Patent Number: 
Section: claims

1. A fuel bundle for a heavy water nuclear reactor, the fuel bundle comprising:a plurality of fuel elements each includinga first fuel component of recycled uranium; anda second fuel component of at least one of depleted uranium and natural uranium blended with the first fuel component,a central fuel element comprising depleted uranium blended with a burnable poison,wherein the central element is centrally located in the fuel bundle,wherein the blended first and second fuel components have a first fissile content of less than 1.2 wt % of 235U, andwherein the plurality of fuel elements, when burned by the nuclear reactor, has a negative fuel temperature coefficient provided at least in part by the depleted uranium blended with the burnable poison being centrally located within the fuel bundle. 2. The fuel bundle of claim 1, wherein the plurality of fuel elements includes a ring of six substantially parallel tubes each containing the blend of the first and second fuel components. 3. The fuel bundle of claim 2, wherein the second fuel component comprises depleted uranium. 4. The fuel bundle of claim 2, wherein the second fuel component comprises natural uranium having a fissile content of approximately 0.71 wt % of 235U. 5. The fuel bundle of claim 1, wherein the plurality of fuel elements is a first plurality of fuel elements, the fuel bundle further comprising a second plurality of fuel elements forming a ring around the first plurality of fuel elements. 6. The fuel bundle of claim 5, wherein the second plurality of fuel elements includes natural uranium having a fissile content of approximately 0.71 wt % of 235U. 7. The fuel bundle of claim 5, wherein the second plurality of fuel elements includes a blend of recycled uranium and depleted uranium. 8. The fuel bundle of claim 7, wherein a fissile content of the blend of recycled uranium and depleted uranium in the second plurality of fuel elements is greater than the first fissile content. 9. The fuel bundle of claim 5, wherein the second plurality of fuel elements includes twelve substantially parallel tubes positioned radially outward from the first plurality of fuel elements. 10. The fuel bundle of claim 5, further comprising a third plurality of fuel elements forming a ring around the second plurality of fuel elements. 11. The fuel bundle of claim 10, wherein the third plurality of fuel elements includes natural uranium having a fissile content of approximately 0.71 wt % of 235U. 12. The fuel bundle of claim 10, wherein the third plurality of fuel elements includes a blend of recycled uranium and depleted uranium. 13. The fuel bundle of claim 12, wherein a fissile content of the blend of recycled uranium and depleted uranium in the third plurality of fuel elements is greater than a fissile content of the blend of recycled uranium and depleted uranium in the second plurality of fuel elements. 14. The fuel bundle of claim 10, wherein the third plurality of fuel elements includes eighteen substantially parallel tubes positioned radially outward from the second plurality of fuel elements. 15. The fuel bundle of claim 1, wherein the central fuel element is located at the center of the fuel bundle. 16. The fuel bundle of claim 15, wherein the central fuel element includes a blend of recycled uranium and depleted uranium. 17. The fuel bundle of claim 16, wherein a fissile content of the blend of recycled uranium and depleted uranium of the central fuel element is less than the first fissile content. 18. The fuel bundle of claim 1, wherein the plurality of fuel elements includes a ring of seven substantially parallel tubes each containing the blend of the first and second fuel components. 19. The fuel bundle of claim 18, wherein the plurality of fuel elements is a first plurality of fuel elements, the fuel bundle further comprising a second plurality of fuel elements located radially outward from the first plurality of fuel elements. 20. The fuel bundle of claim 19, wherein the second plurality of fuel elements includes natural uranium having a fissile content of approximately 0.71 wt % of 235U. 21. The fuel bundle of claim 19, wherein the second plurality of fuel elements includes a blend of recycled uranium and depleted uranium. 22. The fuel bundle of claim 21, wherein a fissile content of the blend of recycled uranium and depleted uranium in the second plurality of fuel elements is greater than the first fissile content. 23. The fuel bundle of claim 19, wherein the second plurality of fuel elements includes fourteen parallel tubes positioned radially outward from first plurality of fuel elements. 24. The fuel bundle of claim 19, wherein at least one of the second plurality of fuel elements is different in cross-sectional size than that of at least one of the first plurality of fuel elements. 25. The fuel bundle of claim 19, further comprising a third plurality of fuel elements forming a ring around the second plurality of fuel elements. 26. The fuel bundle of claim 25, wherein the third plurality of fuel elements includes natural uranium having a fissile content of approximately 0.71 wt % of 235U. 27. The fuel bundle of claim 25, wherein the third plurality of fuel elements includes a blend of recycled uranium and depleted uranium. 28. The fuel bundle of claim 27, wherein a fissile content of the third plurality of fuel elements is greater than a fissile content of the second plurality of fuel elements. 29. The fuel bundle of claim 25, wherein the third plurality of fuel elements includes twenty-one substantially parallel tubes positioned radially outward from the second plurality of fuel elements. 30. The fuel bundle of claim 25, wherein at least one of the third plurality of fuel elements is different in cross-sectional size than that of at least one of the first plurality of fuel elements. 31. The fuel bundle of claim 25, wherein the central fuel element located at the center of the fuel bundle. 32. The fuel bundle of claim 31, wherein the central fuel element includes a blend of recycled uranium and depleted uranium. 33. The fuel bundle of claim 32, wherein a fissile content of the blend of recycled uranium and depleted uranium of the central fuel element is less than the first fissile content.