Patent Number: 053902203
Section: claims

1. In a boiling water reactor fuel bundle which includes a lower tie plate assembly having a fuel rod supporting tie plate grid and an inlet nozzle with an open flow volume defined therebetween, a debris catching grid construction for placement within the open flow volume comprising: at least a first layer of helical springs, said helical springs being placed in side-by-side parallel relation;  at least a second layer of helical springs, said helical springs being placed in side-by-side parallel relation at an angle with respect to said first layer of helical springs so as to intersect at a first plurality of crossing points, said first and second layers of helical springs forming a filter mass within said open flow volume.  wherein means are provided for fastening said first and second layers together at said first plurality of crossing points.  at least a third layer of helical springs, said springs being placed in side-by-side parallel relation at an angle with respect to said second layer of helical springs and arranged to intersect said second layer at a second plurality of crossing points;  at least a fourth layer of helical springs, said springs being placed in side-by-side parallel relation at an angle with respect to said third layer of helical springs so as to intersect said third layer at a third plurality of crossing points.  whereas means are provided for fastening said respective helical springs of said layers one to another at said first, second and third pluralities of crossing points whereby said first, second, third and fourth layers become a unitary filter mass.  a lower tie plate assembly including a fuel rod supporting grid, an inlet nozzle, and sidewall extending between said nozzle to the edges of said grid to define therebetween an open flow volume interior of said tie plate;  a plurality of upstanding fuel rods, said fuel rods supported on said rod supporting grid and extending in upstanding vertical side-by-side relation;  an upper tie plate for supporting at least some of fuel rods and providing connection to said lower tie plate through at least some of said fuel rods;  at least a first layer of helical springs, said springs being placed in side-by-side parallel relation;  at least a second layer of helical springs, said springs being placed in side-by-side parallel relation at an angle with respect to said first layer of helical springs so as to intersect at a first plurality of crossing points, said first and second layers of helical springs forming a filter mass within said open flow volume; and  means mounting said layers of helical springs in said open flow volume of said lower tie plate.  wherein means are provided for fastening said first and second layers together at said first plurality of crossing points.  at least a third layer of helical springs, said springs being placed in side-by-side parallel relation at an angle with respect to said second layer of helical springs and arranged to intersect said second layer at a second plurality of crossing points;  at least a fourth layer of helical springs, said springs being placed in side-by-side parallel relation at an angle with respect to said third layer of helical springs so as to intersect said third layer at a third plurality of crossing points.  whereas means are provided for fastening said respective helical springs of said layers one to another at said first, second and third plurality of crossing points whereby said first, second, third and fourth layers become a unitary filter mass. 2. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 3. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and further including: 4. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 3 5. In a boiling water reactor fuel bundle, comprising in combination: 6. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 5 7. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 5 and further including: 8. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 5