Patent Number: 058928065
Section: claims

1. A spacer for maintaining an inner tube in spaced relation within an outer tube in a nuclear reactor, said spacer comprising: a split ring adapted to be disposed about the outer surface of said inner tube, said ring having a central annular body portion with a raised annular bearing surface thereon adapted to contact the inner surface of said outer tube and prevent contact between said outer surface and said inner surface, an annular land projecting from each side of said central body portion, and a transverse split across said central annular body portion and said lands ;and  a collar adapted to be received on one of said lands and effective to create an interference fit between said ring and said inner tube and thereby constrain axial movement of said spacer on said inner tube.  a split ring adapted to be disposed about the outer surface of said pressure tube, said ring having a central annular body portion with a raised annular bearing surface thereon adapted to contact the inner surface of said calandria tube and prevent contact between said outer surface and said inner surface, an annular land projecting from each side of said central body portion, and a transverse split across said central annular body portion and said lands; and  a collar adapted to be received on one of said lands and effective to create an interference fit between said ring and said pressure tube and thereby constrain axial movement of said spacer on said pressure tube. 2. The spacer of claim 1 wherein each said land has a groove or ridge to retain said collar thereon. 3. The spacer of claim 1 wherein said split ring has a concavity formed in the central annular body portion, said concavity forming an annular void space between said raised bearing surface and said inner tube. 4. The spacer of claim 1 wherein said bearing surface has a coating to reduce heat transfer between said ring and said outer tube. 5. The spacer of claim 1 wherein said bearing surface has a coating to reduce wear between said ring and said outer tube. 6. A spacer for maintaining a pressure tube in spaced relation with a calandria tube of a nuclear reactor, said spacer comprising: 7. The spacer of claim 6 wherein each of said lands has a groove or ridge to retain said collar thereon. 8. The spacer of claim 6 wherein said split ring has a concavity formed in the central annular body portion, said concavity forming an annular void space between said raised bearing surface and said pressure tube. 9. The spacer of claim 6, 7 or 8 wherein said collar is formed of material having substantially the same coefficient of diametrical creep as said pressure tube. 10. The spacer of claim 6, 7 or 8 wherein said collar is formed of the same material as said pressure tube. 11. The spacer of claim 10 wherein said collar is formed of zirconium alloy. 12. The spacer of claim 6, 7 or 8 wherein said collar and said split ring are formed of the same material as said pressure tube. 13. The spacer of claim 12 wherein said collar and said split ring are formed of zirconium alloy. 14. The spacer of claim 6, 7 or 8 where said bearing surface has a coating to reduce heat transfer between said ring and said calandria tube. 15. The spacer of claim 6, 7 or 8 where said bearing surface has a coating to reduce wear between said ring and said calandria tube. 16. The spacer of claim 14 wherein said coating is zirconium oxide.