Patent Number: 055925227
Section: claims

1. A control rod for a nuclear reactor, comprising: a cruciform control rod body having four elongated, substantially vertically extending wings arranged generally 90.degree. relative to one another, each wing including a plurality of elongated, generally vertically extending discrete structural members spaced from one another and discrete horizontally extending structural members adjacent opposite ends of said vertically extending members defining a plurality of vertically extending, side-by-side compartments;  a sheath disposed along opposite sides of said vertically and horizontally extending members, said structural members being welded to one another and said sheaths being welded to said structural members whereby said members and said sheath seal said compartments externally of said wing;  neutron-absorbing material disposed in each said sealed compartment; and  a passage through a vertically extending member in part defining adjacent compartments enabling passage of gas under pressure generated by reaction of at least certain of the neutron-absorbing material with neutrons from one of said adjacent compartments through said passage into another of said adjacent compartments. 2. A control rod according to claim 1 wherein said neutron-absorbing material comprises boron carbide disposed in a plurality of capsules, said plurality of capsules being disposed in said compartments. 3. A control rod according to claim 2 wherein said capsules are confined within said compartments by said members and said sheaths and without structural interconnection therewith. 4. A control rod according to claim 2 wherein said neutron-absorbing material comprises hafnium. 5. A control rod according to claim 1 including a central tie rod comprised of a plurality of planar plates each secured along opposite edges to innermost vertical members of a pair of wings lying in a common plane, the plates being superposed one over the other. 6. A control rod according to claim 5 wherein said tie rod plates have a slot at one end for receiving a portion of a vertically adjacent tie rod plate whereby the tie rod plates interconnect with one another and are alternately secured to right angularly related planar extending wings. 7. A control rod for a nuclear reactor comprising a control rod body having a plurality of elongated, laterally spaced, generally vertically extending parallel discrete structural members in part defining a plurality of side-by-side compartments each containing neutron-absorbing material, discrete structural members generally right angularly related and joined to said parallel vertically extending members at opposite ends of said compartments to close said compartments in the plane thereof, a sheath on opposite sides of said discrete structural members closing the sides of said compartments, said members being welded to one another and said sheaths being welded to said members to form sealed compartments, and an opening in at least one of said members in part defining adjacent compartments enabling passage of gas under pressure generated by reaction of the neutron-absorbing material with neutrons from one of said adjacent compartments through said opening to another of said adjacent compartments to maintain said adjacent compartments under substantially equal pressure. 8. A control rod according to claim 7 wherein said neutron-absorbing material comprises boron carbide disposed in a plurality of capsules, said plurality of capsules being disposed in said compartments. 9. A control rod according to claim 8 wherein said capsules are confined within said compartments by said members and said sheath and without structural interconnection therewith. 10. A control rod according to claim 8 wherein said neutron-absorbing material comprises hafnium. 11. A control rod according to claim 7 including a central tie rod comprised of a plurality of planar plates each secured along opposite edges to innermost structural members of said plurality thereof lying in a common plane, the plates being superposed one over the other. 12. A control rod according to claim 11 wherein said tie rod plates have a slot at one end for receiving a portion of a vertically adjacent tie rod plate whereby the tie rod plates interconnect with one another and are alternately secured to right angularly related planar extending wings.