Patent Number: 046541942
Section: claims

1. A nozzle assembly for directing coolant into the duct tube of a fuel assembly attached thereto compising: an elongated shell having inlet openings adjacent one end thereof for admitting coolant thereinto, an orifice plate assembly in said shell downstream of said inlet openings, neutron shielding means in said shell downstream of said orifice plate assembly, diffusing means in said shell downstream of said neutron shielding means for dispersing said coolant uniformly through said duct tube, said orifice plate assembly comprising a plurality of separable stacked orifice plates having differently configurated and sized openings, respectively, for directing said coolant therethrough in a predetermined flow pattern, and wherein one of said orifice plates includes means for imparting a spiral flow to said coolant, and said shielding means includes a shield block having a central passage for conveying said coolant in a spiral path therethrough, said central passage having at one end thereof a converging inlet adjacent said one orifice plate, and further wherein said shield block is formed with an annular well surrounding said central passage, and a partition defining in part said central passage and separating said well from said passage. 2. A nozzle assembly according to claim 1, wherein said openings in each of said plates are offset from the openings in adjacent plates. 3. A nozzle assembly according to claim 1 said partition formed with slots establishing communication between said passage and said well for passing particulates entrained in said spiraling coolant flow therethrough for entrapment in said well. 4. A nozzle assembly according to claim 1 including an insert removably mounted in said shield block against the distal end of said partition, said insert having a bore communicating with said central passage. 5. A nozzle assembly according to claim 1 wherein said means for imparting a spiral flow to said coolant comprises a plurality of circumferentially spaced curved vanes. 6. A nozzle assembly according to claim 1, wherein said shell comprises a major portion and a lower portion detachably connected to said major portion and sealing means interposed between said major portion and said lower portion 7. A nozzle assembly according to claim 6, including means for threading said lower portion on said major portion, and means for locking said lower portion to said major portion in the assembled relation thereof. 8. A nozzle assembly according to claim 1, wherein said neutron shielding means comprises a shield block and a shield plug disposed in an abutting stacked relation and having passages therethrough for conveying said coolant from said orifice plate assembly to said diffusing means. 9. A nozzle assembly according to claim 8, wherein said diffusing means comprises an individual block having a central bore and a plurality of bores in radial spaced relation to said central bore for conveying coolant from said neutron shielding means into said duct tube for uniform distribution therethrough. 10. A nozzle assembly according to claim 9 wherein said last mentioned block is threaded within said shell in abutting engagement against said shield plug to secure said shield plug, said shield block and said orifice assembly in place in a stacked relation.