Patent Number: 
Section: claims

1. A filter for separating particles in a coolant fluid in a nuclear reactor, the filter comprising:channels for circulation of the coolant fluid through the filter, at least one of the channels extending along a channel centerline, the at least one channel having an inlet upstream section, an outlet downstream section and an intermediate section, the intermediate section extending between the inlet upstream section and the outlet downstream section and being enlarged relative to the inlet upstream section and the outlet downstream section, the inlet upstream section, the intermediate section and the outlet downstream section being arranged along the channel centerline; andat least one separating member defining inside the intermediate section of the at least one channel an annular passage, the annular passage being arranged substantially concentric to the channel centerline in the intermediate section. 2. The filter according to claim 1 further comprising centering elements for maintaining the at least one separating member spaced from an inner surface of the corresponding intermediate section. 3. The filter according to claim 1 wherein the at least one separating member is spherical. 4. The filter according to claim 1 wherein the at least one separating member has an elliptical cross section. 5. The filter according to claim 1 wherein the at least one separating member has a double cone shape. 6. The filter according to claim 1 wherein a first and a second separating member are disposed inside a same intermediate section to define an inner and an outer coaxial annular passage, the inner and outer coaxial annular passage having an axis substantially coaxial to the channel centerline in the same intermediate section, the first separating member being tubular and defining the outer coaxial annular passage with the inner surface of the intermediate section, the second separating member being disposed inside the first separating member and defining therein an inner annular passage. 7. The filter according to claim 1 wherein the at least one separating member has at least one fluid flow hole passing through the separating member. 8. The filter according to claim 1 wherein the channels include at least a first set of channels and a second set of channels, the intermediate sections of the first set of channels being offset relative to the intermediate sections of the second set of channels along a filter main flow direction of the coolant fluid through the filter. 9. The filter according to claim 8 wherein the channels are arranged in a pattern such that each channel of the first set of channels is surrounded by channels of the second set of channels. 10. The filter according to claim 1 wherein the channels are defined by a one-piece filtering plate having a plurality of ducts extending therethrough and a plurality of tubular inserts, each duct having a narrow duct section and an enlarged duct section, each enlarged duct section having a respective one of the tubular inserts inserted therein, each of the channels being defined by one of the ducts and the respective tubular insert inserted inside the enlarged duct section of the duct. 11. The filter according to claim 10 wherein the filtering plate comprises at least two stacked parts, each of the channels extending through the stacked parts and each separating member being disposed between two of the stacked parts. 12. The filter according to claim 11 wherein the filtering plate comprises a lower part, an upper part and an intermediate part interposed between the upper part and the lower part, each separating member being disposed between the intermediate part and one of the upper and lower parts. 13. A nuclear fuel assembly lower nozzle defining a filter as recited in claim 1. 14. The nuclear fuel assembly comprising a bundle of fuel rods and an armature for supporting the fuel rods, the armature comprising a lower nozzle and an upper nozzle, the fuel rods extending between the nozzles, wherein the lower nozzle defines a filter as recited in claim 13. 15. A filter for separating particles in a coolant fluid in a nuclear reactor, the filter comprising:channels for circulation of the coolant fluid through the filter, at least one of the channels extending along a channel centerline, the at least one channel having an upstream section, a downstream section and an intermediate section, the intermediate section extending between the upstream section and the downstream section and being enlarged relative to the upstream section and the downstream section; andat least one separating member defining inside the intermediate section of the at least one channel an annular passage, the annular passage having an axis substantially coaxial to the channel centerline in the intermediate section,wherein a first and a second separating member are disposed inside a same intermediate section to define an inner and an outer coaxial annular passage, the inner and outer coaxial annular passage having an axis substantially coaxial to the channel centerline in the same intermediate section, the first separating member being tubular and defining the outer coaxial annular passage with the inner surface of the intermediate section, the second separating member being disposed inside the first separating member and defining therein an inner annular passage. 16. A nuclear fuel assembly lower nozzle defining a filter as recited in claim 15. 17. The nuclear fuel assembly comprising a bundle of fuel rods and an armature for supporting the fuel rods, the armature comprising a lower nozzle and an upper nozzle, the fuel rods extending between the nozzles, wherein the lower nozzle defines a filter as recited in claim 16. 18. A filter for separating particles in a coolant fluid in a nuclear reactor, the filter comprising:channels for circulation of the coolant fluid through the filter, at least one of the channels extending along a channel centerline, the at least one channel having an inlet upstream section, an outlet downstream section and an intermediate section, the intermediate section extending between the inlet upstream section and the outlet downstream section and being enlarged relative to the inlet upstream section and the outlet downstream section, the inlet upstream section, the intermediate section and the outlet downstream section being arranged along the channel centerline; andat least one separating member defining inside the intermediate section of the at least one channel an annular passage, the annular passage having an axis substantially coaxial to the channel centerline in the intermediate section,wherein the channels are defined by a one-piece filtering plate having a plurality of ducts extending therethrough and a plurality of tubular inserts, each duct having a narrow duct section and an enlarged duct section, each enlarged duct section having a respective one of the tubular inserts inserted therein, each of the channels being defined by one of the ducts and the respective tubular insert inserted inside the enlarged duct section of the duct. 19. The filter according to claim 18 wherein the filtering plate comprises at least two stacked parts, each of the channels extending through the stacked parts and each separating member being disposed between two of the stacked parts. 20. The filter according to claim 19 wherein the filtering plate comprises a lower part, an upper part and an intermediate part interposed between the upper part and the lower part, each separating member being disposed between the intermediate part and one of the upper and lower parts.