Patent Number: 054815789
Section: claims

1. A lower tie plate assembly for a nuclear reactor comprising: an upper grid portion and a lower body portion, the upper grid portion having a plurality of fuel rod supporting bosses interconnected by a plurality of webs thus forming flow openings between the bosses; the body portion including an inlet nozzle and a peripheral wall extending between the bottom nozzle and the upper grid portion to define a flow volume therein; and  a debris catcher including a plurality of perforated tubes having open lower ends, one of said perforated tubes in engagement with a lowermost end of each of said plurality of fuel rod supporting bosses.  an upper grid portion and a lower body portion, the upper grid portion having a plurality of fuel rod supporting bosses interconnected by a plurality of webs thus forming flow openings between the bosses; the body portion including an inlet nozzle and a peripheral wall extending between the bottom nozzle and the upper grid portion to define a flow volume therein; and  a debris catcher including a plurality of perforated tubes having open lower ends, one of said perforated tubes in abutment with a lowermost end of each of said plurality of fuel rod supporting bosses. 2. The lower tie plate assembly of claim 1 wherein a plate is secured to lower ends of said perforated tubes, said plate having an array of openings therein aligned with the open lower ends of respective tubes, such that substantially all coolant flow is caused to flow through said perforated tubes. 3. The lower tie plate assembly of claim 1 wherein each tube has an axial length of between about 0.5 to about 1.0 inch. 4. The lower tie plate assembly of claim 1 wherein each tube includes a peripheral side wall having a plurality of openings therein substantially uniformly distributed about said peripheral side wall. 5. The lower tie plate assembly of claim 4 wherein upper ends of said tubes are capped. 6. The lower tie plate assembly of claim 2 wherein said plate is secured to an inside surface of said peripheral wall. 7. The lower tie plate assembly of claim 1 wherein each of said plurality of tubes is fixed to a respective boss. 8. A fuel bundle and lower tie plate assembly for a nuclear reactor comprising a plurality of fuel rods supported between an upper tie plate and a lower tie plate assembly, the lower tie plate assembly comprising 9. The fuel bundle and lower tie plate assembly of claim 8 wherein a plate is secured to lower ends of said perforated tubes, said plate having an array of openings therein aligned with the open lower ends of respective tubes, such that substantially all coolant flow is caused to flow through said perforated tubes. 10. The fuel bundle and lower tie plate assembly of claim 9 wherein each tube has an axial length of between about 0.5 to about 1.0 inch. 11. The fuel bundle and lower tie plate assembly of claim 9 wherein each tube includes a peripheral side wall having a plurality of openings therein substantially uniformly distributed about said peripheral side wall. 12. The fuel bundle and lower tie plate assembly of claim 8 wherein each of said plurality of tubes is fixed to a respective boss. 13. The fuel bundle and lower tie plate assembly of claim 9 wherein said plate is secured substantially continuously about an inside surface of said peripheral wall.