Patent Number: 
Section: claims

1. In a control rod having a plurality of elongated members for absorbing neutrons within a nuclear reactor to control a nuclear reaction, each elongated member comprising:a cylindrical inner capsule configured to contain neutron absorbing material therein; andan absorber tube enclosing the cylindrical inner capsule, the absorber tube having an outer surface with two opposing generally flat, planar, mating sides each of which is configured to mate flushly with a planar mating side of an adjacent absorber tube without the existence of a gap between the mated absorber tubes, the opposing flat, planar, mating sides each being located directly in between respective adjacent rounded corners that are convex in relation to the center of the capsule,wherein a line bisecting each of the flat, planar, mating sides is substantially collinear with a central axis of the control rod. 2. The control rod of claim 1, wherein the plurality of elongated members are arranged in side-by-side relation. 3. The control rod of claim 1, wherein the plurality of elongated members extend from the central axis of the control rod to form a cruciform shape of the control rod. 4. The control rod of claim 2, wherein each flat, planar, mating side provides a weld surface area for attachment to an adjacent absorber tube. 5. A control rod for absorbing neutrons within reactor core, comprising:four planar members extending from a central axis to form a cruciform shape, each of the planar members including a plurality of elongated members configured in side-by-side relation, wherein each elongated member further comprises:a cylindrical inner capsule configured to contain neutron absorbing material therein; andan absorber tube enclosing the cylindrical inner capsule, the absorber tube having an outer surface configured with two opposing generally flat, planar, mating sides each of which is configured to mate flushly with a planar mating side of an adjacent absorber tube without the existence of a gap between the mated absorber tubes, the opposing flat, planar, mating sides each being located directly in between respective adjacent rounded corners that are convex in relation to the center of the capsule,wherein a line bisecting each of the flat, planar, mating sides is substantially collinear with the central axis of the control rod;a cruciform-shaped tie segment provided along the central axis to brace the four planar members with respect to each other;a velocity limiter attached to the control rod at a lower end thereof; anda handle to the control rod at an upper end thereof. 6. The control rod of claim 5, wherein planar mating sides of the absorber tubes provide weld area surfaces for attachment to an adjacent absorber tube. 7. The control rod of claim 5, wherein the cruciform-shaped tie segment includes a plurality of cruciform-shaped tie segments arranged intermittently along the central axis. 8. The control rod of claim 5, wherein the cruciform-shaped tie segment extends an entire length of the absorber tube. 9. An absorber-tube for a BWR control rod, comprising:an elongate member having a generally cylindrical inner surface enclosing an inner capsule that is configured to contain neutron absorbing material therein, the elongate member having an outer surface with two opposing generally flat, planar, mating sides each of which is configured to mate flushly with a planar, mating side of an adjacent elongate member, the opposing flat, planar, mating sides each being located directly in between respective adjacent rounded corners that are convex in relation to the center of the capsule,wherein a line bisecting each of the flat, planar, mating sides is substantially collinear with a central axis of the control rod. 10. The absorber tube of claim 9, wherein a cylindrical gap is provided between the inner capsule and inner cylindrical surface of the elongate member. 11. The absorber tube of claim 9, wherein the neutron-absorbing material is boron carbide powder. 12. The control rod of claim 1, wherein the two opposing mating sides each include only one generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube. 13. The control rod of claim 1, wherein the two opposing mating sides each include a generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube, the generally flat, planar, mating surface extending from one of the rounded corners to another of the rounded corners. 14. The control rod of claim 5, wherein the two opposing mating sides each include only one generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube. 15. The control rod of claim 5, wherein the two opposing mating sides each include a generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube, the generally flat, planar, mating surface extending from one of the rounded corners to another of the rounded corners. 16. The absorber tube of claim 9, wherein the two opposing mating sides each include only one generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube. 17. The absorber tube of claim 9, wherein the two opposing mating sides each include a generally flat, planar, mating surface configured to mate with an opposing mating side of an adjacent absorber tube, the generally flat, planar, mating surface extending from one of the rounded corners to another of the rounded corners. 18. The absorber tube of claim 9, wherein an outside perimeter of the absorber tube includes only four curved corners and four flat sides.