Patent Number: 
Section: claims

1. A debris filter for use in a nuclear fuel assembly comprising a bundle of fuel rods to be supplied with a coolant fluid flow, the filter comprising:a plurality of walls defining a plurality of flow ducts extending in a longitudinal direction, each duct being delimited between a pair of the walls; anddeflectors protruding into each duct alternately from the corresponding pair of walls and overlapping in the longitudinal direction to define a zigzag shaped flow channel in each duct, the overlapping deflectors in each duct being provided with a set of holes aligned in the longitudinal direction to define through the overlapping deflectors a passage for accommodating a lower end pin of one of the fuel rods. 2. The debris filter according to claim 1, further comprising each duct in register in the longitudinal direction with each passage, one cell for accommodating a bottom end cap of a fuel rod. 3. The debris filter according to claim 2, wherein each cell comprises at least one spring for at least one of transversely and longitudinally supporting the bottom end cap accommodated in the cell. 4. The debris filter according to claim 1, wherein the walls are each made up of at least one metallic sheet provided with at least one deflector fold for forming one deflector. 5. The debris filter according to claim 4, further comprising intermediate walls separating two adjacent ducts and each intermediate wall being made up of two metallic sheets provided with deflector folds protruding on opposite faces of the intermediate wall. 6. The debris filter according to claim 5, wherein each intermediate wall is provided with one deflector fold protruding from one of the opposed faces of the intermediate wall at a level intermediate to two deflector folds protruding from the other one of the opposed faces of the intermediate wall. 7. The debris filter according to claim 1, wherein the deflectors are plates secured to the walls at an angle. 8. The debris filter according to claim 7, comprising intermediate walls separating two adjacent ducts each provided with at least one deflector plate interlocked with the intermediate wall to form two deflectors each protruding on a respective face of the wall. 9. The debris filter according to claim 8, comprising at least one pair of adjacent intermediate walls provided with deflector plates intersecting the corresponding intermediate walls at the same level. 10. The debris filter according to claim 1, further comprising connection strips interlocked perpendicularly with the walls. 11. Nuclear fuel assembly comprising a bundle of fuel rods extending in a longitudinal direction and each fuel rod comprising a pin at a lower end and a debris filter according to claim 1, the pin of each fuel rod being accommodated in one passage. 12. The nuclear fuel assembly according to claim 11, further comprising a grid-shaped support plate disposed below the debris filter, the support plate comprising bars defining between them openings, the bars being arranged for supporting the fuel rods extending through the passages and the openings being arranged to allow coolant flow though the support plate into channels of the filter.