diffuser aligned to diffuse water flow from said core bypass region to and towards the interior of said fuel bundle whereby reflood of said fuel bundle through said aperture and diffuser is expedited. 2. The invention of claim 1 and wherein said labyrinth seal is configured in said lower tie-plate. 3. The invention of claim 2 and wherein said labyrinth seal is configured in said lower tie-plate and said channel. 4. In a fuel bundle for containing fuel rods for the generation of steam in a steam water mixture wherein said fuel bundle includes; a lower tie-plate for supporting said fuel rods and permitting flow from the lower exterior portion of said fuel bundle into the interior portion of said fuel bundle; 5. The invention of claim 4 and wherein said aperture and diffuser is configured in said lower tie-plate. 6. The invention of claim 4 and wherein said aperture and diffuser are configured in the lower portion of said channel. 7. In a fuel bundle for confining fuel rods for the generation of steam in a steam water mixture wherein said fuel bundle includes; 8. The invention of claim 7 and wherein said flow aperture is configured in said lower tie-plate.