Patent Number: 054835640
Section: claims

1. In a boiling water reactor fuel bundle, a debris catching grid construction for placement within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid comprising: first and second overlying and underlying three dimensional, non-planar perforated plate constructions having side-by-side holes, arranged so that a substantial portion of coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid;  each said perforated plate forming a three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid;  said underlying plate having larger holes than said overlying plate;  means for mounting each said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate such that debris passing through the larger holes of the underlying plate will be trapped between the first overlying plate and the second underlying plate.  said sidewalls of said overlying and underlying three dimensional grid construction are corrugated.  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 a 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;  first and second overlying and underlying three dimensional, non-planar perforated plate constructions having side-by-side holes, arranged so that a substantial portion of coolant flowing through said flow volume is caused to change direction between the inlet nozzle and the upper fuel rod supporting grid;  each said perforated plate forming a three dimensional construction having a total cross sectional area exceeding the planar cross sectional area of the flow volume of said lower tie plate between said inlet nozzle and said rod supporting grid,  said underlying plate having larger holes than said overlying plate;  means mounting each said three dimensional perforated plate construction interiorly of the flow volume of said lower tie plate, such that debris passing through the larger holes of the underlying plate will be trapped between the first overlying plate and the second underlying plate.  said sidewalls of said overlying and underlying three dimensional grid construction are corrugated. 2. In a boiling water reactor fuel bundle, a debris catching grid construction according to claim 1 and wherein 3. In a boiling water reactor fuel bundle, comprising in combination: 4. In a boiling water reactor fuel bundle according to claim 3 and wherein: