Nuclear fuel string assembly

• US 4,042,456 A
• Filed: 03/16/1976
• Issued: 08/16/1977
• Est. Priority Date: 03/16/1976
• Status: Expired due to Term

• Current Assignee: General Electric Canada (General Electric Co. (Italy))
• Original Assignee: General Electric Canada (General Electric Co. (Italy))
• Inventors: Ip, Anthony Kwok-Chun, Koyanagi, Ken, Tarasuk, Walter Renald
• Primary Examiner(s): Engle, Samuel W.
• Assistant Examiner(s): Walsh, Donald P.
• Application Number:
  US05/667,419
• Time in Patent Office: 518 Days
• Field of Search: 176/73, 176/75, 176/76, 176/78
• US Class Current: 376/445
• CPC Class Codes: G21C 3/334 Assembling , maintenance or repair of the bundles assembling, maintenance or repair of other reactor components G21C19/207
• CPC Class Codes: G21C 3/336 Spacer elements for fuel rods in the bundle spacer grids G21C3/34
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A reactor fuel system has fuel pins secured to respective carrier rings as an inner sub-assembly and an outer sub-assembly for mutual telescoping relation, with radial spacing thimbles interconnecting the two assemblies and also permitting interconnection to adjacent assemblies to ensure axial coincidence of cooling flow paths. In the case of booster fuel of annular section, which may be rod-mounted for ready insertion into and withdrawal from the reactor core, the center passages of respective pins are brought into axial alignment to foster effective coolant circulation therethrough.

Claims

1. A nuclear fuel bundle for use in a nuclear reactor, comprising a first fuel rod sub-assembly having a first set of axially spaced annular rings with a first plurality of nuclear fuel rods integrally attached to radially inner surfaces of said first rings in annular array therein and extending in mutual parallel relation between the rings, a second fuel rod sub-assembly having a second set of axially spaced annular rings, with a second plurality of nuclear fuel rods integrally attached to radially outer surfaces of said second rings in annular array thereabout and extending in mutual parallel relation between the rings, said second sub-assembly being of smaller diameter than said first sub-assembly, having a radial clearance therefrom, and assembled coaxially in telescoped relation within the other said sub-assembly, and a plurality of hollow thimble means interposed between and supported by said first and second sub-assembly in contacting relation with the ends of said rods to locate said first fuel rods in radially and angularly spaced relation from said second fuel rods, to permit relative differentive axial expansion between said sub-assemblies.

2. The fuel bundle as claimed in claim 1, the radial outer circumference of the smaller one of said assemblies exceeding the radial inner circumference of the larger one of said assemblies.

3. The fuel bundle as claimed in claim 1 having cylindrical surfaced recesses in the ends of said first and second fuel rods to accept axial insertion of said thimble means therein.

4. The fuel bundle as claimed in claim 1 in combination with at least one other like bundle, a plurality of said thimble means extending within both said bundles, to secure said fuel rods in respective axially aligned relation.

5. The combination as claimed in claim 4, including a central mounting rod, inserted through said second sub-assembly annular rings to support a plurality of said bundles to permit insertion of said plurality of said bundles as a booster unit within a nuclear reactor.

6. The fuel bundle combination as claimed in claim 4 wherein at least some of said thimble means are of material having a predetermined neutron absorption characteristic.

7. The fuel bundle combination as claimed in claim 4, wherein said thimble means are made of material selected from the group comprising stainless steel and stainless steel having a predetermined boron content to promote neutron absorption to a desired extent.

8. The combination as claimed in claim 4 wherein said thimble means has a plain cylindrical outer surface.

9. The combination as claimed in claim 4 wherein each said thimble means has a plurality of cylindrical surfaced recesses from the outer surface thereof, to receive the ends of said fuel rods therein.

10. The fuel bundle as claimed in claim 1 in combination with one other like bundle, a plurality of thimble means extending within both said bundles to secure selected ones of said elements in said bundles in axially misaligned relation, in order to achieve a corresponding mismatch of flow channels between said elements to promote improved heat transfer coefficients.