Patent Number: 
Section: claims

1. A control rod guide tube for a nuclear reactor, comprising:a body having an axial length defining a lower end portion and an upper end portion;a cavity within a substantial length of the body including one or more orifices at the upper and lower end portions of the body;a control rod chamber within the cavity for receiving a control rod;a plurality of ports coupled to the cavity and positioned at a substantial length from the upper end portion of the body; andat least two flow channels within the cavity extending a substantial portion of the axial length of the body;wherein each flow channel is fluidly coupled to one or more of the ports for receiving fluid flow from outside the body, andwherein each flow channel is fluidly coupled to an outlet proximate to the upper end portion of the body for providing the received fluid flow. 2. The control rod guide tube of claim 1, wherein the control rod chamber has a cruciform shape. 3. The control rod guide tube of claim 1, wherein the upper end portion of the body is configured to couple to a bottom of a fuel support for fluidly coupling each of the flow channels to an orifice of a fuel assembly cavity defined by the fuel support. 4. The control rod guide tube of claim 3, wherein a cross-sectional area of each flow channel is about equal to or less than a cross-sectional area of the orifice of the fuel assembly cavity. 5. The control rod guide tube of claim 1, wherein a combined cross-sectional area of the ports coupled to each flow channel is greater than a cross-sectional area of the coupled flow channel. 6. The control rod guide tube of claim 1, further comprising:an insert positioned within the cavity;wherein the insert defines the control rod chamber within the cavity, andwherein the insert defines each of the flow channels in conjunction with an inner surface of the body defining the cavity. 7. The control rod guide tube of claim 6, wherein the insert is rotatable within the cavity. 8. The control rod guide tube of claim 6, wherein the insert is fixedly attached to the inner surface of the body. 9. A control rod guide tube for a nuclear reactor, comprising:a body having a wall defining an upper end portion, a lower end portion, a cavity defined by an interior surface of the wall and extending from the upper end portion to the lower end portion, and a plurality of ports positioned axially along the wall between the upper end portion and the lower end portion for providing fluid flow into the cavity; andan insert dimensioned for positioning within the cavity and the insert having an upper end portion and a lower end portion and including a control rod chamber configured to receive a control rod and a plurality of channel fixtures that, at least partially, define one or more flow channels within the body cavity for receiving a fluid flow through one or more of the body ports, for channeling the received fluid flow within the body cavity between the lower end portion and the upper end portion, and for providing the fluid flow to the upper end portion of the body. 10. The control rod guide tube of claim 9, wherein the upper end portion of the body is configured to couple to a bottom of a fuel support, andwherein the upper end portion of the body is configured to fluidly couple each of the flow channels to an orifice of a fuel assembly cavity defined by the fuel support. 11. The control rod guide tube of claim 10, wherein one or more flow channel fixtures and portions of the interior surface of the wall define each of the flow channels within the body cavity,wherein each flow channel extends substantially from the lower end portion to the upper end portion, andwherein each flow channel has a cross-sectional area about equal to or less than a cross-sectional area of the orifice of the fuel support cavity. 12. The control rod guide tube of claim 9, wherein each flow channel is configured to receive fluid flow from two or more ports. 13. The control rod guide tube of claim 12, wherein a combined cross-sectional area of the ports of each flow channel is greater than a cross-sectional area of the flow channel. 14. The control rod guide tube of claim 9, wherein each of the ports are positioned at a distance from the upper end portion in order to establish a substantially symmetrical fluid flow to the upper end portion of each flow channel. 15. The control rod guide tube of claim 9, wherein the insert is fixedly attached to an inner surface of the wall defining the cavity, andwherein each flow channel is substantially enclosed by a portion of the inner surface and a portion of the insert. 16. The control rod guide tube of claim 15, wherein the insert includes a hole between one of the flow channels and the control rod chamber, andwherein the hole is dimensioned and positioned to enable a portion of the fluid flow to enter the control rod chamber. 17. The control rod guide tube of claim 9, wherein the insert is rotatable within the body cavity. 18. The control rod guide tube of claim 9, further comprising:a coupling fixture attached to the lower end portion of the body configured to releasably couple the control rod guide tube within the reactor. 19. The control rod guide tube of claim 9, wherein each pair of channel fixtures is coupled at an outer periphery forming a hollow arm defining a portion of the control rod chamber. 20. The control rod guide tube of claim 19, wherein the channel fixtures define the control rod chamber having a cruciform shape. 21. A control rod guide tube for a nuclear reactor, comprising:means for receiving a control rod; andmeans for channeling a substantially symmetrical fluid flow into a lower orifice of a fuel assembly cavity of a fuel support;wherein the means for channeling includes at least two flow channels within a body of the control rod guide tube that extend a substantial portion of an axial length of the body, andwherein fluid flow in a first channel of the at least two flow channels is substantially parallel to fluid flow in a second channel of the at least two flow channels.