Patent Number: 
Section: claims

1. A method comprising:forming at least one columnar element defining a central passage having a constant cross-section;constructing a control rod guide frame including the at least one columnar element;constructing a control rod assembly comprising a plurality of control rods parallel aligned with the central passage of the control rod guide frame;wherein the plurality of control rods is movable into and out of the central passage of the control rod guide frame, and wherein any portion of the at least one control rod disposed in the central passage is guided by the central passage over the entire length of the portion of the at least one control rod that is disposed in the central passage,wherein the control rod assembly comprises the plurality of control rods connected with a spider or other coupling element, and the spider or other coupling element is disposed in the central passage of the control rod guide frame and moves along the central passage as the plurality of control rods move into or out of the central passage,wherein the spider or other coupling element comprises:a frame comprising a first material and defining cavities; anda filler disposed in the cavities, the filler comprising a second material that is more dense than the first material. 2. The method as set forth in claim 1, wherein the forming comprises: defining at least one fluid flow passage providing fluid communication between the central passage and an exterior of the columnar element. 3. The method as set forth in claim 1, further comprising: installing the control rod guide frame in a nuclear reactor vessel; and operating the nuclear reactor vessel, the operating including adjusting a position of the plurality of control rods in a nuclear reactor core using the control rod guide frame to guide the plurality of control rods during the adjusting. 4. The method as set forth in claim 1, wherein: the forming comprises forming a plurality of the columnar elements; and the constructing comprises constructing the control rod guide frame by stacking the columnar elements end-to-end. 5. The method as set forth in claim 4, wherein:the constructing further comprises forming mating features on ends of the columnar elements wherein the stacking includes mating the mating features on abutting ends of adjacent columnar elements. 6. The method as set forth in claim 1, wherein the forming comprises: extruding the at least one columnar element defining a central passage. 7. The method as set forth in claim 1, wherein the forming comprises: extruding the at least one columnar element comprising stainless steel. 8. The method as set forth in claim 1, wherein the forming comprises: casting the at least one columnar element defining a central passage. 9. The method as set forth in claim 1, wherein the forming comprises: forming the at least one columnar element defining a central passage using electrical discharge machining (EDM). 10. A method comprising:forming a plurality of columnar elements defining a central passage having a constant cross-section;constructing a control rod guide frame including the plurality of columnar elements by stacking the columnar elements end-to-end;providing a control rod assembly comprising a plurality of control rods parallel aligned with the central passage of the control rod guide frame;wherein the plurality of control rods is movable into and out of the central passage of the control rod guide frame, and wherein any portion of the at least one control rod disposed in the central passage is guided by the central passage over the entire length of the portion of the at least one control rod that is disposed in the central passage, andwherein the control rod assembly comprises the plurality of control rods connected with a spider or other coupling element, and the spider or other coupling element is disposed in the central passage of the control rod guide frame and moves along the central passage as the plurality of control rods move into or out of the central passage. 11. The method of claim 10, wherein the spider or other coupling element comprises: a frame comprising a first material and defining cavities; and a filler disposed in the cavities, the filler comprising a second material that is more dense than the first material. 12. The method as set forth in claim 10, wherein the forming comprises one or more from the group comprising: extruding the plurality of columnar elements defining a central passage; extruding the plurality of columnar elements comprising stainless steel; casting the plurality of columnar elements defining a central passage; and forming the plurality of columnar elements defining a central passage using electrical discharge machining (EDM). 13. The method as set forth in claim 10, further comprising: installing the control rod guide frame in a nuclear reactor vessel; and operating the nuclear reactor vessel, the operating including adjusting a position of the plurality of control rods in a nuclear reactor core using the control rod guide frame to guide the plurality of control rods during the adjusting. 14. The method as set forth in claim 10, wherein: the providing further comprises forming mating features on ends of the columnar elements wherein the stacking includes mating the mating features on abutting ends of adjacent columnar elements. 15. The method as set forth in claim 10, wherein the forming comprises defining at least one fluid flow passage providing fluid communication between the central passage and the exterior of the columnar element.