Patent Number: 053274709
Section: claims

1. In a cross point spacer including a spacer grid for defining surrounding cells in a fuel rod matrix interior of a fuel bundle at selected elevations within said fuel bundle comprising: pluralities of normally aligned members for extension between respective rows and columns fuel rods for forming a first part of bounding cells around the fuel rod matrix of a fuel bundle;  vertically aligned subchannel tube connected to said members to form a second part of bounding cells around the fuel rod matrix of a fuel bundle and to form a mechanical interconnection to said grid members and to define subchannel flow volumes at the subchannel between adjacent fuel rods;  the improvement to said subchannel tubes comprising:  peripheral attachments interior of said tubes for providing a spiral flow to at least some of the steam water mixture flowing through said tube whereby at least some water is centrifugally classified from said steam flow through said subchannel tubes upon discharge of said coolant flow from said subchannel tubes; and  said peripheral attachments interior of said tubes defining a central flow free volume in said subchannel tubes for providing the upward unobstructed flow of coolant within said tubes.  pluralities of normally aligned members for extension between respective rows and columns fuel rods for forming a first part of bounding cells around the fuel rod matrix of a fuel bundle;  vertically aligned subchannel tubes connected to said and members to form a second part of bounding cells around the fuel rod matrix of a fuel bundle and to form a mechanical interconnection to said grid members and to define subchannel flow volumes at the subchannel between adjacent fuel rods;  peripheral attachments interior of each of said subchannel tubes for providing a spiral flow to at least some of the steam water mixture flowing through each of said subchannel tubes whereby at least some water is centrifugally classified from said steam flow through said subchannel tubes upon discharge of said coolant flow from said subchannel tubes; and  said peripheral attachments interior of said subchannel tubes defining a central flow free volume in said subchannel tubes for providing the upward unobstructed flow of coolant within said tubes.  providing pluralities of normally aligned members for extension between respective rows and columns fuel rods for forming a first part of bounding cells around the fuel rod matrix of a fuel bundle;  providing vertically aligned subchannel tube connected to said members to form a second part of bounding cells around the fuel rod matrix of a fuel bundle and to form a mechanical interconnection to said grid members and to define subchannel flow volumes at the subchannel between adjacent fuel rods;  placing peripheral attachments interior of said subchannel tubes for providing a spiral flow to at least some of the steam water mixture flowing through said subchannel tubes whereby at least some water is centrifugally classified from said steam flow through said subchannel tubes upon discharge of said coolant flow from said subchannel tubes; and  defining in said peripheral attachments interior of said tubes central flow free volumes in said subchannel tubes for providing the upward unobstructed flow of coolant within said tubes. 2. The invention of claim 1 wherein said internal projections are integral with the tubes and have the form of an internal thread with a very long pitch. 3. The invention of claim 1 and wherein said peripheral attachments interior of said tubes comprise threads. 4. The invention of claim 2 and wherein said internal projections of said tubes comprise spiral metal strips attached to the inside periphery of said tubes. 5. In a cross point spacer including a spacer grid for defining surrounding cells in a fuel rod matrix interior of a fuel bundle at selected elevations within said fuel bundle comprising: 6. The invention of claim 5 and wherein said spacer includes upper and lower grids. 7. The invention of claim 5 and wherein said peripheral attachments interior of said tubes comprise threads. 8. The invention of claim 7 and wherein said peripheral attachments interior of said tubes comprise spiraled metal strips adjacent the inside periphery of said tube. 9. A method of constructing a cross point spacer including a spacer grid for defining surrounding cells in a fuel rod matrix interior of a fuel bundle at selected elevations within said fuel bundle comprising: 10. The process of claim 9 and where said placing peripheral attachments interior of said tubes for providing a spiral flow to a steam water mixture flowing through said tube for enabling water to be centrifugally classified includes placing threads interior of said tubes.